ADA MP-1 Rebuild

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Anyone that grew up in the ’80s as a guitarist knows about the ADA MP-1 and how it was used by the top guitarists of that era. The ADA MP-1 is a classic rack mount tube preamp that features an all analog tube signal path. Its sound has a distinctive mid range and clear articulation. I had one of these in the late ’90s and regrettably sold it. A few years ago, I found one in bad condition, with the front panel mangled and its been sitting in a box ever since, waiting to be revived.

I didn’t take any pictures of the unit in its original state but the completed, repaired unit shows signs of the abuse it went through. The front panel was broken and it was quite noisy, as most of the MP-1s are.

This project was to be done in three steps:

  1. Repair the ADA MP-1  front panel
  2. Refurbish the electronics
  3. Bring the noise floor to a lower level (better “noise mod”)

The Front Panel

The control buttons on this unit were mostly broken: Some worked, some didn’t and some were intermittent. The contacts are a “momentary on” type so I proceeded to start removing the existing control appliqué and replace it with real push buttons. By tracing out the original connections, I could replicate them with hookup wire.

The original appliqué needs to be removed from the faceplate. You need to remove the front panel, then, with a hair dryer, heat up the flexible faceplate that is glued on the metal front panel. It should come off very easily. The faceplate is 3 parts:

  1. The coloured portion that has all the user indications on it.
  2. 1st side of the button connections
  3. 2nd side of the button connections

To trace the circuit, you need to undo the three parts of the flexible faceplate. Again, a little bit of heat is all that’s needed to take everything apart. Just pull slowly and you’ll be fine.

Once you have everything apart, its a game of patience to trace and wire everything up. The front panel need to be drilled to accept the new push buttons and the LEDs on the PCB board removed to make way for the relatively large buttons. Once the buttons are in place, the LEDs can be put back in place with the wires going around the buttons.

As much as I tried to keep everything nice and neat, it was hard. There are a lot of wires that need to be added that cross one another and getting the LED leads to go around the physical buttons to the PCB is quite the challenge. If I were to do this again, I might be able to make it cleaner looking.

The individual LEDs are fixed in place with hot melt glue, as is the main LED display.

Electronics Refurbish

Being that this is an older unit that is over 25 years old, I decided to change out all of the electrolytic capacitors, including all non-polarized coupling caps. This would help in getting a clearer sound with better coupling caps. The power supply could be refreshed at the same time, especially near the tubes where there is a lot of heat accumulation, which degrades the electrolyte in the capacitors.

All capacitors were selected for same value and voltage spec as the original except on the tube board (more on that in the noise reduction section).

For the signal path coupling caps, I selected Panasonic SU Bipolar series capacitors. The 25v/10uf seemed to have the best dissipation factor (tan ∂) spec and are rated for low impedance, which is important in the signal path.

Along with changing out the capacitors, all sockets, jacks, pots, contact points were thoroughly cleaned.

Noise Reduction

The ADA MP-1 is a great sounding unit but one drawback is the amount of noise that it generates. There are some mods out there, notably from ADA Depot, that suggest ways of reducing noise with their “noise mod” but looking through them, it seems that some of the mods listed will increase the noise floor, not reduce them. Things like replacing a 2068 opamp with a TL072 is something that will not only add noise but also degrade audio quality.  I really wonder why anyone would use the TL072 when there are so many better options out there and in this case, to replace a better device.

Here’s a link to a nice writeup on opamps and their performance: http://nwavguy.blogspot.ca/2011/08/op-amp-measurements.html

Below is a description what I did to reduce the noise floor on my ADA MP-1.

Tube board modifications

On the tube board, replace all electrolytic capacitors as follows with better spec’d components:

  • C1 10uf/450v (the one on my MP-1 was 6.8uf!):  Nichicon UV2W220MHD 22uf/450v 105ºC
  • C2, C8 10uf/250v: Panasonic EEU-EB2E101S 100uf/250v 105ºC. They’ll fit and the extra filtering won’t hurt, especially in a high gain setup like this one. If I were to re-order replacements, I’d probably opt for something a little smaller.
  • C6, C7, C13, C12 33uf/50v: Panasonic EEU-EB1J330S 33uf/63v 105ºC

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Still, on the tube board, replace the following plate resistors with metal film, 1/2W.

  • R2/R3/R4/R6: 100k 1/2w metal film.

The capacitors are easy enough to locate and replace. The resistors are on the top portion of the board, close to the C2 & C8 capacitors.

Once the capacitors are soldered in place, make sure that you secure them with a bit of hot melt glue, or any other method if you have other preferences.

Main board modifications

There are a couple of areas that can be improved on the main board to improve the noise performance and the audio quality as well. The idea is to reduce the amount of noise as much as possible early on in the signal chain so that its not amplified by the subsequent gain stages.

Step 1

On the input, I changed resistors R85, R86, R87, R88 and R89 to 1/2 metal film.  With the nearby heat of the tubes and high sensitivity input, this change lowers the noise floor for all modes of operation on this preamp.

ADA MP-1 Input Stage

Step 2

The next modification is really more of a sound quality thing than a noise improvement modification. The C29 & C31 foil capacitors to the input of the tube board are replaced with Wima MKS2 0.33 caps. They are less sensitive to the nearby tube’s heat and have a much better dissipation factor than the original capacitors. This change gives better clarity and detail, especially when the unit has been on for a while.

ADA MP-1 C29 & C31

Step 3

The pre-eq buffer feedback loop needs to be changed to filter out more hiss. This is done by changing C66 near opamp U18 from 150pf to 33nf (see picture below)

Step 4

The quad op-amp that handles the presence, treble, mid and bass eq levels is a TL074. This is a poor choice of op amp but maybe this is all that was available in this form factor at the time of production for the MP-1. Here, I tried to select an opamp that has a similar input bias current and drive capabilities as the original device but with better audio performance.  I hesitated between the TL974 and the MC33079 and ended up trying the MC33079 (quad version of the MC33078), installed in a DIP socket. The MC33079 is nice but the input impedance is much, much lower than the TL074 and it also requires higher bias current. This doesn’t seem to affect performance at these low voltage levels but I think that the OPA4134 is a better fit for this application. The TL974 won’t properly handle the +/- 15vdc power supply, so that’s not a good option.

 

U17 Upgrade

ADA MP-1 Post gain and  EQ upgrade.

Step 5

The output stage needs to have its feedback loop modified in a similar fashion as what was done in step 3.  C53 and C69 that are on the U17 4558 opamp are changed from 100pf to 10nf.

ADA MP-1 Output

ADA MP-1 Output

Step 6

Make sure that the input jacks are isolated from the panels. You can do this with switchcraft insulating washers that have a small shoulder (switchcraft part #S1029).

 

For reference, the full ADA MP-1 Schematics and layout.

Mp-1_FullSchematics

mp-1 V1.xx pcb layout1

mp-1 V1.xx pcb layout2

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NAD 7020 Receiver Refurbish

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In recent months I got back into just listening to music, no distractions, just enjoying it. I got my old Sony PS-X45 turntable back up and running again but the Yamaha integrated amp’s phono stage was disappointing and the Yamaha, although very powerful and clear sounding, needed some TLC. I’d rather just get something nicer and more appropriate for my listening setup than spend time and money on the Yamaha, although it is a great amp, just not what I need.

I settled on a NAD 7020 receiver I found in the local ads. I had the 7020e version years ago and liked it and these amps have an excellent reputation for their power amp, the highly acclaimed 3020 and their phono preamps. The 7020 is basically a 3020 with a tuner added to it.

The amp had a missing bulb for the front panel display but everything else worked fine. The amp is a rev2 with the updated PCB layout, which is nice because the earlier ones apparently had some reliability issues. Everything is original on the amp. Given its age, I opted to do a full recap on it (change out all electrolytic capacitors) and upgrade certain capacitors with Wima MKS series caps, especially in the phono stage.

Here’s the rev2 NAD 7020 service manual, starting at serial number 7218469: NAD 7020 SM

Here are some gut shots of the amp before the refurbish:

New capacitors

For the electrolytics, I chose mostly Nichicon caps, selected for low ESR and life parameters.

In the phono stage, 4.7uf C401/402 are changed to Wima MKS2 film caps. For the 10uf C423/424 caps, the smallest film cap would not fit so this is where I selected a pair a Nichicon Fine Gold Muse audio caps.  I also got Nichicon Muse caps for the 47uf C415/416 capacitors. These upgrades will help in getting in clearer, more authentic sound from the phono stage.

In the amp driver stage board, C604/603/605/608 are also upgraded to Wima MKS2 caps. The goal here is to be as transparent as possible in the audio path.

The driver, phono and tuner boards are best recapped with the board pulled out of their slots. While you’re at it, clean the contact tabs on the pulled boards and connectors on the main pcb.

 

Front Panel Lighting

With all the capacitors refreshed or upgraded, bad solder joints fixed, its time to look at the missing bulb that lights up the front panel. The bulb holder was cracked with bits of plastic missing. Because it was already powered by DC, I decided to replace it with a blue LED. I wired it with an in-line series resistance based on the LED’s current and voltage spec.

The LED must point towards the panel. I glued it in place with hot melt glue. The bare wires are covered in heat shrink.

Biasing the amp

The final step is to power the amp up and start to check the bias and DC offset. The bias is what I set 1st. The instructions are pretty vague in the service manual so I’ll clear it up here. On the 7020, its not a straightforward affair where you simply tweak a pair of variable pots.
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  1. You need to add a 1k resistor in parallel with R648 (right channel) and R647 (left channel). With the amp up on its side, I add the resistors on the underside of the board. See the pics below.
  2. Next, you need to “un-jumper” the 1Ω resistors R660 (right channel) and R659 (left channel). The jumper is basically a blob of solder on the underside of the board. Remove it with a solder sucker and clean the PCB with some Isopropyl alcohol to ensure the traces are properly separated.
  3. Remove the 1Ω R660 and R659 resistors and check their values. When biasing an amplifier, checking these is very important so can you adjust for resistor values that are not 100% to spec. On my amp, one the of resistors measured 3KΩ!  Personally, I find it easier to just remove the resistors that are mounted on the board and temporarily install selected 1Ω resistors to the underside of the board so I have access to the leads where I can hook my multimeter (See pictures).
  4. The bias resistors are Rx2 and Rx1. They must be changed to adjust the bias. A bit of a pain, really. Check the bias with Rx2 and Rx1 unchanged. If the bias is out of spec, remove the resistors.
  5. Install new 1kΩ resistors of a higher value and keep the leads full length under the board. You will use these leads to hook up test leads and hook up a potentiometer to adjust bias.
  6. With Rx1 and Rx2 replaced and a potentiometer hooked up in parrallel to each resistor, tweak the pot until the bias is exactly where you want it. I set mine @ 50mv
  7. Measure the pot’s value and calculate  the equivalent resistor value you will need to Rx1 and Rx2. I ended up requiring 536Ω and 549Ω. I couldn’t find the right mix of resistors in my stock (combination of parralleled resistors) to get to those values so I simply ordered exact value “TT Electronics” RC55LF series resistors from Mouser. They are metal film, low noise, low temp coefficient devices.
  8. Install the new resistors and double check the bias value.

The last step in my biasing procedure is to remove the temporary 1KΩ resistors, remove the 1Ω bias resistors  R660/659 I installed under the board and replace them with jumpers and finally, install the new RX1 and RX2 resistors.

 

DC offset

The DC offset is simple to setup. It is well described on page 4 of the service manual. The adjustment pots are shown on page 5. They are on the vertically mounted power/driver stage board. Following the instructions in the manual, I was able to set the offset to 0v.

Connectors & pots

Make sure you clean all pots and RCA & speaker connectors before plugging anything in. Over the years, there can be quite a bit of contamination that builds up and dirty connectors can result in loss of output, unwanted capacitance and erratic behaviour.

Finish line

The completed amplifier is pictured below. It has absolutely great sound, is very dynamic, has a low noise floor, a solid 20w per channel. I’m very happy with the way this turned out. All the little things add up in this amp to make a very nice sounding unit. The phono stage is particularly nice, as is the power amp.

NAD 7020 Refurbished

 

Reverb footswitching on Marshall DSL JCM2000

Posted on by admin Posted in Electronics Repair

DSCF6980

Here’s a simple problem that I came across on a Marshall JCM2000 DSL amplifier: The Reverb works fine but when plugging in a footswitch to the Reverb jack, you cannot turn it on or off. It could also be the other way around (won’t turn on, stuck “off”).

The reverb’s switching circuitry is actually pretty simple. It is controlled by TR1 transistor on the reverb board that changes state depending on whether the footswitch is depressed or not. You can check whether its working or not by checking for current flow on pin 1 of IC2 (M5201). When R14 has current going through it, reverb channel B of the M5201 is active, and when no current is present, channel A is active.

The schematic for the reverb board can be found here:

http://www.lydian.ca/Marshall_DSL_files/jcm2-63-02-iss3_PowerBoard.pdf

The M5201 datasheet

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The problem on this amp was in fact TR1, an MPSA13 darlington transistor that is easily available from mouser.com.

Here’s the board with the new TR1 installed:

 

With everything connected back up, the reverb footswitch control now works again and all is well 🙂

Yamaha RA-100 Rotating Speaker Organ Amp

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A while back, I found this Yamaha RA-100 organ amplifier in the local ads. I didn’t think much of it but I thought it was very interesting with its dual rotating speakers. It seemed to be in rough shape but the price wasn’t too steep and it would make for a cool project. The person I bought it from couldn’t say whether it worked or not. It looked like it was kept in a barn for a couple of years. We met at a farmer’s supply store. It was in the back of his pickup truck and we eased it into the little Honda Fit. This thing is an absolute beast. Big, bulky and heavy, but the poor little Honda managed to bring it back home.

Cabinetry

The cosmetics were bad, the top grille was ripped and looked like it was been chewed on by a rodent. When I got it home, upon inspection, I found that the power amp was badly distorting, the bottom two 12″ speakers were completely seized, the rear particle board panel was crumbling, but the rotating speakers seemed to work in terms of rotating and producing a sound. That’s the important part.

 

 

I did some research on the ‘net and found little info on these but did manage to find a schematic for it and to my surprise, found out that Gilmour used the 200w, 4×12 version of this very same amp. I was very happy to find that little bit of information out.

David Gilmour’s RA-200

Cabinetry Overhaul

I needed to completely overhaul the electronics. That meant replacing all electrolytics and figuring out what’s broken with the electronics. Cosmetically, I decided that to make this thing a little more practical, I would cut it in half, making it into a two piece amp with the 2×12 cabinet on the bottom and amplifier and rotary speaker assembly on top. This would make it more portable. The thing was is bad shape to start with so might as well redo it all.

Here’s some of the cabinetry cut up in half and the start of the complete dismantling. You can see that the cabinetry is rough. I invested quite a bit of time in fixing it up to make all seams and joints smooth so I could apply new tolex and trim onto a nice surface.

Electronics – Electrolytics

The entire amplifier was fitted with new electrolytics throughout. With a 40yr old amp, this is a must. Electrolytics age and dry out. Most manufacturers don’t spec them for anything more than 15 years, in ideal conditions. I went with a combination of Panasonics and Nichicons, depending on size, type and specs. The two rotating speaker assemblies were refurbished, along with the power amp, crossovers and preamp.

Here are a few “before” shots of the power amp.

Here are some shots of the power amp and preamp PCBs with the new electrolytic capacitors installed.

Electronics – Power Amp

The power amp had been previously been repaired and the 2SC1080 output TR6/TR7 Sziklai pair had been replaced with a Motorola 2N3773 substitute. The amp was behaving badly: Distorted when I could get sound of it it. After a few tests, it started to blow fuses constantly. I took out TR6 and it was shorted out. At this point, with the seized speakers and previous repair, the best way to go in my opinion is to replace the output and driver transistors, along with the emitter resistors. With a shorted TR6, that TR4 driver had certainly been stressed.

Yamaha RA-100 Power Amp Schematic.

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The big problem with some vintage gear is that the older transistors are no longer made so finding a proper substitute can be quite challenging, especially with the TO-66 packages. I found the old TO-3 packaged 2SC1080 spec sheet and started my search for a TR6/TR7 replacement.

2SC1080 Specification

I ended up settling on the ON Semiconductor 2N3442. I wanted something that could obviously handle the voltages and current for the driver stage of the amp but also be close in terms of HFE and power dissipation ratings. The next challenge is to find a proper replacement for the driver transistors. The Toshiba 2SC784/2SA483 NPN/PNP pair is also out of production, in a hard to find TO-66 package. I had a short list of possible candidates but found some apparently NOS transistors from a US seller. I’m always leary of buying NOS parts from sellers I don’t know because of the number of counterfeits flooding the market. After careful examination of the the ad, I decided to go for it. When I received them, they looked very close to the originals I had. The metal work, pins and assembly seemed legit although the lettering was not 100% the same, but that is the kind of thing that can change over the course of the life of a product.I went ahead and soldered them in to the board.

I swapped out the emitter resistors for some Vishay RL series resistors. I plugged in the amp, adjusted bias to about 10ma. I then inserted a 1Khz input signal and measured the output into a 1KΩ load. I was able to get 110w out of the amp, clean with no crossover distortion and no DC voltage on the output.

Tremolo Unit

The tremolo units were refurbished, like the rest of the amplifier but two things need special attention.

RA-100 Tremolo Schematic

The electrolytics are replaced is as the TR1 2SC458A transistor. The 2SC458A is a Hitachi part is notoriously leaky and the ones in this RA-100 is no exception. The Collector to Emitter resistance clocks in at 16kΩ. They are replaced with KSC1845FTA.

On this unit, I also removed the spindle covers on either side to clean the connections and spray some grease into the spindle assembly to lube it.

Re-assembly

With all the pieces in place, basic electronic tests done, it was time to start re-assembling . At this point, all the cabinetry has been completely re-done into 2 pieces (top amp/rotating speakers and bottom 2×12), Marshall black levant tolex applied, aluminium trim and Marshall salt & pepper grille cloth applied.

Plugging in

The next “real” test was with the rotating speakers and bottom 2×12 cab as opposed to a 1KΩ load and an oscilloscope. The 2×12 cab was fitted with Fender special design speakers. I originally wanted the Eminence Legend 1258 but apparently, these OEM speakers are the same thing and I happened to find two for fairly cheap. In my opinions, they are a great speaker. In the rebuilt sealed cabinet, which is pretty large, the low end is tight, it has good midrange although not as “British” as say a G12-M or G12-H. The top end is never piercing; smooth and clear. The attack is somewhat mellow compared to a ceramic magnet Celestion. They sound very good with the Marshall amps I have, but I digress.

There is a footswitch jack to use the RA-100 properly. It is a standard Tip Ring Sleeve (TRS) connection. I plugged in a Leem 2 button footswitch. The 1st option is to enable or disable the top rotating speakers. The 2nd option is to engage the high or low speed for the rotating speakers. The low speed is always the slowest speed for a chorus effect. The high speed is adjusted via the tremolo control on the back of the unit.

I plugged in a guitar and the amp came to life. Very full, clean and lush sound with or without the top speakers. The rotating effect is unreal. In person, you really get a sense of the air moving at different speeds. I must have noodled around for a 1/2 hour just listening to the magic.

 

1997 Marshall JCM2000 DSL 50 Loop Repair

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Marshall JCM2000 DSL50

Marshall JCM2000 DSL50 (Stock)

 

My trusty old Marshall DSL 50 has been my #1 amp since I bought it in 1997. This amp is part of the 1st production run and I got to try it out pretty much as soon as they got delivered to Steve’s music store in Ottawa. Kevin at Steve’s let me bring it to band practice to give it a good workout and I was sold! I bought it and never looked back. This was my first “real” Marshall and it has seen 100’s of shows and tons of band practices.

Its been a reliable amp but last jam, when I plugged into the effect loop, I got a loud hum and the reverb didn’t work anymore. I got through the practice and the next day, I looked into what was wrong.

I started to check all accessory voltages on the rear board and found that the -15vdc rail was missing. I soldered out one leg of zener diode ZD2 and lifted it out of the pcb to test it out of circuit. It was bad (open). As I turned the board around to de-solder the other leg of the diode, I noticed that lifting up one leg of the zener stressed the PCB pad and it came undone 🙁 I’m usually very careful with PCBs and this was a real surprise to me. The PCB pads are fragile on these. Be careful when manipulating them. I hate lifting a pad. This hasn’t happened to me in a long time.

The original ZD2 part is a “Fagor” BZY97C15, 1.5w, 15v zener diode. Theoretically, a 1.5w device should be more than enough to power the 15v accessories in the amp. The current limiting 270Ω resistor would limit the current to 33ma, given an input voltage of 24vdc so we are at about 0.5w at the zener at full power with no load. It may have died due to age, switching transients, every time I mis-cabled the send/return jacks on the effects loop, a power surge, who knows.

I selected an MCC (Micro Commercial Components), 2w, glass encased 15v diode with a lower internal impedance of 7Ω (10Ω in the original part), part # 2EZ15D5-TP. Because the amp is almost 20 years old, I figured that I might as well get fresh new electrolytic capacitors for it. I was compelled to do this now rather than putting it off again, because the 1000µf +/- 15v smoothing caps are rated only for 16vdc, which means that they’re being run right at their limit. That’s a sure way to shorten a capacitor’s life and see it fail and honestly, I don’t understand why Marshall would select such a part for this application.

The 1000µf are definitely on their way out as shown below. The new ones will perform better, especially under load, but these caps aren’t as bad as I thought they would be. The other caps tested good but since I’m working on the board anyways, I might as well simply replace them all. The additional parts cost and time is minimal.

As I stated earlier, this particular amp is a 1st production run. There are a few components that are manually soldered on the boards. For instance, on the rear board, there’s an extra zener on R44 and a non-polarized 220µf electrolytic that’s used for the channel switching between Link 2 and R44. You won’t see these two extra components on the 1997, Issue 1 JCM2-62-00 schematic, the earliest schematic that was released. You won’t see them on later schematics either.

The caps I used on the rear board are all Nichicon or Panasonic caps, selected for correct (or overspec’d) ripple current, size, lead spacing, temperature, hours (life) and ESR (or dissipation factor). I’ll get another 20 years out these caps for sure!

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Here’s the board with the caps in place and the new Zeners installed (both were changed). In the last picture, you can see the bipolar cap that I replaced. The original cap was just soldered on from the cap leads to the components, over the board with no support whatsoever. I decided to clean that up by glueing the cap solid with removable hot glue and use flying leads to get to the soldering points.

 

Did a couple tests, plugged in the amp to a cabinet and guitar with the effect loop engaged and voilà! The amp is now back to normal.

 

Alesis Multimix Hum Repair

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I bought this little Alesis firewire mixer for home use and recording multiple tracks to a Macbook. It has served me well over the years. The sound quality is decent for its price point.
Over the years, the overall level of hum has increased to a point where it became too noisy at idle. There was also an annoying 1Khz whine coming from the unit.

It is worth mentioning that this little mixer gets quite hot when powered on. The power supply regulators are attached to a heat sink that is bolted against the chassis. All the power supply capacitors are very close to this source of heat, which is not a good thing as electrolytic capacitors degrade much faster when the ambient temperature rises.  The entire unit has no ventilation, whether is be active (fan) or passive (convection). Everything is sealed, a mistake that Alesis has fixed on later models.

 

Alesis power board

 

Its pretty clear that the surrounding heat did these caps in. They are low end caps (Lelon and Pamicon, rated @ 85C). The main 2200uf Pamicon cap is definitely out of spec with a dissipation factor of 0.6 and capacitance of 1’435uf (35% off spec):

Alesis Pamicon main 2'200uf capacitor

Alesis Pamicon main 2’200uf capacitor

The solution is to replace all the supply caps at once. The caps have had a tough life in there and are all nearing their end of life. I replaced all of these with caps rated @ 105C, given the design of this power supply.  I went with Panasonic electrolytics from the FR and UHE, rated for a life @ max operating conditions of  between 5’000 to 10’000 hours.

Alesis old caps

 

 
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The new caps all installed and secured with a spot of hot glue:

Alesis power fixed

 

The 1 Khz whine that I could hear, even with nothing connected to the unit, was caused by a weak connection between the power supply board and the board next to it, that houses the DSP chip. I cleaned the connector contacts and re-flowed the solder.

 

 

 

Re-assemble and test. This thing is back up and running as it did when I first got it. To make sure you get the most life out of your Alesis Multimix, make sure you turn it off when not using it.

Alesis MM 8

 

Loose, Rattling truss rod

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A loose truss rod in a guitar neck can absolutely drive you crazy when trying to chase down a buzzing, rattling noise. Its not always clear what is rattling on a guitar. More often than not, determining whether the truss rod is loose is as simple as giving the back of the neck a tap with the palm of your hand. If you hear a clicking, metal on wood sound, odds are, the truss rod is loose.

Before jumping to conclusions that the truss rod installation is problematic, you have to determine whether the truss rod is in its fully neutral position. When in fully neutral position, meaning that no tension is applied on the rod, it can be a little loose at the ends and giving it a small adjustment, just enough so the ends rest fully on a piece of wood, is enough for the rattle to stop.

If the small adjustment doesn’t help, you’ll need to fill the voids in the truss rod slot so that it stops moving around. This type of thing can happen on even the best guitars. As the neck and fretboard woods stabilize and settle in over the years, things can move and cause small problems like this.

There are many ways to fix a rattling rod. My favorite method involves Chair Doctor wood glue, which is available at Lee Valley. It comes with a syringe type applicator and is low viscosity, perfect for getting into small areas. The same product is also available as “Chair-Loc”. I like this product because it swells up the wood enough to help in getting a tighter fit for loose parts. This is mostly due to the high water content in the product.

Chair-Loc

Chair-Loc

Chair Doctor

Chair Doctor Glue

 

The first thing I do is to insert the glue through a hole into the truss rod channel. On this acoustic guitar with a set neck, the easiest way to do that was to drill a tiny hole under the nut and feed the glue through there.

Insert glue from under the nut

Insert glue from under the nut

 

 

Unfortunately, this wasn’t enough to cure the rattle on this guitar, although it did help.  On this guitar, the bulk of rattle seemed to come from between the 3rd and 9th frets. Fixing this would involve removing the dot inlays, drill down to the truss rod route and inject some “Chair-Loc” from those holes.

I want to make sure that the chair-loc gets in to the truss rod channel as much as possible. That’s why I will inject the glue with compressed air. I made a small air nozzle adapter with a piece of foam underneath it to ensure a seal between the fretboard and the adapter so that the air is directly into the hole, forcing the chair-loc in.

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Glue Injection adapter.

Glue Injection adapter.

The inlay dots are removed, I make sure I can see the truss rod and put some glue into the drilled holes. In this case, I did fret positions 3, 5 & 7. When I apply the glue, I adjust the truss rod back and forth creating a bit of movement in the truss rod channel to facilitate the flow of the chair loc.

Inlay dots removed and filled with Chair-Loc

Inlay dots removed and filled with Chair-Loc

Then, I put the compressed air nozzle adapter over the hole and shoot some air in. I set the air pressure at 40 psi.

Injecting compressed air into the dot inlay hole.

Injecting compressed air into the dot inlay hole.

When you start injecting the glue this way, you can hear the air pushing the glue in. I repeated this a few times until I felt that the glue made it everywhere it should.

I waited for the glue to dry, did a tap test on the neck and it seemed ok. Now was time to place new dot inlays. The originals were plastic and all I have is pearl. The difference isn’t that noticeable. I install the new inlays with some epoxy, let it set and sand flush with the fretboard, trying not to sand the fretboard but only the inlay.

 

Inlays put back in place

Inlays put back in place

The guitar, strung up and playing beautifully. No more rattles. When adjusting the truss rod, I can feel that it is tighter but it moves properly and I can still adjust it to taste. The total investment in time was approx 3-4 hours.

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“Ski Jump” hump, Japanese Vintage Bass Restoration.

Posted on by admin Posted in Repair Work

 

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I got this vintage Quest bass in for a new pickguard and general clean up. This bass was in very rough shape when I got it in the shop. The pickguard with the output jack on it were broken, the body was covered in years of dirt, sweat and grime, the intonation was off, the tuner pegs were loose and missing screws, the action was off, the fretboard was damaged: It needed an overhaul. That wasn’t the idea initially but when I test played the bass, I knew something was wrong and it didn’t take very long to figure out what it was.

 

 

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The biggest problem that this bass guitar had was that the neck had developped a hump at the neck to body join. This is commonly referred to as a “ski jump”. What this does is raise up the frets at the end of the neck, towards the strings.

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With a severe hump, strings will buzz or choke out against the high register frets, even when playing in the lower registers. The problem gets worse as you move up the neck. People usually compensate by raising the action, but at some point, you’ll have to get it fixed. The picture to the left shows the hump that this bass had. It is quite large and its why the notes buzzed along the entire length on the neck.

I typically measure the severity of the hump by laying a straight edge between the 12th fret position and the end of the neck.

This type of hump is typical of older instruments and can happen on any guitar.  Quartersawn and Laminated necks tend to be a little more stable and less prone to this type of problem but it can happen on those necks as well. The only way to fix this is to take the frets out and plane the fretboard. The frets were worn out on this guitar so this work absolutely had to be done: The bass was pretty much unplayable. If the hump is slight, you may get away by filing some frets down, but there’s a limit to how much a fret can be filed.

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Above, you can see the neck planed to the factory spec radius of 9.5” and ready to have its fret slots cleaned and deepened to accept its new Stainless Steel frets.

Below are a couple of shots of the completed neck with a new Tusq Nut, sealed fretboard, frets installed, dressed and polished. The neck looks and feel like new but still retains the worn in feel. Notice the nice bullet style truss rod end.
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Quest Bass Truss Rod Nut

The next step was to add a side jack output. The original pickguard had the jack right on it and it broke because of the stress of inserting and removing the jack and the weight of the cable.  A side jack not only looks better, its just a better spot to place it and more practical.

 

Drilling a side mount jack holeInstalled side mount jack

Then, the new custom made pickguard is fitted on the completely cleaned and buffed guitar  body. I don’t know what decade it was when the body last shined like this.

The pickguard is checked for correct fit. I used the old pickguard as a template.

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… And the completed bass, strung up with GHS Boomers, intonated, action setup, truss rod adjusted, rewired, guitar straps solidified and re-installed, bridge re-polished, the tuners correctly installed and missing screws replaced with correct Japanese Gotoh screws.

This is a beautiful instrument if you ask me and definitely worth the time, effort and money to do this work.

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Replacing a Fretboard and using Ebony

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I’ve always liked to experiment with different wood types when building my guitars. Over the years, I’ve tried several fretboard different woods like Cocobolo, Sheduah, Ebony, birdseye and flame maple, baked maple, Ovengkol, Wenge and Rosewood.

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This particular guitar originally got a Padauk board with white pearl dots. After a year of using the guitar with this board, I came to the conclusion that I didn’t like it. The colour of the Padauk had shifted and didn’t go very well with the guitar’s cherry burst finish. More importantly, I didn’t like the feel of the fretboard. Padauk’s grain can be coarse in places and can be inconsistent in density, but this was primarily a cosmetic upgrade.

I decided to simply change the fretboard. This can seem like a daunting task but it is actually quite simple and can be done to look as though the new fretboard was the original. All you need is patience, a clothes iron, a damp towel and a couple of thin drywall spatulas.

I wasn’t sure what to use as a fretboard and I was very tempted to go with a maple board. With the maple, it would prove to be quite the task since I stained the neck shaft. I would risk color bleeding into the new fretboard and not having a nice clean line between the stained neck shaft and the new, unstained board. I already have a couple of maple board fretboard guitars anyways so it was time to try someting new.

I finally settled on Ebony. I put ebony aside for a long time because of the way it is harvested. For decades, companies have been harvesting ebony in the most wasteful way you could imagine and I did not want to support that. Why did I decide to go back to ebony? Because things have changed and we can now get responsibly harvested ebony. Bob Taylor did a very good video on the state of ebony. Here it is for reference.

 

So I got some responsibly harvested ebony in a local wood shop and proceded to make it into a fretboard. The neck got its Padauk board removed and it looked like this when I was done taking it off. It takes about 60 to 90 minutes to do on a neck like this. This doesn’t include any surface prep or refinishing I might have to do if there was a finish on the neck shaft.

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Here’s the neck with the new fretboard in place. You can see that the wood has some beautiful lighter streaks in it. I went with black abalone dots for the markers and white pearl for the side dots. I think it looks great!

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I’m happy I did this. The guitar’s neck feels better with the ebony board, looks better and retains that snappy string attack I loved so much with the Padauk.

The ebony’s vanilla colored streaks are definitely a nice feature and they tend to blend in nicely once the fretboard has been oiled and buffed.

Moral of the story: If you have a guitar you like but would like to try a different fretboard, or your fretboard is worn out, which can happen with multiple refrets, don’t hesitate to consider a new fretboard.

 

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Fretboard Care and Restoration

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A lot of times, when guitarists change strings on their guitar, they don’t always think of cleaning the fretboard and conditioning it. In the case of rosewood, ebony, unfinished maple boards or any unfinished wood for that matter, cleaning and conditioning the wood is very important.

Of course there are other factors that you need to consider with regards to the fretboard. For example, the guitar should be kept in a controlled environment to minimize wood expansion and contraction.

In terms of cleaning, many people will use solvents. I do not recommend this as solvents will get rid of gunk, yes, but they will also have a tendency to dry out the wood’s surface. This is a bit of a shock treatment and it can destabilize the wood. I always clean with the same product I use for conditioning the wood.

There are two products that I use for conditioning fretboards that can double as a cleaner.

  • Lemon oil. This is my personal favorite. It has a nice viscosity and wipes off well when done. Regular mineral oil works fine too but it a little thicker.
  • Polymerized Tung oil. I use this when I feel that the wood needs a little more protection. The tung oil will dry and harden forming a very thin protective film. Its has to dry, which can take 24 to 48 hours.

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There are 3 steps I follow to condition a fretboard:

  1. I do a first pass with a rag that is wetted with the product and use that to remove and clean the fretboard.
  2. I then carefully wipe down the fretboard, removing as much leftover oil as possible.
  3. Re-apply the conditioner, let it sit for 15mins and wipe off again.

Its simple and completely worth the effort. Your frets will remain seated more consistently, the playing surface will be clean and smooth, which improves playability: The wood will be less susceptible to changes in relative humidity.

For the guitar fretboard that is pictured above, you can see that the wood grain was so dry that the grain ws starting to pop up. I basically took 400 grit sandpaper wrapped around a small block and lightly sanded the board until it was smooth again. I did that between every fret. I followed that up with the usual conditioning of the board and you can see the result below.

 

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