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Repair

Takamine AccurAcoustic Preamp Recap Repair

EDIT 3/6/2021: I’ve got a new post up with a video of this repair. I’m embedding it near the bottom of this post as well for convenience

The world is a small place sometimes. Last year, I was cruising Craigslist and came across a Technics tape deck and some classic gaming accessories. Met the guy, made the exchange. Mentioned what I do — a few weeks later he texted me asking if I would like to take a look at seven or eight Takamine preamps that had low or no output. Turns out he’s the admin of a multi-thousand member Facebook group for the guitars! Some worked in ‘Pass’ mode or picked up on a digital tuner, but weren’t getting a signal to the amp.

I said that I’d take a look at them (I figured they just needed recapped), and he neglected to tell me that the units had been deemed “unrepairable” by most techs for some reason. So I designed a repair. Charlie supplied me with these schematics:

AAP Circuit Diagram 01
‘Pass’ and power circuits
AAP Circuit Diagram 02
‘EQ’ circuit

And I got to work. First, we’d need to depopulate the six surface mount caps present in between the sliders, the cap on the volume board, and the radial power cap on the mainboard.

AAP Top

The integrity of the pads isn’t of much concern. The plastic sliders make putting in new surface mount caps unfeasible, and the back of the board has adequate room in the plastic casing to insert radial caps in circuit. I started by yanking these and their pins off with needlenose pliers.

One quirk is that the volume board could have a tantalum capacitor or an aluminum electrolytic. I replace the tantalum when I recap them (because why not), though it’s worth noting that you’ll experience a degraded signal if you replace a tantalum with an aluminum — I suspect that a different component is used elsewhere though the board revision is the same. I have a photo of each type:

AAP Volume Board Aluminum
Aluminum
AAP Volume Board Tantalum
Tantalum
Reference DesignatorCapacitance/VoltagePositive LeadNegative LeadNotes
C301Aluminum: 4.7 uF/25V
Tantalum: 4.7 uF/16V
Marked on boardMarked on boardOn some units, negative lead is bridged to R301; this is fine
C16470 uF/16VBy wire pad 1By wire pad 2Polarity marked on board
C100.47 uF/50VSouth pin of R1North pin of R1 
C110.47 uF/50VSouth pin of R5North pin of R6 
C120.47 uF/50VPoint north of R22North pin of R25Orange Circle 
C130.47 uF/50VSouth pin of R30Emitter of Q3Q3’s Emitter marked with ‘E’
C144.7 uF/25VPin west of Q1’s Gate RefNorth pin of R7 Green Circle
C1510 uF/16VSouth pin of R14North pin of R21 

With this parts list and connection points, one can restore an AAP to full functionality! If using quality caps, it’ll perform just like new. The cardinal directions from the table are based on the board’s orientation that I use, and I’ve marked some of the confusing spots:

AAP Bottom With Repair Info
Repair Map

Yet another issue can arise though — depending on whether or not a certain pad is lifted or corroded when ripping out the surface mount caps, you may require a lead wire to restore functionality to the battery LEDs. It doesn’t hurt anything to include it even if it’s not needed, so I put it in every one just in case. Put it between the south pin of R30 and the collector of Q2 (marked with a C, conveniently).

When you’re done it should look something like this:

AAP Repaired
So pretty

I’ve embedded a video below, thanks to Peter for sending me one to repair and film!

For your viewing pleasure

That leads us to the question of how well this repair works, and if it’s worth the time. I did a spectrum analysis using RightMark Audio Analyzer on a completely dead unit, and performed it again after the repair with a test signal. Since the units only have one input, the white line is of interest on the following graphs, and unfortunately I couldn’t turn the other channel (green) off.

AAP Degraded Spectrum EQ
Real Dead
AAP Repaired Spectrum EQ
It’s an improvement, trust me

If you’d like to repair one of these yourself (or live overseas), I’ve created a repair document for these. One link is to Google Docs which displays better on a mobile device, and there’s also a .docx version that prints well. You’re free to use my repair and reproduce the document, as long as you don’t remove the attribution to me! Help keep these units out of the trash bin!

Google Docs: https://docs.google.com/document/d/13MOxv4_ibWleL4FQmpPmd2tt4dgot6HWJ-0pBwnpou4/edit?usp=sharing

Microsoft Word (docx): https://drive.google.com/file/d/1zgc5hUz_NwyO6gO1QureVq51Zp5IEC7O/view?usp=sharing

13 replies on “Takamine AccurAcoustic Preamp Recap Repair”

This is brilliant. Thank you. I’d definitely like to get you to fix my Accuracoustic when travel to the US is back on.

Hi there …

I suck at soldering and would rather have someone else change capacitors for me on this one.

Mine is dead on EQ mode, works in PASS, 95% capacitors just leaked or alike.

How much would you take for such a fix – minus shipment which is on me ? I am in Stoughton, MA

So glad you’ve got this post up. Really hope you get a lot of keyword-search traffic through here. Can’t thank you enough for your contribution to the Takamine guitar community!

Sometimes when removing the old caps (since the easiest method to avoid damage to the sliders is to just wiggle them off with a pair of needlenose pliers), you might lift a pad connecting the LED circuit to the rest of the unit. The jumper wire will add this connection back in so that the LEDs light when the battery check button is pressed in. If the pad is lifted and the jumper wire is absent, the LEDs won’t be able to light.

You can check continuity between the listed jumper wire points with a multimeter and you don’t need to add it if there is continuity between those two points — though I did omit that to keep the document straightforward and concise.

Let me know if this helps!

Hi Bradley,
Thank you for sharing your hard work. I’m not setup to do micro-type soldering or repair. Problem with hands, too. Would you consider repairing my Takamine GRAPH-EX PreAmp at a quoted cost?
Thank you for your consideration.

Hi, I have not worked on a Graph-Ex previously, but I’d be willing to take a look at it for you. However, I just moved from Indiana to Texas — if you could give me 3 – 4 weeks to get settled in, I’ll hopefully have some time to look at it then.

Hi, I do offer repairs of the units. However, I just moved from Indiana to Texas — if you could give me 3 – 4 weeks to get settled in, I’ll hopefully have some time to take it on then.

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