ASAT wiring

[KenC]

This is one of those things I've meant to get around to, and today was the day.

I've read several comments about certain ASATs having a thin tone, 60-cycle hum and a quacky tone in the middle position. I've been through my share of ASATs, and finally came across one that had these problems. I've actually had it for about a year now. I'm not sure about its history, other than that the date stamps are from 1986 and it's in the production log on 10/16/86. I haven't taken good photos yet, but I believe it is this one from Greg Gagliano's website: http://www.ggjaguar.com/86bldasat.htm.

Anyway, this is a beautiful guitar with less-than-stellar tone. There is quite a bit of 60-cycle hum in all positions, the pickups sound thin compared to my other ASATs, and the middle position gives a significant volume drop and sounds almost out-of-phase. I finally got around to popping the hood and comparing the wiring to the diagram in the Gallery. Here's the diagram:



Here is the actual wiring in this '86 ASAT:











What I can see so far is that:

1. There is no wire running from the volume pot to the body of the switch.

2. The grounding wire to the bridge is attached to the volume pot instead of the tone pot.

3. There is a resistor rather than a wire connecting one tab to the casing of the tone pot.

4. The wires to the jack are not the same color as in the diagram.

I'm thinking at this point it will need a trip to the technician to fix #1-#3, as my soldering skills leave much to be desired. Before I do that, does anybody see anything I've missed?

Also, if anybody currently owns an ASAT with similar tone issues would you mind comparing yours to this? I am going to pop the hood on a couple of other early ASATs tonight to see if they match the circuit from the Gallery.

Ken

[glvourot]

Interesting. I have some photos of my ASAT wiring but it is a lot different due to the push/pull tone pot. I am happy to post but I do not want to hijack your thread. The middle position on my guitar sounds great and it is the position I use the most. There is hum on the bridge and neck position. I have a feeling that my bridge pup would be much quieter if I get it back to spec. I am fortunate to have received the original tone pot when I bought the guitar. Hopefully someone else will be able to help you out. Keep us updated.

Paul

[Elwood]

Just some thoughts that may or may not be in play.

Have you checked the wire to bridge contact under the saddlelock?
That could account for some hum.
edit: The bridge ground solder joint on the tone pot chassis does look like a cold joint, that could be it (?).

If the jack negative is connected to the tone, and bridge and switch negative to the volume,
but no other ground jumpers between the pots, then the control plate is part of the signal path,
as opposed to just a part of the shielding. That path would have more resistance , I'm guessing,
than a short wire between the pot casings. That could making things lower in volume, and
maybe a place where hum could be induced easily.
Try connecting the pot casings with a jumper wire and see if anything changes.
Maybe the pot lock washers aren't quite working as a great connection.

I'll open up my 86 ASAT and see how things are. I should have that tackled sometime tonight.
(unless I get trapped against the rock by it's siren song, I'll tie my self to the mast...wish me luck )

[fianoman]

What about that joint tells you it may be cold Elwood? I have never been able to see a difference. You must have some good eyes.

[glvourot]

Good catch Elwood. That ground solder on the tone pot does look suspect. A quick re-flow and it can be confirmed or ruled out.

[KenC]

The bridge ground solder joint on the tone pot chassis does look like a cold joint, that could be it (?)

I'll check that out. I did pop the hood on my two other ASATs ('86 and '87), and the wiring in both of them was the same as the Blonde '86. That makes me think the wiring diagram in the Gallery is not correct for all years. Either that, or I just happened to end up with three ASATs built within 18 months that have all had an identical mod by previous owners. Two of them did pass through a single collection at some point, but the third came to me from a different part of the country.

I noticed that the hum drops a bit if I touch the exposed part of the switch (between the control plate and the plastic tip), and it goes away entirely if I touch the back of the volume pot. Of course, I can't play test while I'm doing that to check the tone. I think my next step will be to do a string change and fretboard conditioning, and check the bridge and pickup grounds while the strings are off.

A quick re-flow and it can be confirmed or ruled out.

Do you mean just heating the old solder up, or applying more to the joint?

Ken

[yowhatsshakin]

I did pop the hood on my two other ASATs ('86 and '87), and the wiring in both of them was the same as the Blonde '86. That makes me think the wiring diagram in the Gallery is not correct for all years. Either that, or I just happened to end up with three ASATs built within 18 months that have all had an identical mod by previous owners. Two of them did pass through a single collection at some point, but the third came to me from a different part of the country.

Ken,

You are right at that. The schematic is not valid for ASATs built before 1990, the date of this schematic. At that point, G&L decided to use the same wiring harness as for the ASAT Classic. one of the things that thereby disappeared is the 6.8kΩ resistor on the tone pot that still shows in your picture but not on the schematic. In addition the cap values were adjusted too from .100μF to .022μF. Around 1993 this cap changed one more time to .047μF.

Hope this helps,

- Jos

[glvourot]

Do you mean just heating the old solder up, or applying more to the joint?

On looking at the picture again it probably needs a bit of solder. It wouldn't hurt to tin the end of the wire again too.

[KenC]

Update: I added a bit of solder to the green wire's joint on the tone pot. That made the 60-cycle hum go down to a normal level with either pickup solo, and either pickup on its own growls and barks like a Leo-era ASAT should. There was still a bit of hum in the middle position, with the same volume drop and quackiness. I also noticed a popping sound when I switched between pickups. I applied Deoxit to the contacts on the switch, which took care of the popping and some of the tonal shortcomings. I don't notice the quack very much now, but I can hear that there is clearly a loss of low end with both pickups combined. It sounds like I'm running through a high pass filter. All the treble is there, but the low end is missing.

So now both pickups sound great on their own, and the hum is back to normal for a Leo-era ASAT. I'm wondering what could account for the loss of low end in the middle position. Could it be a problem with the switch? Any other ideas out there?

Ken

[Elwood]

Good news!

Are the pup heights and pole pieces similar to your other ASATs?
Can you raise the neck pickup some before it pulls on the strings?

Maybe changing strings, especially if it has a light bottom set on it.
Try some TI Heavy bottom Power Brights



Another thought, maybe the vol pot is dirty at the end of it's run,
and the weaker 'combed' signal from both pups that is heard is bleeding through the
cap more than it should. I'd spray and exercise the pots for a minute or so.

Fingers crossed.

[fianoman]

Ignore my comment. Looking at the wrong pot.

[andy_tchp]

tonal shortcomings. I don't notice the quack very much now, but I can hear that there is clearly a loss of low end with both pickups combined. It sounds like I'm running through a high pass filter. All the treble is there, but the low end is missing.

So now both pickups sound great on their own, and the hum is back to normal for a Leo-era ASAT. I'm wondering what could account for the loss of low end in the middle position. Could it be a problem with the switch? Any other ideas out there?

You've just perfectly described what a pair of pickups sound like when they're wired up out of phase.

Fortunately it's easy to check; switch the connections of the hot/ground lead on one of the pickups and re-test.

If this fixes the issue then one of the pickups has the leads attached back to front to how they 'should' be according to the wiring diagram.

Cheers!
Andrew.

[NickHorne]

Reversing pup wires will almost certainly result in monster hum from that pickup, as I'm sure you know!
But if it fixes the phase issue, then the pickup chassis ground will need re-wiring, to the other lead. As you may very well also already know, do be sure to NOT use a soldering "gun"! These do a lovely job of solder work on substantial bits of metal, like pickup backplates, but they also demagnetise pickup magnets significantly if you're the least bit unlucky. A big regular iron, that's beefy enough to keep its temperature up so that the job can be done in a really quick-but-thorough melt, is the way.
I remember seeing this at the Seymour Duncan site once, and thought it must be a myth until I tried it for myself (with a discarded magnet). It's all true! There's a big alternating magnetic field around a "gun", just like a tape-head demagnetiser only huge. Not for guitars.

[KenC]

Thanks for the suggestions. My soldering iron is not up to the task, so I will most likely head to the tech next weekend.

Ken

[glvourot]

Is there a schematic that is valid for pre 1990 Asat's? I want to return my 86 to spec ( it has a push/pull tonepot ) . The guy I want to take it too should know what he is doing but I would like have something to reference.