Tarnishing and electronics - 77 Series 1 Guitar

[jon_jackson]

Nice work. Looks great.

[pauldo]

Nice job!

[flavofive]

Agreed, great work with the cleaning!

[bob311]

Thanks all! Now on to getting the electronics all good by continuing to flip the switches and move the knobs! And I hope to hear back from the Alembic team about the file, if they still have, on this guitar!

[bob311]

Update, I’ve isolated the electronics issues. Not sure how to fix.

When the neck pickup is engaged, there is some buzzing in the amp. When the bridge pickup is solo, no buzzing. But if it’s in both pickup mode or neck solo, there is buzzing. So at least something is happening there. So I don’t think it’s standard single coil hum, because the bridge pickup doesn’t have any when isolated.

Also, when I flip the neck dynamic switch down pointing to the ground, and I move the dynamic knob, it pops and screeches and otherwise is not happy. I don’t mess with it much because I don’t want to harm my amp. But something is going on with that switch in the down position and the dynamic neck knob when I move it.

Any thoughts? I can try to take some pictures of the guts tomorrow.

[JimmyJ]

OK, you're making progress!  Since you've got the bridge pickup working we might even say you're halfway there. 

Here is a good explanation of the controls on a Series I:
https://club.alembicguitars.com/index.php?topic=271.0
That will help us with the names...  Q-boost, filter control, etc...

And you may not realize there are also output level and hum balance trim pots accessible through the rear panel?  Info on that is here:
https://club.alembicguitars.com/index.php?topic=269.0

If the bridge pickup is already nice and clear then don't touch those trim pots.  But it might be worth moving the neck pickup's output and hum balance trim pots just to see what happens.  You may find that the trim pots themselves need to be exercised a bit like the front panel controls did.  Then see if you can dial out some of the hum coming through the neck pickup channel.

The squeal is a known issue that can happen when the pots and switches are old and haven't been moved for years.  That filter circuit can act as an oscillator if things are out of spec.  But again, this can usually be cleared up by exercising the switches and pots involved.  (Just don't have your amp turned up when you do that!)

I'm thinking of building a machine that just spin our pots back and forth repeatedly and can be left running overnight.    

Keep going!  We're all pleased to see you bringing this axe back to life!

Jimmy J

[StephenR]

A number of years ago I pulled out my 78 Series I five-string and started to gig with it after it had been mainly sitting in the case for over 20 years. I got the squealing noise from the pickup selector, rotating it a number of times prevented it from happening again. The pots and switches can wear out but it is a fairly rare thing and the parts Alembic uses are somewhat expensive to replace, don’t give up on excercising them yet, it sounds like you are close. If you are worried about damage to your amp then excercise the pots with it unplugged then plug it in and see if the noise is gone. You may have to repeat this process a number of times but it is pretty rare for it not to work. Good luck, you have already done an excellent job of cleaning the instrument up!

One last thing. If your tailpiece still has the original brass screws I suggest changing them to stainless steel screws at some point. Alembic no longer uses the brass screws because they can break, I had this happen to one of the tailpiece screws on my 78 Series bass. I didn’t realize it had broken until I removed the tailpiece to clean it. Luckily just enough of the broken screw was protruding into the battery cavity that I was able to extract it. You can get the proper replacement screws from Alembic...

[Artgeckko]

Nice work on bringing it back to life!
Looks like with a bit of patience and elbow grease it will be as good as new.
I had a similar wood crack from the wood screw on the back panel with a 80's omega bass.
This bass's wood is (I believe, still awaiting build card info...) padauk wood which is very red and figured.
I collected some sanding dust from refinishing, applied some thin super glue to the gap with some of the wood dust collected.
Took a few coats and the glue did darken the wood dust, but it seems to have completely stabilized the crack and filled the gap.

[bob311]

So still the same electronics issues after continuing to work that knob and switch. I looked at the electronics board and there is some corrosion. I was able to wipe away some of it, but not all and still the same issue. Wonder what to do next.

[Artgeckko]

Hello - I'm an Alembic newbie here, and certainly not a electronics expert, but you may want to look at pot side of that card. 
Unscrew the 4 screws from the brass plate (if you havent already)  and see if you notice any obvious corrosion on that side as well?  Be very careful with it once removed from brass plate.  I have mine ( series 1 bass electronics  ) at alembic because many of the trim pots were somewhat stripped and the whole PF6 card was somewhat microphonic and noisy.  Not sure if using a standard circuit cleaner is recommended on this kind of component. 
There are some very knowledgable folks in this club. I hope one of them can get you past the noise issue.

[pauldo]

Ed (Artgecko) offers some solid advice.

Some spray contact cleaners can be detrimental to certain plastics, this MAY be an issue with a circuit board from 1977…. just sayin’. 🤷🏻‍♂️

Suggest waiting until a high-level electronics person chimes in (no offense Ed - I also am not savvy in the electronics field). 

[gtrguy]

I would initially pull the main wire connector and re-seat it. Also do the same with the Molex pickup connectors on the pickup wires. You can switch the pickup leads there to see if any of your problems 'follow' the pickups too. I am assuming the old style board has the chips on the back side hard wired, which means there are no socketed chips to pull and re-seat.