Author Topic: 20th Anniversary wiring woes (Read 794 times)

son_of_magni · « **on:** April 16, 2016, 03:57:19 PM »

Hi friends,

I used to frequent this forum quite some years ago after I bought a beautiful custom fretless 6. Many things have happened in my life since then, some good, some bad. But as it turns out I recently purchased a 20th Anniversary Alembic, #29 of 200 as part of an estate sale. Some silly person has been mucking with the wiring and I haven't been able to discover how to restore it to the original condition.

So, I was wondering whether there was someone here with another 20th who would be willing to make some point-to-point comparisons to help me out? There are some wires that are cut and left dangling, others might have been moved.

If anyone is willing to work with me, I'll find a way to get some pics and more details to you.
- Karl

son_of_magni · « **Reply #1 on:** April 16, 2016, 05:11:35 PM »

Here's my notes from visual inspection:

- Brown wire from 4-way is cut off, goes nowhere
- Brown wire from volume is connected to the bottom wire (red/yellow?) on the bridge filter control
- On the corner of the jack there's a red/white that goes to the 4-way, there's also another red/white from the same point that is cut (goes nowhere)
- Jack also has a black/ground wire that goes nowhere (cut off)
- Vol has a black wire soldered to another black wire that goes the the top connection of the bridge filter

FC Bass · « **Reply #2 on:** April 16, 2016, 06:33:58 PM »

Pictures would be helpful, you can send them to the address in my profile if you can't get them posted. (click my name for profile)

FC Bass · « **Reply #3 on:** April 17, 2016, 10:28:23 AM »

Here's the first pic:

son_of_magni · « **Reply #4 on:** April 17, 2016, 10:39:41 AM »

Seems I can't edit older posts so here I'm restating the issues with some corrections:

- Brown wire from 4-way is cut off, goes nowhere
- Purple wire from volume is connected to the bottom wire (pink/white?) on the bridge filter control
- On the corner of the jack there's a red/white that goes to the Vol, there's also another red/white from the same point that is cut (goes nowhere)
- Jack also has a black/ground wire that goes nowhere (cut off)
- Vol has a black wire soldered to another black wire that goes the the top connection of the bridge filter

son_of_magni · « **Reply #5 on:** April 17, 2016, 10:50:00 AM »

So the obvious questions are:
- Where should the brown wire from the 4-way go to?
- Where should the second red/white from the Jack to to?
- The purple that is tied to the pink/white probably each should lead somewhere else, where?
- The blacks are probably all grounds, I'll check to see if they are all actually grounded.

son_of_magni · « **Reply #6 on:** April 17, 2016, 01:16:02 PM »

One thing that is likely an issue is the blend control has no ground. There's a cross wire for the blend-output, and the two wires for the inputs, but the other two which should be ground are about 25 ohms from ground. Probably just picking up some ground from the shielding paint. I can connect the free ground wire from the jack to fix that, but the other issues remain.

StephenR · « **Reply #7 on:** April 17, 2016, 01:39:54 PM »

You may want to try giving Alembic a call on Monday. Pretty sure they will be able to supply a wiring schematic for your model. You can register the instrument with them at the same time.

gtrguy · « **Reply #8 on:** April 17, 2016, 02:13:22 PM »

How does the bass function at this time -or- what works and what does not?

son_of_magni · « **Reply #9 on:** April 17, 2016, 02:23:42 PM »

Hi Stephen, I've tried the support route but that schematic is apparently either lost (it was like 25 years ago) or is not publicly available. After having a disfunctional bass for a few months now I thought this was my only remaining option.

son_of_magni · « **Reply #10 on:** April 17, 2016, 03:02:32 PM »

gtrguy, the 4-way switch gives me mute/mute/both/both. With the stereo switch in the other position it's still mute/mute/both/both except that one of the both positions sounds a little different. In either both position the blend control sweeps between the two pups (though clockwise goes to bridge and ccw goes to neck which seems backwards to me). The Q switches and knobs seem to work fine.

I'm guessing a lot of this points to that brown wire from the 4-way. A pinout of the 4-way and the volume control would possibly be enough for me to figure the rest out...

I do have lots of experience in electronics so I could get the scope out and look at signals but without knowing where the wires are supposed to be connected I don't think there's much point in that yet.

(Message edited by son_of_magni on April 17, 2016)

FC Bass · « **Reply #11 on:** April 17, 2016, 04:35:53 PM »

There shouldn't be a blend (Pan)
I'm not sure, but the double pot doesn't look familiar to me... (Mica will know if its original)

Controls should be Volume x2 Filter + Q switch x 2, Filter (volume and filter for each pickup), Pickup selector (including silent standby position) and the switch is for stereo/mono.

keith_h · « **Reply #12 on:** April 17, 2016, 05:03:37 PM »

My guess is the wiring changes were to convert the bass to a pan control instead of a volume/volume setup. I'll try to get some pics of my Brown Bass Anniversary electronics tomorrow and post it here.

Keith

son_of_magni · « **Reply #13 on:** April 17, 2016, 06:56:01 PM »

Ah ha! Getting somewhere!

FC Bass · « **Reply #14 on:** April 17, 2016, 07:31:56 PM »

Not 100% sure if this is true for the Anniversary electronics, but I think the volume controls should look like this:

(2 identical boards)

So you should have two Filter boards (with the blue trimpot) and two volume controls, once you have that sorted out it shouldn't be too complicated to figure out how everything connects together. :-)

Correction to my previous post: -Filter, edited while posting and forgot to erase. (60 minutes threshold for editing post is way to short...)