Cavity conundrum

[mtjam]

Happy New Year everyone!  So I've been enjoying my 81 (I think) Series 1 for almost 3 months, and I thought I would post pictures of the weirdness going on inside the electronics cavity. There is some sort of epoxy or something sloppily applied over some of the connections. Some of the wiring looks like it's seen better days. I love the sound of the bass, and my only complaint is that the neck pickup has far less output than the bridge pickup, even with its trimpot turned all the way up.  I've never seen such a substance inside any Alembic that I've ever seen. Any ideas about what's going on here? Looks like some hack was tinkering around in there. Or maybe it should be there. Not sure.  If I were to ever do the upgrade, would this issue be fixed in that process? I am hesitant to ship this bass out west, especially since it's working well and I wouldn't want to be without it for long.

 

 

 

  [edited for picture alignment]  (Message edited by adriaan on January 07, 2015)

[mica]

Ew.
 
I will ask my dad about how to remove that gunk. You describe it as epoxy... is it hard like epoxy or pliable like silicone?
 
I'm gonna say it again. Ew.

[mtjam]

Eww is right! I was 110% sure this wasn't a factory job! I poked around, and the stuff was hard but seemed like it may have once been pliable like silicone. It's not very pliable now, although I was able to scrape it a little with a screwdriver. I don't want to poke at it too much! Why in the world would someone do that?
 
Anything else look out of whack in there? Like I mentioned, the bass sounds and plays great, but the the neck pickup has nowhere near the gain of the bridge pick up despite having the neck pickup's trimpot turned all the way up. I've experimented with the height of the neck pickup, but that hasn't made much of a difference.
 
I know those pickups on Series basses are additive (I think that's the term you used); I usually set the pickup selector to use both pickups. However, switching from both to the bridge pickup does not decrease the volume much while switching from both to the neck pickup causes a huge loss of volume.

[keith_h]

My guess is a connector loosened up at some point and after being reseated someone applied the gunk to keep them from possibly doing it again. I do a similar thing to my power amps when I first get them along with potting, for lack of a better word, the on board capacitors. I use hot glue as it is easily removed in the event I need to service the amplifier. I do this as the amps get a lot of bumping and vibration. On the other hand I see no reason to do this to any of my basses as they don't get jostled like my amps do.
 
Keith

[pauldo]

+1 to Keith.
It looks like carefully applied Great Stuff.
It is an adhesive/ gap filler that sprays from can, expands and then drys to a 'styrofoam' type consistency.
 
However it expands a lot; someone would have been VERY proficient at applying it in that manner.

[mtjam]

Any thoughts out there on getting rid of this stuff, or should I just leave it alone?
 
The only issue I'm having with this bass is the very low output from the neck pickup. I would imagine the goo would make that problem harder to investigate.

[JimmyJ]

I have a couple thoughts...  My #1 theory as to why somebody thought it a good idea to add the goop is that while taking the bass apart they broke or misplaced the small nylon "clamp" that snaps over the multi-pin harness connector. (see pic 1 below)  Fearing that it wouldn't stay put they decided to goop it.  And while they were at it, they did the pickup connections - which is really not necessary as there isn't much chance of them disconnecting on their own.  It's true that the first logical test for your level discrepancy would have been to switch the T & B connectors at the board to see what happens.  But that idea has been gooped up...  You must first make certain that the level issue is not later in the signal path.  As in, are you seeing the same situation from the 1/4" output jack as from the DS-5 outputs?  How about in stereo?  (Is your 1/4" jack stereo or mono?)  If all things point to the board and can't free up those pickup connections - I will point point out that the op-amps are all in sockets and interchangeable.  Still would be best to be able to swap the pickup inputs first, but...  Is that goop hard or flexible like silicone?  The board has 3 amp stages.  (See pic 2 below.)  Stage 1 is the FETs.  Stage two is the first time through the 5534s.  There are 3 channels to this point - one extra for the hum coil.  Stage 3 is the final two 5534s - the two stereo output amps.  If you were to get into swapping those around (tedious with the small pins), I would first try swapping the final output pair and see if your level problem changes.  More ideas later.  Jimmy J

 

[terryc]

If Alembic made beer, it would most probably be the best in the world!
Jimmy...are you sure you don't work at Santa Rosa in between your gigs with Alan Holdsworth and James Taylor?
You sure know your stuff, that is two valuable posts that I have read tonight(UK time)

[mtjam]

Jimmy, thanks for your ideas about my problem. After reading your post, I decided to try the 1/4 jack for the first time! I always use the power supply, so I had no need to try the 1/4 jack. When I plugged in to my amp, I was able to hear the neck pickup only, and it was loud and clear. Much different from the anemic output I get from it when using the power supply. I think that means my jack is stereo, if I recall correctly from other posts I've read here. Does this narrow down the cause of my problem?
 
The goop seems pretty hard, and I'm leery of poking around too much in there. I don't want to make my pride and joy unusable!
 
I'm eager to hear your other thoughts about this when you have a chance. Meanwhile, I'm using my Alembic a EVH tonight. No goop inside that one!

[mtjam]

You've really got me exploring the sonic capabilities of Series basses this weekend. This morning, I hooked up my Series 1 in stereo (first time). Set up this way, the neck pickup once again had less output than the bridge pickup. Using my power supply and 5-pin cable, here's my signal path:
 
Bridge pickup >Aguilar Tone Hammer 500> 2 Aguilar SL 112s
 
Neck pickup  > F1X> Eden 1205 > 2 Aguilar NT 112s
 
Of course, I know I can tweak the volumes of the amps to achieve similar output from both pickups, but this is not how I run my bass at gigs. Typically, I am playing live connected only to the Tone Hammer and the SL 112s. Therefore, I would like to have similar pickup output when using such a rig.
 
So...my experimentation has revealed that the neck pickup has plenty of power when I use the standard 1/4 jack, but does not have much output when I use the power supply in mono of stereo. I have 2 power supplies and 2 5-pin cables, and the issue seems to occur no matter which ones I use.
 
What does it all mean, o knowledgeable Club members? Any advice is appreciated. Thanks!

[JimmyJ]

Hey Rob,
 
Conundrum is right...  
 
Checking it with both your PSUs and cables was good sleuthing.  That does point us to the bass.
 
Excuse the dumb question but, you are tweaking the correct trimpots right?  Here's a pic:
 

 
It does sound like you have a stereo 1/4 jack.  Quick test of that concept would be to plug a pair of headphones into it.  If your batteries are good and the preamp board is somewhat cranked, you should hear something and be able to determine if one p/u is left and one is right.  It won't be a good sound because the circuit us not meant to drive phones (wrong impedance to begin with).  And you may need to exercise the plug a bit in case the jack is corroded from non-use.  But this could answer the question about that jack being mono or stereo.  Also, if you can hear something, you can get a quick general reference as to the level differences, although it will be very low volume.
 
Really, the next best test would be to swap the T & B connectors where they attatch to the board...  If it were mine I would take my tiny diagonal cutters and see if I could carefully break some of that goop off and free those connectors.  But I don't want to send you on a destructive assignment so maybe don't go there.
 
Do you still have the '78 Series bass?  Because if you could free up the p/u connectors on this bass you could plug them into that bass as a test...
 
Next best thing to try I guess would be to swap the two output op-amps if you have the stomach for messing with tiny pins in tiny sockets.  The chips themselves are not very expensive but I don't expect you have any spares laying around.  Ha!  Be sure to observe their orientation before you pop them both out.
 
OR ... turn down the output of the bridge p/u to match the level of the neck p/u and run the bass at an overall lower mono output level..........
 
Jimmy J

[mtjam]

Good question about the trimpots! Yes, I consulted that very same picture before fooling around with the trimpots. : )
 
I definitely lack the patience and expertise to switch those op-amps. Your idea to switch the pickup connectors is doable for me...if it wasn't for the goop! Maybe I'll investigate that stuff a little more. Mica said earlier that she would check with her dad on how to remove that stuff. For now, turning my amp up louder and lowering the bridge pickup's trimpot would be the easiest fix (without me doing any damage!). I am still puzzled though about why the neck pickup has plenty of output through the 1/4 inch jack but not through the power supply. Baffling.
 
By the way, I just saw you on TV this afternoon playing with James Taylor during a replay of the Crossroads festival. Looked like a great time!

[mtjam]

OK, I played with the trimpots more and got the two pickups balanced out better. I guess my main problem was that the bridge pickup was dominant in my sound (I usually set the selector switch to the both pickup setting), and I wanted more of that neck pickup sound.
 
However, I hope the goop doesn't slowly encase my bass in an Invasion of the Body Snatchers fashion!

[mtjam]

I showed a friend the pictures of the mystery goop, and he also thought it might be hot glue. I found a video on YouTube where someone showed how to remove hot glue with rubbing alcohol. Anyone think I should give this a try, or could that possibly create other issues?
 
I'm not all that eager to try this. Just wanted to get opinions! My pickup balance issue is better these days, but that goop is annoying!
 
Mica? Bueller? Anyone?

[sonicus]

I have serviced a variety of audio devices such as audio desks / mixers and signal processing equipment where I have seen hideous appearing remedies in an attempt to correct  electric continuity failures due to faulty Molex / ribbon-foxcon / and other non soldered connection failures.            ( Soundcraft/ Mackie/ MCI ,  etc ... _) Some have used hot glue, silicon caulk and other such adhesive material. EW and yucko pucky is often my initial reaction ! NEXT : Then I am sad that someone found it a matter of necessity to do this for the repair  .  Then  ; I want information on WHO did this , and their technical experience,   If I  get answers to my questions , very often it has been clear that it was a last ditch resort due too connector failure to some extent , and the individual was justified to make it work other then the  correct replacement of the connectors at failure .    Therefore until someone who has their face and mind into this that really knows what they are looking at , _____do  not mess with it if it is currently in full operating order. If you remove the adhesive material your results may be total loss of continuity ( no sound at all ) until the connector is correctly replaced completely .  
   Sometimes stuff like this is done just to keep the show on the road  in a pinch .
 My 2 cents Sir .  
( If everything works right now , close up that control plate and just play it until a tech has some time with it )