Author Topic: Volume pot broken (Read 293 times)

patrik · « **on:** September 02, 2008, 07:18:11 AM »

Hello and greetings from Finland

A while ago some part of the elctronics (don't remember what anymore) fell loose inside my bass, with the result that the bass would make very loud random noises. Anyway, since it was pretty clear to me what the problem was, and since I am a very un-practical guy myself, I took it to a local electronics shop to have it fixed. They did fix the problem, but without asking me they also did what seems to be their standard program on handling instruments, which included oiling the pots. I do not know if this is what caused it but shortly afterwards the volume pot stopped working. It now permanently on, but not at top volume it seems.

I am obviously hesitant to take it back to the same place (as you notice in the picture, the decided that glue was needed. I didn't ask for that either), so now I am looking for advice. should the pot be replaced, or can the problem be elsewhere? Where can I get a proper spare part?

Thanks in advance,

Patrik

FC Bass · « **Reply #1 on:** September 02, 2008, 08:08:38 AM »

Welcome to the board! Is this an Elan? Could be a very close relative of mine (90H6003) Body looks like Mahogany though... The pots are of the "maintenance free, self cleaning" type any attempt to repair other than simply exercise (bij turning the knob up/down many times) would be bad I guess... The glue looks kinda scary to me...

We like pictures of Alembic electronics cavities here, but we love full frontal/backside/neat detail pictures (at least I do

) Good luck & cheerz! Flip (Message edited by fc_spoiler on September 02, 2008)

patrik · « **Reply #2 on:** September 05, 2008, 12:41:41 AM »

I think it is a close relative of the Elan, but its body is shaped sort of like a Jazzbass. Its an amzing bass, very low on maintanance (stuff other people do, like tuning, is mostly unnecessary).

terryc · « **Reply #3 on:** September 05, 2008, 01:25:50 AM »

patrik
I know this is too late but you should have got onto the forum before you took it to that shop.
Mica visits here most times and picks up owners problems and give THE best advice along with many of us on here. That glue on the board connectors is either going to make it impossible to or very difficult to carry out any component replacement. Alembic have made life very easy for us all by using non solderless connectors if we do have trouble.
I would contact Alembic thru' their website for advice on this.
Putting glue or any resin inside is a definite non starter.
Good luck

David Houck · « **Reply #4 on:** September 09, 2008, 10:53:55 AM »

Will the volume knob turn?
Will it move freely through its entire range?
Is the pot touching the pc board?

patrik · « **Reply #5 on:** September 10, 2008, 04:46:54 AM »

The knob turns ok, usually nothing happens, but sometimes the sound temporarily disappears. It is not stuck in any way.

As far as I can see it is not touching the board.

FC Bass · « **Reply #6 on:** September 10, 2008, 09:10:06 AM »

You should also make sure that none of the connections are touching the silver paint.

David Houck · « **Reply #7 on:** September 10, 2008, 11:21:56 AM »

With the amp low or off, run the volume knob back and forth through its full travel thirty times in succession and then see if it makes any difference at all.

mica · « **Reply #8 on:** September 10, 2008, 06:29:33 PM »

I can see the adhesive fixing the board to the edge of the cavity (?!). I can't quite tell in the picture, but is there adhesive or something where I've marked the image?

If the top volume has changed, maybe they adjusted the trimpots as well. You can turn up the gain there.

The pots are sealed, so oil shouldn't be able to get inside them. The 475-020 is the volume pot, the same we still use, and you can always get a spare from us. If you're able to get the electronics out of the bass, you're welcome to send them in for us to test here.

patrik · « **Reply #9 on:** September 11, 2008, 12:41:33 AM »

Ok, Now it behaves like this.

The knob moves full range, and feels exactly normal.

At 0% - no sound.
At ~5% full sound (as far as I can tell, it might be a fraction of the normal full voulme but I am unsure now)
At ~10% no sound again or almost no sound (maybe 10% who knows)

after that full sound

But, Occasionally, when turning the knob down from 100% there is some kind of decrease in volume that feels like it should. But this now happens about a third of the times, one third is complete drop off at some point, and a third is some kind of mixture, so it starts with a little normal decrease, than suddenly dropps of or jumps back up or something.

Actually, during this experimentation, it might have improved some.

Yes now, it sometimes works back up again.

Actually, now it works in a way I can live with, I only ever use the volume as an on/off switch anyway..

Wow, now I definitely get full volume too.

My alembic is healing it self!

Actually, now (another 20 turns later) It works 95 % of the times.

And mica, Yep, all the yellow stuff is glue.

Well, thanks for the help. SO it seems there was some dust in it or something, then?

Patrik

patrik · « **Reply #10 on:** September 17, 2008, 12:13:28 AM »

Well, sadly the problem returned after the bass was in its case for a few days. After turning the knob lots of times it got a little better, but still not good, and not as good as it was when writing the last post. So is there something stuck in the pot or what?

(Message edited by patrik on September 17, 2008)

dfung60 · « **Reply #11 on:** September 18, 2008, 11:37:55 PM »

I think you'll find that best fix will be to replace the pot. The kind of symptoms you have are probably reflective of a worn, damaged, or contaminated pot. Internally, the pot has a conductive wiper arm that's attached to the shaft and which moves along a circular track around the circumference of the pot.

You can get these jumps in output if there's physical damage to the wiper or track or if some dirt has insinuated itself on the track. All these rotations may clean surface contaminents, but if there's a problem with the mechanism it probably won't help.

I'm not all that surprised about the glue, even if it's not necessary. If you were concerned about things shaking around in there, they probably felt they found the problem when they saw that big ferrite bead shaking around in there, and hit the molex connectors just to keep them from coming loose. Even though it's unnecessary, it shouldn't hurt either.

I'd order a new pot from Alembic. If you can't install it yourself, and can't find somebody that feels confident replacing it for you, I think you can take the part back to this same shop and have them do it. They may have realized that the pot was suspect, but there's no way they would have been able to order a replacement part for this.

David Fung