Genz Benz Streamliner 600 sudden jumps in volume

[Julto]

Hi everyone, hope you are doing great !

Would any GB streamliner users have come accross the same issue ?
I've been using a GB streamliner for 12 years, but since a few weeks something really strange is happenning : while playing the sound is anormally thin/empty, and all of a sudden there are big spikes in volume, like the output goes from 70dB to 100dB (heart attack level jumps), at the very high volume the sound is "full" again, but then it goes back and forth to lower volume and so on.
I have tested this with an external preamp, going into the poweramp directly, and the same thing happens.

Could this be related to the master volume pot ?
It is a bit scratchy at times but to be fair, as far as I remember, it has always been a bit scratchy.

Many thanks guys !

 

[J-Bass RMR]

You came to the right place... https://www.talkbass.com/threads/genz-benz-streamliner-900-saved-by-agedhorse.1605059/


@agedhorse should be around shortly.

 

[Julto]

Thanks !
In the meantime I openned the top pannel and tried to spray some contact cleaner to the Master volume pot, but it's hard to get to the pot's side hole because of how it is mounted (close to the side of the box and with an additional pcb covering its top).
Not sure if this would be more effective to spray from the exterior of the case, along the shaft of the pot... I just need to find a way to remove the knob which is held in place quite strongly (don't want to break anything...).

 

[Blues Bass 2]

Don't spray it . Agedhorse should be around to get it right soon . He says lots of his repairs are from spray cleaners .

 

[agedhorse]

Please don't spray anything into the pot or ANYWHERE in the amp as it increases the cost of any followup repair.

Message me and I will get you information on the factory service program. There are many possible causes, I don't guess about what it might be because I will be wrong more often than not.

 

[Julto]

Hey thanks for the proposal but I live accross the atlantic so not sure this is a viable option for this one.
I can test if changing the master volume pot for a new one does the trick, as it is scratchy anyway and it appears to be a quite standard pot from alpha.

Also thanks for the warning not to use spray cleaner guys, but I thought this was a very standard way of dealing with scratchy pots ?
If you do not use spray cleaner, what should you do when you have one ?

 

[agedhorse]

Hey thanks for the proposal but I live accross the atlantic so not sure this is a viable option for this one.
I can test if changing the master volume pot for a new one does the trick, as it is scratchy anyway and it appears to be a quite standard pot from alpha.

Also thanks for the warning not to use spray cleaner guys, but I thought this was a very standard way of dealing with scratchy pots ?
If you do not use spray cleaner, what should you do when you have one ?

The only cleaner I have found to work safety is Caig DeOxit D5, and only the tiniest amount possible. It's a standard way to ruin a set of pots when used inappropriately... it dissolves the lubricants which then get to places they shouldn't be. Less is more and it needs to stay off the PCB as it will attract conductive debris which is a problem (especially with high voltage circuitry).

There is nothing I hate more than cleaning up miracle cure-all spray messes, and changing out a set of pots can get costly. If a customer has attempted to do it themselves and damages the PCB (these are all double sided PCBs with plated holes, which take additional skill and experience), it often makes the repair uneconomical unless I have a replacement PCB that I can change it out with.

We still have service centers in the UK, Australia and New Zealand, and there may be a few in the EU too but I haven't looked in a while.

 

[HowieD72]

@Julto What country are you in? Did you get this sorted?