TREMOVERB fx loop, found the problem now need a solution...

[gambit]

I know taking it to a tech will fix it for 200 bux but if I can do it myself I will.

I was having massive problems with the tremoverb FX loop and the reason is I apparantly have a busted or bad pot on the knob itself... when I jiggle it, it works... when I don't, it doesn't.

Anyone have any clue how complex it is to change a single pot on a knob?

Id love to be able to do this myself, thanks so much guys!!!

 

[stephen sawall]

Something tells me you can find someone to do it for less. Have you tried a cleaner yet ?

 

[94Tremoverb]

A tech that charges $200 for changing one pot is a scam artist.

Is it either the Send or Mix pot, or the big rotary switch? If it's one of the pots, it's three solder connections and one panel nut. The pot is $5 at most, and you could do the whole job in ten minutes including taking the amp apart, putting it back together, and testing it afterwards. If it's the switch it's five connections and a panel nut and you're probably looking at $10 for the switch and fifteen minutes max.

If you're not experienced at soldering you should still leave it to a pro, but find one that isn't ripping you off.

 

[gambit]

just the send knob guys.... should I do this myself? I have some experience soldering.

 

[94Tremoverb]

Yes, if you can solder cleanly you can easily do it yourself. You don't even need to take the chassis fully out, just drop it and slide it a couple of inches back, it will sit there safely enough.

The only thing I can even think of that might catch you out, is when you're getting it out and especially when putting it back together - to get the chassis to move easily under the foam strip along the top front edge, you need to undo the front grille screws (6, inside the cabinet) and take the grille off, so the chassis can then slide in and out lower down and lift straight up under the strip - otherwise it's hard to get in and you'll chew up the foam.

 

[gambit]

If its the send knob, anyone know which pot I have to go to the store and buy?

Where do I go, home depot?

 

[94Tremoverb]

It's a 25Kohm Linear. Try Radio Shack - the pot quality isn't really that important for this place in the circuit, it's the value that matters. Make sure it's a miniature type not a full size or it probably won't fit, and plain shaft not split since the knob is held on with a set screw. If that's no good, try a guitar store that does repairs and see if they have any left-overs from EMG installations, they also use 25K (unlike most other guitar electrics which use 250K or 500K). I think the EMG volume pot is a linear, although I don't know if they come with a plain shaft. If not, you can use a split shaft if you put something (like a cut down piece of a pick) in the slot to stop the screw crushing it.

 

[gambit]

coool man, so I remove the pot with the soldering iron and then re-apply the new one?

 

[stephen sawall]

Do you understand that you can be electrocuted by a amp without it being plugged in ? You may want to read up on this before removing it from the head box. We do not want you to have that problem ....

 

[94Tremoverb]

That is true, but it depends on the design of the amp's power supply, and most newer designs are fairly safe. If you first put the amp onto standby, wait a few seconds, then turn the power off, unplug it and wait a couple of minutes - which is about as long as it will take you to unbolt the chassis anyway - you're safe with a Tremoverb, as with most other modern amps. This is because the standby switch disconnects all the filter caps except the first stage, and these will drain via the tubes when they're still hot. The first filter cap (which is a stacked pair) has divider resistors on it so the caps will discharge through these in a minute or so at most once the power is off. If you leave the standby switch to 'play' all the caps will discharge through the resistors anyway. The only really dangerous amps are older ones with non-stacked first filter stages and the standby downstream of them (eg Fender Deluxe Reverb, very old 50W Marshalls), which certainly can store a lethal charge even when they're unplugged, and are not drained when on standby. If in doubt, flip the power off (without putting the amp on standby first) while playing a loud chord through the amp, and it should discharge the caps down to at least a safe level, if not always quite down to nothing.

When you unsolder the old pot, just make sure you make a note of where the three wires go.

 

[gambit]

ok dude... let me get this straight...

I unplugg the amp and then hit the standby switch or do I unplugg the amp, then hit power and then stand by?

I take it everything should be done with the amp unplugged.

By hitting these switches it empties the pots I take it even when the amps off.

Just trying to clarify.

 

[94Tremoverb]

With *this* particular amp it doesn't really matter, but it's still safest to just switch off the power and leave the standby switch set to 'play'. The caps will then all drain via the divider resistors. You can unplug the amp at any point, it doesn't make any difference to draining the caps, and you should not work on it with it plugged in.

 

[gambit]

wow man, thats really helpful better safe than sorry...

So basically if I feel I can take on this task, before I open her up I'll switch the standby on and leave it for a few minutes to drain whatever power may be left in there.

thx dude, im new to a lot this tech stuff, i appreciate your time in answering questions which may seem redundant!

 

[94Tremoverb]

No problem, everyone has to start somewhere and it's better to ask first than to have a go without knowing what you're doing and break something or give yourself a shock .

I'm speaking as someone who gave himself a nasty shock from the first tube amp he opened up... which was an old 50W Marshall.

 

[gambit]

cool man, so you think I can safely remove and re-install the pot which is for the send fx knob?

Should I buy a tool to measure electricity so I know nothing is still in there?

I was told to buy a 25KOhm Parallel Pot.. correct?