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Post subject: 94 Twin – interesting problem (volume/static)
Posted: Fri Jul 27, 2012 10:38 am
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OK – so I’m not looking for advice so that I can fix anything electronic in the amp myself as I am not particularly practiced or skilled at dealing with electronics (I did switch out pick-ups in my Strat, but that’s about as much as I’ve ever tried).

What I am looking for for advice is in consideration of two possibilities:

1: There may be a simple fix that’s not related to the Amp’s electronics.
2: If not, so that I can give as much info as possible to the Amp tech when I get it repaired.

The issue I’m having is that occasionally the amp will lose volume and put out a static-y type of tone.

By occasionally I mean that it does not happen every time that I play. When it does happen it seems to do so out of nowhere (e.g., I may be playing for an hour and it will be fine for all that time and then just start in with no indication of something else going wrong) and usually only lasts for a few minutes before stopping again.

When I have the foot-switch attached this will sometimes be accompanied by a sort of faux-Channel switching – the indicator lights on the Channel 1 gain and/or Channel two will flicker a little. This has happened even with a brand new speaker cable connecting the amp to the foot-switch, though it did happen more often and prominently when I had an older one attached.

I am running some effects ahead of the amp and some in the effects loop. I can go into details on those, but I do know that all of the cables/connectors are new and/or otherwise in good shape.


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Post subject: Re: 94 Twin – interesting problem (volume/static)
Posted: Fri Jul 27, 2012 11:03 am
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If you are absolutely positive that the problems are not caused by the cables, pedals or guitar, you either have a bad tube or bad solder joints. There is not enough information to guess at what tube it might be and a bad solder joint should be handled by a pro tech.

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Post subject: Re: 94 Twin – interesting problem (volume/static)
Posted: Fri Jul 27, 2012 11:35 am
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bluesky636 wrote:
If you are absolutely positive that the problems are not caused by the cables, pedals or guitar, you either have a bad tube or bad solder joints. There is not enough information to guess at what tube it might be and a bad solder joint should be handled by a pro tech.


"Absolutely" might be too strong, but reasonably certain (EDIT: It's not the guitar. I have two I'm using regularly right now and it happens with about the same consistency with both of them). I might try experimenting with pulling out certain elements and seeing if it continues. Unfortunately it's so sporadic that it's hard to know if any one change is having an effect or not.

And yes, any work on the electronics is going to be handled by an Amp tech. I'm just hoping that if I do have to bring it to one that any info I can learn ahead of time might make their job easier.


Last edited by RedShark92 on Fri Jul 27, 2012 11:38 am, edited 1 time in total.

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Post subject: Re: 94 Twin – interesting problem (volume/static)
Posted: Fri Jul 27, 2012 11:37 am
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Re: Bad tubes: Is there a simple way to test or check them to see if that's a possibility?

Secondarily, this amp runs on 4 6L6 power tubes with an option to remove two of them to run it at a lower power mode.

I am running it like that - so I have two of those tubes set aside that are not currently being used. I could try switching those out for the other two.


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Post subject: Re: 94 Twin – interesting problem (volume/static)
Posted: Fri Jul 27, 2012 1:04 pm
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When you removed two of the power tubes, did you check the power tube bias and adjust it if necessary?

You could try swapping tubes, but since the problem appears to be sporadic, it is going to be awfully hard to trace. Unless you can provide more detail regarding what is going on when the problem occurs (you are dancing around and twisitng the guitar cable, or beating the amp with your guitar :lol: ) it would be best to just have it looked at.

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Post subject: Re: 94 Twin – interesting problem (volume/static)
Posted: Fri Jul 27, 2012 1:17 pm
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bluesky636 wrote:
or beating the amp with your guitar :lol: )


Oh. Hmmm.

Is that bad?

:mrgreen:


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Post subject: Re: 94 Twin – interesting problem (volume/static)
Posted: Fri Jul 27, 2012 2:21 pm
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The channel switching light coming on, indicates a bad solder joint in the +/- 16 volt supply, requiring removal of the main board to repair. :idea:

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Post subject: Re: 94 Twin – interesting problem (volume/static)
Posted: Thu Aug 02, 2012 7:15 am
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OK, to clarify this may be two different problems. When it does happen, the volume/tone problem is consistent, but the Channel Switching part does not always happen.

Anyway - I actually have the amp at home for a while (I usually just leave it at the site of our band practices, but we're on a break for a bit), so I've been playing through it some in the morning.

This morning I plugged in and turned it on and it was immediately off.

This was: Guitar -> Pedalboard -> Amp (NOTHING in the effects loop) with the footswitch plugged in.

I immediately put it in Standby and removed the Pedalboard from the equation, so it was just Guitar -> Amp with the footswitch. Problem continued.

I unplugged the Footswitch and the problem immediately disappeared. I re-plugged in the Footswitch with a different cord (because I had suspected earlier that the cord might be part of the Footswitch problem) and it was fine briefly, but then started in again. Upon unplugging the Footswitch once more the problem was immediately resolved again.

So there is definitely a problem in that area and it’s not the cord itself as the problem was apparent with two different cords, one of them brand new.

However, this isn’t the only thing going on as I still have occasionally seen the scratchy sound/tone problems (without the channel switching weirdness) when the Footswitch is not plugged in at all.

So does any of this help at all, or just muddy the waters more?


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Post subject: Re: 94 Twin – interesting problem (volume/static)
Posted: Thu Aug 02, 2012 7:28 am
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I think bluesky636 nailed it, solder joints are the likely suspect. You may have two different problems, maybe solder joints in a couple of different areas (foot switch jack, and power supply), and possibly a preamp tube(s) problem. Maybe even the pots need to be cleaned too.

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Post subject: Re: 94 Twin – interesting problem (volume/static)
Posted: Thu Aug 02, 2012 7:30 am
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Thanks. Definitely a more involved project than I want to tackle myself, but the extra info will be helpful when I bring it to the Tech.


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Post subject: Re: 94 Twin – interesting problem (volume/static)
Posted: Thu Aug 02, 2012 7:37 am
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Let us know what you find, it can be helpful to someone else in the future.

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Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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Post subject: Re: 94 Twin – interesting problem (volume/static)
Posted: Mon May 12, 2014 3:58 pm
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I have been having (part of) this exact same problem since I bought my used 94 Twin Amp from this local guitar/music store, Shake Rag Music.

While playing my guitar through the Twin Amp (direct or through a MXR Micro Amp, EHX Small Stone, and Boss Tuner) with the footswitch plugged in, when I play aggressively through the vintage gain clean channel, the amp kicks over into the gain channel (causing a static-like sound) and the indicator lights turn on/off intermittently between the two channels. The guitar sound cuts in and out of the gain channel and eventually returns to the clean channel/green-yellow light again. It doesn't seem to do this through the pure clean channel (no vintage gain), nor does it happen when playing through the gain channel.

I bought a new footswitch speaker cable and it seemed to make the problem go away for a bit, but it eventually came back, although it's intermittent. I suspected it was something to do with the inner circuitry/soldering/jacks and not power related (I also removed 2 of the 4 tubes and halved the Ohms to run it at lower power), since the problem persists at all power levels.

This topic was super helpful in finding out exactly what to tell the Amp tech when I take it in to get fixed. Frankly, I'm not surprised to find something wrong with this, as I bought it used and everything I've got from this store has turned out to have some issue (the guy who runs the place is not technical at all). I'm just glad it's something that is fairly simple to repair.

Other than this little problem, I absolutely love this amp. I got it for half the price of the tattered and beat up Silverface Master Volume Twin Reverb that was also at the shop and it pretty much gets the exact same tones save for the "Vibrato", which the 94 Twin Amp is missing (I'm much happier with my Boss Tremolo pedal anyway). One way I use the amp is playing through the Gain Channel for a dirty "clean" sound that I can push with my MXR Micro Amp into a Overdriven heavy sound. Another way I like to use it is playing through the clean channel with vintage gain all the way to 10, treble to 10, and mids and bass at 0 or close to, in order to get the D. Boon Post-Punk angular/shattered sound. Finally, I can use the clean channel by itself with the Bright knob pulled to get the chimey and chewy early-R.E.M./Big Star shimmering Fender Tube clean sound. It's a really versatile amp and worth above the low prices they can be had for on eBay and in stores.

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Post subject: Re: 94 Twin – interesting problem (volume/static)
Posted: Mon May 12, 2014 10:24 pm
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bennyshambles wrote:
...This topic was super helpful in finding out exactly what to tell the Amp tech when I take it in to get fixed...


You can return the favor by giving us a report of what you find out.

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