So having managed to set aside the next couple of days to make demos I go out the the garage/studio to rig up some mics and find my twin verb not working.
I don't get any guitar noise on any of the inputs.
I do get a faint thud every 5(ish) seconds, this disappears when the amp is put onto stand by.
The thud is accompanied by a little flash/spark in the power valves.
I don't know a huge amount about amp circuits but my first thought is this is a transformer problem, which is going to require a proper technician to fix. Does that sound right? What else could it be?
I'm highly frustrated as last time I set aside time for making music, I couldn't get my line6 tone port to talk to garageband in my newly upgraded to LION MBP...now I've solved that problem my main amp has gone down!
SilverFace twin verb problem
Moderated By: mods
SilverFace twin verb problem
obscure pop culture reference
Total sympathy!
I don't know much about amp circuits (hence not replying), but, my gut feeling is the same as yours; a transformer issue. But, gut feeling aside, I really have no idea.
I don't know much about amp circuits (hence not replying), but, my gut feeling is the same as yours; a transformer issue. But, gut feeling aside, I really have no idea.
Donate to Ankhanu Pressekwatts wrote:That's American cinema, that is. Fucking sparkles.
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spellcaster
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I'm not technically inclined either, but I do have one suggestion of something you could try yourself before taking it to a tech. One of the common methods of reducing the power on a Twin Reverb is to remove two of the 6L6 power tubes....either the two inside ones, or the two outside ones. (In theory, you should also disconnect one speaker because of the change in the amp's output impedance requirement, but in practice it's not a problem since Fender tube amps will tolerate a single-step impedance mis-match). The reason I think it might be worthwhile is because you mentioned a light show in the power tubes. If it is a single bad tube, trying the amp with only two 6L6's will give you a chance to substitute and find a potentially bad power tube.
I know just enough to be dangerous....
spellcaster wrote:I'm not technically inclined either, but I do have one suggestion of something you could try yourself before taking it to a tech. One of the common methods of reducing the power on a Twin Reverb is to remove two of the 6L6 power tubes....either the two inside ones, or the two outside ones. (In theory, you should also disconnect one speaker because of the change in the amp's output impedance requirement, but in practice it's not a problem since Fender tube amps will tolerate a single-step impedance mis-match). The reason I think it might be worthwhile is because you mentioned a light show in the power tubes. If it is a single bad tube, trying the amp with only two 6L6's will give you a chance to substitute and find a potentially bad power tube.
Thats for the idea. First thing I did was switch all the power valves for spares. Which I guess means it is the amp workings them selves.
I have read something about potentially removing carbon build up from where the valves go in, with a pencil rubber/eraser but to be honest not sure I want to turn it back on for fear of causing more damage/my own electrocution.
obscure pop culture reference
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Concretebadger
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Your logic makes sense. I'm too scared to go poking around inside a valve amp too, so if the problem's still there after you've replaced the output valves I'd take it to a tech as well. Out of interest, ow do you go about finding a reputable one? I really ought to get my amps checked out every now and then, since crossing my fingers and hoping nothing goes wrong isn't a particularly sensible idea...even if it's worked for me so far. Only a matter of time.
My condolences for an ailing Twin BTW.
Hope you get the problem sorted!
My condolences for an ailing Twin BTW.
Hope you get the problem sorted!Hard to say on the knowing who to trust with your gear thing.
The shop I use has been around since 1982 and steadily growing over that time, and owned and run by the same people during that time
It is always busy
All the best local music teachers work from it
It has a work shop with more than one tech in it, ie a guy that just works on electronics, I guy that just works on guitars et cetera ... I know that other shops including in other towns, send their harder repair work to these guys. One time I went in to have my 50s framus acoustic fixed thinking it needed a new tuning machine but they told me to just replace the actual plastic knob which had snapped and lube the gear....being honest rather than grabbing the work is a good sign.
They cater for and are well respected by a large covers band scene ( lots of working men's clubs round here still) and most people that work there are musicians who play real gigs a lot.
These are all reasons why I trust them but if I didn't know all this or this place didn't exist I'm not sure where I'd start either to be honest.
The shop I use has been around since 1982 and steadily growing over that time, and owned and run by the same people during that time
It is always busy
All the best local music teachers work from it
It has a work shop with more than one tech in it, ie a guy that just works on electronics, I guy that just works on guitars et cetera ... I know that other shops including in other towns, send their harder repair work to these guys. One time I went in to have my 50s framus acoustic fixed thinking it needed a new tuning machine but they told me to just replace the actual plastic knob which had snapped and lube the gear....being honest rather than grabbing the work is a good sign.
They cater for and are well respected by a large covers band scene ( lots of working men's clubs round here still) and most people that work there are musicians who play real gigs a lot.
These are all reasons why I trust them but if I didn't know all this or this place didn't exist I'm not sure where I'd start either to be honest.
obscure pop culture reference
Yeah I was going to say it sounds like something went out in the trem/reverb section, that would be causing the "thud" sound. The choke is part of that circuit.
I would have suggested pulling a few of the tubes for that section and seeing if it came to life, there's a few of the smaller valves that control that circuit. For future use, try that. I can't remember which valves off the top of my head but I think it's the 4-5 12AX7 tubes that drive that.
I would have suggested pulling a few of the tubes for that section and seeing if it came to life, there's a few of the smaller valves that control that circuit. For future use, try that. I can't remember which valves off the top of my head but I think it's the 4-5 12AX7 tubes that drive that.
euan wrote: I'm running in monoscope right now. I can't read multiple dimensions of meta right now
Yeah if I remember right, the Twin circuit only has a choke where it blends the reverb/vibrato signal back into the main signal path, so if you pulled the choke you would eliminate the reverb/tremolo but it should allow the rest of the circuit to work fine.
It's been a while since I looked at the schematic, but valve 1 is the input for channel A, v2 is input for channel B, v3 is the second stage pre that's shared between them, then 4-5 are vibrato/reverb stages that's separate from the rest, and v6 is the final pre-gain stage before going into the power section. Might be a bit off about v6 but I know the first three for certain, I recently had to look at that part for some issues I was having with my own Twin.
The "spark" likely isn't a spark so much as just voltage spikes to the tubes, which will cause a power tube to light up. It's just because most likely the vibrato section was spewing voltage spikes into the signal path at the power section, and that's audible as a "thud".
I mean, let the tech do all the shit he said to do, his diagnosis sounds right to me, but the vibrato section could have been eliminated by just taking out the valve in that section, since there would be nothing to send the signal into the path then. No need to take out the choke which would involve soldering.
You probably also had some bad valves in v1-3 since the amp was "dead" aside from the thud.
It's been a while since I looked at the schematic, but valve 1 is the input for channel A, v2 is input for channel B, v3 is the second stage pre that's shared between them, then 4-5 are vibrato/reverb stages that's separate from the rest, and v6 is the final pre-gain stage before going into the power section. Might be a bit off about v6 but I know the first three for certain, I recently had to look at that part for some issues I was having with my own Twin.
The "spark" likely isn't a spark so much as just voltage spikes to the tubes, which will cause a power tube to light up. It's just because most likely the vibrato section was spewing voltage spikes into the signal path at the power section, and that's audible as a "thud".
I mean, let the tech do all the shit he said to do, his diagnosis sounds right to me, but the vibrato section could have been eliminated by just taking out the valve in that section, since there would be nothing to send the signal into the path then. No need to take out the choke which would involve soldering.
You probably also had some bad valves in v1-3 since the amp was "dead" aside from the thud.
euan wrote: I'm running in monoscope right now. I can't read multiple dimensions of meta right now
Yeah strange that I didn't think of isolating the amp section as I'd done just this earlier in the year when I had an issue with the Tremolo inputs. In any case I got the thing about 4 years ago for an absolute bargain price, so I'm pretty happy to to spend some money now to get it fixed up and serviced... Even with this cost I'm still below the price of a reissue or even the going rate for earlier silver faces.Pens wrote:Yeah if I remember right, the Twin circuit only has a choke where it blends the reverb/vibrato signal back into the main signal path, so if you pulled the choke you would eliminate the reverb/tremolo but it should allow the rest of the circuit to work fine.
It's been a while since I looked at the schematic, but valve 1 is the input for channel A, v2 is input for channel B, v3 is the second stage pre that's shared between them, then 4-5 are vibrato/reverb stages that's separate from the rest, and v6 is the final pre-gain stage before going into the power section. Might be a bit off about v6 but I know the first three for certain, I recently had to look at that part for some issues I was having with my own Twin.
The "spark" likely isn't a spark so much as just voltage spikes to the tubes, which will cause a power tube to light up. It's just because most likely the vibrato section was spewing voltage spikes into the signal path at the power section, and that's audible as a "thud".
I mean, let the tech do all the shit he said to do, his diagnosis sounds right to me, but the vibrato section could have been eliminated by just taking out the valve in that section, since there would be nothing to send the signal into the path then. No need to take out the choke which would involve soldering.
You probably also had some bad valves in v1-3 since the amp was "dead" aside from the thud.
obscure pop culture reference
Yep, sometimes it's just nice to have an amp sent in to have a proper tech do the work to get it all nice and shiny again. The problem with my Twin ended up being a loose cap and a few valves, which technically I could have done myself but I did not want to take all of the knobs and wiring out to get to the cap and whatnot. Just let the old guy do his thing and he did it better than I could have done. At least when you get it back it'll be like new again.
euan wrote: I'm running in monoscope right now. I can't read multiple dimensions of meta right now
