BadLife

It's sitting in the other room Marshall 100 watt half-stack. It does everything 3 channel switching amp.

Hum I fired up another old amp and something similar happened. Dang I guess you need to turn them on more often than I have been. It was noisy at startup and the volume pots are again the culprit. This is an old Ampeg VT-22 I have had for a long time. It's also about a 1973 vintage and has been rebuilt fairly recently. After a while most of the noise went away but the channel one volume pot is still a little noisy I may have to replace those pots but I will have to pull the chassis to see what I need that is a fair amount of work Oh well I feel sorry for anyone who collects amps. I read an article In GP about a guy who is know for that sort of thing, but in this case is a popular contemporary guitarist. He had about 15 old amps in his parents basement (that had been there for around 15 years) and wanted something for a new record ( is that what we call it now?) anyway he was only able to find two that actually worked correctly. (GP April 2009)

Looks like Miles is still around, I guess to busy to check in here.

Dang it was a 7025. That's $200 for NOS and I believe anything new labeled that way is just a 12ax7(ecc83) so I popped in a new ECC83 S I had laying around. That fixed the noise at startup but the real problem now it the volume pots. Both channels are extremely noisy is you even touch the knobs Going to have to pull the chassis and either replace them or clean the crap out of them. Not sure why but it is almost always the volume pots that do this. The rest of the controls are reasonable quite. It may be because I usually set the volume and don't mess with it much Not really sure really. Wonder whats up with Miles? Guess I should check his web site.

Yeah I have a pile of tubes from old tube stuff. Not sure how much I trust them though. I don't play out so all but two of my amps are tube. Those are just tiny practice amps Almost got around to replacing the tube. I have more new and NOS power tubes than preamp for some reason I do have several of the correct preamp tubes that are pulls

Yeah could be dust, but I suspect the old tube its one of the preamp tubes in the second channel. I think it's in the vibrato circuit if I remember correctly. I will pull it and replace. May need to order tubes. It has not been unused all the long a couple of months at most. I fire up all the tube amps every so often to make sure they are working correctly.

Ha Ha yeah that might be a good idea, but I have built amps from scratch so I'll probably do it myself I think it's a tube and I know just the one I suspect as the problem was somewhere in the 2nd channel the one with reverb and virbrato and that is where the 40 year old tube is. I may have a new one laying around somewhere so I will try that first. Then yank the chassis and do a visual inspection for any leaking, swollen, burst or otherwise unusual looking parts. Could be a literal bug crawled in there. I am pretty sure what part of the circuit to start looking in and have the schematic on hand. So it's just a matter of discharging the capacitors and not getting zapped I doubt it's anything except the very old tube as it has been rebuilt and only lightly used since then, but you never know

I have a Fender Vibrolux Reverb from about 1970 or so. It had been unused for quite some time and I decided to fire it up today. It made a terrible noise for about ten minutes after I hit the standby switch. The power switch had been on for about 10 minutes before I hit the standby. After a while and several on off with the reverb and vibrato it cleared up. Any ideas ? Maybe a tube going out? One of the tubes is original as the new one from the last rebuild blew out. It is probably micro-phonic to some extent. I don't really want to open it up without some idea of what to look for I posted this in the Ask Myles thread but he seems to have not replied to the last several posts so I thought I would toss it out here in case anyone had any thoughts

I have a Fender Vibrolux Reverb from about 1970 or so. It had been unused for quite some time and I decided to fire it up today. It made a terrible noise for about ten minutes after I hit the standby switch. The power switch had been on for about 10 minutes before I hit the standby. After a while and several on off with the reverb and vibrato it cleared up. Any ideas ? Maybe a tube going out? One of the tubes is original as the new one from the last rebuild blew out. It is probably micro-phonic to some extent. I don't really want to open it up without some idea of what to look for

I have a Raspberry Pi that is just gathering dust after going through a bunch of different projects, also have a touchscreen for it. May have to give this a try.

Hum is that the 7025 which is 4th from the right looking at the back of the amp or the 12AT7? The 7025 was bad and I replaced it. Before I replaced it the amp was going crazy when the vibrato was on. That tube was the original as the one installed during the rebuild was bad. It was all frosty looking and the vibrato channel did not work at all if I remember correctly. I need to order some new Preamp tubes anyway as I have several tube amps as well as two I built from scratch. I don't get why it goes away at full intensity.

I have a silverface Fender Vibrolux Reverb I think its a 1973 anyway when I turn on the vibrato it makes a thub thub thub heartbeat noise but only if the intensity is 2 to 9 at 10 it works fine. Any idea about where to start. I know how to work on amps but not sure where the problem could be as my knowledge is limited as far as circuit design goes I think it is the AA964 layout but will have to pull the chassis to be sure. I had the amp rebuilt several years ago and I don't think it did that before. It is pretty annoying if I don't leave the intensity all the way up but other than that it seems to work great.

Thanks

I am sure you have covered this before but could not find anything with a search. What books or other resources are good if I want to learn how to rebuild and maintain my amps. I woluld at least like to be able to rebias and replace parts. I have some understanding of basic concepts. I known basic electronics is the place to start but amp specific resources are what I am looking for.

This is a dumb question. I have a tube and I can't figure out what the heck it is. I am pretty sure I got it to use in a Valve Junior. It has a diamond with an O in it on the top left is OTK on the top right is 2 on the bottom left is V on the bottom left is 82. On the other side it has 6111411-EB with 0582 under it and 17 under that. It looks like an EL84 to me. Any idea? It has 9 pins if that helps.

Thanks for the information. I was leaning to the loss of vacuum as the cause. Never had that happen before. I tried one of the old 7025s in it and its seems to work fine.

I just blew a tube in my Fender Vibrolux Reverb it is in the 4th position looking at it from the back and counting from the right. It looks like alka seltzer in the pointy end of the tube. It had 7025 RCA tubes in it and had recently been retubed with Tung-Sol 12AX7 tubes. Does this sound like a bad tube or an amp problem? Also what tubes interchange with the 7025? I was under the impression that the old 7025 tubes were able to take a lot more abuse that the 12AX7? Is it safe to stick in one of the old 7025 tubes? They were supposed to be microphonic but I never noticed if they were. This is the same amp I inquired about earlier that had the feed back problem and this is one of the tubes you suggested that I move although the tube I traded with was also a 12AX7. Also the pointy end of the tube is black. Maybe it lost its vacum?

I have a question about my Fender Vibrolux Reverb. I just had it gone over by a good amp tech I have used in the past. It sounds great but the reverb and vibrato sound noisy. This is about a 1974 vintage amp. The reverb is sort of noisy and if its turned all the way up sort of makes a feedback sound. When the vibrato is turned on it makes a slight vibrato noise even when I am not playing. The reverb/vibrato channel is now the blackface circut and the normal channel is the tweed circut. Both channels sound great and are dead quite except for the reverb/vibrato channel. It is only noisy when the reverb or vibrato are turned on. Is this normal? I usually use Marshall amps so I have little experience with Fender amps. I got the amp used so I have little experience with this amp.