I'm sorry, but I've warned people time and time again - these amps are
AT LEAST 45 years old. A few cap changes and new cathode resistors is a band aid. These amps now have reached the point where a total rebuild is required for reliable performance.
Guys, this is an audio hot rod! It demands careful attention to a lot of different things. You can't just soup up the engine and go for a drive - the brakes may not work! What you see is typical of what occurs when you try to band-aid one of these amps. Let me point out just a few of the obvious issues...
1. What's up with the photoflash caps?? The Marcon/Rubycon caps are very good, and if they properly re-form (under MY criteria!) they can provide excellent performance. But why 3 of them? Both original voltage doubler caps are missing, so I'm assuming the Rubycons are to replace them. If so, it appears part of the doubler used two of them and part used one. This means the voltage will not divide equally, and one of those caps could easily be at risk. Rip that out of there and re-do the doubler right!
The rest of the PS caps appear to have been changed at some point. I don't trust them for a second. They all gotta go.
2. The 2 watt cathode resistors are fine. You can't use tiny wattage resistors in a Cit II. 1 watt is absolute minimum to keep the fuse from popping during transients - I use 2 watters in my rebuild kit and they perform well.
3. Those are the original tube sockets. They're shot. Replace them. How do I know they are original? See the rivets holding them in? That means this is a factory built unit, they had rivets, the kits used screws. It's a pain, but new octal sockets are a must! There's a good chance that what caused the meltdown was bad contact on pin 5 of the socket. Bad contact = no negative bias voltage = runaway tube.
4. This amp still has the original selenium rectifier! How can any "tech" leave that in there? The bias circuit is at risk with this in place!!
5. I have no idea what that is clipped in the diode holder. It's certainly not what belongs there!
6. Look at channel B, terminal post number three. See that wire just to the right of the yellow wire? It's
SUPPOSED to be red! It carries supply voltage from the AC balance pot to the terminal board. That wire and many more like it in the amp are toast - and were toast before the meltdown. EVERY wire in that amp needs to be replaced - and now the trafo lead wires need to be cut back to get rid of the damaged parts. New wires need to be carefully and professionally spliced onto the original trafo leads, the splice needs to be double insulated (two layers of good polyolefin heat shrink).
BTW, the AC balance pots are toast - replace them or you'll risk more meltdowns in the future.
7. On the terminal boards themselves I see
two resistors that were replaced. Two... just two. I typically find 50 or more bad ones when I redo a Cit II. You can try to save the large brownish resistors, but the old carbons gotta go. Most are well out of any reasonable spec by now. Replace every resistor in the amp - you MAY be able to save a few brown ones. Oh, while the board is being reworked replace those awful (and tired) ceramic disc caps. And replace the screen bypass electrolytics used on V1 and V4 - they are toast for sure.
8. It looks like the speaker terminal screws are rusty. Replace them - and replace the tired RCAs as well.
I could go on and on, but I think the point is clear.
The amp you have is a factory built example, and it has the last generation output trafos - trafos with a resonant frequency of 450KHz, and flat frequency response well beyond 100K. It's worth investing what it takes to make it work right. And what it'll take is a COMPLETE rebuild.
That's going to cost a lot of money, the parts alone are going to be $600.00 or so. And you need tubes virtually for sure. If you aren't capable of doing the work yourself then you need to pay a qualified tech (more about techs in a minute) to install the parts, that won't be cheap by any means. If you can't swing the funds don't use the amp. Set it aside and start saving up to get it done. Or sell the amp. Because trying to use it is asking for even more serious damage.
The damage can be repaired relatively easily at this point - and since the sockets and wiring need replacement anyway it really amounts to very little extra to repair the trafo wires and clean the soot out. The likelihood of any trafo damage is VERY small now - the second time you may not be so lucky. :nono:
Finally, I was not privy to the instructions you gave your tech. If you told him to do the absolute minimum needed to run the amp maybe he did that. But I would have turned you down if you asked me to do that. The workmanship inside this amp is appalling - it's a ticking time bomb. There are more potential failure points than I can begin to point out. How any tech could give that back to you and say it was okay to use is beyond my comprehension. And if he didn't say it was safe to use - well, now you know why he said it.
Why did it occur? The amp is WORN OUT. It should NEVER have been operated in the condition I see from the pictures.
I am sorry if I made you mad - but if this amp is in decent cosmetic condition and fully rebuilt it can go for $2500 plus. Or it can provide years and years of great performance and great music.
As it stands - or victimized by another band-aid - it's value is only what can be salvaged from it. :tears:
If you want my help feel free to contact me.
If so get that crap outta there, it has no buisness having 300+ volts going through it.
