Thanks for confirming the 1N4007 would be ok. I know I could order UF version from other places, but the shipping costs for such a small order would make them pretty expensive. If I'm ordering tubes from Parts Connexion, adding a couple diodes to the order makes sense. I'll give it some thought.
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I wouldn't worry about it. I'm not looking forward to the cost of my next order from Canada... :-(
I pulled the bottom covers off to look inside and there are already two IN4006 diodes on the 5AR4 tube sockets. Have these amps already been modded, or would the 4007s be in addition? I've been trying to find more info about performing this mod on the QS mono amps, but haven't found much yet.
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That sounds good, but are you sure? I found this post over at audiokarma that references the schematic Burnedfingers posted earlier. It also includes the image below that shows eight diodes installed as in that schematic.
As @hooman indicated, this solution (330uF as first capacitor) is rectifier killer!
5AR4 datasheet suggest 60uF as maximum value (for one tube), so in this case 120uF is the recommended.
I suggest to change the "red" wire (from rectifiers to first cap) with 22-33R 3-5W resistor, and put 47-100uF smoothing capacitor between rectifiers output and "ground".
p.s.
sample (another amp PSU):
5AR4 datasheet suggest 60uF as maximum value (for one tube), so in this case 120uF is the recommended.
I suggest to change the "red" wire (from rectifiers to first cap) with 22-33R 3-5W resistor, and put 47-100uF smoothing capacitor between rectifiers output and "ground".
p.s.
sample (another amp PSU):
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I don't understand what he's doing there. It seems like he's trying to put diodes in series with each plate of the dual 5AR4's, but it looks like one pair of plates are bridged while the others are not. One the right tube the HV secondaries are wired in parallel but on the left tube they're not. It's a mess. The way yours is wired is the correct way.
I would suggest not trying to rebuild a pair of amps that are working. Yours has the diode modification that should relieve the stress on the 5AR4s. How long have you had these? With the diode mod they seem to be working (with the proper tubes, of course!). They are quite old and still running, yes?
I think I'll order a new 5AR4 tube (maybe a quad) and leave them alone. I've only had them a couple days and other than the wrong tube causing the startup noise, they seem to be working fine.
I took them on a trade for a Rogue amp I was having trouble selling and may not keep them anyway. I just thought if the diode mod was inexpensive, easy to do, and would prolong the life of the rectifier tubes, then it might be worthwhile doing and might add some value if I'm reselling.
It sounds like there are various different approaches to this type of mod, but if it looks like something has already been done to these amps I'm happy to leave them alone.
I took them on a trade for a Rogue amp I was having trouble selling and may not keep them anyway. I just thought if the diode mod was inexpensive, easy to do, and would prolong the life of the rectifier tubes, then it might be worthwhile doing and might add some value if I'm reselling.
It sounds like there are various different approaches to this type of mod, but if it looks like something has already been done to these amps I'm happy to leave them alone.
Did you watch that video (in #27 post) from 5 to 6 minutes?
Each 5AR4 will break sooner or later if you use its in -original- bad environment.
Only one resistor and one capacitor requiring for safety operation.
Each 5AR4 will break sooner or later if you use its in -original- bad environment.
Only one resistor and one capacitor requiring for safety operation.
i would just order a single tube. The other three are most likely fine. The diode mod was done to both amps right?
jeff
In his amps the 5AR4s are no longer doing the rectification. They are just passing DC.
Both amps are the same and have the two diodes on the rectifier tube sockets. I don't know enough about them to know whether they came like that from the factory or if they were modified later.
Sorry, I didn't notice the video link in your first post. I'll check it out, but from what others are saying it looks my amps gave already been modified to protect the 5AR4 tubes.
Are you kidding?
Series SS and vacuum diodes acts as one rectifier (the SS provides some protection), the latter may be ruined if the first cap has such large value.