Audio Asylum Thread Printer
Get a view of an entire thread on one page
|For Sale Ads|
In Reply to: RE: Serious Micro-Phonics and Hum from Citation V posted by mr9iron on July 07, 2012 at 01:06:10
For a moment let's assume you haven't made a wiring error, and it is likely that if there had been a hyper-microphonic tube in there that it's not there now.
And I can be 100% sure the kits are not at fault, there are hundreds of them out there working great.
Of late there have been some cases reported of problems related to output trafo issues. There have been a few cases of oscillation as well as various other issues. But the likelihood of it happening in BOTH channels is fairly low. Does the amp make the noise from both channels or just one? I don't mean which one you are tapping, I mean does the noise come out of one or both speakers? And is this the amp that had the broken internal connection that you and Mike Samra sorted out?
Next - we'll now assume a wiring error could be at fault. It is not difficult to hook up the output trafo wrong - especially since after 50 years the wire colors have changed quite a bit and they are difficult to sort out.
Check the heater voltages on the tubes too - especially the 12BY7As.
Let us know what you find! We'll continue from that point when you reply.
man hate to drag you into this, yes the micro phonic sound will transmit through both channels, the hum is a tad higher in one channel than the other.I am suspicious about it being a tube issue. The tubes I am using are the new ones you sent..
and yes this is the same amp that Samra and I fixed the trafo on.
I can check the heater voltages on the 12by's tonight..
I suspect some trafo rewinding is in your future I'm afraid. But the unit is worth it!!
But maybe it's something else, so I'll keep my fingers crossed!!
Jim, is that due to them needing some wax like potting to dampen the wire like is done with guitar pickups? I'm guessing done with tar instead.
The insulation on the wires and the wires themselves can both fail. The windings are subjected to repeated heating/cooling cycles, they move ever so slightly as a result of expansion/contraction from heat, and from magnetostriction; and if there are any solder joints inside them they can work harden. See the pic of a Cit II trafo I posted as an example of an internal wire failure. This pic is of a power trafo but the failure can occur in an OPT too.
Keep in mind too that magnet wire now is FAR better, especially the insulation.
BTW, getting Cit V trafos rewound is significantly less than getting Cit II trafos done since the V's aren't potted. I wouldn't rule out keeping the amp - but Triode Kingdom's offer is nice to see - this particular amp's life is FAR from finished!
Oh - the potting material used in a Cit II is called "permafil" it's a mixture of tar and ground slate.
wow, that would be very serious, what would cause this? I thought that the windings are very "inert" and if they are wound and stable through their life they would not "wear" out..
Man, I hope you find it and don't have to incur the high price of a rewind. That would be heart breaking.
I am not sure what I'll do if that's the case. I'd probably sell it for parts, it's all new.. It wouldn't be hardly worth it to re-wind the transformers.. I have another one I could upgrade and just call it a learning experience..
I hope this works out OK for you. If not, and you do indeed decide to sell this for parts, I'd like a crack at it. Please keep me in mind.
Buy Chinese. Bury freedom.
Post a Followup:
Post a Message!
This post is made possible by the generous support of people like you and our sponsors: