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In Reply to: RE: OK, here is a pic of the belly... posted by gkargreen on November 01, 2014 at 21:16:59
Wow, that's umm... Interesting....Good news is that most of the amp is in terrific shape from the looks of it.
Other than just the obvious, the oddball transformer and the e-tape connections, one thing stands out like a sore thumb: Where the hell is the bias rectifier? Stock S-5000 has a selenium rectifier on the other side of the amp, and the wires to it pass through the eye hole you see on the upper right hand corner of the picture. It feeds into the cap near that hole, which provides both the bias voltage and the DC filament supply. At least from this picture, I don't see how the hell that is even being powered. Are there diodes hidden in that big ol' wad of e-tape?
Anyhow, I sent an email to my buddy who has a lot of my Sherwood stuff in storage. He said he'd go check out the transformer this weekend, measure it to see if it's dead, and pull it out.
I guess the thing to do, if you want to see if this transformer in there has any hope of working, is to figure out what the various taps are and if they are even close the the proper arrangement. Apart from having a HV secondary that is good and high, as well as a bias tap that properly powers the DC filaments and still results in the correct bias voltage to the balance pot, well... It's a tough proposition frankly.
At the end of the day, this amp looks really good, though I'd like to see more of it! I don't see any evidence of rust or hackery beyond the obvious power transformer issue. A proper tranny and some power supply caps ought to make this amp sing.
Also, how did you fare on the tube compliment? Did you manage to get any of the original set?
Cheers!
-SF
Edits: 11/01/14Follow Ups:
SF, don't know if I posted this back o you before, but if you have the dimensions on the S-5000 shorty power tranny, could you send that to me, I am in contact with Arlyn @ Heyboer and she needs that info to give me an answer on making a new PS tranny... thanks!
Hi,I only have mine on hand to measure, and it's in my amp. Hopefully laminate dimensions are enough...
4.15" long
3.45" wide
1.35" thickAlso, it does have a copper shield band, so that might effect the price a little.
Cheers,
-SF
Edits: 11/06/14
thanks, SF, that will do nicely, I will send that info onto Heyboer and see what the hit will be...
yes, you see the issue, I don't think the replacement tranny HAS a bias voltage winding, the wired kludge I removed I believe was used to provide bias from an outside source, you will see from the top pic that the selenium is totally missing and it was in that hole that the kludge wire was passed thru to the underneath. I should get around to doing a measurement of the voltages on the replacement, but even so, I think that the replacement is not even close to what I would need to get this right. The top is pretty dirty as you see, but it does clean up to a fair shine, not much in the way of corrosion. I did get tubes with it, including a Mullard 5AR4, but the remaining tubes were all Sylvanias with a bad 6BQ5. If you have the cover plate for the front tubes, mine is missing, and the power tranny would be useful even if blown as I could have it rewound at TRS, they did a Mac tranny from a C10 (preamp), as well I need a front knob, I'll post a pic from the front to you to see tomorrow, thanks SF!
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