B52 AT-100 Power transformer measurements?

[techineer]

Has anyone measured and recorded the secondary winding voltages for the B-52 AT-100 head? (Or do you have a working one that you can take measurements on?)

If I can get a good set of values for them, I may be able to get another transformer manufacturer to make them besides Mercury. (They want over $300 retail for theirs, and often they do not physically fit the amplifier properly.)

I'm trying to revive a unit with a shorted PT.

Alternatively (or additionally) does anyone have a boneyard unit with a good PT?

[J M Fahey]

Syart by posting schematic here.
If supply (DC) voltages are shown, PT AC voltages can be calculated.

[techineer]

B52 AT100 schematic

Syart by posting schematic here.
If supply (DC) voltages are shown, PT AC voltages can be calculated.

Hi, Juan!

Enzo put it up in another thread: https://music-electronics-forum.com/...6&d=1224581192

[DrGonz78]

Pretty sure this is a power tranny for an AT100 USA model. I have sourced other pictures that show an AT100 in Europe where the transformer code is AT10023050. Which I take that to mean AT100 = Model 230 = Mains voltage and 50 = main frequency. The one on the ebay site is AT10012060, so it makes me think it is the American 120v 60hz version. Now the price is right but who knows if that PT on eBay is any good? The seller says guaranteed to not be DOA. Personally I would be curious if this is a working transformer gutted from an AT100 where they did not want to repair something so they sold the parts separately. Who knows, buyer beware.
http://4.bp.blogspot.com/-f91w64oDVX...0/PTDC0187.JPG
https://www.ebay.com/itm/Tube-Amp-Po...cUPfw#viTabs_0

[J M Fahey]

Not enough information on the EBay one; "continuity" means nothing in a shorted turns transformer.
IF he could apply mains voltage to primary without blowing fuses or overheating that would be almost enough, but clearly he won´t do that.

Sadly schemayic shows no voltages, in fact shows the trivial ones such as 6.3 and 5V ones, but others can be reasonably estimated.

* +V uses 250V caps in series, so it will be around 450V ,tops, so 318+318VAC or thereabouts.
Round it to 2 x 315 or 320VAC if you like nice even numbers.
Current: same as required by any 4 bottle amp.

* Low voltage taps: bridge rectified and filtered with 63V caps, so definitely not higher than -55V DC (enough to bias 6L6/5881 and even more EL34) so around 39/40VAC x 2 .

Positive +55VDC "a little too much" to be reduced to 12V, so notice R124, 100 ohm 5W to make LM317 life somewhat easier.

IF it dissipates, say, 2W , then:
2W=V^2/100 ohm, so V=14VDC which sound reasonable: resistor drops 14V so LM 317 gets 55-14=41V ; not a picnic but more reasonable.
For a current consumption of some 14V/100 ohm=140mA

So rate that winding 200/250mA and it will be fine.

So in a nutshell, that transformer specs should be:
* 315or 320VAC x 2 , whatever current take a typical 100W amp
* 6.3VAC , add up filaments and add a little extra
* 5VAC , whatever a 5AR4 takes.
* 39/40 VAC x 2 ... maybe taps from main +V winding or a separate one, your choice or what fits in window space.

It will definitely not cost 300 bucks but neither $29 ... flip a coin or take your chances.

If it were local I would try the EBay one, but not sure about freight, which must be substantial.

And Ad looks carefully worded to skip refund complaints.