Need Help with output transformers.

[sir_modulus]

I found an old RCA console.It ran two El34's and a 12AX7 and a 6V6. No I don't not have the record player, and there are two output trannies. Both are identical and have 2 copper wire leads on one side (0.8 Ohms (not 8 ohm)) and 3 on the other side (blue, brown, and red) . Measurements for second side are:
Blue and Brown = 311 Ohms
Blue and Red   = 311 Ohms
Red  and Brown = 80  Ohms  
The console ran some not too big 4 Ohm speakers. The Power Transformer is 600V CTed and has 30V and 40V coils also (note these are no load voltages. Probably will be more with load. There were no components inside, xcept pots (some dual ganged ones) and a Cap can (3 x 40uf @ 450 VDC and 1 x 80uf @ 450 VDC) and that at least is worth something.

Anyone know if these output trannies can be used? or for that fact, anything from this pile of junk?

P.S. It's toasted and most of the original components are gone, so don't suggest using it as an Amp. I've already smacked the guy who messed it up for some bloody stripboard.

Thanks,

[petemoore]

If you have iron tubes and frame, that's a nice start.
 Did you check out the amp forums links?
 The AX84 site has nice amps.
 I'd try to find a schematic for the amp 'as is' and try just rebuilding it to specs... :roll:  ..if..you can find the schem, this would be the easiest way.
 Have you tried searching for the schematic for this one, it's got to be around ... ... somewhere.
 I have a working model of the RCA Victor, ripped from it's console, rehoused it  in 3/4'' plywood box...great tube amp sound, old though, needs new sockets to be road worthy, I have it working well in it's 'static condition' [tubes just 'so' and the connections are made] and don't plan on moving it around...I use it for testing/playing.

[Peter Snowberg]

Those voltages will go way down with loads. I'm really wondering about the readings and the tube combination. Is that really an 2*EL34 + 12AX7 + 6V6? The combo of 2*EL34 and 6V6 is somewhat strange. If the final tube was something more like a 5AR4 or GZ34 things would make a little more sense. Could it be that somebody plugged a 6V6 into a 5AR4 socket and decided that the whole thing was busted because it didn't work?

I'm wondering if your meter is seeing some inductive kickback from the HV winding and telling you that the voltages of the LV windings are actually much higher than they actually are. The 30V winding might actually be a 5V winding for the rectifier while the 40V winding might in reality be the 6.3V winding for the EL34 and 12AX7 heaters.

Something is just hitting me oddly here... I'm assuming that the is 6V6 should be a rectifier, but with two output trannies I assume this was a stereo player too. That would mean that the EL34s were used in single ended mode. I don't know what to make of the trannies in this case unless they were some kind of universal unit and the blue lead was not used. Hammond 125 series trannies can be used this way. It's so hard to tell much from the DC resistance. The low brown to red resistance with equal red-blue and brown-blue doesn't seem right for some reason.

There are ways to determine the primary impedance of those outputs by injecting 1V into the 4 ohm side and measuring what you get out the primary, but if they were made for EL34s, just use EL34s with them. The only real question is mono or stereo? If it was stereo, the trannies were single ended and wired one per EL34. If it was mono, the trannies may have been used in parallel with the EL34s being push-pull. The input jack might tell you which it was.

Figure out the transformers, use some decent speakers, and you'll have a nice little amp on your hands with some really respectable volume.

Good luck,
-Peter

[sir_modulus]

Well.... I reread the box, and looked at the tube carefully. It says 6V6 on the tube sticker, but the leads from the PT go t it and two leads come off (B+ I guess) so it's a rectifier. The tube is unmakred and it's blown. The amp is ripped apart by someone who thought it was broken and no components are in place. They came in a small bag attached to the thing. Now this inductive kickback...how do you mesure the actual voltage without this kickback? The output trannies are connected as so. the outputs of the trannies have two leads per tran. Lead A on one and Lead A on the other are hooked together and go to one side of the speaker set. Lead B from one of them is unconnected, while Lead B from the other one goes to the other side of the speaker set.

[Peter Snowberg]

How interesting. Can you draw up a diagram?

The way to measure without the inductive kickback is to load the transformer down a bit. Attach a big load to the winding that's showing 40V and I'll bet it will drop right down to something more like 7V. A 12V car headlight works very well as a load. Are you 100% sure you have the primary connected correctly?

Take care,
-Peter

[petemoore]

I do not remember seeing a 6V6 in my RCA.
 I could disassemble the amp, and take some pics if you think that would help....assuming it IS the same amp you have most of.
 I'm good for sending Pics, but can't seem to post them.

[sir_modulus]

Wow that would be great pete. Can you take some general pics, and just sketch out (if possible) how the ouput goes (very generally, like Out Tube #1 goes to such and such lead of transform...etc...) That would be really great. Thnx

[Lonestarjohnny]

Peter, It's not so strange to see a 6V6 inside a radio or tube amp 35 or 40 years ago, when it is just one 6V6 you should look closer at the circuit, I bet the 6V6 was a reverb driver tube.
JD

[sir_modulus]

Whoops sorry forgot to tell you which tube!(read Above post by me about the crap sticker) The amp has two EL84's, a 12AX7A, and a 5Y3GT rectifier  (all new). No 6V6 (why didn't i look earlier! The tube was marked on the base)