Welcome to Tech Jeopardy, I'll Take Transformers for $50 Alex

[Jecarroll7]

I apologize for the sarcastic title, this month seems to be filled with transformer questions.

Working on an oddball 50's Grundig speaker amp/cab.

Power Transformer had a melt down, probably taken out by the 6X4 rectifier.

I clipped all wires out of the circuit and live tested the transformer, yea I know.

But it stayed up long enough for me to measure the only good section of the secondary from the CT to one end - 145VAC RMS - no load

Tubes are 1x6AN8A - triode/pentode, 2x6CZ5 Pentodes P/P I think - no schematic so writing one, 1x6x4 Full Wave Rect.

Should I shop for a ~130-0-130 power transformer (with a 6.3v filiment winding) to compensate for the no load measurement, or beef it up a bit?

[Jecarroll7]

Forgot to mention, thus far I haven't been able to cross the transformer (Better Coil & Transformer TR-31) or find any information on it.

[Enzo]

It was probably made to spec for Grundig, and probably not out of a catalog.

If the thing was smoking or bubbling or whatever it was doing as it failed, I wouldn't just assume it was unloaded. SHorted turns in the transformer constitute a load. It can be a substantial load. Your 145VAC could be corrent or it could be low. What voltage are the main filter caps? That would result in under 200v B+.


How about the model name of the grundig? hard to look up a schemtic without it.

[Jecarroll7]

Filters are 450 WV, sticker on the back says Mystic Maestro but no model numbers anywhere. I'm told there were remote speakers that attached to this cab for a 3D sound effect.

Sorry for the sideways photos.

[Jecarroll7]

Pentode tube specs say "typical" plate voltage of 350 in push pull configuration. 250 if single tube.

[nosaj]

Forgot to mention, thus far I haven't been able to cross the transformer (Better Coil & Transformer TR-31) or find any information on it.

What model of grundig? Any numbers on chassis?

Thanks,
nosaj

[52 Bill]

Grundig was manufactured in Germany, the transformer sounds like it was already replaced. Better Coil and Transformer was a replacement part company here in the US. I think that they were part of Triad Transformers or maybe they merged with them.

I'm with Enzo, if the filter caps are rated for 450v, the B+ would probably be somewhere just below that number.

[Jecarroll7]

No numbers on the chassis, inside cab is stamped Kontr.4, that's it.

[Jecarroll7]

It also has a better coil OT (TR-29) and the can multi-cap is USA. The amp looks original to me.

[g1]

I'm told there were remote speakers that attached to this cab for a 3D sound effect.

I believe what you have are in fact the remote speakers. Seems there were both powered and unpowered versions, and the powered versions amps could also be bypassed.
See post #2 here: Grundig Mystic Maestro ? PhonoLand.com
My opinions and hobbies: Grundig 5299

[Jecarroll7]

Update - Found the schematic. The amp is a Symphonic, model 1263, I was able to obtain a Photofact for it. Amp dates about '59.

The Symphonic cab pictured in the photofact is different, but it is definitely the same amp. US made out of New Brunswick NJ. Must have had a deal with Grundig back in the day.

How I found it - Interesting search tool at Tube Search

It allows you to search radios/amps by tube. Since the amp had an unusual pentode (6CZ5) it popped up quickly.

Good call Enzo, the correct transformer specs at 630VCT @.072A,

I have Stancore and Triad part numbers now, see if I can find one of these or something close.

G-one - Thanks, certainly possible, not a lot of information out there on mystic maestro, very rare. Check these out Majestic Mystic Maestro Speaker-P Grundig Radio-Vertrieb, RV

Thanks guys.