$5 SE amp... but is it fried?!

SHiFTY · 15th January 2004, 07:39 AM

Well I picked up an ancient Sony reel to reel recorder for $5 from a junk store. It was a pretty solidly made stereo beasty, but in pretty bad exterior condition.

Anyway I opened it up, turns out it has a pretty sweet amp in it, 6AQ5 in SEP in their own amp chassis, which can be totally removed as a self contained unit (with cool retro mesh!)

The power transformer is beefy too, and nicely potted (black box in the top right of the photo.)

Also in it was a telefunken ECC83... made by Mullard!? Weird...

Anyway it seems that the output trannies might be fubared, one the primary resistance measures 450 ohm, the other 1300 ohm. Not shorted to ground though.

Any ideas? Should two identical transformers vary this much?

Cheers
Henry

Frank Berry · 15th January 2004, 10:32 AM

The primary resistances of the two transformers should be a closer match. Did you remove the 6AQ5 tubes before measuring?
Do the trannies have a screen tap?

dhaen · 15th January 2004, 12:31 PM

Measuring inductors with an autoranging meter can give misleading results.
If you use this kind of meter, I suggest repeating the test with the secondaries loaded or shorted.

battradio · 18th January 2004, 03:13 PM

Noticed A black spot on one of the transformers ,is that the one that reads low .

15th January 2004, 10:32 AM	#2
Frank Berry diyAudio Member Join Date: Sep 2003 Location: Midland, Michigan	The primary resistances of the two transformers should be a closer match. Did you remove the 6AQ5 tubes before measuring? Do the trannies have a screen tap? __________________ Frank

18th January 2004, 03:13 PM	#4
battradio diyAudio Member Join Date: Dec 2003 Location: near ST. Louis MO.	Noticed A black spot on one of the transformers ,is that the one that reads low . __________________ To be better one must be different ,but to be different is not necessarily better .

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15th January 2004, 12:31 PM	#3
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	Measuring inductors with an autoranging meter can give misleading results. If you use this kind of meter, I suggest repeating the test with the secondaries loaded or shorted.