diytube.com

Time to thin the heard,
I have for sale what looks like a home brew or maybe it was a kit 6V6 Push-Pull amplifier that someone never finished. It comes with 2 6V6's, 1 12SN7 and 1 5Y3 tube. There are also 3 potentiometers. I have no idea what tubes might have gone in the other 2 sockets. I also don't know who manufactured the transformers

Here is your chance to experiment building own your mono-block tube amp since you have pretty much all you need. Photo is below. There is some rust on the transformers as seen in the picture.

Price is $60.00 plus shipping.

Regards,
Sal Brisindi

That looks like a Heathkit A-7 or one of it's variants.

What's the number on the larger, rustier transformer?

The smaller audio transformer numbers are 51-21 and 138752, the larger power transformer are 54-25 and 138752

Sal Brisindi

Dag--So close! I'm looking for the 54-32 tranny for one of my Heathkit W5m monoblocks.

The 51- and 54- numbers indicate it's a heathkit. The 54s are usually power trannies, 51s are OPTs (usually) chokes are 46 numbered, generally.

I had thought it looked like a hacked A-7, but wasn't completely confident Yellow_Light_Colorz_PDT_02 IIRC they originally used 12A6s.



I've got a Grommes "Little Jewel" 6V6'er I was thinking of possibly putting up for adoption. No tubes (those on board when I got it were about as dead as I've ever seen that still-glowing tubes could be. They were basically "flatliners"...)

Option 2, and the most likely scenario) is to completely gut it and start fresh with all new everything except the chassis and iron.

/ed B in NH

I'll second the ID: Heath A-7. There were several versions - I have schematics for B, C, D, and E versions on my web page: http://www.audiophool.cjb.net/Audio.html The "138" indicates that Stancor made the transformers.

I've seen these with 12A6, 6V6, and 12V6. 6V6s need heaters connected in series - it has a 12V heater winding. As I recall, an additional 180 or maybe 270 Ohm resistor was added at the cathodes for 12V6 / 6V6 - the plate voltage is QUITE high.

Amp has been sold.

Well, it is the fifth anniversary of the last posting on the A-7 amp,

And yes inded, it was a Heath A-7, as shown here:




http://www.kta-hifi.net/projects/amp_page/a7amp/a7.htm

The Heathkit A-7 amplifier was produced over a relatively long span of time from about 1952 until the early 1960's. Four versions are known to exist including the A-7 thru A-7D. The smallish chassis was finished in a gray hammer tone enamel, and had a detachable front plate with the model designation and control markings screened on it. (This may have been to facilitate cabinet mounting. The chassis has no provisions for a bottom plate or cage. Some models have phono amplifiers and some do not. The tube complement is one 12SL7 (phono version only), one 12SQ7 utilized as a tone control amplifier, a 12SN7 as a voltage amplifier, and cathodyne phase inverter, and a pair of cathode biased 12A6/VT134A beam power pentodes in an ultra-linear connection. Output power is estimated at about 7 watts, and although the original output tubes are metal, the glass 12A6GT can be substituted. The transformers are reputedly of Chicago manufacture, but I had problems with the power transformer in the older of the two units.

Schematic can be found here (PDF format):

http://www.nostalgickitscentral.com/hea ... ma_a7e.pdf

Take note that the Heathkit A7 runs the 12A6S really hot, with a B+ of 390V

And in gif format:

http://www.audiophool.cjb.net/Schem_A/Heath_A7.gif


/ed B (looking for something useful to do with a gaggle of 12A6s I have laying around)

Wow, Ed... you sure dug up an old post of mine... :-)

I don't even remember who I sold it to...

Sal

Sal Brisindi wrote:...sure dug up an old post...

I saw it pop up, and nearly rushed to send you an "I'll take it!"

I suppose that I should give the A7 a topic of its own, off pre-bay

/ed B