Heathkit GR64 shortwave radio

[reeferman]

I am in need of the Stancor part number for the power transformer. It is printed on the the brown paper. I know the values (105, 12 VAC secondaries) but I just can't find a replacement. I inadvertently destroyed the number on my transformer.
thanks
Phil

[bob91343]

Heath part no. 54-155.

[reeferman]

Bob,
The heath part number draws nothing on the web. The Stancor number (PA-###) is what I need. Much better chance of finding it that way. So, if you ever have the cover of the radio off I would appreciate you taking a look.
Thanks
Phil

[bob91343]

I don't have the radio. I do have the manual and that's where I got the number.

You could rather easily, I think, reverse engineer the unit and come up with a ball park specification for the transformer.

Armed with the tube complement and a tube manual, you can estimate the current draw. Looking at the voltage ratings of the filter capacitors you can estimate the needed voltage.

[reeferman]

What I thought was the original transformer turns out not to be. The secondaries are listed on the schematic as 105 VAC and 12 VAC. The draw on the heater winding is 1 amp. Will get around to the 105 volt soon. C to C on the mounting holes are 2 13/16.
Thanks
Phil

[bob91343]

Those ratings were very common; every transformer catalog had something close. Just find an old catalog from Stancor, Thordarson, Merit, etc. and you will find almost the exact part.

Finding the hardware would be a different story. Perhaps you should rewind the transformer; what's wrong with it?

[dieseljeep]

Originally Posted by bob91343

Those ratings were very common; every transformer catalog had something close. Just find an old catalog from Stancor, Thordarson, Merit, etc. and you will find almost the exact part.

Finding the hardware would be a different story. Perhaps you should rewind the transformer; what's wrong with it?

I've been working on this stuff for quite awhile now and the ratings are a little strange. The schematic shows two secondary windings. One 12VAC winding for the heaters and one 105vac for the voltage doubler B+ source.
Not all that common. Heath carried this idea from their early days of using war surplus parts and had their transformers wound accordingly.

[bob91343]

You can use a transformer with a 6.3V winding and either retrofit different tubes (I don't recall the setup) or add a little 6.3V transformer to raise the voltage. There are many ways to do the job.

[dieseljeep]

Originally Posted by bob91343

You can use a transformer with a 6.3V winding and either retrofit different tubes (I don't recall the setup) or add a little 6.3V transformer to raise the voltage. There are many ways to do the job.

I replaced the transformer in a Heath AR2 receiver, with one from a scrap set. It looked almost identical to the original, but it had a 6 volt heater winding. I just replaced all the tubes with their 6 volt equivalents.
Heath used 12 volt tubes so they could use their beloved 12A6, as an audio output. They used that tube for everything, even as a rectifier.

[bob91343]

For many units, you don't have to replace the tubes, just rewire the heaters. I am not familiar with yours so I can't advise, but you seem to know enough to figure that out.

Meanwhile, while working on my HP651A output amplifier, my Tektronix 453 died. So now I have a bench full of projects.

[Electronic M]

Originally Posted by dieseljeep

I replaced the transformer in a Heath AR2 receiver, with one from a scrap set. It looked almost identical to the original, but it had a 6 volt heater winding. I just replaced all the tubes with their 6 volt equivalents.
Heath used 12 volt tubes so they could use their beloved 12A6, as an audio output. They used that tube for everything, even as a rectifier.

I've got two Heathkit A-7E monoblocks (the ones with the ultra linear screen taped output transformers and phono pre amp stage) which use two 12A6 tubes each as PP outputs. I'm listening to them now and it sounds awesome!

Always was curious why they used that type as an output, and not a 6V6 or some more common type for that, but I can't really complain that they did.

[dieseljeep]

Originally Posted by Electronic M

I've got two Heathkit A-7E monoblocks (the ones with the ultra linear screen taped output transformers and phono pre amp stage) which use two 12A6 tubes each as PP outputs. I'm listening to them now and it sounds awesome!

Always was curious why they used that type as an output, and not a 6V6 or some more common type for that, but I can't really complain that they did.

Those tubes a very touchy and pushed to their limits. I had problems with them shorting easily. I have several AR2's etc. I replaced the 12A6's with 12V6 car radio tubes. Plus they run hotter than a pistol, for tubes with a 150ma heater.

[reeferman]

Maybe 25-30 years ago the original went "poof" so I replaced it by literally stuffing two separate transformers inside the cabinet.

I'm now going thru the radio and replacing all wiring, re-stuffing the caps, etc. and thought it would be a good time to go back to one transformer if possible.
I found a small filament transformer at Radio Shack that I will mount under the chassis. Back to one transformer on top of the chassis gives it that uncluttered look.

I appreciate all that have taken time to respond. And if you ever run across a replacement transformer, please let me know.

Thanks
Phil

[dieseljeep]

Originally Posted by Electronic M

I've got two Heathkit A-7E monoblocks (the ones with the ultra linear screen taped output transformers and phono pre amp stage) which use two 12A6 tubes each as PP outputs. I'm listening to them now and it sounds awesome!

Always was curious why they used that type as an output, and not a 6V6 or some more common type for that, but I can't really complain that they did.

I was talking to a man that used to buy and sell war surplus electronics. When I inquired about the 12A6, he replied that they were sold for something like ten cents each, in quantity.
The 211's were sold for less than $1.00 each.

[Electronic M]

Originally Posted by dieseljeep

I was talking to a man that used to buy and sell war surplus electronics. When I inquired about the 12A6, he replied that they were sold for something like ten cents each, in quantity.
The 211's were sold for less than $1.00 each.

Is it really bad to operate my amps with the 12A6 tubes? I've put a lot of hours on those mono blocks and aside from some caps and a resistor they have been quite reliable....Not like I have or can afford getting two new pairs of output tubes for the next couple of months anyway....

What are 211's BTW?