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Heathkit console pulls come my way . . . plus questions for Heathkit experts

audiodon

audiodon

Addicted Member
Hi,
There'd been an ad on the Boston local craigslist a couple of weeks ago, for some Heathkit gear for too much money.
I'd watched it, jotted down the phone # and waited until the ad expired.
A few days later I called and the owner was ready to deal. So, deal we did.
Now I'd bought a couple of Heathkit W4Ms from Hatrack71 about six weeks ago and had arranged a trade with Chinacave.

They weren't cheap, but they're still in the fair-good deal category.

After powering the one one Chinacave sent me in trade up, I have to say that I was quite impressed.
The journey begins. Now of course, I already have two, though one's trashed and I didn't need any, but they sure seem nice.

I've been trying to pick up stuff that's clean and in good shape for restorations later.

These all resided in the same console, so they're very clean.

There are three amps:
1. A Heathkit W4 AM (hammertone color).
2. A HeathKit W4 B (gold)
3. A Heathkit AA-71

There was also an AA-141 preamp and a solid-state Heathkit tuner.

Does anyone know the difference between a W4M and a W4B, other than the power switch?
What's the difference between the W4M, and the AA-71?

These are going to be checked to see if they work and then shelved for later restoration.
 

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Saw the same ad Don but just too much scratch for me. I'm glad you ending up with them and look forward to your restore posts in the future..
 
Can't read the number on the W4-M... but the W4-B and AA-71 both have the exact same output transformer (on the right in the pics). IIRC, that transformer number is the same for all W4-M amps, too. With that, even if there were any minor differences in circuit configuration, they could all be made exactly the same, during restoration (use the same parts values in all of them). Same tubes, same transformers == same sound, as long as the caps and resistor values are the same too...

So... did someone originally have a 3-channel stereo (Klipsch-style) setup going on there with that console? Just wondering why there were three amps...

Regards,
Gordon.
 
The big difference in the W-4 series of amplifiers came between the W4-M, and the W4-AM. The original W3-M and W4-M amplifiers were rather unstable versions of the Williamson design, with necessitated circuit changes to enhance stability. These changes started with the W4-AM (and W3-AM). Changes made to any succeeding versions after that in the W-4 series were either cosmetic or convenience (i.e. the power switch) based changes. It wouldn't surprise me if the AA-71 was nothing more than a move to bring all of the model numbers within their audio equipment line into agreement by using the "AA" designation for all of them.

Dave
 
Yep. Just make sure when you update them, that you use the W4-AM circuit component values... or even better, do the mod that Bricktop did to the feedback circuit, that made them not only normally stable, but pretty much UNCONDITIONALLY stable- see here:

attachment.php


It's a pretty simple mod... some resistor changes to the front end, and resistor changes in the driver stage and output. Well worth-it, IMHO, to make it able to drive ANYTHING and still produce clean square waves (without ringing)!

Regards,
Gordon.
 
When I get to them, I will do this mod and wire all the same way.

This was a three-channel stereo setup from what I was told. All three amps were in the same console. Someone gutted the console when the movers had trouble lifting it. All associated hardware and connectors are lost though, due to the inexperience of the console gutter. Apparently there was a "center fill" channel associated with it and powered by one of the amps.
 
Tested most everything now.
Brought 'em up on a variac and took them up to full voltage.
AA-141 preamp - Five Daystrom by Mullard 12AX7s. Works. Something distorting inside. Tube fuzziness. Pots need a cleaning. Sounded Ok until about 100 volts.

Moved a few 6SN7s around to make two sets of matched pairs.
W4AM - Two short boy clear top 6SN7s, one a GT, one a GTB. Two TS 5881s and a 5V4 RCA. Works, sounds fine, trannies & choke don't get hot. Can cap gets hot though and leaked some goo out the bottom. No hum, no buzz.
W4B - Two Tung Sol 6SN7GTB, the very good looking ones. Two TS 5881s, Fat bottle 5V4. Works, sounds fine, trannies & choke don't get hot. No hum, no buzz.
AA71 - One CTS hytron 6SN7 and an RCA 6SN7 GTB, RCA 5V4. Works, sounds fine, GE 6L6GC outputs instead of Tung Sol 5881s. Trannies & choke don't get hot. No hum, no buzz.
Solid state tuna- didn't try that yet.

All in all, a good acquisition.
Now they'll get shelved until it's their turn on the bench.
 
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nice find....couldn't happen to a nicer guy.

I am about to tackle the beast I got from you a few months ago.....clear the decks!
 
That's such a beautiful receiver. I really liked it Dadbar. Super nice 340.
I just thought I wasn't going Scott . . . until that EL-34 integrated came my way.
The last impulse buy before these monoblocs was a Scott 272 that looked like it had been in a time capsule.
 
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