ANOTHER HAMMOND TRANSFORMER QUESTION

[nineno]

Hi, I was poking around eBay looking for tube parts and I came across the auction for this most intruiging product. I have essentially all the parts needed just sitting around in boxes, so for $50 i may as well build the amp, right?

THe one part I may be missing is the power transformer. I don't have a Hammond 272__, but I do have a Hammond 276X.

The specs are as follows:
Model: 276X
VA: 150
VAC: 115
Hz: 60

Sec
RMS: 320-0-320
DC: 150
Fil 1: 5 V@3 A ct
Fil2: 6.3 V@5 A ct

If anyone can suggest weather this will work, I would greatly appriate it, and I would be one step closer to making the purchase!

Thanks again!
drew*

[Shannon Parks]

THe one part I may be missing is the power transformer. I don't have a Hammond 272__, but I do have a Hammond 276X.

The specs are as follows:
Model: 276X
VA: 150
VAC: 115
Hz: 60

Sec
RMS: 320-0-320
DC: 150
Fil 1: 5 V@3 A ct
Fil2: 6.3 V@5 A ct

If anyone can suggest weather this will work, I would greatly appriate it, and I would be one step closer to making the purchase!

Sure. Use a 220ohm 10W power resistor instead of the stock 50ohms. That should get the B+ down. You can adjust the cathode circuits a little more conservatively, too. I wouldn't recommend using a tube rectifier, though, due to the overall VA rating of the transformer.

Shannon

[nineno]

Thanks for the advice on the B+ regulation. I think I can handle swapping out resistors.

As for the cathode circuits, I'll have to look into your suggestion of conservative modification.

I was drawn to this project because, frankly, the last several tube projects I've done have taken way too long, and the results iffy at best.

I want to build something that has the best potential of delivering high quality results.

I liked this kit because it seemed to me that I could put it together in "stock" form, get something functional, and then go back and tinker from there. Much more rewarding than my last SC-35 project that had a nightmare internal feedback problem.

As for the rectifier, I wouldn't plan to use a tube. This circuit is "developed" with a half-wave diode rectifier on the CT power transformer, right?

Thanks for the support, and appologies for anything "ignorant,"

drew*

[Shannon Parks]

I was drawn to this project because, frankly, the last several tube projects I've done have taken way too long, and the results iffy at best.

I want to build something that has the best potential of delivering high quality results.

I liked this kit because it seemed to me that I could put it together in "stock" form, get something functional, and then go back and tinker from there. Much more rewarding than my last SC-35 project that had a nightmare internal feedback problem.

Me too! I actually have a point-to-point prototype of the stereo 35. It is a mess of wires. The globs of solder on the socket pins threaten to short on each other. Filament lines criss-cross everything. Trying to do a 'star ground' for me didn't work out - I ended up soldering to the socket lugs.

The PCB prevents 90% of wiring errors, although one could still hook up the transformers incorrectly. The diagrams make this pretty painless though. And the silkscreen makes part placement too easy.

As for the rectifier, I wouldn't plan to use a tube. This circuit is "developed" with a half-wave diode rectifier on the CT power transformer, right?

Actually, it is full wave rectified. The circuit uses two UF4007 diodes which are pretty much equivalent to Hexfreds, and a whole lot cheaper. This is a real nice feature of the design I haven't really focused on. No big deal, tho, as any amp can use them. The main gripe the tube rectifier users have with diodes is the RF switching noise they create. Here's a little Usenet link to a post if anyone is interested:
http://groups.google.com/groups?q=uf400 ... .uk&rnum=1

Thanks for the support, and appologies for anything "ignorant,"

drew*

No apologies needed for that! ::wink:
It's a continual learning process.

Shannon