diy guitar tube amp help.

[EC8010]

The HP200B isn't a function generator, it's a Wien bridge oscillator. Big difference.

[Dr. Photon]

I wasn't calling the HP a function generator. I was just saying that some sort of generator is useful on the bench. I use a HP3312A function generator, but I mostly use it to generate audio frequency sine waves when I'm messing around with audio circuits (and I don't play with square wave response on guitar amps).

I was just aying that if that HP oscilator worked and had adjustable output level and could be moved accross most of the audio band it would serve just fine for guiitar amp debugging purposes and be a very useful tool.

[Tekko]

Yup! I want a cro and a signal generator.

[EC8010]

Originally posted by Dr. Photon
I was just saying that if that HP oscillator worked and had adjustable output level and could be moved accross most of the audio band it would serve just fine for guitar amp debugging purposes and be a very useful tool.

Absolutely. Couldn't agree more.

[Newpaltzwonder]

I looked around this morning to see if I could find out the value of this but no luck. The closest value I could find was on ebay and that was under $30.

Besides, I'm looking at the value for myself....I tinker with simple op amps and that's about it. I still have so much to learn it's crazy. I still get caught up in schematics and sometimes look for pictures of the boards to go by.

I also sat down and cleaned out the insides a bit. It had some foam packing material in it!!!!! I also cleaned off the tubes and even the 3w light bulb. Then I took some pictures and tested it out.

I hooked up a spare speaker to the front connectors and fired it up. I works just fine. The dials are good, no pops or cracks when I turn them. So this baby works just fine.

Here is a pick of the bottom with the cover off.

[Newpaltzwonder]

Here are some close ups on the bottom. This is the left side when looking down on it.

[Newpaltzwonder]

Ok The other side.


I know that I could go out and buy the transformers for my DIY, but that is hard when you are on the "college budget" and you try to use what you find.

[tubelab.com]

I have dissasembled several HP oscillators that were slightly newer than the one you describe. I have used the power transformers and filter chokes for guitar amps. The power transformer in these units is good for a 15 to 30 watt guitar amp. The 6k6 tubes could also be used in a guitar amp. Find a schematic that uses 6V6's.
The output transformer in this unit has a 600 ohm secondary, so it is probably useless for driving a speaker. It might be possible to take the output transformer apart and rewind the secondary, but due to its age, this is not likely. A new output transformer will be needed. Find a transformer made for two 6V6 tubes in push pull. About 6000 ohms centertapped. I used Schumaker transformers that I got cheap on Ebay.
As stated earlier I wouldn't trust the capacitors and resistors because of their age, but these are usually pretty cheap.
If budget is tight, and you are careful you can re-use the chassis and tube sockets. Since the sockets are all 8 pin octal, and most guitar amp schematics use 12AX7's for preamp tubes, you will have to find an octal preamp tube. I have used a 6SL7 for this purpose.

[bear]

Oddly, I have several of these here.

I looked at them and said to myself:

- great air variable cap, suitable for medium power RF, yummy!
- (iirc) nice reduction drive too... or was it a worm drive to the cap?
- single ended broadband output xfrmr that is gonna be good out to 20kHz or better... (ok so they used feedback and it was only sinewaves)
- power transformer (ho hum)
- real tubes!

Might make a decent amp, but as noted, it's a 600 ohm output in all likelyhood.

BUT, maybe not - gotta measure.

Anyhow I kept a few of them here...

_-_-bear

PS. think I'd prefer a PP output guitar amp... not sure though.

[Newpaltzwonder]

Thanks for your responses!!!!

I think for the moment, I 'm going to hold off on the idea involving disassembling and start learning how to use it the way it is intended for.

Thanks a lot !!!!!!

Newpaltzwonder