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A place to discuss member's DIY audio projects & post pictures/schematics. NOTE: There is a limit of 2MB per attachment, and a maximum of 3 attachments per message. If you need to post more than 3 attachments, just add another message.
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Breadboard disaster?

October 9th, 2018, 10:53 pm

So I decided to breadboard the "Musicians Amplifier" because I had all the components.

https://www.google.com/url?sa=t&source= ... 4sADn0VS0Q

It's a very basic, "unimproved" Williamson circuit. I substituted 1625's and 12SN7's because I had the 1625's and they are 12v filaments. The original design calles for a Peerless S-265-Q. I have a pair of Pacific Transformer Peerless 16309 clones made for a Heathkit W5. My understanding is that they are electrically similar, certainly 10K P-P.

Everything was according to the schematic, within 10 percent. I got oscillation for days. And no, it wasn't phase because I reversed the OPT leads and the problem remained. I think I had the phase right to begin with.

So I'm asking the old hands--what happened? RF? Lousy breadboard wiring with no shielding? OPT not within spec? I'm just curious because I think it would sound lovely but I can't tell!

Re: Breadboard disaster?

October 10th, 2018, 11:28 am

NEVER MIND. I was standing in the shower this morning and realized I forgot to ground the OPT secondary. Back to the breadboard!

Re: Breadboard disaster?

October 10th, 2018, 11:31 am

That was a visual I didn't need... Yeah, floating the feedback connection can cause all sorts of problems ;)

Re: Breadboard disaster?

October 10th, 2018, 4:17 pm

It is sort of funny to think that you realized this in the shower and not while you were peering at the breadboard circuit!


Grover Gardner wrote:NEVER MIND. I was standing in the shower this morning and realized I forgot to ground the OPT secondary. Back to the breadboard!

Re: Breadboard disaster?

October 10th, 2018, 6:20 pm

Showers have a habit of washing away the clutter.

Re: Breadboard disaster?

October 11th, 2018, 10:26 pm

Well, it certainly did the trick this time. ;-) The shower--and grounding the output.

Re: Breadboard disaster?

October 11th, 2018, 10:27 pm

TubeDriver wrote:It is sort of funny to think that you realized this in the shower and not while you were peering at the breadboard circuit!


Grover Gardner wrote:NEVER MIND. I was standing in the shower this morning and realized I forgot to ground the OPT secondary. Back to the breadboard!


I think walking away from it for 12 hours helped. ;-)
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