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 Post subject: Breadboard disaster?
PostPosted: October 9th, 2018, 10:53 pm 
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Joined: June 4th, 2013, 2:39 pm
Posts: 133
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!


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 Post subject: Re: Breadboard disaster?
PostPosted: October 10th, 2018, 11:28 am 
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Joined: June 4th, 2013, 2:39 pm
Posts: 133
NEVER MIND. I was standing in the shower this morning and realized I forgot to ground the OPT secondary. Back to the breadboard!


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 Post subject: Re: Breadboard disaster?
PostPosted: October 10th, 2018, 11:31 am 
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Joined: February 28th, 2013, 10:38 am
Posts: 1007
That was a visual I didn't need... Yeah, floating the feedback connection can cause all sorts of problems ;)


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 Post subject: Re: Breadboard disaster?
PostPosted: October 10th, 2018, 4:17 pm 
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Joined: March 12th, 2013, 11:12 am
Posts: 460
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!


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 Post subject: Re: Breadboard disaster?
PostPosted: October 10th, 2018, 6:20 pm 
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Joined: February 28th, 2013, 3:31 pm
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Showers have a habit of washing away the clutter.


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 Post subject: Re: Breadboard disaster?
PostPosted: October 11th, 2018, 10:26 pm 
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Joined: June 4th, 2013, 2:39 pm
Posts: 133
Well, it certainly did the trick this time. ;-) The shower--and grounding the output.


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 Post subject: Re: Breadboard disaster?
PostPosted: October 11th, 2018, 10:27 pm 
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Joined: June 4th, 2013, 2:39 pm
Posts: 133
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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