[sdiy] First Fire Jitters?

[mike ruberto]

Anthony

I'm going through that right now see the thread about Stupid PSU. I
just rebuilt a high current power supply and I'll be damned if I'm
gonna let my workmanship destroy the gear the PSU connects to.

Take every precaution you can think of and ask others for ideas for
more like I have.

Mike

On Feb 19, 2008 8:37 PM, anthony <aankrom at bluemarble.net> wrote:
> Does this just happen to me: you finish up a projct and it's ready to fire
> up for the first time, but you just can't do it? You go over everything and
> hem & haw, but you can't commit to finding out if it's a success or step 1
> in a troubleshooting regimen?
>
> Admittedly since this is a tube amp circuit. I should actually test the
> power supply and everything before trying it out and maybe that's the source
> of my jitters. But I can't even bring myself to seating the 5Y3GT in its
> socket and throwing juice at it. I even do it with a Variac (Powerstat,
> whatever...) real smoothlike. it all checked out fine before I gutted the
> radio chassis to make this amp: a nice AA764 Fender Champ copy, but with a
> Princeton "tone stack" (knob, whatever...). And I didn't mess with the power
> supply wires all that much, new resistors and caps in exactly the same place
> the old ones were. But I am using a higher screen voltage than the radio
> used, but it's within spec as far as I can see. My transformer doesn't put
> out as much voltage as the AA764 version did (and definitely not as much as
> the Bronco AB764 amp tranny did...)
>
> Part of my hesistance i think comes from my earlier plan to add two gain
> stages at the beginning of the amp using a 12AU7. I thought I'd go easy on
> the bias and since I only have a space for two knobs I thought I could use a
> row of switches (where the tuning indicator used to be) for different
> voicings and to turn each stage in or out of the signal path kind of like a
> Premier 88N. I have some nice C-H (what does that stand for? they made great
> switches anyways...) toggle switches - big & beefy - probably 3 amp or 5 amp
> jobs. And I certainly didn't want to go the way of the "Remaking of a Champ"
> article that I stumbled across. Killing the spirit of a genuine Fender Champ
> just because the guy couldn't think of an easy way to add two extra gain
> stages? A newer adaptation of that was a little better. But I have just a
> radio chassis with all the right sockts plus ONE more 9-pin mini. I'm not
> very experienced in desiging amps but I think the idea of adding a gain
> stage to a Champ would be a simple one: use a medium mu tube with a low
> plate voltage and modest bias. It'd be like putting a Tube Screamer in front
> of it maybe. But I digres...
>
> But I thought since I had the main Champ circuit wired amp (super simple
> even with needing to run two lengths of shielded cable across the chassis).
>
> Part of it could be that I only have the one 5Y3GT and it's a gorgeous
> Tung-Sol. I guess I don't have a spare 6V6GT if I should end up trashing
> that instead. I have enough twin triodes of the 12A-whatever-7 ilk to not
> worry there.
>
> I tried the speaker and the bakelite cabinet through my 50L6 amp and I was
> very impressed by the 4.5"x6.5" speaker. Very sensitive & loud. Definitely
> better with the back open.
>
> And one final thing. I don't know why I'm so hesitant to do it, but I need a
> handle for this thing and I haven't been able to bring myself to drill holes
> in the Bakelite for a leather suitcase-style handle. The Bakelite is in good
> shape, but not pristine. Should I just drill and not look back? I suppose
> I'm worried it'll crack the top, but I figured if I used big fender washers
> (no pun intended) on the bottom, I should be OK.
>
> So do youse guys get the jitters like I do?
>
> cheers,
> Anthony
>
>
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