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Vintage threads from the first ten years

Odd Schematic needed

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2/22/2000 5:09 PM
Rebel420	Odd Schematic needed I desperately need the schematics for an old Davis PA head, we are talking 1950's? 1960's? vintage, the model is a model 10, has a single preamp tube, (2) 6bq5 power tubes, and a 6ca4 recto. any help would be appreciated! (some parts are missing, and others are fried, so tracing it out myself would be impossible now.

2/22/2000 7:19 PM
Brad	Boy....and I thought I dug up some weird stuff. Good luck to ya. Brad

2/22/2000 8:18 PM
pumpstein	you'll need the model #, but try this: http://www.hwsams.com/photofacts.html

2/22/2000 9:21 PM

Heh, cant find it on their site, plus evne downloaded the full index, just in case.. nothing. I"m not trying to rebuild it, but IIRC, it did something weird using the 2el84's (i.e) no phase splitter tube, but I KNOW it's not running SE. the odd thing was the PT taps, you ahve 2 hv taps and 2 filament taps to the rectifier, you hve 2 tps going to ground, and an extra tap going to the cathodes of the 2 power tubes.. mind you this is a CATHODE biased amp, and you had a 220ohm resistor parallel with a 33uF cap on the cathodes). the B+ on the 6ca4 is not riding on the filament taps as with something like a 5y3, I havent taken the time to ohm out the pt, but this is like nothng i've ever seen.

2/23/2000 6:10 AM
Marc	Rebel: Check out the dusty files at triode electronics. There is a P-P amp with no PI using EL84's. It's a 6 watt hifi something or other Or you could email Bob Pilcher RPilc99206@aol.com and see if he has the schematic on file. I got an oddball PA schematic from him for $11 pp. that was very helpful since it had a strange tube controlled bias circuit. good luck Marc

2/25/2000 11:16 PM

Hi Reb & All:

Well, I've got the Davis model 106 here in EX+ condition, still never plugged it in, or even opened it (until now). Just pulled the tubes years ago, they were good RCA's.

Could be the same thing from a later decade, mine has 1973 date code on the can cap which looks original and overall seems like a period correct assembly for 1973. Probably one of the later examples of true point-to-point wiring, no component board of any type, actually the only kind of wiring I was *formally* trained to work on, so you know how long its been since I had electronics classes ;-)

;-)

Has knobs for MIC, MUSIC, and TONE, plus power switch and screw-on mic connector on front.

Rear panel has fuse, 2-prong unpolarized line cord, 8 screw terminals L to R: C, 4, 8, 16, 25V, 70V, and a pair for Low Z in. Then two RCA jacks; Booster Out, and Phono In.

Lay down Power xfmr about the size of a Champ next to the 6CA4, then OPT bigger than a 125E vertical mounted by the 6BQ5s, then a 40/40/30@450 can cap by the 6EU7 which has a conical press-on shield.

I always thought this would be worth study but I usually prefer to convert single-end PA's for guitar, and this seemed too clean to change anything so far.

I will trace it out for you, that will be easy, getting it into a graphics file will take time though . . . what software would you suggest for quick drawing or what file type, I tend to prefer JPG.

Until then I've just taken a couple fuzzy digital pictures, I'll try to post them and let you know the URL before too long.

Hope this helps,
Mike

2/26/2000 7:35 AM

that's the EXACT amp I have... quite a beefy OT on that baby... I"m going to use the iron to build either a vox clone or a low-power plexi clone (similar to the AX84's November, but more voiced like a plexi than a metal panel marshall) thanx for your help on this, I had to rob some parts from this, so tracing it is out of the question... while you are tracing, if you can get the voltages off of the PT leads that woudl be cool as well (since you can put yours under an actual load, and mine, well.. I can't yet... thanx

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