Old Ironsides - Transformers

So here are the transformers that came with the chassis...old iron for this Old Ironsides. 

First the output transformer, made by Stancor, Part A-3311. Conveniently, I found an old Stancor catalog from 1961-1962 here in PDF format (thank you internet!) that lists the following specs for it:

Application: 10KΩ CT (center tapped) to 500Ω /15Ω /8Ω /4Ω 

Max primary DC: 70mA

Audio watts: 25W

There are 5 wires coming out of this output transformer:

• Black: output jack negative (sleeve)
• Dark brown: output jack, positive (tip)
• 3 other leads were tied off (i.e, not connected to anything):
• Yellow
• Red/Orange
• Light brown

What the hell do they mean? Well, this web site has a convenient guide to standard output transformer wiring; in this case, it's a"push-pull" transformer, so it should follow:

 Plate lead (pri.) -------------- blue (start)
 B+ (power supply) lead --------- red (center tap)
 Plate lead (pri.) -------------- brown (finish)
 speaker (typ. +) (sec.) -------- green (or yellow)
 speaker return (sec.) ---------- black

Next, the power transformer, another Stancor model, Part number P-6012. Again, thanks to that old Stancor catalog from 1961-1962 here in PDF format, here's what I learned:

Stancor P-6012: 

Plate supply: 350-0-350 AC Volts, DC 90 mA

Rectifier filament: 5.0V CT @ 3A

Other windings: 6.3VCT @ 3.5A

Here's a picture of the wires coming out of it. 

What the hell do they mean? Well, this web site has a convenient guide to standard power transformer wiring:

Primary leads -------------- black

   (if tapped)

     Common ----------------- black

     Tap -------------------- black/yellow

     End -------------------- black/red

 High voltage secondary ----- red

     Center tap ------------- red/yellow

 Rectifier filament winding - yellow

     Center tap ------------- yellow/blue

 Filament winding No. 1 ----- green

     Center tap ------------- green/yellow

 Filament winding No. 2 ----- brown

     Center tap ------------- brown/yellow

 Filament winding No. 3 ----- slate

     Center tap ------------- slate/yellow

Here's what I identified, and how it's currently wired:

• 2 black: connected to 120VAC (one side to power switch, one side directly to AC power wire) - this appears correct.
• 3 dark green (black?), currently wired as follows:
• 1 to ground
• 1 to 6V6 pin 2
• 1 to 6V6 pin 7
• 2 brown, as follows (on closer inspection, and scraping down insulation anti-mold coating, it's clear these are RED):
• 1 to rectifier pin 4
• 1 to rectifier pin 6
• 3 yellow, as follows:
• 1 to rectifier pin 2
• 1 to rectifier pin 8
• 1 to ground
• 1 red: wired to ground (on closer inspection, I can see this has tiny yellow dashes on it, indicating red-yellow)

The starting point - Old Ironsides...

So I'm starting this journey (again) with an old amp I started building from spare parts, sometime in the late 1990's, until about the early 2000's. I'm pretty sure it was based on a vintage Fender Deluxe, although I wish I could remember which schematic version. I located a schematic in my copy of Aspen Pittman's excellent reference The Tube Amp Book, and started wiring it point to point from there.

Here's a picture of where I'm starting from:




The thing needs a name...I think Old Ironsides is nice. Here's a shot from the front panel, input jack on left, power switch on right. I don't remember what the 3 controls are for, I'll dig around and figure it out.



Another shot from the top. I used a little copper plate to enable me to mount the jacks for the 12AX7s.




From what I remember last working on it, I added the tubes, fired it up with the guitar plugged in, but got no sound. I think the rectifier did light up though, that's a good thing I think.

So now back to it.

Some the parts sources for this franken-amp:

Chassis and transformers: from Angela Instruments, from the mid to late 1990's, when they used to have a cool old catalog printed in newsprint, sort of retro-looking, lots of irreverant commentary. I bought this around the same time I bought a Sovtek Mig50 from them, not long after they came out. They were so cheap, I think I paid $200 or so for it new. It actually had a pretty good clean fender sound, good iron but parts were kind of crappy: loose knobs, etc.

Small parts: Antique Electronic Supply, also Mouser, and Radio Shack. Some new, some used...including some crazy surplus shit I found in the trash near the facilities department at LMU in the early to mid 1990's...they were throwing out all of these cool panels and things with banana jacks, and huge bags of electrolytic caps.