Wednesday, August 1, 2012

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)


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