Hi,
I believe I have a bad output transformer for a Stromberg Carlson AU-34 PA head. This amp uses a pair of 6L6GB tubes in a PP configuration.
I've tested the OT, left installed but with all tubes removed and the caps drained.
I get the following readings
Primary:
P1 to B+ = 112 ohms
P2 to B+ = 105.7 ohms
P1 to chassis - 22.5K ohms
P2 to Chassis - 22.9K ohms
CT to Chassis - 22.5K ohms
Secondary to Chassis:
Black/Ground = 0 ohms
Brown/4 ohm tap = 0 ohms
Red/8 ohm tap = 0 ohms
Orange/15 ohm tap = 1 ohm
Blk/yellow/250 ohm Tap = 10 ohms
Yellow/500 ohm Tap = 12.5 ohms
Primary to secondary:
All combination's of any primary to any secondary result in readings around 22K ohms.
I believe this is a dead OT with a short to the core the most likely problem. Assuming I'm not wrong and have not made some really obvious mistake here, I need to order a replacement OT.
I found a Hammond replacement that has the same set of secondary taps,
It's primary impedance is listed at 6,600CT
I looked at a GE Tube Essential Characteristics manual I have and 6L6GB has a rating for "Load for Rated Output, Ohms" at 5,000 Ohms.
Will anyone be able to tell me if this sounds correct or, if not, point me in the right direction to understand the procedure for calculating what the specs are for selecting a replacement transformer?
Thanks,
Chris
I believe I have a bad output transformer for a Stromberg Carlson AU-34 PA head. This amp uses a pair of 6L6GB tubes in a PP configuration.
I've tested the OT, left installed but with all tubes removed and the caps drained.
I get the following readings
Primary:
P1 to B+ = 112 ohms
P2 to B+ = 105.7 ohms
P1 to chassis - 22.5K ohms
P2 to Chassis - 22.9K ohms
CT to Chassis - 22.5K ohms
Secondary to Chassis:
Black/Ground = 0 ohms
Brown/4 ohm tap = 0 ohms
Red/8 ohm tap = 0 ohms
Orange/15 ohm tap = 1 ohm
Blk/yellow/250 ohm Tap = 10 ohms
Yellow/500 ohm Tap = 12.5 ohms
Primary to secondary:
All combination's of any primary to any secondary result in readings around 22K ohms.
I believe this is a dead OT with a short to the core the most likely problem. Assuming I'm not wrong and have not made some really obvious mistake here, I need to order a replacement OT.
I found a Hammond replacement that has the same set of secondary taps,
It's primary impedance is listed at 6,600CT
I looked at a GE Tube Essential Characteristics manual I have and 6L6GB has a rating for "Load for Rated Output, Ohms" at 5,000 Ohms.
Will anyone be able to tell me if this sounds correct or, if not, point me in the right direction to understand the procedure for calculating what the specs are for selecting a replacement transformer?
Thanks,
Chris