I'm looking for a good source of transformer codes.
Better put on your Sherlock hat, as nobody ever has
everything rolled up in one place.
The
6G13A Vibrasonic schematic lists the PT as part number 67233 (almost certainly an old Triad part number, but not one you'll find in a Triad catalog).
In Fender Transformer Charts (example
here), 45548 (or 45550) is listed as the output transformer for the 6G8 Twin. Checking the
6G8 Twin schematic, 45548 is indeed listed as the OT.
BTW: the first time I ever saw one of those charts was in Dave Funk's Tube Amp Workbook, but I don't know if someone published earlier than that. The chart I linked doesn't even have the Vibrasonic at all.
The code is 022897/606-2-36 and is stamped FENDER.
Possibly a Schumacher from the 36th week of 1962?
Schumacher, yes. But other 60's Fender amps seemed to transition to the "125P___" or "125A___" numbering system. Look for yourself at Fender schematics from the early-mid 60's.
The main question is, if it is a replacement, was it a direct replacement?
So early on, there seemed to be a link between the Vibrasonic and the Twin, even though the Vibrasonic only had a pair of 6L6 output tubes.
Maybe you never ran across the "
Vibrosonic Reverb" which was around a decade later. This was basically a silverface Twin Reverb, but with a different nameplate and a 15" speaker. I briefly had one a long while back.
If you look at the
schematic for that amp (silverface Twin Reverb/Vibrosonic Reverb), you see the part # 022897 cross-referenced with 125A30A and noted as for the Vibrosonic only.
Now all the "Twin Reverb" power transformers were called "125A29A" and referred to 4x 6L6 to 4Ω; the single Showman and Vibrasonic Reverb 125A30A would be 4x 6L6's to 8Ω. When the Vibrasonic was first introduced, it made sense to take the 45548 (4x 6L6:4Ω) and attached a single 8Ω speaker to reflect the appropriate load for 2x 6L6's.
The code is 022897/606-2-36 and is stamped FENDER.
...
Possibly a Schumacher from the 36th week of 1962?
Based on the evidence from the silverface Twin Reverb/Vibrasonic Reverb schematic and the date range given for the Vibrosonic Reverb on the Fender Amp Field Guide, I'd say the OT is 36th week of 19
72, and was ordered as a replacement for a damaged Vibrasonic OT. Unfortunately, when that repair was made, the model of the similar name was really 4x 6L6's:8Ω. As you suspected, this had to be an old repair.
So your output tubes probably see half the load they were intended to see when the amp was originally designed. Unless your speaker is a 16Ω JBL D-130 (the Field Guide suggests the stock speaker was a D-130F, but the prototype D-130 was most-commonly seen as a 16Ω speaker).
Other than impedance mismatch, the core is bigger to handle more power than the original 2x 6L6 unit, so it no doubt gets good, wide clean frequency response.
Whether to change the OT for the smaller version, or swap speakers to correct impedance mismatch and enjoy the bigger OT... well that's another call only your customer can make. Maybe present pros/cons for both this and the speaker repair issue & let him decide.
Topic: 1960's Fender Transformer codes (Read 7851 times)