Silvertone 1484 Output Transformer Troubleshooting

[Spock]

Hi folks. I'm working on repairing a Silvertone 1484 twin twelve. Quick backstory: this beast had a low and distorted output volume when I received it. Tubes were good. Turned out it had a low B+. I replaced all the original (now leaky) electrolytics, which brought the B+ back to normal. I also added a three-prong power cord with the earth lug grounded to the chassis. However I'm still getting low output volume at the speaker. I've turned my attention to the output transformer. From what I've read, it looks like the OT's in these things are somewhat notorious for failing.

Here's my test setup: The amp is OFF and unplugged. To completely isolate and test the OT by itself, I removed both power tubes and desoldered the primary center tap connection. I have my signal generator across the primary. With the speaker load disconnected, I have my AC voltmeter across the secondary. Although not shown on the schematic (attached), the 1484 OT has a 4ohm tap and an 8ohm tap, but only uses the 4ohm tap to run two parallel 8ohm speakers. With 7.35V AC (at 1kHz) on the primary, I'm getting 197.4mV AC on the 8ohm tap and 162.9mV on the 4ohm tap. For the 4ohm tap, that's a 45:1 transformer ratio. Anyone have any thoughts on if this OT looks good or bad? Is this the correct load for a 6L6 push/pull? Anyone with any insight on these 1484 transformers?

I've attached the 1484 schematic.

Sorry for the long read. I really appreciate any help, cheers!

[Enzo]

Your turns ratio will not have changed. Even if one turn shorted, you'd never see the difference. What you need to do is go to RG's Geofex web site and find the transformer tester. it is very simple, basically a battery and a neon bulb. it will identify if any windings are shorted. You can measure for open windings with your ohm meter. Open windings is what I usually find when these fail.


Meanwhile isolate the problem. Transformers are low on my list. Do both sides of the push pull circuit get signal? Is there B+ on both plates of the phase inverter? There are voltage readings on the schematic, how do your match up?