'66 Ampeg Reverbrocket Transformers

[KingCameron]

Does anyone have a sugestion for transformers on a 1966 Ampeg Reverbrocket GS12-R?

I am most likely going to order the Mercury Magnetics trannies, but am open to discussion.

[MWJB]

Wouldn't that be an RB or RT? By '64 they had the RB, SS rectified.

Mine put out around 350-370vdc on the plates, depending on tubes/bias, to ground...so what 270-0-270 or 280-0-280VAC region, 130mA-ish? 4A 6.3VAC secondary.

BF Deluxe OT would work OK with 7591a, or even 6L6 if necessary.

[Bruce / Mission Amps]

I just had another Ampeg G12R in for a serious distortion problem that turned out to be the OT again.
A blown OT is not the first time I've replaced an OT in one of these amps, I've done quite a few, so keep that in mind.

I always use a reissue standard Deluxe Reverb OT from MOJO and they sound really good with the stock tubes.
The PT is a different matter though and I have not had the occasion to replace one in those amps.

[telemoxy]

Ampeg Replaement Transformers

Does anyone have a sugestion for transformers on a 1966 Ampeg Reverbrocket GS12-R?

I am most likely going to order the Mercury Magnetics trannies, but am open to discussion.

You could also call Hammond and ask them for their recommendation.

[KingCameron]

Mercury Mag Tone Clone Trannies

I just had another Ampeg G12R in for a serious distortion problem that turned out to be the OT again.
A blown OT is not the first time I've replaced an OT in one of these amps, I've done quite a few, so keep that in mind.

I always use a reissue standard Deluxe Reverb OT from MOJO and they sound really good with the stock tubes.
The PT is a different matter though and I have not had the occasion to replace one in those amps.

Hey Bruce,
I went ahead with a set of Mercury Magnetics Tone Clone Trannies. The PT wired in nicely using my vintage endbells. The Ot is a nice fit too...Not sure if Mercury is the best, but I know the plug-and-play well.

Now the only problem is the amp is squealing like pissed witch, right when I turn her on....still working on that...any ideas?

Thanks,
Cameron

[dwhutchens]

Now the only problem is the amp is squealing like pissed witch, right when I turn her on....still working on that...any ideas?

Maybe try switching the phase of the primarys on the output tubes or the secondaries on the speaker.

David

[Bruce / Mission Amps]

Probably an OT phase reversal as mentioned above... but I wouldn't reverse the secondary leads on these... look again at the way the OT is grounded at the main filter cap with respect to the true chassis ground.
Just try reversing the leads on the power tube sockets first and see what happens.

[KingCameron]

Success!

Probably an OT phase reversal as mentioned above... but I wouldn't reverse the secondary leads on these... look again at the way the OT is grounded at the main filter cap with respect to the true chassis ground.
Just try reversing the leads on the power tube sockets first and see what happens.

Yup. A quick switch of the the OT primaries on the power tubes and the witch is tamed...

Attached is my initial test data...
The amp is running a tad hot. The MM PT is kicking out 291.5VAC to the diodes and 7.2VAC to the heaters. I am getting 388VDC, on A, where I need 365VDC...
I'll probably try to tame down the B, C, F power supply stages by fiddling with the power supply resistors.