Output transformer for a SF Basman 100

[diydidi]

Hi There.
I have this amp for repair. I'm convinced the OP transformer is shot. Can anyone tell me if a Twin reverb or Showman Output transformer will work in this amp??
Here is the schematic for what it's worth.

[Bruce / Mission Amps]

Looks like a good old, generic Twin Reverb OT clone should work OK.
Before you buy one though... convince us the OT is bad.....

[52 Bill]

Looks like a good old, generic Twin Reverb OT clone should work OK.
Before you buy one though... convince us the OT is bad.....

Will the amp be used for Bass or Guitar?

I believe that the original one has a larger core that any standard Twin transformer.

[Justin Thomas]

Hi,

I'd ask the same q as 52 Bill - bass or guitar? I've got two 100s in the house, and in both the OT is about the same size as the PT. I've also got a Fender-branded Twin OT lying around, 606-1-10/022889, and it's definitely smaller than the 100 OTs. Of course I understand cost/availability issues; I see no reason a Twin OT wouldn't work... But it's worth consideration. Bruce brings up a good point, too...

Justin

[diydidi]

It will be used for guitar mostly. Damn there aren't many online guys selling these op's. They don't ship to South Africa.
Maybe have to check ebay .........

[Bruce / Mission Amps]

It will be used for guitar mostly. Damn there aren't many online guys selling these op's. They don't ship to South Africa.
Maybe have to check ebay .........

I'll repeat my light hearted comment.... convince us the original OT is bad.... trust me, after MANY years of tech work, a bad OT is fairly rare.

[diydidi]

I'll repeat my light hearted comment.... convince us the original OT is bad.... trust me, after MANY years of tech work, a bad OT is fairly rare.

Well, if i apply a small voltage 3,15v to the sec 4 ohm tap, i get a reading of about 24Volts on the plate wires. Then from the CT to the plate wires, i measure 20V and 4v respectively. Weird. Thats a ratio of like 8 or something. A bit low?
Also used my ring tester on the primary windings wrt CT. The one side gives a very low Q as opposed to the other side.
The OP tranny put aside, the grids of the output valves are lous, nice and clean, while the speaker output is weak and distorted, low volume.

[Bruce / Mission Amps]

OK, I agree, the test sounds bad.
With an OT like that, 3.15vac on the secondary should have made closer to 70vac-75vac across the full primary side.
Just to be clear, can we assume that you did this with no tubes, the secondary wires disconnected from anything and the OT primary center tap removed from any filtering caps? etc.

Also, I understand the shipping costs are brutal but what is so hard about shipping an OT to South Africa?

The one from Mag-Com looks good and reasonably priced.
http://www.classictone.net/40-18012.html

[Alan0354]

There is no reason why it won't. The power amp are very similar. The OT of the Bassman 100 is bigger, more iron. But people use Showman for bass amp too. The OT in Twin/Showman is no small tx either. I just changed out the big OT in my Bassman 100 to a smaller one because I don't want to have all the headroom and all the dead weight. I have a perfectly good one here, but I am not going to do the shipping and all!!! It's better off to put the smaller one in if the person is using it for guitar anyway.