Not Working: Ampeg pf-50t Transformer Balanced Out

[stephenleejp]

Anyone else have this problem and find a fix?

preamp out and speaker out both work and sound amazing. I purchased the amp with the Transformer out not working. All I get is a loud hum/buzz, regardless if I’m plugged into the input or not.

I took it to my local repair shop and they said everything was working.

Cheers,

 

[Passinwind]

Cabling? Are you using a true balanced system, or ?

 

[stephenleejp]

Cabling? Are you using a true balanced system, or ?

I’ve swapped out between two different balanced xlr’s I own. If the labeling is wrong or I’m mistaken I doubt both cables would be a unbalanced.

I’m trying to swing by the music store today to try an adapter or two to see if that works or if I can get a different error, maybe.

Also, both of my xlr cables work with the preamp output.

 

[Passinwind]

I’ve swapped out between two different balanced xlr’s I own. If the labeling is wrong or I’m mistaken I doubt both cables would be a unbalanced.

I’m trying to swing by the music store today to try an adapter or two to see if that works or if I can get a different error, maybe.

Also, both of my xlr cables work with the preamp output.

What's the downstream piece? Interface, mixer, or...?

 

[stephenleejp]

Passive J > pf50 > xformer out > xlr > focusrite Scarlett 2i2 (usb powered) > headphone out > Blue powered headphones

*phatom disengaged

thank you, btw

 

[Passinwind]

Passive J > pf50 > xformer out > xlr > focusrite Scarlett 2i2 (usb powered) > headphone out > Blue powered headphones

*phatom disengaged

thank you, btw

Your plan for trying adapters sounds solid, I'd be fairly surprised if cabling isn't at least partly to blame here.

 

[stephenleejp]

Your plan for trying adapters sounds solid, I'd be fairly surprised if cabling isn't at least partly to blame here.

That would be a wonderful and cheap problem that I’d like to have.

 

[Old Garage-Bander]

Anyone else have this problem and find a fix?

preamp out and speaker out both work and sound amazing. I purchased the amp with the Transformer out not working. All I get is a loud hum/buzz, regardless if I’m plugged into the input or not.

I took it to my local repair shop and they said everything was working.

Cheers,

Do you have a multimeter, like for checking resistance? If so maybe we could check a couple of easy things?

 

[Old Garage-Bander]

That would be a wonderful and cheap problem that I’d like to have.

I'm curious about what adapters you have in mind to try? Wouldn't be so cheap if you got the wrong things.

 

[Wasnex]

Sounds like you need to take the amp in for repair.

The labeling is not accurate. It's not a transformer driven output. It's an output that is derived from the transformer.

Here is the block diagram.

The little triangles in the signal path typically indicate solid state amplification stages.

Most likely a component has failed in the Transformer Balanced Line Out signal path.

 

[stephenleejp]

Do you have a multimeter, like for checking resistance? If so maybe we could check a couple of easy things?

I think I’ve got a multimeter buried somewhere, I’ll have to get it out.

 

[stephenleejp]

Sounds like you need to take the amp in for repair.

The labeling is not accurate. It's not a transformer driven output. It's an output that is derived from the transformer.

Here is the block diagram.
View attachment 4815890

The little triangles in the signal path typically indicate solid state amplification stages.

Most likely a component has failed in the Transformer Balanced Line Out signal path.

Where is the labeling wrong, on the back of the pf50 or in that diagram?

 

[Old Garage-Bander]

Sounds like you need to take the amp in for repair.

The labeling is not accurate. It's not a transformer driven output. It's an output that is derived from the transformer.

Here is the block diagram.
View attachment 4815890

The little triangles in the signal path typically indicate solid state amplification stages.

Most likely a component has failed in the Transformer Balanced Line Out signal path.

Oh yeah! Op amps! Active balanced output! Now we know why the transformer output isn't working like a transformer output.

 

[Wasnex]

Where is the labeling wrong, on the back of the pf50 or in that diagram?

Both normally imply a transformer driven circuit. But the circuit is solid state. So IMHO both are misleading.

 

[Old Garage-Bander]

Where is the labeling wrong, on the back of the pf50 or in that diagram?

Well "Transformer Output" it ain't. That's for danged sure.

When you took it to the repair guy, did you specifically mention the problem at the XLR output? Did they write it down so they wouldn't forget the nature of the complaint? After they said "everything" was OK, did you go back to them to say it wasn't? Did they show you the XLR worked on their bench?

Before you spend a lot of money on new cables, adapters, and whatnot, you need to really get the amp's condition confirmed. Start with asking the original tech why they OK'd "everything" when everything doesn't seem to be OK.
Then you may need to get a second opinion.

 

[Old Garage-Bander]

I think I’ve got a multimeter buried somewhere, I’ll have to get it out.

Not much help, now that we know we're not dealing with a transformer. Sorry.

 

[Old Garage-Bander]

Both normally imply a transformer driven circuit. But the circuit is solid state. So IMHO both are misleading.

Yup! "Balanced Output" would be the correct labeling and cover transformers as well as actives.

 

[Old Garage-Bander]

Sounds like you need to take the amp in for repair.

The labeling is not accurate. It's not a transformer driven output. It's an output that is derived from the transformer.

Here is the block diagram.
View attachment 4815890

The little triangles in the signal path typically indicate solid state amplification stages.

Most likely a component has failed in the Transformer Balanced Line Out signal path.

Wonder if by "Transformer Output" they mean that the signal came from the transformer. Still, goes through an op amp before you see it though, so yeah, misleading.

 

[stephenleejp]

Ya, I’m planning on calling or coming through again to go over the repair. The work order that the tech wrote out lists my problem pretty specifically. There still may be some miscommunication, which is what I’m hoping it is.

 

[Old Garage-Bander]

Just a long shot... Have you tried using the transformer output XLR to see if the problem is the same with an 8 Ohm cab connected and switched to 8 Ohms, AND then with 4 Ohms worth of cab and switched to 4 Ohms?