replacing transformer in MAG amp

Why are you wanting to replace the power transformer?

 

Maybe it's "bad", along with "bad" caps

Must be a rash of bad transformer, bad cap threads on the internet this week!

 

RECAP RECAP RECAP!

 

I love this cap...

 

I’ve never seen a schematic available publically for your amp.

Sometimes the Ashdown transformers have the top metal cap that holds it in place overtightened. This can lead to physical hum problems and even damage to the windings which can cause a short to the chassis.

If there is no obvious visible issue, disassembling the mount and inspecting the transformer and insulating pad may provide some insight. Sometimes the transformers can be repaired.

 

Definitely a DIY project, along with other "hold my beer, watch this" activities.

When working on any power transformer, it's a REALLY good idea to verify proper safety and isolation with a HI-POT test to be sure there are no safety issues that could hurt somebody down the road. This would be the classic poster-child for doing so.

 

I was suggesting a course of action to help determine what the issue may be, not who would undertake it.

I’m surprised by the number of Ashdown toriod related problems that keep coming up. There has been no indication if this is an older UK manufactured unit, which from what I’ve see have lower fairure rates, or a later Chinese one.

 

OP, Forgive my manners. I just noticed that you joined today so may I be the first to welcome you to Talk Bass.

That said, what’s wrong with your amp that leads you to believe that the power Toroid needs to be replaced.

 

Most likely custom.
Most likely not the problem.

Electronic repair is not the same as replacing parts.

 

Maybe Ashdown will sell you a replacement?

 

my ashdown is broke too. same model.. just kinda popped and very very low volume and then nothing..i have it for sale on reverb

 

If all the secondry windings are not working, then there is a good chance that the problem is in the primary. A fuse or varistor may have blown open on the primary side.

The first step that a tech would normally take would be to isolate the transformer. Disconnect the primary and secondary, using a variac and current limiter, take voltage readings at both the primary and secondary. This tests the transformer under no load. Without a schematic it will be difficult to know what wire colors go with which windings. The PCB has labels otherwise circuits would have to be traced at the connectors.

Ashdown amps tend to be very well fused on every power winding before rectifiers. A short in a circuit after the transformer would have blown one of these fuses.

 

Note that the wrapping material is an essential part of the safety system.

 

A simple resistance test will determine if the primary or secondary winding is open.

 

I can see this not ending well!!

 

I would hold back on dis-assembling anything until you narrow down exactly what the problem is. You're likely to create more problems and / or safety issues by blindly tearing into things.

The secondary is least likely to be open as it's usually wound with heavier gauge wire, and also cools better because it's the outside winding. Also, if it's center tapped, both windings and the center tap lead would have to be completely open from each other to yield absolutely no output on any of the secondary windings. This isn't very likely unless something catastrophic happened to the amp.

I would be looking at the primary winding continuity first.