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Power transformer for Harman Kardon A224

A

A Wallace

New Member
I was recently given a broken Harman Kardon A224. Supposedly the power transformer is broken. I am a complete newbie to tub amps. How can I get a parts/spec list? How can I get a service manual? Does anyone know the type of power transformer it uses?

AK
 
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A Wallace said:
I was recently given a broken Harman Kardon A224. Supposedly the power transformer is broken. I am a complete newbie to tub amps. How can I get a parts/spec list? How can I get a service manual? Does anyone know the type of power transformer it uses?

AK
Click to expand...
Lots of hits on Google.
 
I have a schematic, have the Sams folder too, most likely, but would have to find and scan it. First step would be to measure the transformer windings for continuity and ASSURE NO LEAKAGE to chassis, then plug it in with GZ34 removed and check voltages. And watch for signs of heating - it should not heat much with this reduced load. Transformer ratings would be in Sams folder, but size is an issue - integrated amps and receivers used low-profile transformer designs.
 
I would also make sure proof positive that the power transformer is bad before going any further especially if it is on hear say. Check the fuses if any!
 
Give it the sniff test too. If it smells like burnt roofing tar, that is not a good sign. You will also often see evidence of leakage from the transformer if it burned out.
 
I rebuilt one of those a while ago, was given to me, I'll check and see if I have the manual with it,,, In the meantime, you can pull the tubes, plug it into your DBT and test the PT windings... if it passes the sniff test or is dripping tar, that is....
 
An amazed newbie thanks you all.

Unfortunately, there is a puddle of roof tar on the bottom of the unit, so it does sound like the transformer is probably gone. Tom, I have a schematic, but I would love the SAMS folder (though I don't know what that is.) If you use dropbox, I could invite you to a link.

Thank you, thank you!

A
 
The tar doesn't *always* mean its bad, but its not a good sign. An ohm check for open coils or shorts to the chassis is the first step. If that passes, try to power it with all tubes removed. If it doesn't draw a lot of current or make a lot of heat, you might have something. Check output voltages and if that all comes out, the transformer is fine. They can sometimes get hot and survive, especially if its got a fuse. No fuse, well, who knows. The last dead transformer I ran into had an open primary and shorted secondaries, along with incinerated under-hood parts and no fuse in the unit. One simple fuse would have probably saved all of that.
 
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