help repairing Hafler xl280

[Truckee_Tango]

Hi Chris,

Good ideas. Any suggestions for transformer rewinders, or how to find available "pulls"?

Also, depending on the cost of a pull or rewinding, what do you think about getting a new transformer or using the 65v windings of this one to build a more modern amp using the nice chassis and heatsinks of this unit. The bones seem pretty good. I have all the pieces for a Pass A-40 I could put in it, and although a pretty old design, it is a good one, and then there is the Audio Electronics pudate of that unit as a possibility.

Marshall

[anatech]

Hi Marshall,
Since I am in Canada, I am not familiar with American Vendors. I'm sure there are some members who can direct you better with regard to repairing or getting a new transformer.

That was a pretty good amp, and everyone has an opinion. My normal response would be to repair it. The transformer needs work regardless.

-Chris

[Truckee_Tango]

I guess my worry is that if I spend big $$$ repairing/replacing the transformer, I may just find that the channel which was not working will still be non-working because of a bad FET. If it is one or both of the matched input FETs, they may be impossible or very expensive to replace. Output FETs may not be quite as bad, but still a problem.

Maybe a solution would be to use a small pair of auxiliary transformers wired in series with the original transformers working secondary windings in order to get the desired 75vac for the input boards, and then test for problems in the input board by checking voltages and signal tracing? Not an easy job, but....

Marshall

[anatech]

Hi Marshall,
I'm just saying that you need to fix th transformer anyway if you want to use it for anything. It's possible some other windings are damaged and can fail later.

The rest of the circuit is really not a consideration. If it can be fixed - GREAT! If not, now you have a transformer, etc ....

-Chris

[Dick West]

Marshall,

I have a working XL-280 power transformer. How about $20 plus postage from ZIP 61111? It will fit in the USPS flat rate box ($8.20) plus insurance and a few pennies to pay the PayPal fee = $30 to you.

Interested? If so contact me via DIYaudio messaging.

Whatta' hobby! Right?

The XL-280 is a great amp and should be worth fixing.

Dick

[Truckee_Tango]

Dick,

That is great! With a new tranny, we'll see what other trouble this amp has. When I first got the amp, one channel seemed to work fine, but not the other. Then we find the input boards are getting the same voltage as the output FETs (due to the open winding).

Now with a new tranny, we'll have to find out what is wrong with that other channel. Oh my! Guess I could do worse than putting things back together with the old tranny and measure voltages on the input board for the bad channel and see if I can find other problems before dropping in the replacement tran.

Marshall