Hafler DH 200 problem

[guy_b_g]

I recently bought a DH-200 on ebay.

Not knowing anything about these amps I hooked it up and ran it.

The yellow overheat light comes on at startup, but I didn't know that it was problem indicator.

Both channels work, and the amp doesn't get hot (in fact, it runs much ccoler than my Perreaux does at the same volume levels).

The sound is terrible, very thin and flat in the high end/upper mid- range, and hiss.

The amp runs quiet with no input.

Any help would be appreciated!

Thanks!

[Dick West]

Well, you have a way to go as your description defies logic.

Get a copy of the manual from Hafler.com. Remove the lid by taking out the top 4 sheet metal screws on both sides and loosen the remaining 4 a little bit on one heat sink to make it a little "wobbly." Then, remove the lid.

Be careful of the charge in the large filter caps. It can be lethal.

Trace the wiring and compare it to the diagram in the manual. You are correct, the yellow light should not come on ulnless the thermal switch becomes hot. I suppose the switch could be defective or stuck ON.

Get a VOM and check each channel separately for DC offset and the bias setting. The manual will tell you how to do it these things. Check this thread as it should help:

http://www.diyaudio.com/forums/showt...643#post465643

Check all the fuses to make sure they are OK and are of the proper value.

Once you have checked out all these items post back here with your results.

Good luck

Dick