Hafler DH200 testing

[Birstall]

I bought this amp in 1981.
It has been unused for at least 15 years and when turned on recently, it started smoking. After some research this turned out to be a common issue with the power switch which I have replaced. The amp now turns on normally and all seems to be working but don't trust it.

The two power supply capacitors are rated at 16000uF 75v. When powered up they both maintain 62DC Volts. However they dissipate almost immediately when the power is turned off.

I have some expensive stereo speakers and don't want to test this amp with those. Knowing nothing about testing amplifier outputs, could someone guide me as to what tests could be used to ensure that they won't blow a speaker at normal output levels.

Thanks

[mzacharias]

Not a Hafler expert but I have some experience on them. The bias pots tend to be very flaky and bias will drift or go way out of spec. The spec is that if you remove one of the amp channel B+ fuses, and substitute a milli-ammeter, there should be 250mA when properly adjusted. FYI - for the DH-220 the spec is 275mA and the XL-280, 300mA. If the bias jumps around excessively and is hart to adjust, better replace those pots - they're very hard to clean.