Hi, what were your DC offset readings.I have very low volume out of both channels. It sounds pretty clean but mostly upper frequencies. Source is directly from cd player(2) so should be plenty loud. All fuses test good. Power supply is +/-60VDC. Looked at bias both sides were at ~450ma,both heatsinks warm to touch (Adj. bias to 275ma). These are old amps from friend and noticed this one has 1/4 phone jack as input connectors???
I have worked on many SS amps and Tube also. I have electronics degree and experience. I have the schematic.
Looks like all original caps. I did come across an older thread talking about "220 with tin can sound". That sounds very close to my problem. Did pull a couple of the output transistors and measured with Fluke DMM. Measured results would at one time look like shorted and remeasure and would look ok??? I'm assuming that if it biases though the outputs are ok?
Thanks for any help provided
RG
I have a TA1600 that I've relegated to the junk pile for the exact same reason...and because I have no desire to replace surface-mount devices.
The TA1600 used early SMD electrolytics on the PC board; when these dried up, it was as though someone put a big pad and a 1 K high-pass filter on the inputs of this thing.
If the DH200 is at all similar, you will likely find a few dried out small signal caps in the input/driver stages.
Just to let everybody know latest status. Saw the original Dh-200 repair thread and read about the input blocking caps going bad (C1 i think). Pulled mine and were only measuring in the pico range. Replaced and all is working correctly now. First hafler I've heard and I am quite surprised at it's sound. Better than I expected.
I still have another one that doesn't bias up at all in the left channel. BTW what is the "perfect" bias point for this amp??
RG
http://www.diyaudio.com/forums/solid-state/31131-hafler-dh-200-220-mods-3.html#post398116Does anybody know what Inrush current limiter works well in the DH200?
RG