Hafler P500, need schematic, manual, and some help - Page 2 - diyAudio
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Old 14th April 2005, 11:47 PM   #11
djk is offline djk
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"zero tempco point for the Hitachi lateral MOSFETs is ~100mA per device. "

Bias spec on the DH500 is 350mA, 100mA per device (pair) plus 50mA to run the front end.

Line idle current will be on the order of 2A; this is bias, fan, and transformer loss.
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Old 22nd August 2006, 03:59 PM   #12
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Still4given,

Sorry to bring this post back up from the dead, but I'm not able to e-mail you since I'm a new user.

Do you still have the Hafler P500 manual that Hafler sent you? My amp works good but the fan kicks into a high-speed mode after only a few minutes of listening. I think there may be something internally wrong causing it to heat up faster.

Please let me know

Thanks,
Mike
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Old 22nd August 2006, 04:10 PM   #13
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Hi Mike,
The fan speed is controlled by thermal switches. They short out resistors as the heatsink gets hotter (looks like two stages, three speeds). Either a switch is faulty (unlikely) or the heatsink is running that hot.

-Chris
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Old 22nd August 2006, 05:24 PM   #14
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Chris,

Thanks for the information. I would have to agree with you that the switch is not likely at fault since I can feel the warm air blowing out the back of the unit. I'm going to attempt a "bias adjustment" and report back on if that helps or not.

Thanks!
Mike
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Old 22nd August 2006, 05:58 PM   #15
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Good luck Mike.

-Chris
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Old 22nd August 2006, 06:02 PM   #16
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A few years back I was told by the factory that bias should be 450 mA total per side (ammeter in place of rail fuse). At that level mine would kick up to the mid speed all the time. I reduced bias to 200 mA total and it stays on low unless I go crazy. It hasn't runaway despite 10 years of nearly continous use since.

Dust in the tunnel will have a tremendous effect on the efficiency of the sinks and therefore fan speed. Clean them out if you haven't done so already. At least a blast of compressed air helps but is not as good as brushes/pipe cleaners.
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Old 2nd April 2007, 03:19 AM   #17
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Default Hafler P 505

I just obtained one to replace a DH 500, any suggestions on how to obtain manual/schematic, for upgrades, and changing the inputs to unbalanced RCA 's ? Thanks.
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Old 17th November 2007, 06:41 AM   #18
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Hi Terry,

Can I have a copy of the service manual including the schematic ?
My P500 has been sitting at the corner in basement for years. I recently hooked it up to my speakers. It powers up but nothing can be heard from the speaker. Thanks.
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Old 17th November 2007, 05:15 PM   #19
anatech is offline anatech  Canada
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Hi Bob,
Quote:
Dust in the tunnel will have a tremendous effect on the efficiency of the sinks and therefore fan speed. Clean them out if you haven't done so already. At least a blast of compressed air helps but is not as good as brushes/pipe cleaners.
It sure will!
I generally blow them out first, then wash them in a degreaser to get rid of any deposits. Obviously this is an overhaul at that point. Not a yearly thing. Compressed air once a year will keep it pretty clean.

Hi Cheaplow,
Too bad you aren't any closer to me.

-Chris
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Old 19th November 2007, 01:41 AM   #20
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Chris,

Yes, it's too bad that there's at least 45 min driving from Ajax to Georgetown. In fact, there is nothing wrong with my p500. The problem is with myself because I forgot that my p500 is a 220v version. As I connected it to 220v ac, the light is up. Anyway, I would appreciate if somebody can let me have a copy of the schematic for future reference. My p500 sounds very good but I hate the noise from the cooling fan.

Tom
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