Hafler P500, need schematic, manual, and some help

[still4given]

Hi folks,

I have acquired a Hafler P500 that is not working. Hafler has the DH-500 manual on their website but nothing for the P500. The P500 has a PCB for the gain controls and balanced inputs. I'm hoping someone here has a schematic or manual or even a wiring diagram for this amp.

The bridge had been removed as well as three of the N channel MOSFETs. I am trying to get it hooked back up properly so I can begin testing things to find why they decided to start using it for a parts supply. I would really like to get this beast up and running.

If no one has a manual, perhaps someone owns one of these and would mind opening the top and at least giving me an idea of which wires hook up where.

Thanks Terry

 

[still4given]

Back to the top in hopes that someone will see this and be able to help.

I mostly need info on the gain circuit board. One of the wires was cut and I have no idea where it originally hooked up. It should only take a few minutes for someone to look as see for me if they own one of these. Of course having the schematics and wire management pics would be ever so helpful as well.

Thanks, Terry

 

[still4given]

BTTT

 

[AcidJazz]

I got a P505..

and it uses the PC-19c driver board, which is the same as that in the DH500. I would think the circuit is the same, but I will have to check when I get home. The DH500 circuit should be available on the Hafler website, under the Library Archive section.

 

[still4given]

Re: I got a P505..

and it uses the PC-19c driver board, which is the same as that in the DH500. I would think the circuit is the same, but I will have to check when I get home. The DH500 circuit should be available on the Hafler website, under the Library Archive section.

How are you going to check? Could I be so lucky as to have found someone who owns a P500?

Thanks, Terry

 

[AcidJazz]

I sent you an email with the link to the 500 manual. Did you get it?

 

[still4given]

Hi AJ,

Yes I got the email, thanks.

I had already D/L'd the DH-500 manual. I wasn't sure if it was the same. Thanks for verifying it.

I was able to do some voltage checking last night. I didn't have a voltage table for the DH-500 so I used the one for the DH-220 which uses the same boards. I used a variac so I could adjust the rails to 64V which is what the DH-220 uses. For some reason I'm reading +3VDC too high on the bases of Q3,Q4,Q5,Q6,Q9,Q12,Q13, Q401, Q402, Q403, Q404, Q405 & Q406. Does anyone have an idea of what componant would cause the voltage to be three volts higher than it should be on these transistors?

If I can scan the schematic I'll try and post it. It can be found here in PDF form.

http://www.hafler.com/techsupport/pdf/DH-220_amp_man.pdf

The reason I was hoping for a schematic or wiring diagram for the P500 was so I could tell where the wires for the PC-20D board hook up. I have one W/BRN wire that has been cut and I can't find where it should land.

Thanks, Terry

 

[still4given]

Hi guys,

Well I just wanted to follow up on my success. First, I emailed Hafler about the manual and they were kind enough to email the P500 manual to me so I now have it. If anyone here needs it, send me an email and I send it to you.

I now have the amp up and running and it sounds very good. I had to replace 6 MOSFETS and the filter caps.

The P500 manual doesn't give the bias setting for this amp so I set it per the instructions for the DH220 which calls for 275mA. When I first hooked up the ammeter it read 350mA on both channels. I have to wonder if this amp should be biased higher than 275mA. If any of you know for sure I would love to have that information.

A special thanks to Dick West for all of his help both here and through email.

Thanks all of you.

Blessings, Terry

 

[mlloyd1]

zero tempco point for the Hitachi lateral MOSFETs is ~100mA per device. so, a decent rule of thumb is set bais for 100mA per device on each power rail. So, if you have 6 output devices total (3 N channel, 3 P channel), you'd set bais for 3 * 100mA or 300mA total. If you had 12 output devices total (6 N, 6P channel), set the bais for 6*100mA or 600mA per rail.

FYI - many have said the Hafler amps sound better with more bias. Try it and see what you think

mlloyd1

 

[anatech]

Hi Terry,
Could I trouble you for a copy please? bhome at sympatico dot ca .

Thanks Terry!

-Chris

 

[djk]

"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.

 

[audioguru7]

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

 

[anatech]

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

 

[audioguru7]

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

 

[anatech]

Good luck Mike.

-Chris

 

[BobEllis]

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.

 

[jdqb7@yahoo.com]

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.

 

[Cheaplow]

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.

 

[anatech]

Hi Bob,

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

 

[Cheaplow]

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