Hi Tom,
Sometimes fan noise can be reduced with a good cleaning. Behind the fan blades too. You really have to remove it for this. Failing that, a new fan is required. These should not be very noisy in normal use as they are not turning at full speed, that's why I think there may be an issue there.
-Chris
Sometimes fan noise can be reduced with a good cleaning. Behind the fan blades too. You really have to remove it for this. Failing that, a new fan is required. These should not be very noisy in normal use as they are not turning at full speed, that's why I think there may be an issue there.
I used to drive that often enough. I'd call it 1 1/2 hours if traffic is really good. The moon if your running around after 4:30 PM on a weekday.
-Chris
Hi Chris,
Thank you so much for the information. I will try to clean the fan again in X'mas time.
Tom
Thank you so much for the information. I will try to clean the fan again in X'mas time.
Tom
Question to those with the P-500 - Which potentiometer do you adjust the bias at and which fuse do you use to measure?
On my P-500 I see 4 potentiometers and 2 pairs of fuses. A picture would be great.
Thanks
Mike
On my P-500 I see 4 potentiometers and 2 pairs of fuses. A picture would be great.
Thanks
Mike
http://www.hafler.com/techsupport/pdf/DH-500_amp_man.pdf
Bias pot P2 is right in the middle of the board. Adjust to 350mA.
There is one dual fuseholder per channel. Pull one fuse (either one) and measure the current (to avoid killing yourself turn amp off and wait a minute before sticking your fingers in it). Repeat for other channel.
Bias pot P2 is right in the middle of the board. Adjust to 350mA.
There is one dual fuseholder per channel. Pull one fuse (either one) and measure the current (to avoid killing yourself turn amp off and wait a minute before sticking your fingers in it). Repeat for other channel.
Thanks djk. I do have the DH-500 manual but the layout of the P-500 is different, so I wasn't sure how similar it was.
Will give it a try and report back. Also, I'll try cleaning the heat sink as I am still trying to eliminate the high-speed fan mode after only a few minutes of listening.
Mike
Will give it a try and report back. Also, I'll try cleaning the heat sink as I am still trying to eliminate the high-speed fan mode after only a few minutes of listening.
Mike
"Also, I'll try cleaning the heat sink as I am still trying to eliminate the high-speed fan mode after only a few minutes of listening."
They get hot when you run them hard, or at 4R.
I replaced the quiet 35CFM stock fan with a 110CFM howler to keep the amp running at 4R (with the stock fan it will shut down).
No matter how quiet of a fan you use, you will still be able to hear it at low volume levels.
This is one of the quieter fans on the market:
http://www.comairrotron.com/cgi-bin...ure_unit=inh2o&diameter_val=&diameter_unit=in
You might want to try something like this and re-wire the fan switches for medium and high speed only with a single resistor for an appropriate speed. I find it less annoying if it isn't switching speeds all the time.
They get hot when you run them hard, or at 4R.
I replaced the quiet 35CFM stock fan with a 110CFM howler to keep the amp running at 4R (with the stock fan it will shut down).
No matter how quiet of a fan you use, you will still be able to hear it at low volume levels.
This is one of the quieter fans on the market:
http://www.comairrotron.com/cgi-bin...ure_unit=inh2o&diameter_val=&diameter_unit=in
You might want to try something like this and re-wire the fan switches for medium and high speed only with a single resistor for an appropriate speed. I find it less annoying if it isn't switching speeds all the time.
I too have acquired a Hafler P 500 to work on for our sound company. It has virtually no output But all of the voltages from the power supply our correct. Could it be that the final output transistors are just old and need to be replaced . Along with the 20K Uf caps used in the power supply. If anyone has any ideas on this amp please let me know.
Hafler P500 Power Amp
Hi I have a Hafler power amp on my bench model P-500 . If anyone has a Service manual or a schematic on this animal ,that would be great. It has a very low output signal but all of the voltages from power supply are there. Could it be that the final output transistors are old and need to be replaced along with the 20K UF caps in the power supply. I checked the voltages to the _+- output section and they are symetrical. +- 90 volts. Please help if you can. As I really need that schematic. Thanks one and all.
Hi I have a Hafler power amp on my bench model P-500 . If anyone has a Service manual or a schematic on this animal ,that would be great. It has a very low output signal but all of the voltages from power supply are there. Could it be that the final output transistors are old and need to be replaced along with the 20K UF caps in the power supply. I checked the voltages to the _+- output section and they are symetrical. +- 90 volts. Please help if you can. As I really need that schematic. Thanks one and all.
Update on the Hafler P500 I'm working on , There is plenty of output signal coming from the collectors of the output transistors, QP & QN 113s , as I can see it on my scope , but if I go to the output terminals there is little if any signal at all. In between the output transistors and the output terminals there is , I think its a relay. That may be my problem as its not clicking to let the signal pass on to output terminals. Any help is greatly appreciated . Thanks.
I pulled the relay out and soaked it in alcahole for a day . Reinstalled it unit still wont pass signal.
Have you searched on the web for a schematic?
http://www.hafler.com/pdf/archive/P-500C.pdf
You can check for the output at the input of that relay board and monitor any amp issues there.
As for the relay circuit, it needs to have certain conditions met in order to click on, power, low D.C. offset from the amp.
http://www.hafler.com/pdf/archive/P-500C.pdf
You can check for the output at the input of that relay board and monitor any amp issues there.
As for the relay circuit, it needs to have certain conditions met in order to click on, power, low D.C. offset from the amp.
Check for DC on pin 8 of each driver board, it needs to be less than 1V or so (I recommend changing the trip point to 7.5V for PA use).
Check the relay for continuity, I have had them go open.
Check the relay driver transistor, I have had them fail.
Check the relay for continuity, I have had them go open.
Check the relay driver transistor, I have had them fail.
Hi djk,
What reason is there to change the offset trip voltage to 7.5 V ??! That's almost like no having output protection for the load. If the amps can't hold DC offset below 100 mV, they are broken in my view. Just my opinion.
If it's LF extension you are looking at, why not just increase the value of the detection filter capacitors?
I know you are well aware of what you are doing, but the reasons for suggesting (or practicing) this modification escape me. I am not trying to insult you at all.
-Chris
What reason is there to change the offset trip voltage to 7.5 V ??! That's almost like no having output protection for the load. If the amps can't hold DC offset below 100 mV, they are broken in my view. Just my opinion.
If it's LF extension you are looking at, why not just increase the value of the detection filter capacitors?
I know you are well aware of what you are doing, but the reasons for suggesting (or practicing) this modification escape me. I am not trying to insult you at all.
-Chris
"What reason is there to change the offset trip voltage to 7.5 V ??! "
That's what most PA amps trip out at, BGW, Peavey, etc.
"That's almost like no having output protection for the load. "
For hi-fi I will agree with you.
"If the amps can't hold DC offset below 100 mV, they are broken in my view. Just my opinion."
I like to clip the living daylights out of PA amps (on live music), the typical DC detect circuit will trip with even slight clipping on an asymmetrical music waveform. This is inaudible if less than about 40mS duration (Peavey DDT has a 100mS delay).
Back in the day I used to modify hi-fi amps and abuse them for PA, my PA's in general sounded better than others that spent 5x the money.
"On the other hand there are a small number of people who judge how hard
there (sic)driving speakers by the level of distortion and /or consider the
duty cycle of the red lights on there power amp as indicators of getting
there monies worth."
That's what most PA amps trip out at, BGW, Peavey, etc.
"That's almost like no having output protection for the load. "
For hi-fi I will agree with you.
"If the amps can't hold DC offset below 100 mV, they are broken in my view. Just my opinion."
I like to clip the living daylights out of PA amps (on live music), the typical DC detect circuit will trip with even slight clipping on an asymmetrical music waveform. This is inaudible if less than about 40mS duration (Peavey DDT has a 100mS delay).
Back in the day I used to modify hi-fi amps and abuse them for PA, my PA's in general sounded better than others that spent 5x the money.
"On the other hand there are a small number of people who judge how hard
there (sic)driving speakers by the level of distortion and /or consider the
duty cycle of the red lights on there power amp as indicators of getting
there monies worth."
Hi djk,
Big amps run into hard clipping normally = blown woofers. Best avoided. Of course if it was <note past tense> a full range box, exit tweeters, midrange drivers - then woofers. Those amps will easily turn most DJ speakers inside-out.
-Chris
Okay, that 'splains it.
Big amps run into hard clipping normally = blown woofers. Best avoided. Of course if it was <note past tense> a full range box, exit tweeters, midrange drivers - then woofers. Those amps will easily turn most DJ speakers inside-out.
-Chris
A DH500 can roast most anything.
"Big amps run into hard clipping normally = blown woofers."
Dynamic offset mechanically will tear up the woofers. I have to change the time constants on the input caps, feedback caps, and the power supply, as well as the gain of the DH500 before using for PA.
"Big amps run into hard clipping normally = blown woofers."
Dynamic offset mechanically will tear up the woofers. I have to change the time constants on the input caps, feedback caps, and the power supply, as well as the gain of the DH500 before using for PA.
Hi djk,
I think that's true of most large, half decent amplifiers. Once you get into hard clipping, all kinds of things can happen. The 7.5 VDC offset is high enough to do damage to a speaker.
-Chris
I think that's true of most large, half decent amplifiers. Once you get into hard clipping, all kinds of things can happen. The 7.5 VDC offset is high enough to do damage to a speaker.
-Chris
"The 7.5 VDC offset is high enough to do damage to a speaker."
Never lost a PA driver from 7.5V DC, was I lucky?
Why did BGW, Peavey, QSC, etc choose 7.5V as their protect point?
Quad used the same circuit in their '57 crowbar (T2=2N4992, 8V
SOLID STATE 2N4992 Triac, Bilateral Switch, 200 mA, TO-92, 5 mA, 300 mW ).
https://images.search.yahoo.com/images/view;_ylt=AwrB8pIMWNRYb1QAVAMunIlQ;_ylu=X3oDMTIyZHIyMmwyBHNlYwNzcgRzbGsDaW1nBG9pZANlNGNjZjE0ODcyMzc1MjFjNWQyM2RkYTMzY2RlYjRjOARncG9zAzYEaXQDYmluZw--?.origin=&back=https%3A%2F%2Fimages.search.yahoo.com%2Fyhs%2Fsearch%3Fp%3Dquad%2B57%2Bschematic%26fr%3Dyhs-mozilla-003%26fr2%3Dpiv-web%26hsimp%3Dyhs-003%26hspart%3Dmozilla%26tab%3Dorganic%26ri%3D6&w=1444&h=1070&imgurl=user.tninet.se%2F~vhw129w%2Fmt_audio_design%2Fimages%2Fquad63_schematic.gif&rurl=http%3A%2F%2Fwww.integracoustics.com%2FMUG%2FMUG%2Ftweaks%2Fquad%2F&size=40.9KB&name=%3Cb%3EQuad%3C%2Fb%3E+ESL-63+crossover+%28+newer+version+%29&p=quad+57+schematic&oid=e4ccf1487237521c5d23dda33cdeb4c8&fr2=piv-web&fr=yhs-mozilla-003&tt=%3Cb%3EQuad%3C%2Fb%3E+ESL-63+crossover+%28+newer+version+%29&b=0&ni=21&no=6&ts=&tab=organic&sigr=11jtftj2p&sigb=14bmarb55&sigi=1234e54cs&sigt=11esa1bug&sign=11esa1bug&.crumb=UX57/nTa8k5&fr=yhs-mozilla-003&fr2=piv-web&hsimp=yhs-003&hspart=mozilla
Never lost a PA driver from 7.5V DC, was I lucky?
Why did BGW, Peavey, QSC, etc choose 7.5V as their protect point?
Quad used the same circuit in their '57 crowbar (T2=2N4992, 8V
SOLID STATE 2N4992 Triac, Bilateral Switch, 200 mA, TO-92, 5 mA, 300 mW ).
https://images.search.yahoo.com/images/view;_ylt=AwrB8pIMWNRYb1QAVAMunIlQ;_ylu=X3oDMTIyZHIyMmwyBHNlYwNzcgRzbGsDaW1nBG9pZANlNGNjZjE0ODcyMzc1MjFjNWQyM2RkYTMzY2RlYjRjOARncG9zAzYEaXQDYmluZw--?.origin=&back=https%3A%2F%2Fimages.search.yahoo.com%2Fyhs%2Fsearch%3Fp%3Dquad%2B57%2Bschematic%26fr%3Dyhs-mozilla-003%26fr2%3Dpiv-web%26hsimp%3Dyhs-003%26hspart%3Dmozilla%26tab%3Dorganic%26ri%3D6&w=1444&h=1070&imgurl=user.tninet.se%2F~vhw129w%2Fmt_audio_design%2Fimages%2Fquad63_schematic.gif&rurl=http%3A%2F%2Fwww.integracoustics.com%2FMUG%2FMUG%2Ftweaks%2Fquad%2F&size=40.9KB&name=%3Cb%3EQuad%3C%2Fb%3E+ESL-63+crossover+%28+newer+version+%29&p=quad+57+schematic&oid=e4ccf1487237521c5d23dda33cdeb4c8&fr2=piv-web&fr=yhs-mozilla-003&tt=%3Cb%3EQuad%3C%2Fb%3E+ESL-63+crossover+%28+newer+version+%29&b=0&ni=21&no=6&ts=&tab=organic&sigr=11jtftj2p&sigb=14bmarb55&sigi=1234e54cs&sigt=11esa1bug&sign=11esa1bug&.crumb=UX57/nTa8k5&fr=yhs-mozilla-003&fr2=piv-web&hsimp=yhs-003&hspart=mozilla
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Your guess would be as good as mine. I am used to dealing with the physics of situations and not what people "think". Therefore it seems rather silly to me to set the protect point where there will be more than an ampere of fault current flowing.
I can see a crowbar set to this level as that is a brutal way to limit damage to a speaker system. Quad wasn't the only one, and there were some issues with dv/dt bringing triacs into conduction. With rather messy results actually in one 600 watt amplifier. Lot's of copper sacrificed in the name of the ultimate protection method. The crowbar.
There are more thoughtful ways of protecting the load in the event of a fault condition. Using a soft limiter would help a great deal in keeping the effective DC offset in line. Nuisance protection would be a good way to resolve the deep clipping issue. Shut the audio input off when your output begins going DC. If all is well, restore the signal, if not you know it is a real fault condition instead of cockpit error (sorry). I have yet to understand how deep clipping was good. If you want the sound, it could be done in a controlled way via an effects stage. That way you could clip away all night without overdriving the woofers. The exact opposite of an "over-easy" limiter. You might need a circuit to keep the signal centered around zero. I think the only reason why this hasn't been done is that it costs money. Much easier to let the DJ roast the system I guess.
-Chris 🙂
I can see a crowbar set to this level as that is a brutal way to limit damage to a speaker system. Quad wasn't the only one, and there were some issues with dv/dt bringing triacs into conduction. With rather messy results actually in one 600 watt amplifier. Lot's of copper sacrificed in the name of the ultimate protection method. The crowbar.
There are more thoughtful ways of protecting the load in the event of a fault condition. Using a soft limiter would help a great deal in keeping the effective DC offset in line. Nuisance protection would be a good way to resolve the deep clipping issue. Shut the audio input off when your output begins going DC. If all is well, restore the signal, if not you know it is a real fault condition instead of cockpit error (sorry). I have yet to understand how deep clipping was good. If you want the sound, it could be done in a controlled way via an effects stage. That way you could clip away all night without overdriving the woofers. The exact opposite of an "over-easy" limiter. You might need a circuit to keep the signal centered around zero. I think the only reason why this hasn't been done is that it costs money. Much easier to let the DJ roast the system I guess.
-Chris 🙂
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