Looking for some help with a Punch 45HD amp. I have about 4.5 v DC on both speaker leads.
In idle and no speakers connected on turn on the current ramps quickly past 10 amps and the fets get hot.
I have pulled the fets the DC is still there. I replaced the caps C16,17 C21,22, the DC went away with them out but returned when I replaced them. On the PPM of both channels I have
Pin 1 >> 1.2v
Pin 2 >> 5.3v
Pin 3 >> 15v
Pin 4 >> 4.5v this is the pin that has the voltage on the speaker wire.
Pins 5-11 seem normal?
Any help is greatly appreciated
In idle and no speakers connected on turn on the current ramps quickly past 10 amps and the fets get hot.
I have pulled the fets the DC is still there. I replaced the caps C16,17 C21,22, the DC went away with them out but returned when I replaced them. On the PPM of both channels I have
Pin 1 >> 1.2v
Pin 2 >> 5.3v
Pin 3 >> 15v
Pin 4 >> 4.5v this is the pin that has the voltage on the speaker wire.
Pins 5-11 seem normal?
Any help is greatly appreciated
The capacitors should not have have made a difference in the DC.
If you touch a load across the speaker terminals, does the current draw increase or does it simply drain off the DCV?
I don't think I've ever had trouble with the PPM board.
What work did you do other than to remove the output FETs?
If you touch a load across the speaker terminals, does the current draw increase or does it simply drain off the DCV?
I don't think I've ever had trouble with the PPM board.
What work did you do other than to remove the output FETs?
The DC went away when I put a load on, no other work done. I think I found the issue, was able to get it stable by turning the 2 pots in the center of the board all the way down, they were fully clockwise. Not sure how to adjust them properly RV3 and RV4? Turning them all the way down also removed the 4.5 vdc from the speaker wires. By the way I just downloaded your updated course a few days ago, I recently retired and now have the time to go thru your course, I am really looking forward to it!
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Those are the bias pots. People go in and turn them fully clockwise in an effort to get more power from the amp but it generally just causes the amp to fail.
Does your 12v power supply have an amp meter?
Does your 12v power supply have an amp meter?
With the amp on, no input and no speakers, with all semiconductors tightly clamped to the heatsink (with new heatsink compound) slowly rotate the pots clockwise until you just see the current draw increase. Do this for both channels.
Do you have a sine wave generator?
Dummy loads?
Do you have a sine wave generator?
Dummy loads?
Ok I will get that done, Yes sir I do have all of that. I have read several posts where they say to change or recap these old amps. What do you recommend?
Ok completed, the first pot I adjusted till the current draw went from .41 to .43 second pot from .43 to .44
Cap replacement is, for me, on a case by case basis.
The DSM amps are generally a yes on the replacement of the 10uF@16v SMD electrolytic caps. Many of the older Orions are a complete recap. Most all of the recapping that people do is pure nonsense... and worse, causes severe damage to vias in the board because the ones doing the work don't have the tools or experience to do the job right.
Was there any corrosion around the capacitors on your preamp board?
You need to connect a dummy load and drive the output into that load to about 1v RMS (not critical). Then sweep the spectrum up to 20kHz. Is it clean up to 20k? If so, the bias is OK. If not, increase it slightly and try again.
The DSM amps are generally a yes on the replacement of the 10uF@16v SMD electrolytic caps. Many of the older Orions are a complete recap. Most all of the recapping that people do is pure nonsense... and worse, causes severe damage to vias in the board because the ones doing the work don't have the tools or experience to do the job right.
Was there any corrosion around the capacitors on your preamp board?
You need to connect a dummy load and drive the output into that load to about 1v RMS (not critical). Then sweep the spectrum up to 20kHz. Is it clean up to 20k? If so, the bias is OK. If not, increase it slightly and try again.
Getting 26 volts peak to peak across full BW with no clipping at 13.8 volts supply around 7.5 amps draw.
For some amplifiers, driving them to full power at high frequencies (pure sine wave) can cause the amp to fail. That's why 1v was specified.
Poor biasing won't show up at high output unless it's EXTREMELY bad.
Poor biasing won't show up at high output unless it's EXTREMELY bad.