Hello fellow techs i need help so I recently got a punch P1000-1bd on a trade so it would power on but had strange waveforms almost like multiple waves amplitudes picked up at same time. After looking closely I found R9 30ohm 2/3 watt resistor had broke a lead so I replaced it with a 30ohm 5 watt resistor I had on hand and now the amp powers on and power supply waveforms look great.
When measuring between rectifiers I get 53.3vdc @2.18Amps on the lab P.S. there's no DC offset and with signals injected there's no audio. So after probing the output section with the scope I found that half of the output section appears to be wonky from what I'm used to seeing.
So highside A & lowside A looks how I would assume it should however
highside B & lowside B looks off. I believe im getting voltage were there shouldn't be and it looks like it's picking up 2 frequencies on the same waveform.
I added pics of the resistor R9 that broke and of the waveforms from the output section labeled as above.
Any help would be greatly appreciated this amp circuit is a new one for me and I can't find a service manual thanks for reading.
When measuring between rectifiers I get 53.3vdc @2.18Amps on the lab P.S. there's no DC offset and with signals injected there's no audio. So after probing the output section with the scope I found that half of the output section appears to be wonky from what I'm used to seeing.
So highside A & lowside A looks how I would assume it should however
highside B & lowside B looks off. I believe im getting voltage were there shouldn't be and it looks like it's picking up 2 frequencies on the same waveform.
I added pics of the resistor R9 that broke and of the waveforms from the output section labeled as above.
Any help would be greatly appreciated this amp circuit is a new one for me and I can't find a service manual thanks for reading.
Attachments
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When measuring between rectifiers I get 53.3vdc @2.18Amps on the lab P.S.
^^^ Measuring between the center legs of the rectifiers and you read 53v?
And as a completely separate issue, there is a 2 amp draw from your 12v power supply?
What is the DCV across Ground and B+? Across ground and remote?
Are all parts in the amp?
^^^ Measuring between the center legs of the rectifiers and you read 53v?
And as a completely separate issue, there is a 2 amp draw from your 12v power supply?
What is the DCV across Ground and B+? Across ground and remote?
Are all parts in the amp?
Sorry for the confusion Perry when measuring between rectifiers middle legs it is 53.4vdc.
The 2.18amps is being drawn from my 12v supply when amp is powered on.
Across the B+ and ground is 11.8vdc
Across remote and ground is 11.6vdc
All parts are in amp and is fully assembled except top cover is off and clear plastic led light stand offs.
The 2.18amps is being drawn from my 12v supply when amp is powered on.
Across the B+ and ground is 11.8vdc
Across remote and ground is 11.6vdc
All parts are in amp and is fully assembled except top cover is off and clear plastic led light stand offs.
Yes I can so after raising to 13.5vdc the current stay at 2.18amps.
I get 60.1vdc measured between rectifiers middle legs.
Across B+ and ground 13.25vdc
Across remote and ground 13.2vdc
I get 60.1vdc measured between rectifiers middle legs.
Across B+ and ground 13.25vdc
Across remote and ground 13.2vdc
Do you have a clean square wave with an amplitude of ~2xB+ supply voltage on the drains of all of the PS FETs?
Is the duty cycle ~50%? << may be easier to check on the gate legs.
Is the duty cycle ~50%? << may be easier to check on the gate legs.
It takes only about 5 seconds.
I don't think 60v is enough rail voltage. I also believe that it should have hit regulation well before 13.5v. I'm trying to see if there is some problem with the supply.
I don't think 60v is enough rail voltage. I also believe that it should have hit regulation well before 13.5v. I'm trying to see if there is some problem with the supply.
What voltage does your scope display if you touch the probe to the B+ terminal of the amp?
To the amp ground terminal?
With a multimeter, what DCV do you read across the B+ and ground terminals?
To the amp ground terminal?
With a multimeter, what DCV do you read across the B+ and ground terminals?
My scopes displays 13.8vdc when touching B+.
Touching amp ground scope displays 277.2mv and bounces up to 280mv and back down and repeats.
With my multimeter I get 13.54vdc across the B+ and ground terminals
Touching amp ground scope displays 277.2mv and bounces up to 280mv and back down and repeats.
With my multimeter I get 13.54vdc across the B+ and ground terminals
Did you read across the two center terminals of the rectifiers with your multimeter?
Do you know how to use your scope in differential mode?
Or do you have a handheld scope (no connection to the mains)?
Do you know how to use your scope in differential mode?
Or do you have a handheld scope (no connection to the mains)?
Yes when I took the measurements from the center legs of the rectifiers on post #3 I used my multimeter.
I don't know how to use my scope in differential mode.
I do have a small handheld scope.
I don't know how to use my scope in differential mode.
I do have a small handheld scope.
Check the voltage across the rectifiers with the handheld scope. You see clean DC voltage or is there a significant amount of noise (anything that's not a straight line/trace on the scope)?
On the handheld scope the scope grounded to the center of one rectifier and the probe touching the center of the other rectifier displays 60.8vdc and is a straight line.
I'll confirm the following voltage measurements and get back to you.
I'll confirm the following voltage measurements and get back to you.
All the voltages are basically spot on.
Ok so I realized I made a mistake when I hooked the speaker up to the amp earlier I had the speaker wires in both positive terminals smh.
So when I went to connect the subwoofer to test output waveform I realized I had it wired wrong so I put them in correctly and the amp is playing audio and sounds clean no distortion.
And the wonky waveform from post #1 on highsideB gate and source legs and lowside B drain is modulating with the audio but still nothing on highside And lowside A that's what through me of on this one why one side of the output section different?
Ok so I realized I made a mistake when I hooked the speaker up to the amp earlier I had the speaker wires in both positive terminals smh.
So when I went to connect the subwoofer to test output waveform I realized I had it wired wrong so I put them in correctly and the amp is playing audio and sounds clean no distortion.
And the wonky waveform from post #1 on highsideB gate and source legs and lowside B drain is modulating with the audio but still nothing on highside And lowside A that's what through me of on this one why one side of the output section different?
Attachments
So it would appear that after replacing the R9 30ohm resistor it was working but I had the speaker wire locations mixed up and that's why I had no output on scope or speaker. However the waveforms on highside B and lowside B since they were different from highside A & lowside A
I assumed there was an issue. I'm so sorry Perry if I wasted your time at all.
So would it appear it is working or should I be worried about the 2.18amps of draw.
I assumed there was an issue. I'm so sorry Perry if I wasted your time at all.
So would it appear it is working or should I be worried about the 2.18amps of draw.
I don't think the current draw is excessive.
In notes for a T1500, I have 1.3 amps draw before the output stage engages and 3.2 amps after the output begins to oscillate.
Those waveforms were strange but if the amp drives the lowest rated load symmetrically rail to rail, it could have been the way the waveforms were captured.
For future reference, if there is a drive issue with BD amplifiers, it's typically easiest to troubleshoot to do so without rail voltage. A,, you need to do is to close the feedback loop at the feedback/servo op-amp and you will get a 50% duty cycle. That was going to be my next step.
As a side note, that 30 ohm resistor is a 5w.
In notes for a T1500, I have 1.3 amps draw before the output stage engages and 3.2 amps after the output begins to oscillate.
Those waveforms were strange but if the amp drives the lowest rated load symmetrically rail to rail, it could have been the way the waveforms were captured.
For future reference, if there is a drive issue with BD amplifiers, it's typically easiest to troubleshoot to do so without rail voltage. A,, you need to do is to close the feedback loop at the feedback/servo op-amp and you will get a 50% duty cycle. That was going to be my next step.
As a side note, that 30 ohm resistor is a 5w.
Ok thanks for helping me out and thanks for the future heads up on the BD amps.
The 30ohm 5watt resistor is all I had on hand.
I figured since its a tad bit bigger it wouldn't hurt. the original was a 2 or 3 watt resistor.
The 30ohm 5watt resistor is all I had on hand.
I figured since its a tad bit bigger it wouldn't hurt. the original was a 2 or 3 watt resistor.