still4given said:I've inspected the board and I don't see any more solder bridges. I'm hopeful that I didn't ruin one or more of my output transistors. Could that cause the high voltage reading at the speaker outputs?
Thanks, Terry
Terry,
Pull your outputs and check for shorts. Hate to be the bearer of bad news, but having rail voltage on the output is a sign that they are blown. Ckeck for shorts on the other transisitors - especially one that would have been turned on hard by your solder bridge. Q7 is suspect.
report your findings and we'll go to the next step.
Good luck
BobEllis said:
Terry,
Pull your outputs and check for shorts. Hate to be the bearer of bad news, but having rail voltage on the output is a sign that they are blown. Ckeck for shorts on the other transisitors - especially one that would have been turned on hard by your solder bridge. Q7 is suspect.
report your findings and we'll go to the next step.
Good luck
I hate to keep sounding like a nube but I am.

How do I do a check for shorts. I suppose I have to remove them from the board. Can I do this with an ohm meter? Diode checker?
Any help will be greatly appreciated.
Thanks Terry
Check the resistance from collector to emitter, it should be near infinite or show as an open if the transistor is good, if it has a low resistance or short, it's bad.
Also, check the voltage drop from base to emitter, with the diode checker on the meter, and it should be between 0.6 and 0.7V, if not, bad transistor.
Also, check the voltage drop from base to emitter, with the diode checker on the meter, and it should be between 0.6 and 0.7V, if not, bad transistor.
If not already done, try AKSA, can be the last amplifier
It sounds great.... was the end of my 45 years search of good sound...also Graham Maynard JLH and JLH class A designs also are very nice.
Of course i am talking about normal, standard amplifiers...there are some Ferrari, Lamborghini, Porshe amplifiers.....i cannot talk about those...as i never touched those 10K dollares amplifiers...they can be great...i do not know.
regards,
Carlos
It sounds great.... was the end of my 45 years search of good sound...also Graham Maynard JLH and JLH class A designs also are very nice.
Of course i am talking about normal, standard amplifiers...there are some Ferrari, Lamborghini, Porshe amplifiers.....i cannot talk about those...as i never touched those 10K dollares amplifiers...they can be great...i do not know.
regards,
Carlos
P101 testing
Hi Terry,
Channel #1 = 10.7 mV
Channel #2 = 10.7 mV
Channel #3 = 43V
If channel no. 3 measures the postive voltage supply to the speaker output. Test the low resistance (probably less than 100 ohms) between the supply and the speaker output. Test again reversing the test leads.
Desolder the three leads to Q8 mosfet and remove from circuit board and retest the circuit board resistance. Test again reversing the test leads. If the resistance increased (probably in the megs) the mosfet removed is faulty. Next remove Q10 and test as above. If low resistance is still measured then remove one at a time all transistors and diodes.
If channel no. 3 measured the negative supply voltage then the problem would be mainly in the negative Q9 & Q11. Test as above.
The P101 uses two 5 amp fuses which I presume should be the fast blow type. Remove the fuses and test. P101 boards also use four fuse resistors 0.33 ohms do a resistance test that are within specs.
If one of the mosfets are blown I would replace all four as the others may have been stressed.
Personally even with a digital voltmeter the resistance test is not conclusive and does not mimic real circuit conditions. Your best off replacing all transistors, diodes and capacitors. Do a resistance to all resistors.
Good luck and let us know.
Joe
Visit DIY Amplifiers Yahoo Group, is a place for sharing Solid State amplifier info:
http://groups.yahoo.com/group/diyamplifiers/
Hi Terry,
Channel #1 = 10.7 mV
Channel #2 = 10.7 mV
Channel #3 = 43V
If channel no. 3 measures the postive voltage supply to the speaker output. Test the low resistance (probably less than 100 ohms) between the supply and the speaker output. Test again reversing the test leads.
Desolder the three leads to Q8 mosfet and remove from circuit board and retest the circuit board resistance. Test again reversing the test leads. If the resistance increased (probably in the megs) the mosfet removed is faulty. Next remove Q10 and test as above. If low resistance is still measured then remove one at a time all transistors and diodes.
If channel no. 3 measured the negative supply voltage then the problem would be mainly in the negative Q9 & Q11. Test as above.
The P101 uses two 5 amp fuses which I presume should be the fast blow type. Remove the fuses and test. P101 boards also use four fuse resistors 0.33 ohms do a resistance test that are within specs.
If one of the mosfets are blown I would replace all four as the others may have been stressed.
Personally even with a digital voltmeter the resistance test is not conclusive and does not mimic real circuit conditions. Your best off replacing all transistors, diodes and capacitors. Do a resistance to all resistors.
Good luck and let us know.
Joe
Visit DIY Amplifiers Yahoo Group, is a place for sharing Solid State amplifier info:
http://groups.yahoo.com/group/diyamplifiers/
EWorkshop1708 said:Check the resistance from collector to emitter, it should be near infinite or show as an open if the transistor is good, if it has a low resistance or short, it's bad.
Also, check the voltage drop from base to emitter, with the diode checker on the meter, and it should be between 0.6 and 0.7V, if not, bad transistor.
I'm not sure I understand what the collector, base and the emitter are. The pins are listed as gate, source and gain. Could you elaborate a little?
Jennice said:I thought this amp was FET based, and not Bipolar !?
Jennice
It is MOSFET based if that answers it.
If channel no. 3 measures the postive voltage supply to the speaker output. Test the low resistance (probably less than 100 ohms) between the supply and the speaker output. Test again reversing the test leads.
By this do you mean that I would see a + voltage by attaching the - probe on my voltage meter to the star ground and the + probe to the speaker out?
Do I first check for voltage and then test the resistance?
Desolder the three leads to Q8 mosfet and remove from circuit board and retest the circuit board resistance. Test again reversing the test leads. If the resistance increased (probably in the megs) the mosfet removed is faulty. Next remove Q10 and test as above. If low resistance is still measured then remove one at a time all transistors and diodes.
Is this done with power applied? I'm not sure I understand the reason for reversing the leads.
Is this test only if the result from the initial test was +?
The P101 uses two 5 amp fuses which I presume should be the fast blow type. Remove the fuses and test. P101 boards also use four fuse resistors 0.33 ohms do a resistance test that are within specs.
Actually, I thought it called for 3 amp fuses. I used slow-blow. If this is not right I will change them.
Do you know what the PCB numbers are for the fuse resistors?
Personally even with a digital voltmeter the resistance test is not conclusive and does not mimic real circuit conditions. Your best off replacing all transistors, diodes and capacitors. Do a resistance to all resistors.
I'd rather not replace everything if possible. Not so much to save the money or the work, but I feel like I will learn something if I can find out just what is bad and why. If I just replace everything, I may never understand what happened. Hope this makes sense.
Again, sorry for all the newbee questions, but I really do want to learn this stuff. I'm very greatful for all your help.
Blessings, Terry
Mosfet is a flavor of FET
Gate Source and Drain are the counterparts to a bipolar device's base, collector and emitter.
Use your ohmmeter to check for shorts between any pins of the mosfets. usually you'll find a source-drain short - it should read several megohms on a good device. A gate shorted to another pin indicates that you applied too much voltage to the gate relative to the source. Could be static, or your solder bridge, etc. Remember that MOSFETS are static sensitive devices, be sure to ground yourself before touching the parts. If you built the amp on the table in the pictures, your seat cushions could have caused a static buildup.
The other devices in your amp are bipolar. You should have a .6V diode emitter to base, and emitter to collector ought to be open circuit.
the output to rail check mentioned should just be done with your ohmmeter - no need to connect the board to the ps, just measure the resistance from the + output connection to each rail connection. Low resistance = bad device.
Gate Source and Drain are the counterparts to a bipolar device's base, collector and emitter.
Use your ohmmeter to check for shorts between any pins of the mosfets. usually you'll find a source-drain short - it should read several megohms on a good device. A gate shorted to another pin indicates that you applied too much voltage to the gate relative to the source. Could be static, or your solder bridge, etc. Remember that MOSFETS are static sensitive devices, be sure to ground yourself before touching the parts. If you built the amp on the table in the pictures, your seat cushions could have caused a static buildup.
The other devices in your amp are bipolar. You should have a .6V diode emitter to base, and emitter to collector ought to be open circuit.
the output to rail check mentioned should just be done with your ohmmeter - no need to connect the board to the ps, just measure the resistance from the + output connection to each rail connection. Low resistance = bad device.
TErry,
These tests are always done without power applied. Preferrably with power leads removed, to make sure you don't have power stored from the caps. This could (worst case) blow your ohm-meter or diode tester.
A lot of newer multimeters have a diode tester build-in. some even transistor testers for BJT's. Haven't seen them for FET's.
Jennice
These tests are always done without power applied. Preferrably with power leads removed, to make sure you don't have power stored from the caps. This could (worst case) blow your ohm-meter or diode tester.
A lot of newer multimeters have a diode tester build-in. some even transistor testers for BJT's. Haven't seen them for FET's.
Jennice
Rember, youhave two GOOD units. They will give you what any resistance readings SHOULD be. Just look for readings that are different on the non-functioning unit.
BobEllis said:Mosfet is a flavor of FET
Gate Source and Drain are the counterparts to a bipolar device's base, collector and emitter.
Use your ohmmeter to check for shorts between any pins of the mosfets. usually you'll find a source-drain short - it should read several megohms on a good device. A gate shorted to another pin indicates that you applied too much voltage to the gate relative to the source. Could be static, or your solder bridge, etc. Remember that MOSFETS are static sensitive devices, be sure to ground yourself before touching the parts. If you built the amp on the table in the pictures, your seat cushions could have caused a static buildup.
The other devices in your amp are bipolar. You should have a .6V diode emitter to base, and emitter to collector ought to be open circuit.
the output to rail check mentioned should just be done with your ohmmeter - no need to connect the board to the ps, just measure the resistance from the + output connection to each rail connection. Low resistance = bad device.
OK, so that I'm clear,
gate = base
source = collector
drain = emitter
Is this correct?
Do the devices need to be removed from the board before I test them?
As to the output to rail check, what do you mean by low resistance? Could you give me an idea of what would be normal? I guess I could check it on the good boards.
Jennice said:TErry,
These tests are always done without power applied. Preferrably with power leads removed, to make sure you don't have power stored from the caps. This could (worst case) blow your ohm-meter or diode tester.
A lot of newer multimeters have a diode tester build-in. some even transistor testers for BJT's. Haven't seen them for FET's.
Jennice
Both of my multimeters have a diode tester on them. My newer meter has transistor tester built into the front of it but I have not yet learned how to use that feature. I think it's for small stuff since the holes for the pins are fairly small.
I will try and do the tests you guys have suggested when I get home from work.
Thanks, Terry
Testing P101
Hello Terry,
quote:
If channel no. 3 measures the postive voltage supply to the speaker output. Test the low resistance (probably less than 100 ohms) between the supply and the speaker output. Test again reversing the test leads.
Your amps problem is a short circuit from the positive or negative DC power supply going to the speaker output. This is best tested using the resistance function of your meter(not the diode function)and with the power off. Attach either lead from your meter on the speaker output and the other lead on the positive rail. If you measure under 100 ohms it is Q8 or Q10 at fault. You may have to reverse the meters leads and test again. The resistance test is powered by a battery within the meter.
Next test the negative dc power supply to the speaker output in the same way as above.
quote:
If channel no. 3 measures the postive voltage supply to the speaker output. Test the low resistance (probably less than 100 ohms) between the supply and the speaker output. Test again reversing the test leads.
By this do you mean that I would see a + voltage by attaching the - probe on my voltage meter to the star ground and the + probe to the speaker out?
Please see above.
Do I first check for voltage and then test the resistance?
Do not check with voltage Terry!
Your amps problem is a short circuit from the positive or negative DC power supply going to the speaker output. This is best tested using the resistance function of your meter(not the diode function)and with the power off.
quote:
Desolder the three leads to Q8 mosfet and remove from circuit board and retest the circuit board resistance. Test again reversing the test leads. If the resistance increased (probably in the megs) the mosfet removed is faulty. Next remove Q10 and test as above. If low resistance is still measured then remove one at a time all transistors and diodes.
quote:
The P101 uses two 5 amp fuses which I presume should be the fast blow type. Remove the fuses and test. P101 boards also use four fuse resistors 0.33 ohms do a resistance test that are within specs.
Actually, I thought it called for 3 amp fuses. I used slow-blow. If this is not right I will change them.
P101, the low power version calls for 3 amp fuses on the circuit board and the high power calls for 5 amp fuses. The fuses should be the quick blow type.
Do you know what the PCB numbers are for the fuse resistors?
The fuse resistors are R12, R13, R16, R17 valued at 0.33 ohms. These small ohm resistors pass a large amount of current and can blow quickly. Resistance is checked with all power off!!So check the resistance by putting a meter probe on each side of the resistor and with the meter set for resistance measure the resistor. If you measure more than a few ohms replace the resistor.
quote:
Personally even with a digital voltmeter the resistance test is not conclusive and does not mimic real circuit conditions. Your best off replacing all transistors, diodes and capacitors. Do a resistance to all resistors.
I'd rather not replace everything if possible. Not so much to save the money or the work, but I feel like I will learn something if I can find out just what is bad and why. If I just replace everything, I may never understand what happened. Hope this makes sense.
Having the power supply voltage at the speaker output will damage speakers. I didn't feel you wanted to sacrifice speakers for a 50 cent component.
Try the above tests and let us know how you make out. Then we go through the remainder of the components.
Joe
Visit DIY Amplifiers Yahoo Group is a place for sharing Solid State amplifier info:
http://groups.yahoo.com/group/diyamplifiers/
Hello Terry,
quote:
If channel no. 3 measures the postive voltage supply to the speaker output. Test the low resistance (probably less than 100 ohms) between the supply and the speaker output. Test again reversing the test leads.
Your amps problem is a short circuit from the positive or negative DC power supply going to the speaker output. This is best tested using the resistance function of your meter(not the diode function)and with the power off. Attach either lead from your meter on the speaker output and the other lead on the positive rail. If you measure under 100 ohms it is Q8 or Q10 at fault. You may have to reverse the meters leads and test again. The resistance test is powered by a battery within the meter.
Next test the negative dc power supply to the speaker output in the same way as above.
quote:
If channel no. 3 measures the postive voltage supply to the speaker output. Test the low resistance (probably less than 100 ohms) between the supply and the speaker output. Test again reversing the test leads.
By this do you mean that I would see a + voltage by attaching the - probe on my voltage meter to the star ground and the + probe to the speaker out?
Please see above.
Do I first check for voltage and then test the resistance?
Do not check with voltage Terry!
Your amps problem is a short circuit from the positive or negative DC power supply going to the speaker output. This is best tested using the resistance function of your meter(not the diode function)and with the power off.
quote:
Desolder the three leads to Q8 mosfet and remove from circuit board and retest the circuit board resistance. Test again reversing the test leads. If the resistance increased (probably in the megs) the mosfet removed is faulty. Next remove Q10 and test as above. If low resistance is still measured then remove one at a time all transistors and diodes.
quote:
The P101 uses two 5 amp fuses which I presume should be the fast blow type. Remove the fuses and test. P101 boards also use four fuse resistors 0.33 ohms do a resistance test that are within specs.
Actually, I thought it called for 3 amp fuses. I used slow-blow. If this is not right I will change them.
P101, the low power version calls for 3 amp fuses on the circuit board and the high power calls for 5 amp fuses. The fuses should be the quick blow type.
Do you know what the PCB numbers are for the fuse resistors?
The fuse resistors are R12, R13, R16, R17 valued at 0.33 ohms. These small ohm resistors pass a large amount of current and can blow quickly. Resistance is checked with all power off!!So check the resistance by putting a meter probe on each side of the resistor and with the meter set for resistance measure the resistor. If you measure more than a few ohms replace the resistor.
quote:
Personally even with a digital voltmeter the resistance test is not conclusive and does not mimic real circuit conditions. Your best off replacing all transistors, diodes and capacitors. Do a resistance to all resistors.
I'd rather not replace everything if possible. Not so much to save the money or the work, but I feel like I will learn something if I can find out just what is bad and why. If I just replace everything, I may never understand what happened. Hope this makes sense.
Having the power supply voltage at the speaker output will damage speakers. I didn't feel you wanted to sacrifice speakers for a 50 cent component.
Try the above tests and let us know how you make out. Then we go through the remainder of the components.
Joe
Visit DIY Amplifiers Yahoo Group is a place for sharing Solid State amplifier info:
http://groups.yahoo.com/group/diyamplifiers/
Terry,
Something that occured to me at lunch - check the condition of the solder joints of the feedback resistor (R9) - a small offset at the input will drive the output to the rail if you don't have feedback. your output resistance to ground should be roughly R9+R4. If it significantly higher then you have a bad connection somewhere and have made a high power comparator
Something that occured to me at lunch - check the condition of the solder joints of the feedback resistor (R9) - a small offset at the input will drive the output to the rail if you don't have feedback. your output resistance to ground should be roughly R9+R4. If it significantly higher then you have a bad connection somewhere and have made a high power comparator
Hi Joe,
Thanks so much for the detailed response. I have a much better understanding now. I will happily report all that I find.
I have the board completely removed from the amp, so I am glad I don't need power for any of these tests.
I agree 100%. I have no intention of connecting any speakers until this is resolved. I just don't want to arbitrarily replace the MOSFET's if they are not bad. They cost more than all the other parts combined, and they are matched. If they're bad, so be it, I'll replace them.
Thanks again, Terry
Thanks so much for the detailed response. I have a much better understanding now. I will happily report all that I find.
I have the board completely removed from the amp, so I am glad I don't need power for any of these tests.
I'd rather not replace everything if possible. Not so much to save the money or the work, but I feel like I will learn something if I can find out just what is bad and why. If I just replace everything, I may never understand what happened. Hope this makes sense.
Having the power supply voltage at the speaker output will damage speakers. I didn't feel you wanted to sacrifice speakers for a 50 cent component.
I agree 100%. I have no intention of connecting any speakers until this is resolved. I just don't want to arbitrarily replace the MOSFET's if they are not bad. They cost more than all the other parts combined, and they are matched. If they're bad, so be it, I'll replace them.
Thanks again, Terry
BobEllis said:Terry,
Something that occured to me at lunch - check the condition of the solder joints of the feedback resistor (R9) - a small offset at the input will drive the output to the rail if you don't have feedback. your output resistance to ground should be roughly R9+R4. If it significantly higher then you have a bad connection somewhere and have made a high power comparator
Thanks Bob,
I'll be sure to check that.
Blessings, Terry
re post 251
Hi,
I think you should swap emitter & collector
gate = base
drain = collector
source = emitter
anyone confirm?
regards Andrew T.
Hi,
I think you should swap emitter & collector
gate = base
drain = collector
source = emitter
anyone confirm?
regards Andrew T.
Hi Terry, amps looking great, at least 2 channels are working so you can enjoy it in the meantime, finges crossed its not a FET
OK, I checked THe - rail to outpit and it reads 14k ohms on all three boards. The + rail to output measures inf. on both good boards and 30ohms on the bad one. I replaced Q7 because it tested bad. I had resistance on all combinations of pins. The only way to get inf was to remove both Q8 and Q10. I guess I will order new and see where I'm at after that.
Thanks, Terry
Thanks, Terry
- Status
- Not open for further replies.
- Home
- Amplifiers
- Solid State
- Want to build my first amp