I was hoping someone here could give me suggestions to solving the following problem. I recently built two channel, Leach V4.3. Built power supply, no problems, went smooth. Connected both channels to the power supply and power transistors and diodes on the heat sink. Powered one channel up at a time with no input and no load. I used the suggested 100 ohm, 1/4W resistors in place of the 5A fuses. These resistors promptly burned out and I have not been able to trace the cause. This is what I have done so far.
1. Heat sink - confirmed NPN and PNP transistors connected properly to PCB and no shorts to the heat sink.
2. Heat sink - confirmed bias diodes are correct using DC source to forward bias, confirmed diodes are not shorted to heat sink.
3. PCB - confirmed polarity of electrolytic capacitors and diodes, checked PNP and NPN transistors for correct location. Adjusted the bias pot to maximum resistance.
Both boards smoke the jumper resistors at power up exactly the same. Dr. Leach recommended short circuiting the Q12 and Q13 collectors. This was tried with basically the same results (the resistor in VCC- burned allot quicker). I also disconnected the power transistors and got the same results.
During power up I have measured >150 amps from the PCB to central ground. Is this normal or does it indicate a leaking transistor, diode or capacitor.
I have also measure 14K ohms between VCC+ / VCC- and ground. Does this sound normal? Looking at the schematic I would think the resistance should be very high.
Any help would be greatly appreciated!
1. Heat sink - confirmed NPN and PNP transistors connected properly to PCB and no shorts to the heat sink.
2. Heat sink - confirmed bias diodes are correct using DC source to forward bias, confirmed diodes are not shorted to heat sink.
3. PCB - confirmed polarity of electrolytic capacitors and diodes, checked PNP and NPN transistors for correct location. Adjusted the bias pot to maximum resistance.
Both boards smoke the jumper resistors at power up exactly the same. Dr. Leach recommended short circuiting the Q12 and Q13 collectors. This was tried with basically the same results (the resistor in VCC- burned allot quicker). I also disconnected the power transistors and got the same results.
During power up I have measured >150 amps from the PCB to central ground. Is this normal or does it indicate a leaking transistor, diode or capacitor.
I have also measure 14K ohms between VCC+ / VCC- and ground. Does this sound normal? Looking at the schematic I would think the resistance should be very high.
Any help would be greatly appreciated!
What is the voltage output of your power supply?
Prof. Leach recommends:
"The recommended transformers have a secondary rating of 80 V AC rms. With these transformers, the power supply puts out about +58 V and -58 V."
You say. "
During power up I have measured >150 amps from the PCB to central ground."
Did you mean 150 Volts? This clue could mean +75/-75 bolts on the rails and is too much.
In addition from the Leach site:
"The circuit board has two ground leads, both of which connect to the central power supply ground. One lead grounds the signal reference points for the diff amp input stage. The other grounds the power supply decoupling capacitors and provides a ground reference for the protection circuit. R51 connects the two ground leads together on the circuit board. This resistor is small enough to look like a signal short circuit between the two grounds but large enough to force the currents in the two grounds to flow to central ground through the separate wires. This helps to prevent hum induced by power supply ripple currents in the ground system."
150 volts from any point on the PCB to ground is not correct.
Refer to the "Initial Tests on the Completed Amplifier"
here: http://users.ece.gatech.edu/~mleach/lowtim/part2.html
Good Luck
Prof. Leach recommends:
"The recommended transformers have a secondary rating of 80 V AC rms. With these transformers, the power supply puts out about +58 V and -58 V."
You say. "
During power up I have measured >150 amps from the PCB to central ground."
Did you mean 150 Volts? This clue could mean +75/-75 bolts on the rails and is too much.
In addition from the Leach site:
"The circuit board has two ground leads, both of which connect to the central power supply ground. One lead grounds the signal reference points for the diff amp input stage. The other grounds the power supply decoupling capacitors and provides a ground reference for the protection circuit. R51 connects the two ground leads together on the circuit board. This resistor is small enough to look like a signal short circuit between the two grounds but large enough to force the currents in the two grounds to flow to central ground through the separate wires. This helps to prevent hum induced by power supply ripple currents in the ground system."
150 volts from any point on the PCB to ground is not correct.
Refer to the "Initial Tests on the Completed Amplifier"
here: http://users.ece.gatech.edu/~mleach/lowtim/part2.html
Good Luck
Power it up with no output transistors connected. If there is still a short, remove the drivers. If there's still a short after that that's allowing 100 ohm power resistors to smoke without parts exploding, there is most likely a PCB error.
Test your output transistors aren't already shorted.
Test your output transistors aren't already shorted.
Problem Solved
Thanks to all for your thoughtful help. I had some excellent help from Dr. Leach on this one. Lesson learned and smoking cheeks for me. The out come is posted here ... beware!
http://users.ece.gatech.edu/~mleach/lowtim/
"Forward Warning to amplifier builders! Dated 08/14/06. One amplifier builder found that the 2N5416 PNP transistors that he purchased were NPN. I have tested them and verified this. Two of the transistors are shown in the linked photo. They are identified by the letters ON surrounded by a circle, signifying they are products of ON Semiconductor. You can check for a transistor type as follows: Connect an ohmmeter from base to emitter. You should get a low resistance with the positive lead to the base if it is NPN, otherwise it is PNP. With the ohmmeter connected from base to collector, you should get the same result. Repeat the tests with the negative lead connected to the base. The resistances should be reversed. You should get an open circuit from collector to emitter with both polarities of the ohmmeter. Defective transistors usually can be determined with these tests. The transistors should be removed from the circuit for the most reliable results."
Thanks to all for your thoughtful help. I had some excellent help from Dr. Leach on this one. Lesson learned and smoking cheeks for me. The out come is posted here ... beware!
http://users.ece.gatech.edu/~mleach/lowtim/
"Forward Warning to amplifier builders! Dated 08/14/06. One amplifier builder found that the 2N5416 PNP transistors that he purchased were NPN. I have tested them and verified this. Two of the transistors are shown in the linked photo. They are identified by the letters ON surrounded by a circle, signifying they are products of ON Semiconductor. You can check for a transistor type as follows: Connect an ohmmeter from base to emitter. You should get a low resistance with the positive lead to the base if it is NPN, otherwise it is PNP. With the ohmmeter connected from base to collector, you should get the same result. Repeat the tests with the negative lead connected to the base. The resistances should be reversed. You should get an open circuit from collector to emitter with both polarities of the ohmmeter. Defective transistors usually can be determined with these tests. The transistors should be removed from the circuit for the most reliable results."
These transistors are obviously the most terrible fake devices possible...
OnSemi does not have a 2n5416 in their program, nor do they produce transistors in this package i know of. Also, the original onsemi logo looks different.
At least you can't blame onsemi for that ! Dr.Leach should comment this fact on his site...
http://www.onsemi.com/PowerSolution...416&searchType=others&tabbed=Y&clearFilters=Y
Were the hell did you purchase this insanity ?
Mike
OnSemi does not have a 2n5416 in their program, nor do they produce transistors in this package i know of. Also, the original onsemi logo looks different.
At least you can't blame onsemi for that ! Dr.Leach should comment this fact on his site...
http://www.onsemi.com/PowerSolution...416&searchType=others&tabbed=Y&clearFilters=Y
Were the hell did you purchase this insanity ?
Mike
Hi Mike,
These guys are not even technical, so getting NPN and PNP mixed up isn't the least bit surprising.
There are some second source manufacturers out there. But you need to be buying from the big guys to be semi safe.
Hi jackinnj,
Yeah. That's about all you can say really.
What? You expect quality control with fake dealers?
These guys are not even technical, so getting NPN and PNP mixed up isn't the least bit surprising.There are some second source manufacturers out there. But you need to be buying from the big guys to be semi safe.
Hi jackinnj,
Yeah. That's about all you can say really.
Hi ptah,
Did you complain to them? It only takes one moron to mess things up. Give them the chance to fire the idiot.
Digikey, Newark, Mouser all seem to be very good. I am sure there are others. I am also sure these companies are cabable of making mistakes from time to time. It's how they handle their errors that makes the difference.
-Chris
Did you complain to them? It only takes one moron to mess things up. Give them the chance to fire the idiot.
Digikey, Newark, Mouser all seem to be very good. I am sure there are others. I am also sure these companies are cabable of making mistakes from time to time. It's how they handle their errors that makes the difference.
-Chris
Okay this is the MCM response to my complaint -
Checked stock. PNP. Markings appear correct. You may have received old stock.
Gary
MCM tech. dept
ph 937-434-0030
ph 800-543-4330
fx 800-765-6960
e techc@mcminone.com <mailto:techc@mcminone.com>
650 Congress Park Dr.
Centerville, OH 45459
-----Original Message-----
From: brett_h_l@qwest.net [mailto:brett_h_l@qwest.net]
Sent: Wednesday, September 06, 2006 11:03 AM
To: tech@mcminone.com
Subject: Technical+Questions Form Submission
Customer_Number = xxxxx
Name = xxxxxx
Company_Name =
Question = Dear MCM;
I refer you to my sales order number 105168 / invoice number 816712 / order date 04/24/06 catalog number 2N5416 (a PNP transistor). Although marked correctly on the case, the four sold to me tuned out to be NPN. I refer you to this web link to view a picture and independent confirmation that they are the wrong gender - http://users.ece.gatech.edu/~mleach/lowtim/. I have the originals in my possession.
Others have examined the cases and comment that they are probable counterfeits of ON Semiconductor because of logo irregularities and this particular transistor not supplied by On Semi. You can read comments in the discussion thread here -
http://www.diyaudio.com/forums/showthread.php?s-&threadid-84352&perpage-10&pagenumber-1
Can I please receive 4 correct replacement transistors?
Regards,
xxxxxx
Checked stock. PNP. Markings appear correct. You may have received old stock.
Gary
MCM tech. dept
ph 937-434-0030
ph 800-543-4330
fx 800-765-6960
e techc@mcminone.com <mailto:techc@mcminone.com>
650 Congress Park Dr.
Centerville, OH 45459
-----Original Message-----
From: brett_h_l@qwest.net [mailto:brett_h_l@qwest.net]
Sent: Wednesday, September 06, 2006 11:03 AM
To: tech@mcminone.com
Subject: Technical+Questions Form Submission
Customer_Number = xxxxx
Name = xxxxxx
Company_Name =
Question = Dear MCM;
I refer you to my sales order number 105168 / invoice number 816712 / order date 04/24/06 catalog number 2N5416 (a PNP transistor). Although marked correctly on the case, the four sold to me tuned out to be NPN. I refer you to this web link to view a picture and independent confirmation that they are the wrong gender - http://users.ece.gatech.edu/~mleach/lowtim/. I have the originals in my possession.
Others have examined the cases and comment that they are probable counterfeits of ON Semiconductor because of logo irregularities and this particular transistor not supplied by On Semi. You can read comments in the discussion thread here -
http://www.diyaudio.com/forums/showthread.php?s-&threadid-84352&perpage-10&pagenumber-1
Can I please receive 4 correct replacement transistors?
Regards,
xxxxxx
I guess I'll keep posting on this topic as MCM provides feedback ...
My product manager is checking into this, we will be in touch as soon as we have more information.
Thank you
Internet Sales
MCM, an InOne company
T 800-543-4330
F 800-765-6960
E talk@mcminone.com
www.mcminone.com
My product manager is checking into this, we will be in touch as soon as we have more information.
Thank you
Internet Sales
MCM, an InOne company
T 800-543-4330
F 800-765-6960
E talk@mcminone.com
www.mcminone.com
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.