Ok I will look deeper in to the drive circuit. The transformer looks ok. Is there a way to check the transformer?
I'm using a Blue Point, Snap-on meter thats made by Fluke
Model DMSC683
I'm using a Blue Point, Snap-on meter thats made by Fluke
Model DMSC683
If the meter is made by fluke, it should give reliable readings on AC when looking at the drive signal.
To check the drive signal, you'd either have to pull the MPSA06 driver transistors or pull the power supply FETs.
With only the drivers pulled, you can only determine if the signal 'up to' the drivers is OK. If you pull the FETs (leaving the A06 drivers in place), you can check the drive signal all the way to the gates (more reliable). You can try pulling the A06s first, if it appears that you have a good signal, then you'd need to pull the power supply FETs.
If you decide to pull the A06s, set the meter to AC volts and touch the red lead to the center pad for the A06. The black lead would be on the chassis ground terminal. Check both AC and DC voltage on both banks of the power supply. Post your results.
There's no easy way to check the transformer with a multimeter. You could determine if the primary is shorted to the secondary but it's difficult to check anything else.
Also check the drive signal (AC and DC) on pins 9 and 10 of the power supply driver IC (TLx94).
Have you confirmed that the amp only draws excessive current AFTER remote voltage is applied?
To check the drive signal, you'd either have to pull the MPSA06 driver transistors or pull the power supply FETs.
With only the drivers pulled, you can only determine if the signal 'up to' the drivers is OK. If you pull the FETs (leaving the A06 drivers in place), you can check the drive signal all the way to the gates (more reliable). You can try pulling the A06s first, if it appears that you have a good signal, then you'd need to pull the power supply FETs.
If you decide to pull the A06s, set the meter to AC volts and touch the red lead to the center pad for the A06. The black lead would be on the chassis ground terminal. Check both AC and DC voltage on both banks of the power supply. Post your results.
There's no easy way to check the transformer with a multimeter. You could determine if the primary is shorted to the secondary but it's difficult to check anything else.
Also check the drive signal (AC and DC) on pins 9 and 10 of the power supply driver IC (TLx94).
Have you confirmed that the amp only draws excessive current AFTER remote voltage is applied?
Ok, I havent had time to check the voltages yet but I know for sure that it only draws excessive current when the remote voltage is applied.
I also pulled the transformers today and I'm getting them re varnished.
I also pulled the transformers today and I'm getting them re varnished.
It only has one transformer (the large one). The other one is a filter inductor.
If the transformer is out, you can check the drive signals without pulling the power supply transistors. The transistors needed to be pulled because the amp was drawing excessive current. It shouldn't draw excessive current with the transformer out of the circuit.
If you haven't done anything to the transformer and inductor yet, leave them as they are until you determine the cause of the excessive current draw. You may have rewind the transformer and an extra coating of varnish or epoxy will make that more difficult.
If the transformer is out, you can check the drive signals without pulling the power supply transistors. The transistors needed to be pulled because the amp was drawing excessive current. It shouldn't draw excessive current with the transformer out of the circuit.
If you haven't done anything to the transformer and inductor yet, leave them as they are until you determine the cause of the excessive current draw. You may have rewind the transformer and an extra coating of varnish or epoxy will make that more difficult.
First The TL494cn
Pin 9 reads 1.517 VAC and 5.45VDC
Pin 10 reads 1.516 VAC and 5.44VDC
Center pin on the 06's with fets pulled
1.130 VAC and 3.958VDC on one
1.117VAC and 3.943VDC on the other
Gates for the fets
1.012 VAC and 3.7 VDC
If the inductor was shorted would this cause the problem.
Pin 9 reads 1.517 VAC and 5.45VDC
Pin 10 reads 1.516 VAC and 5.44VDC
Center pin on the 06's with fets pulled
1.130 VAC and 3.958VDC on one
1.117VAC and 3.943VDC on the other
Gates for the fets
1.012 VAC and 3.7 VDC
If the inductor was shorted would this cause the problem.
A shorted inductor would not cause this problem unless it was shorted to the transformer.
The drive circuit looks OK. These are from a 225 g2 but the drive circuit is very similar to yours.
Both banks were essentially the same. I used a Fluke 12 to measure the voltage. I defeated the regulator to make the amp drive as hard as it would without the transformer.
Pins 9/10 of the TLx94:
5.32v DC
1.20v AC
Base of driver transistors:
4.35V DC
0.957v AC
Gate of FET:
4.1v DC
0.875v AC
The drive circuit looks OK. These are from a 225 g2 but the drive circuit is very similar to yours.
Both banks were essentially the same. I used a Fluke 12 to measure the voltage. I defeated the regulator to make the amp drive as hard as it would without the transformer.
Pins 9/10 of the TLx94:
5.32v DC
1.20v AC
Base of driver transistors:
4.35V DC
0.957v AC
Gate of FET:
4.1v DC
0.875v AC
Ok heres the latest. Now only one side gets hot on the fet supply. The other side is ok. Where do I go from here?
If the FETs are not new, you should install new parts. Sometimes leaking transistors can cause this sort of problem.
Confirm that you have ~0 ohms from one bank to the other on both the drain and source legs.
Is it still blowing fuses or drawing excessive current?
If it is, pull the FETs off of the supply and measure the DC voltage on each of the legs of the TLx94.
IC#
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
Also measure the DC voltage from pin 9 to pin 10 (one probe on 9, the other probe on 10).
Did you check the small orange ceramic capacitors (at the base of the primary windings) while you had the transformer out?
Confirm that you have ~0 ohms from one bank to the other on both the drain and source legs.
Is it still blowing fuses or drawing excessive current?
If it is, pull the FETs off of the supply and measure the DC voltage on each of the legs of the TLx94.
IC#
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
Also measure the DC voltage from pin 9 to pin 10 (one probe on 9, the other probe on 10).
Did you check the small orange ceramic capacitors (at the base of the primary windings) while you had the transformer out?
I will post the results of the pins today. The creamic caps looked ok but i will investigate them more.
And yes I'm using new transisors.
And I also checked my e mail today. I will be more than happy to take pictures of it and send them to you when Im done. Right now it looks like S*** and I don't think it could help anybody.
On another note I took apart my other 250 and it was exactly like the one you thought mine was Perry. It has the rectifiers and regulator. I guess the one I burnt up was a really old revision.
And yes I'm using new transisors.
And I also checked my e mail today. I will be more than happy to take pictures of it and send them to you when Im done. Right now it looks like S*** and I don't think it could help anybody.
On another note I took apart my other 250 and it was exactly like the one you thought mine was Perry. It has the rectifiers and regulator. I guess the one I burnt up was a really old revision.
Ok. These are the results with the negative lead to ground. All measurements in DC
Pin 1 0.00
Pin 2 0.060
Pin 3 0.060
Pin 4 0.044
Pin 5 1.458
Pin 6 3.391
Pin 7 0.000
Pin 8 13.32
Pin 9 5.450
Pin 10 5.560
Pin 11 13.32
Pin 12 13.53
Pin 13 4.920
Pin 14 4.94
Pin 15 0.060
Pin 16 0.000
And the voltages between pins 9 and 10 are 3.132 VAC
Pin 1 0.00
Pin 2 0.060
Pin 3 0.060
Pin 4 0.044
Pin 5 1.458
Pin 6 3.391
Pin 7 0.000
Pin 8 13.32
Pin 9 5.450
Pin 10 5.560
Pin 11 13.32
Pin 12 13.53
Pin 13 4.920
Pin 14 4.94
Pin 15 0.060
Pin 16 0.000
And the voltages between pins 9 and 10 are 3.132 VAC
I don't see any problems with those voltages.
At one time it was blowing fuses and was causing the FETs to get hot immediately. Is it drawing less current now and causing less heating of the FETs?
At one time it was blowing fuses and was causing the FETs to get hot immediately. Is it drawing less current now and causing less heating of the FETs?
Yes It is drawing a lot less current. But the fets only on one side get hot. I have replaced the 56 and 06's twice just to make sure that I have good ones. And One thing I didn't notice before is that now when I power it up the Power light does come on. So I guess that is an improvement. It has me puzzled.
I'm not completely dumb when it comes to electronics but this thing has me pulling my hair out.
I'm not completely dumb when it comes to electronics but this thing has me pulling my hair out.
Do you have access to an oscilloscope?
What's the rail voltage?
I remember that someone was having similar trouble and it was due to the regulator. The drive was cut back too far and it caused half of the FETs to overheat.
What's the rail voltage?
I remember that someone was having similar trouble and it was due to the regulator. The drive was cut back too far and it caused half of the FETs to overheat.
pull the fets and check them (i know you didnt want to hear this)
ive pulled so many fets from these boards they dont phase me anymore.
try waiting until the board has cooled down after soldering before applying power.
dont know if your board is simliar to a 2150sx, but if you look at this post, i seemed to have fixed the hot fet bank problem (by accident of course)
http://www.diyaudio.com/forums/showthread.php?s=&threadid=97689&perpage=25&highlight=&pagenumber=5
you may want to go back a page or two to get the pictures.
ive pulled so many fets from these boards they dont phase me anymore.
try waiting until the board has cooled down after soldering before applying power.
dont know if your board is simliar to a 2150sx, but if you look at this post, i seemed to have fixed the hot fet bank problem (by accident of course)
http://www.diyaudio.com/forums/showthread.php?s=&threadid=97689&perpage=25&highlight=&pagenumber=5
you may want to go back a page or two to get the pictures.
I do have a 10 mhz Tektronix.
I get 13.8 VDC with no fets in and with my negative lead to ground.
I only have a 1-1 scope Will that work?
Clipped,
I have all the Fets pulled , all the outputs pulled and all the drivers pulled. I'll go buy some more 56 and 06's and replace them all.
I get 13.8 VDC with no fets in and with my negative lead to ground.
I only have a 1-1 scope Will that work?
Clipped,
I have all the Fets pulled , all the outputs pulled and all the drivers pulled. I'll go buy some more 56 and 06's and replace them all.
Post photos of the gate drive (on the gate pad) with at least one FET per bank.
Also post photos of the gate drive of the power supply without FETs in the supply.
Note the timebase (time/div) and vertical amplifier (v/div) settings. The 1:1 probe will work.
What's the rail voltage when the FETs are in the supply?
Also post photos of the gate drive of the power supply without FETs in the supply.
Note the timebase (time/div) and vertical amplifier (v/div) settings. The 1:1 probe will work.
What's the rail voltage when the FETs are in the supply?
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