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?
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.
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
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
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.
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.
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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