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SAZ-1500D V2 Repair Questions
SAZ-1500D V2 Repair Questions
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Old 15th November 2017, 04:11 AM   #11
Perry Babin is offline Perry Babin  United States
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Do you have the test signal present at pins 1/2 of IC1?
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Old 28th November 2017, 11:41 PM   #12
midnightg35x is offline midnightg35x  United States
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Quote:
Originally Posted by Perry Babin View Post
Do you have the test signal present at pins 1/2 of IC1?
If I have pins 1 and 2 jumpered, I do not see my test signal. Resistance to ground is 14k (just checking for a short). If I remove the jumper, I get -13V on Pin 1 with no signal applied. With signal applied I get a +13V to -13V square wave at the signal generator frequency. Pin 2 looks like 0V when no signal is applied. When signal is applied it is a +600mV to - 600mV "square" wave at my signal generator frequency, but the signal looks like it has some good high frequency content riding on top of it making it look pretty bad.

IC1 does get warm (~65C) when jumpered and ~60C when not jumpered.

There is a comparator underneath IC1 (IC2) that was also getting semi-warm. I checked the output on pin 12 and that looked good, but I can't get to the other output. When I checked TR1 and TR2 (looks to be the drive transistors), they both diode checked OK. The NPN (TR1 MPSA42) had 15V on the collector, and both the base and emitter had 0 to 10V square waves. The PNP (TR2 MPSA92) had a 0 to 3.5V square wave on all pins. I'm not sure what to make of that. Not sure if that points me still to the comparator (IC2) or the PNP (TR2). TR2 does not bug as a short, so I'm not sure what else would cause it to look bad besides IC2.

Thoughts?
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Old 29th November 2017, 12:30 AM   #13
Perry Babin is offline Perry Babin  United States
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I don't think IC1 should be heating like that, jumped or not. It could be defective.
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Old 29th November 2017, 05:26 AM   #14
midnightg35x is offline midnightg35x  United States
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Quote:
Originally Posted by Perry Babin View Post
I don't think IC1 should be heating like that, jumped or not. It could be defective.
If pin 1 (the output) in the non-shorted case shows a strong, clean rail to rail signal, wouldn't that indicate it is working properly enough to at least get a signal out? Or is a square wave not what it is supposed to be putting out? I couldn't trace everything due to space, but I think IC1 feeds into IC2. One side of the driver transistors look OK, but one does not. Wouldn't both sides be bad if IC1 was bad?
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Old 4th January 2018, 12:06 AM   #15
midnightg35x is offline midnightg35x  United States
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Bringing this thread back. I also found a resistor R204 that looks like it was there at one point but is not anymore. Can you send me another picture with that value? It is just off the screen up and right of the picture you sent earlier. It is right by the LM293N comparator.

Also wondering if you had any insight into the previous post. I will get some parts on order, but I'd rather only replace the parts necessary on that driver board as it can be a little bit of a pain to get to some of the chips.
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Old 4th January 2018, 12:12 AM   #16
Perry Babin is offline Perry Babin  United States
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See attached.
Attached Images
File Type: jpg IMG_0163x2.jpg (959.8 KB, 48 views)
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Old 5th January 2018, 05:10 AM   #17
midnightg35x is offline midnightg35x  United States
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Quote:
Originally Posted by Perry Babin View Post
See attached.
Thanks. I'll get the known resistors on order along with the JRC5532 and JRC319 IC's. I'll go about replacing just the JRC5532 first and see if that makes a clean drive signal at that point.
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Old 5th January 2018, 05:27 AM   #18
Perry Babin is offline Perry Babin  United States
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NJM is the likely prefix. JRC is the manufacturer.
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Old 8th January 2018, 03:42 AM   #19
midnightg35x is offline midnightg35x  United States
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Quote:
Originally Posted by Perry Babin View Post
NJM is the likely prefix. JRC is the manufacturer.
Yep, found that. the NJM5532 were readily available, the NJM319's were not. I ordered a LM319 as a substitute if necessary and I'll make it fit if I have to go that route. When the parts come in, I'll report back.
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Old 21st January 2018, 11:27 PM   #20
midnightg35x is offline midnightg35x  United States
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So I got the parts in, but I still have issues. I replaced the NJM5532, the NJM319, MPSA42, MPSA92, and IR2113S on the driver board. The NJM319 was replaced by a LM319, the MPSA42 by a KSP42, the MPSA92 by a KSP92, and the IR2113S by an IRS2113S. I could not find the exact originals so I went with things that I thought were appropriate replacements. Tell me if you don't think that is the case. I did not replace the MC14070B. Everything else on the driver is passive and those parts all looked good.

I also reinstalled all of the other parts (rectifiers and the new 4 output FET's). When I power it up, it does not go into protect, but there is a slight squeal coming from the board. I have it current protected and this was with no speaker load, so I felt comfortable with this configuration.

On the top half of the output FET's, the gates looked normal. The new replaced bottom half still looks bad. Channel 1 is top, Channel 2 is the bottom

Click the image to open in full size.

I looked at the bases of the driver BJT's and they look similar. The bases are tied together between the PNP and NPN's it seems.

Click the image to open in full size.

I started going back up the line to the IRS2113S then to figure out where my problem might lie. I checked the HIN and LIN pins of the IRS2113S and they look OK to me.

Click the image to open in full size.

When I look at the HO and LO pins, I see the problem coming back. I assume the IRS2113S is OK as I just replaced it. I bugged the drivers with a multimeter previously and they seemed OK. They bug similar to the "good" top side. They are the only components I can think of that are still in line that are not new.

Click the image to open in full size.

The original drivers are an NPN KTC2814 and PNP KTA1715. I could not find these as an exact replacement so I didn't order them initially. Would the KSC2690A be an appropriate NPN replacement and the KSA1220A be an appropriate PNP replacement?

Are there any other things I should be trying to look at?
Attached Images
File Type: png Output_FET_Gate.png (74.9 KB, 5 views)
File Type: png IRS2113S_HO_LO_PINS.png (75.0 KB, 4 views)
File Type: png IRS2113S_HIN_LIN_PINS.png (70.2 KB, 3 views)
File Type: png DRIVER_BJT_BASE.png (76.0 KB, 3 views)
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