Sony PVM-20M4E Blowing HOT and other ICs - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

agardiner · 19th May 2022, 1:14 pm

Agreed - a new chip before going much further.

Retrorepair · 19th May 2022, 7:21 pm

Going to have to do some serious digging I think. The usual sources I'm pretty sure just get their supply from the same place I got this from.

agardiner · 19th May 2022, 8:29 pm

Depending on your budget; there is a seller on ebay who is claiming to have original Sanken ICs, but they are in the states so the postage is horrible.

Maarten · 19th May 2022, 11:38 pm

Just curious, where can I find the mask number on Sanken IC's? There's often 4 digits on them, but not straightforward for me to read.

I am aware that Sony often used selected parts, but they weren't always marked as such as far as I've seen.

Retrorepair · 20th May 2022, 8:36 am

Quote:

Originally Posted by Maarten

Just curious, where can I find the mask number on Sanken IC's? There's often 4 digits on them, but not straightforward for me to read.

I am aware that Sony often used selected parts, but they weren't always marked as such as far as I've seen.

As far as I can tell, these ICs aren't really used on anything other than PVMs. At least, I can't find reference to any other devices they're used in.

Aren't the digits on the them just the batch codes?

FrankB · 20th May 2022, 9:05 am

https://www.circuitsthyristors.com/5...age-TO-3P.html
Shows the IC at $23.85 USD. I know nothing about this company.

I can tell you that if it's not an original part, it is very likely not to work, based on many years working on Sony equipment.

It is quite likely you got a counterfeit IC if it's out of China.
Sanken has discontinued the part.
I do not recommend using a "universal" replacement for the part either.

(If I was in better shape, I would dig into storage & see if I had a new or used one to just send you, but I am unable to lift boxes to get into the parts area right now. Botched knee surgery.)

Retrorepair · 20th May 2022, 8:26 pm

Quote:

Originally Posted by FrankB

https://www.circuitsthyristors.com/5...age-TO-3P.html
Shows the IC at $23.85 USD. I know nothing about this company.

I can tell you that if it's not an original part, it is very likely not to work, based on many years working on Sony equipment.

It is quite likely you got a counterfeit IC if it's out of China.
Sanken has discontinued the part.
I do not recommend using a "universal" replacement for the part either.

(If I was in better shape, I would dig into storage & see if I had a new or used one to just send you, but I am unable to lift boxes to get into the parts area right now. Botched knee surgery.)

Thank you, I really appreciate the thought! I hope they sort your knee properly!

I think I'm going to have to bite the bullet and get one of the genuine used ones on ebay from the US. I just pray I find the original problem before that ones explodes too

agardiner · 20th May 2022, 9:49 pm

OK, so finally managed to pull my old service manuals and notes at work, and have had a good look. First, given the age now, ensure you have carried out the recommendations as in post #10. Apologies if any of the below then repeats any of this.

Next; power supply. As well as the 2 ICs, change the following regardless of how they read - D610, C621, R621, C616, C619, C618, D618 & the Opto coupler PH601. Also check the bridge rectifier and replace if any doubt or imbalance in your readings in case it has suffered damage. Next leaving the power supply disconnected from the rest of the set, connect a dummy load, ideally a 40W incandescent bulb to the B+ rail of the supply, and then you can power it up. Check that the 115V is correct and if you have the equipment, scope it to ensure stable. You can then check the other voltages. Continue to run it for a good burn in test, monitoring the temperature of the two STR ICs.

Moving on; line output stage. Along with Q501, replace C525, C514, C527 and D502. Ensure you use a suitable replacement for the damper diode, and correct part for Q501. When you are ready for power up, keep a close eye on the temperature of Q501, and if possible, scope the drive waveform.

Finally; sadly I do have a note that I added to the SM years ago. 'Repeated failure of power supply ICs and flyback transistor, replace LOPT' so the original suggestion maybe correct. Not a common failure on Sony PVMs, but I remember that occasionally they flashed over internally. Fingers crossed that yours will be fixed by the previous efforts.

agardiner · 20th May 2022, 9:51 pm

As a side note; I would expect the power supply to shut down without any load, hence the need for the 40W lamp.

Retrorepair · 21st May 2022, 11:13 am

Quote:

Originally Posted by agardiner

As a side note; I would expect the power supply to shut down without any load, hence the need for the 40W lamp.

Thank you very much for all that amazing info!

I'm a bit concerned if I'm honest as frankly, when it did work it was perfect and got a solid half hour out of it before it went bang. We will see anyway.

FYI connecting the PSU to the A board doesn't power it up, it just makes a high pitch whine somewhere on the A board and that's it.

Anyway, I'll follow those suggestions and see what comes of it, thank you again

Retrorepair · 21st May 2022, 11:19 am

I think I know the answer but would the flyback from a 14" be the same as the FB in this model?

Retrorepair · 21st May 2022, 11:53 am

Quote:

Originally Posted by Retrorepair

I think I know the answer but would the flyback from a 14" be the same as the FB in this model?

The 14" part code is 1-453-233-11 and the 20" is 1-453-234-11 but I don't know much else about it. I'm guessing they're specific to the tube sizes anyway. I'd have expected them to be to be honest.

agardiner · 21st May 2022, 12:39 pm

Yes, different LOPT depending on tube size. If you end up needing one, then you may end up being able to locate another PVM. They do come up with bad screen burns which makes them affordable.

Retrorepair · 21st May 2022, 12:55 pm

I will keep an eye out then.

In the mean time I'll try your notes, thank you again

Retrorepair · 25th May 2022, 10:01 pm

If the flyback is shorting, surely I'd read a slight short on it?

Does anyone have access to one to tell me what it should look like?

I am seriously leaning toward this being the issue

agardiner · 26th May 2022, 12:10 pm

You would read it if it was actually shorting. My experience is that they can 'flash over' internally causing the catastrophic failure, but then quite happily carry on working for a while after rebuilding the damaged circuit. Not a short, but internal breakdown on the EHT section.

Have you tried rebuilding the supply yet and running a 40W lamp as the load?

Retrorepair · 2nd Jun 2022, 12:31 pm

I've given up, someone offered me a 2130qm in part ex and I took it.

I really appreciate all your help, just a shame it didn't work out.

19th May 2022, 1:14 pm	#41
agardiner Octode Join Date: Sep 2020 Location: Thetford, Norfolk, UK. Posts: 1,743	Re: Sony PVM-20M4E Blowing HOT and other ICs Agreed - a new chip before going much further.

19th May 2022, 7:21 pm	#42
Retrorepair Pentode Join Date: Apr 2019 Location: Denbigh, Wales Posts: 154	Re: Sony PVM-20M4E Blowing HOT and other ICs Going to have to do some serious digging I think. The usual sources I'm pretty sure just get their supply from the same place I got this from.

19th May 2022, 8:29 pm	#43
agardiner Octode Join Date: Sep 2020 Location: Thetford, Norfolk, UK. Posts: 1,743	Re: Sony PVM-20M4E Blowing HOT and other ICs Depending on your budget; there is a seller on ebay who is claiming to have original Sanken ICs, but they are in the states so the postage is horrible.

19th May 2022, 11:38 pm	#44
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 4,203	Re: Sony PVM-20M4E Blowing HOT and other ICs Just curious, where can I find the mask number on Sanken IC's? There's often 4 digits on them, but not straightforward for me to read. I am aware that Sony often used selected parts, but they weren't always marked as such as far as I've seen.

20th May 2022, 9:05 am	#46
FrankB Heptode Join Date: Oct 2005 Location: Olympia, Washington, USA. Posts: 664	Re: Sony PVM-20M4E Blowing HOT and other ICs https://www.circuitsthyristors.com/5...age-TO-3P.html Shows the IC at $23.85 USD. I know nothing about this company. I can tell you that if it's not an original part, it is very likely not to work, based on many years working on Sony equipment. It is quite likely you got a counterfeit IC if it's out of China. Sanken has discontinued the part. I do not recommend using a "universal" replacement for the part either. (If I was in better shape, I would dig into storage & see if I had a new or used one to just send you, but I am unable to lift boxes to get into the parts area right now. Botched knee surgery.)

20th May 2022, 9:49 pm	#48
agardiner Octode Join Date: Sep 2020 Location: Thetford, Norfolk, UK. Posts: 1,743	Re: Sony PVM-20M4E Blowing HOT and other ICs OK, so finally managed to pull my old service manuals and notes at work, and have had a good look. First, given the age now, ensure you have carried out the recommendations as in post #10. Apologies if any of the below then repeats any of this. Next; power supply. As well as the 2 ICs, change the following regardless of how they read - D610, C621, R621, C616, C619, C618, D618 & the Opto coupler PH601. Also check the bridge rectifier and replace if any doubt or imbalance in your readings in case it has suffered damage. Next leaving the power supply disconnected from the rest of the set, connect a dummy load, ideally a 40W incandescent bulb to the B+ rail of the supply, and then you can power it up. Check that the 115V is correct and if you have the equipment, scope it to ensure stable. You can then check the other voltages. Continue to run it for a good burn in test, monitoring the temperature of the two STR ICs. Moving on; line output stage. Along with Q501, replace C525, C514, C527 and D502. Ensure you use a suitable replacement for the damper diode, and correct part for Q501. When you are ready for power up, keep a close eye on the temperature of Q501, and if possible, scope the drive waveform. Finally; sadly I do have a note that I added to the SM years ago. 'Repeated failure of power supply ICs and flyback transistor, replace LOPT' so the original suggestion maybe correct. Not a common failure on Sony PVMs, but I remember that occasionally they flashed over internally. Fingers crossed that yours will be fixed by the previous efforts.

20th May 2022, 9:51 pm	#49
agardiner Octode Join Date: Sep 2020 Location: Thetford, Norfolk, UK. Posts: 1,743	Re: Sony PVM-20M4E Blowing HOT and other ICs As a side note; I would expect the power supply to shut down without any load, hence the need for the 40W lamp.

21st May 2022, 11:19 am	#51
Retrorepair Pentode Join Date: Apr 2019 Location: Denbigh, Wales Posts: 154	Re: Sony PVM-20M4E Blowing HOT and other ICs I think I know the answer but would the flyback from a 14" be the same as the FB in this model?

21st May 2022, 12:39 pm	#53
agardiner Octode Join Date: Sep 2020 Location: Thetford, Norfolk, UK. Posts: 1,743	Re: Sony PVM-20M4E Blowing HOT and other ICs Yes, different LOPT depending on tube size. If you end up needing one, then you may end up being able to locate another PVM. They do come up with bad screen burns which makes them affordable.

21st May 2022, 12:55 pm	#54
Retrorepair Pentode Join Date: Apr 2019 Location: Denbigh, Wales Posts: 154	Re: Sony PVM-20M4E Blowing HOT and other ICs I will keep an eye out then. In the mean time I'll try your notes, thank you again

25th May 2022, 10:01 pm	#55
Retrorepair Pentode Join Date: Apr 2019 Location: Denbigh, Wales Posts: 154	Re: Sony PVM-20M4E Blowing HOT and other ICs If the flyback is shorting, surely I'd read a slight short on it? Does anyone have access to one to tell me what it should look like? I am seriously leaning toward this being the issue

26th May 2022, 12:10 pm	#56
agardiner Octode Join Date: Sep 2020 Location: Thetford, Norfolk, UK. Posts: 1,743	Re: Sony PVM-20M4E Blowing HOT and other ICs You would read it if it was actually shorting. My experience is that they can 'flash over' internally causing the catastrophic failure, but then quite happily carry on working for a while after rebuilding the damaged circuit. Not a short, but internal breakdown on the EHT section. Have you tried rebuilding the supply yet and running a 40W lamp as the load?

2nd Jun 2022, 12:31 pm	#57
Retrorepair Pentode Join Date: Apr 2019 Location: Denbigh, Wales Posts: 154	Re: Sony PVM-20M4E Blowing HOT and other ICs I've given up, someone offered me a 2130qm in part ex and I took it. I really appreciate all your help, just a shame it didn't work out.