question about diodes in a PVM(edit:FIXED! was bad film cap)

[jd213]

Long story short, I want to replace a RGP02-17EL-6433 diode in a PVM, but looks like I might be SOL due to the parts shortage...

Got an Olympus OEV 143 a while ago with a stretched out horizontal that neither the service menu nor a recap could fix: https://postimg.cc/gallery/wxv9WZd

Steve of Retrotech USA suggested that it was a problem with one of the through-hole diodes, and after testing all of them out of circuit, there was just one that seemed suspect, D505 (which has a part# of RGP02-17EL-6433 according to the Sony M2 service manual) read over 1300 forward (still 1 in reverse), which I assume is out of spec, right?

I know jack about diodes, but I assume I can use a diode that starts with RGP02-17E or higher, but places like Digikey and Mouser apparently won't have any until the end of 2022 or 2023.

Is there any other kind of diode I can try? I couldn't find the spec sheet for the specific RGP02-17EL-6433 diode, but here's the one for the RGP02 series from Vishay: https://www.vishay.com/docs/88699/rgp02.pdf

[MKL]

That diode is fine and not related to the pincushion issue. What's the resistance across the legs of D502?

[jd213]

Ah, thanks for the correction. That saves me some trouble.

Both D502 and D512 read about 0.6 Mohms when out of circuit (and 0.1 ohms when in), and with forward readings in the 400s (1 reverse) with the multimeter in diode mode. Is that OK for these?

Incidentally, the Sony M2 manual lists a part number of UF5406 for these diodes, while the ones on my board are UF5408, but not sure if it matters.

[MKL]

Resistance from ground (heat sink of Q501) to the trace where the cathode of D502/512 or the anode of D506 are soldered to.

[jd213]

Thanks again for your help.

Resistance to the cathodes for D502/D512 reads about 0.68 Mohms in circuit, while the resistance to the D506 anode fluctuates from 0.5 to around 5 ohms. Is that bad?

I tried to study the schematics and notes in the PVM-M2MD_Service_Manual for clues for faulty components, but didn't see anything obvious since I'm just an idiot who can solder somewhat OK. This was a PVM that was probably going to be thrown out, was hoping I could rescue it with just a recap.

[MKL]

Anode of D506 is the same as cathode of D502/D512. If it's confirmed that the resistance from any of the yellow points and the red point is very low, desolder Q503, then measure resistance across those points again. If it's now much higher, run the monitor (with Q503 off but all other parts in and with the correct polarity) and confirm that picture still has picushion distortion but has shrunk horizontally.

https://postimg.cc/KRRX87Jw

[jd213]

Thank you again.

Unfortunately the resistance is still low without Q503.

[MKL]

Desolder C514 and measure again.

[jd213]

Still getting low resistance, sorry to say.

[MKL]

L509 is soldered on three pins. Each pin now has low resistance to ground. Desolder L509, then see if the low resistance to ground is on pins 1-2 and not on 3 or viceversa.

https://postimg.cc/qzF6mXcy

[jd213]

After removing L509, I still get low resistance at all the 4 of the yellow circles. I think I didn't have the diodes soldered back in properly before, so that's probably why I was getting a higher resistance on the D502/D512 cathodes.

Not sure if I was supposed to measure the empty pins for L509, but I got 59.1 kohms on pin 1, and OF on the other pins.

[MKL]

I still get low resistance at all the 4 of the yellow circles.

What you're doing is measuring resistance from one (any) of them to ground, correct? You're not measuring resistance across them, are you?

This is getting harder as I'm not sure I can rely on your measurements. Pin 3 of L509 is the same as the four yellow circles. Zero resistance across these points and same resistance to ground from any of them. As far as I see pin 1 and 2 of L509 are connected by a trace on parts side so they are the same and this means that when you measure resistance to ground you must have the same reading whether you are on 1 or on 2. And yes, I mean the empty pads on the PCB. If you're in doubt post pics of where on the PCB you put the leads and corresponding readings.

[jd213]

What you're doing is measuring resistance from one (any) of them to ground, correct? You're not measuring resistance across them, are you?

Right. I measured from ground to each of circles and from ground to each the 3 points (after removing L509) in the 2nd image you linked.

This is getting harder as I'm not sure I can rely on your measurements. Pin 3 of L509 is the same as the four yellow circles. Zero resistance across these points and same resistance to ground from any of them. As far as I see pin 1 and 2 of L509 are connected by a trace on parts side so they are the same and this means that when you measure resistance to ground you must have the same reading whether you are on 1 or on 2. And yes, I mean the empty pads on the PCB. If you're in doubt post pics of where on the PCB you put the leads and corresponding readings.

Truly sorry about that. Looked over the board and couldn't figure out the problem at first, but then I looked more closely at L509 and saw that a thin copper sleeve (?) is still attached to 2 of the legs of L509. I assume these sleeves connect the traces on the top and bottom of the board. I've gotten fairly good at desoldering with a Hakko and L509 seemed pretty loose when I pulled it out, but maybe not...
But at any rate, now there's no continuity between the top and bottom of pins 1 and 3. (checked continuity at other points I've desoldered and resoldered, and thankfully didn't find any other problems, will be sure to check the top and bottom traces for L509 after I solder it back in)

I re-took the readings, measuring from ground at each of the 3 points (the ones you marked in the 2nd linked image), this time measuring from ground to the points at both the top and the bottom of the board (previous measurements were from the bottom of the board, and are consistent with these new readings):

1: top: OF, bottom: 59.1 kohms
2: top: OF, bottom: OF
3: top: 0.1 ohms (same as the 4 yellow circles), bottom: OF

Also, Q503 and C514 are still removed. LMK If I should solder either or both of them back in and re-do the readings.

I can understand how this would be frustrating for you, but I appreciate your help regardless. Would really like to get this PVM restored as I feel responsible for it after rescuing it from getting dumped, and the picture seems really good except for the horizontal stretching.

LMK if there's anything I can do for you in return (something from Japan, Japanese>English translation, or whatever).

[MKL]

There seems to be some pad/trace damage. I would need to see pics though.

Pad 3 of L509 is connected to one side of R1562. If you measure resistance from that side of R1562 to any of the yellow circles do you have zero ohm (or the same reading as when you touch each other leads of the multimeter)? You should or there is some problem with the trace.

If you desolder C514 do you still have the low resistance to ground? If you do, lift one side (any) of R1562 and check again. Be careful not to damage the pads on the PCB where R1562 is soldered to. Carefully straighten its leads first.

[jd213]

There seems to be some pad/trace damage. I would need to see pics though.

Thankfully the traces seemed fine when I tested continuity. The top/bottom traces of pins 1 and 3 of L509 don't appear to be connected with L509 removed, but I assume they'll be fine once it's soldered back in.

Pad 3 of L509 is connected to one side of R1562. If you measure resistance from that side of R1562 to any of the yellow circles do you have zero ohm (or the same reading as when you touch each other leads of the multimeter)? You should or there is some problem with the trace.

If you desolder C514 do you still have the low resistance to ground? If you do, lift one side (any) of R1562 and check again. Be careful not to damage the pads on the PCB where R1562 is soldered to. Carefully straighten its leads first.

My board doesn't actually have an R1562, it's an Olympus OEV143 which seems to match the PVM-M2MD_Service_Manual AFAIK. Pin 3 of L509 seems to connect directly to the yellow circles, and it does indeed have continuity/low resistance when I test it.

[MKL]

Top and bottom of a plated through hole (like the holes where L509 is/was soldered to) are one thing. Putting the multimeter lead on top or bottom shouldn't make a difference. A few posts above you gave different readings for top and bottom of same holes. If this is true there's something wrong. I hope it's just some flux residue that prevents contact with the hole or else I don't know what to think (especially since I couldn't see a pic so far). Clean up the area with alcohol or other cleaner.

Desolder C514 and see if low resistance to ground becomes high. If still low do the same with C2510.

[jd213]

Top and bottom of a plated through hole (like the holes where L509 is/was soldered to) are one thing. Putting the multimeter lead on top or bottom shouldn't make a difference. A few posts above you gave different readings for top and bottom of same holes. If this is true there's something wrong. I hope it's just some flux residue that prevents contact with the hole or else I don't know what to think (especially since I couldn't see a pic so far). Clean up the area with alcohol or other cleaner.

It seems that the through-holes for pins 1 and 3 were only plated on the bottom (not sure about 2, looks like some solder remained on the top so it might be plated on the top).





Pins 1 and 3 of L509 appear to have a copper sleeve stuck on them, so I assume there is only substrate between the top and bottom of the board for these pins. I will make sure to test the top and bottom connections after resoldering L509, but hopefully there won't be any problems.

Desolder C514 and see if low resistance to ground becomes high. If still low do the same with C2510.

OK, was still low after desoldering C514, but after desoldering C2510 I'm now getting around 154kOhms at the 4 yellow circles and pin 3 of L509. Does that mean C2510 needs replacing?

[MKL]

Yes, it looks like the issue was caused by a shorted C2510. Checking resistance across its legs will confirm it's shorted. According to the manual it's a 0.0015uF (= 1500pF) 630V polypropylene capacitor. The marking on the cap should be either 0.0015 or 152. If the numbers are different, post a pic. I see there are two mount options. Measure the spacing across the pads and make sure you buy a cap that fits either spacing. Voltage rating can be higher than 630V (e.g. 1KV) if you can't find one rated the same.

The through holes for L509 look damaged. Two of them remained stuck on the legs. Remove them if you can. The connections can be restored with a couple of jumper wires if needed:

https://i.postimg.cc/65hqVCL5/wires.jpg
(from positive of C572 to L509 and from the other side of L509 to C578)

Replacing the capacitor should fix the issue but it's a good idea to test Q503 when it's still out of circuit (I hope its through holes are fine). A good transistor will test like this:

https://i.postimg.cc/SQDBSQWR/transistor.jpg

The readings on yours will probably be in the 600 range. All other combinations will give OL.

[jd213]

Great, really glad you were able to help me narrow down the apparent problem. C2510 does indeed have low resistance.

Yes, it looks like the issue was caused by a shorted C2510. Checking resistance across its legs will confirm it's shorted. According to the manual it's a 0.0015uF (= 1500pF) 630V polypropylene capacitor. The marking on the cap should be either 0.0015 or 152. If the numbers are different, post a pic.

It says 152J 630, so looks like you're right, although my copy of the PVM-M2MD_Service_Manual.pdf says C2510 is 0.0015MF 630V. I assume this is a different spec for medical use or something. What is the filename of the manual you're referencing? I never was able to find an actual OEV 143/203 manual.

Will try looking locally first, but this looks like it will fit the specs and lead spacing:
https://www.digikey.com/en/products/det ... JF/2567800

[MKL]

0.0015uf (microfarad) is the same as 1500pf (picofarad). That cap from digikey is fine but shipping will be expensive. Ebay probably has something cheaper.

[jd213]

Ah, I see now that Sony was using MF for microfarad, thought it was millifarad. That explains a lot. Sorry for the confusion.

[jd213]

Finally got it fixed!
https://postimg.cc/WDQFLHKw
https://postimg.cc/rDNQpSc4

Still need to calibrate it, but the horizontal stretching is finally gone. Convergence looks pretty good at a quick glance.

Replacing the capacitor should fix the issue but it's a good idea to test Q503 when it's still out of circuit (I hope its through holes are fine). A good transistor will test like this:

https://i.postimg.cc/SQDBSQWR/transistor.jpg

The readings on yours will probably be in the 600 range. All other combinations will give OL.

Yeah, the middle leg was 644, and the right was 740. I assume this is fine.

That cap from digikey is fine but shipping will be expensive. Ebay probably has something cheaper.

Couldn't find anything locally, so I went with DigiKey. Needed to order a Triad for a Twin Famicom I recently found anyway, and it wasn't too hard to find some other stuff to bring my order up to $50 in order to get free shipping.

Thanks again, the offer I previously mentioned still stands, just send me a PM if there's anything you need.

[MKL]

Thanks but your satisfaction is enough for me.

[jd213]

OK, if you ever change your mind just LMK.

[jd213]

Ugh, starting to get minor glitches again, the H (and maybe V, hard to tell) shrinks a tiny bit for a split second every so often.

I already replaced all the deflection caps, but maybe it's time to recap the power board. Anything else I should check?

Still need to finish recapping my main PVM ( https://shmups.system11.org/viewtopic.p ... 3#p1511323 ), figures that this one would start giving me problems too...

[jd213]

Still haven't recapped the power board , but some new dielectric grease seems to have fixed the shrinking picture.

Wish I had the time to work on my 20L5...