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Sony PVM-2130QM - Color RED bleeds and is blurry.
buttersoft:
The elevated 200V might be a function of the bias voltage pulling high to compensate for the increased value of R704, though at only ~520k rather than 470k I wouldn't expect things to go pear-shaped. Maybe it's going funny under load. Did you replace any resistors yet?
arcadeswede:
--- Quote from: buttersoft on August 11, 2020, 02:30:50 am ---Did you replace any resistors yet?
--- End quote ---
No, I haven't got around ordering parts yet.
I just wanted to do some more troubleshooting, hoping to find more components that was bad to add to my order.
I'm thinking about just ordering some of the components for each color channel, just in case I find something strange later (and have some spare ones in the future).
Although, I'm having a hard time finding a new equivilant transistor for 2SA1091, 2SC2611 and 2SC2785. You can find A1091s on Ebay but it's $5 a piece, that adds up!
The diodes are tricky to find too, at least for me since I'm not that great with components :)
I'm looking at the datasheets and comparing parameters trying to find them on Digikey, Mouser, Tme.eu etc but I'm not 100% sure if I pick the right one. Maybe I'll just go with the resistors.
Here's the R704 with bad value (I just soldered it on the other side for easy removal later). The parts list says SOLID resistor but I'm guessing it's some kind of carbon that could be replaced with metal film ones as you guys said?
Zebidee:
https://alltransistors.com/crsearch.php?mat=Si&struct=NPN&pc=1.25&ucb=300&uce=300&ueb=5&ic=0.1&tj=150&ft=80&cc=4&hfe=30&caps=TO126
These are a common type of transistor with many possible substitutes. That site lets you review and compare the key data/characteristics for different parts. If you google up for example "2SC2611 equivalent datasheet" you'll find similar information on many site.
Those "SOLID" (solid carbon) resistors can be replaced with metal film resistors that have same-or-higher wattage ratings. I think those SOLID resistors are 1W rated? I got a bunch of 2W and 3W rated for my PVM2730QM. In my case I ended up only having to replace one SOLID resistor (the one on power coming to neckboard was failing slowly but tragicly) and a couple of electrolytic caps.
May as well check everything around Q707,Q718 and Q716 and the diodes, caps and resistors around them including the actual D707. Something there is giving weird voltages. Did these voltages change much after adjusting B+? What do you get where it says 200, up near top of your pic a few posts back?
arcadeswede:
--- Quote from: Zebidee on August 11, 2020, 04:59:51 am ---https://alltransistors.com/crsearch.php?mat=Si&struct=NPN&pc=1.25&ucb=300&uce=300&ueb=5&ic=0.1&tj=150&ft=80&cc=4&hfe=30&caps=TO126
These are a common type of transistor with many possible substitutes. That site lets you review and compare the key data/characteristics for different parts. If you google up for example "2SC2611 equivalent datasheet" you'll find similar information on many site.
Those "SOLID" (solid carbon) resistors can be replaced with metal film resistors that have same-or-higher wattage ratings. I think those SOLID resistors are 1W rated? I got a bunch of 2W and 3W rated for my PVM2730QM. In my case I ended up only having to replace one SOLID resistor (the one on power coming to neckboard was failing slowly but tragicly) and a couple of electrolytic caps.
May as well check everything around Q707,Q718 and Q716 and the diodes, caps and resistors around them including the actual D707. Something there is giving weird voltages. Did these voltages change much after adjusting B+? What do you get where it says 200, up near top of your pic a few posts back?
--- End quote ---
Great link! I'll check it out.
They are 1/2 W resistors but 2W would do, apart from being a little bit bigger I guess?
I'll replace all those solid resistors while I'm at it.
Hmm, very strange. Went back to measure the B, C, E of Q707 but now Collector shows 129V instead of 100-105V as earlier. Maybe a bad joint? I'm super confused. Red is still the same though.
These are my values as of right now.
What I've done compared to my last image with values is, adjusted +B voltage to exactly 140V. Switched transistors, the RED Q707 with BLUE Q703. Checked the D712 diode.
Where it says 200, I get 220V.
I'll remove the neck board and start desolder some components. just to check values of resistors. Electrolytic caps are already checked and swapped. Even the old ones was withing specs. What about ceramic caps? Should I bother checking them?
arcadeswede:
Oh, I just remembered!
There was a cap (C704) on the neck board that was very close (if not touching) a resistor (R711). The shell off the cap was in contact with the leg going to GND of R711.
I don't know if that was responsible for the low value of the collector on Q707, but I added some electrical tape between the two and got a decent value this time. I can't believe I didn't remember that! I blame the lack of sleep ;)
Before I created this post, I recapped the neck board but the replacement cap for C704 that I had was to big so I ended up using the old one (good and within specs), so maybe I soldered it back on in an angle or something.
Anyway, enough rambling. I'll do some proper work and order new resistors once and for all.
Thanks Zedibee and buttersoft for your patient! :)