I've had this PVM for 4 months now. It was working fine and could switch between consoles normally using gscart lite via scart to bnc. I could power off any console and power on another with no issues. However, a problem occurred after hooking up a gamecube to Line A via RCA cables (yellow using a rca to bnc adapter). I got a picture by deselecting EXT sync. However when I turned off the gamecube the PVM buzzed and after a few seconds powered off. Now the PVM cannot be powered on at all.
What do you think happened? and what can I do about it?
Cheers.
Sony PVM 20m4u won't power on
Re: Sony PVM 20m4u won't power on
Please describe the symptoms in greater detail.
When you press the power switch, is there absolutely zero reaction? Does it come on and quickly go right back off again? Can you hear a light clicking sound, or any other noise? Do any indicator lamps light up?
I think it's very unlikely that any particular signal being fed into the unit could cause a total failure. If your PVM really is dead, it's probably just a coincidence that it happened after you connected your Gamecube for the first time.
When you press the power switch, is there absolutely zero reaction? Does it come on and quickly go right back off again? Can you hear a light clicking sound, or any other noise? Do any indicator lamps light up?
I think it's very unlikely that any particular signal being fed into the unit could cause a total failure. If your PVM really is dead, it's probably just a coincidence that it happened after you connected your Gamecube for the first time.
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MrObliverate
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- Joined: Mon Feb 12, 2018 4:44 am
Re: Sony PVM 20m4u won't power on
Absolutely zero reaction best describes it. When I turned off my gamecube console, a short but loud buzz occurred followed by the picture collapsing to the center of the monitor and then shutting off. Now the PVM doesn't respond to power (i) button and no indicator lights up.
Re: Sony PVM 20m4u won't power on
Did the picture collapse to a single horizontal line in the center of the screen?
If it did, there are a few things we can suppose:
1. The vertical deflection circuitry has failed. This much is virtually guaranteed.
2. The most likely cause of vertical deflection failing is the vertical output chip that drives the electromagnetic yoke coils failing. This could have easily caused a short and triggered over-current protection, which would explain your zero-reaction. EDIT: It probably wouldn't have blown the fuse, as I had written before, actually.
3. The vertical deflection chip is likely dead, but there could be other components around it that are also dead or dying. Once you identify the chip, replace any electrolytic capacitor connected to it, and test any low-ohm resistors connected to it, too.
Did you ever have to crank up the vertical size potentiometer in order for the image to fill the screen? Electrolytic capacitors going bad can cause you to have to do that, but this puts more stress on the vertical output chip.
Anyway, I would check the fuse first just in case, then look at the schematics for the 20M4U's deflection board to identify the vertical output chip, which would be last major transistor or amp-like component before the vertical deflection coils. Find it on the board, then order a replacement.
If it did, there are a few things we can suppose:
1. The vertical deflection circuitry has failed. This much is virtually guaranteed.
2. The most likely cause of vertical deflection failing is the vertical output chip that drives the electromagnetic yoke coils failing. This could have easily caused a short and triggered over-current protection, which would explain your zero-reaction. EDIT: It probably wouldn't have blown the fuse, as I had written before, actually.
3. The vertical deflection chip is likely dead, but there could be other components around it that are also dead or dying. Once you identify the chip, replace any electrolytic capacitor connected to it, and test any low-ohm resistors connected to it, too.
Did you ever have to crank up the vertical size potentiometer in order for the image to fill the screen? Electrolytic capacitors going bad can cause you to have to do that, but this puts more stress on the vertical output chip.
Anyway, I would check the fuse first just in case, then look at the schematics for the 20M4U's deflection board to identify the vertical output chip, which would be last major transistor or amp-like component before the vertical deflection coils. Find it on the board, then order a replacement.
Last edited by SamIAm on Thu Feb 15, 2018 12:20 pm, edited 2 times in total.
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MrObliverate
- Posts: 4
- Joined: Mon Feb 12, 2018 4:44 am
Re: Sony PVM 20m4u won't power on
I remember it collapsing like a circle, if that changes your diagnostic. And no, I never had tweak with anything to get the image to fit the screen
Re: Sony PVM 20m4u won't power on
Oh. Well, the problem is probably not related to vertical deflection, then.
How big was the circle, and how long was it on the screen?
If it was a very short-lived little dot, then the problem probably isn't related to deflection at all, but rather to something else.
Do you have a digital multimeter? The next thing to check is probably the voltages coming off the power supply board. That, and the fuse.
How big was the circle, and how long was it on the screen?
If it was a very short-lived little dot, then the problem probably isn't related to deflection at all, but rather to something else.
Do you have a digital multimeter? The next thing to check is probably the voltages coming off the power supply board. That, and the fuse.
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MrObliverate
- Posts: 4
- Joined: Mon Feb 12, 2018 4:44 am
Re: Sony PVM 20m4u won't power on
It was big but it quickly collapsed to nothing. All happened within a second.
Re: Sony PVM 20m4u won't power on
That makes remote diagnosis pretty difficult. You've probably got to go step-by-step through the system until you find the fault.
I would still guess that this is related to either something in the power supply going bad or something on the deflection board shorting. If I were you, I'd take off the panels of the unit and inspect those boards for burnt-out-looking parts, then proceed to use a multimeter to check the various power supply voltages. This might necessitate disconnecting the power supply from the rest of the unit, because a short somewhere else could be tripping some sort of protection.
If all voltages are coming out of the power supply properly, the problem could still be the vertical output chip failing, or something like a failed horizontal output transistor on the deflection board causing a short. That would be common.
It's worth it to check the fuse, but it's possible with shorts that over-current protection is stopping the system from coming on. I'd turn the monitor on and listen really carefully one more time for a light ticking sound, because over-current protection tends to make little noises when it's active.
Good luck.
I would still guess that this is related to either something in the power supply going bad or something on the deflection board shorting. If I were you, I'd take off the panels of the unit and inspect those boards for burnt-out-looking parts, then proceed to use a multimeter to check the various power supply voltages. This might necessitate disconnecting the power supply from the rest of the unit, because a short somewhere else could be tripping some sort of protection.
If all voltages are coming out of the power supply properly, the problem could still be the vertical output chip failing, or something like a failed horizontal output transistor on the deflection board causing a short. That would be common.
It's worth it to check the fuse, but it's possible with shorts that over-current protection is stopping the system from coming on. I'd turn the monitor on and listen really carefully one more time for a light ticking sound, because over-current protection tends to make little noises when it's active.
Good luck.
Re: Sony PVM 20m4u won't power on
I am having the same problem with my 20M4U - won't power on after feeding it a bad (24kHz) signal. I could hear ticking from the power supply so I tested the transistors on the deflection board - looks as though the following 6 transistors failed:SamIAm wrote:If all voltages are coming out of the power supply properly, the problem could still be the vertical output chip failing, or something like a failed horizontal output transistor on the deflection board causing a short. That would be common.
It's worth it to check the fuse, but it's possible with shorts that over-current protection is stopping the system from coming on. I'd turn the monitor on and listen really carefully one more time for a light ticking sound, because over-current protection tends to make little noises when it's active.
Q704 B Buff
Q705 G Buff
Q706 R Buff
Q707 B Out
Q708 G Out
Q709 R Out
I've got replacements on order, but is there anything else I should test while I wait for parts?