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PVM-1454QM repair logs (Vertical foldover, Orange tally lamp of death + more?)


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Hitachi-vfoldover.jpg.1acb3608d861a0d36f0f5d409639cbe3.jpg

 

(OK, so as with a few posts, the top of this one was eaten with the forum upgrade in early 2020. Apologies for that, but there's nothing to be done about it. Msg me if you can't translate anything and i'll try to help.)

 

The greyish lines above are a general image of the problem called vertical foldover.

*Not* PVM schematics below

TA8403K.PNG.e1e8b0a2ac34718b1526ad6cc2588506.PNG

1314726054_teac_ctm5122hVerticaldefcircuit.PNG.eddff0dacfc30e048ed57b84a3de5f3b.PNG

 

But Sony, being Sony, never liked to do anything easily when something five times as complicated would do. So the vertical section in a PVM looks completely different to a consumer set like the above. Scanning the schematics for the PVM-1354 (which will be identical to the missing 1454 schematics possibly bar the power-supply section and probably even then) I came up with a short list of electrolytic caps in the vertical deflection section to check. The deflection section is located on the A-board. Google told me that for a PVM-1954 there was one particular cap that caused this exact problem - C584 at 2.2uF/160V.

 

This is the PVM schematic below, showing the relevant portion of the A-board:

PVM-1354_vdef.thumb.PNG.2c0ee5273f7ca467af314e17875c111c.PNG

 

Examining the schematics for a few different PVM's, the vertical section of the 1354 is the same circuit used in the PVM-1954, 2054, 1454, 14M2, 14M4 and 20M2, 20M4 series if not more. This does not necessarily mean the same power supply or circuit-boards or even component numbers are used, though they might be. The identified cap was near the top of my list to check anyway, and turned out to be well out of spec. I changed it, along with C590 and C588 because they were next door. Problem fixed. The vertical size of the screen had been set to compensate for the failing cap, so I went into the service menu and shrank it again. With a quick convergence and geometry adjustment the picture is now looking great.

 

EDIT: Elsewhere on the net

Edited by buttersoft
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  • 1 year later...

So, the orange tally lamp of death. I have no idea if the fix is going to be similar or even related for every instance of this. It certainly appears that the fault condition can be intermittent, or delayed, but if it happens at all it probably means the set will need to be looked at soon.

 

The tally lamp is at the top of the bezel and it's normally used for indicating the monitor is active, being recorded from, for studio use, etc. It's toggled by an external remote bridging two pins IIRC, and does nothing but show a light, sometimes in green unless that's only for medical models. However, if you look at the schematics in the service manual the lamp is wired into the circuitry in a way that makes little sense if that’s all it does, and anyway it might have other colours. It must be connected to a fault-finding function, but i haven't been able to find out how far that function goes.

 

This PVM-1454 never powered up for me. Previous symptoms were described as a loss of sync after ten minutes operating. When I turned the set on, the startup didn’t sound quite right, the high-voltage was obviously shutting off almost instantly, faster than any image could come up on the screen. The power light was on, and the tally lamp was lit up in orange, so the set was getting power in some form. But, very importantly, none of the buttons lit up (in the blue rectangle below). One button at least is always meant to be lit to show you which input you are displaying, line A, line B, etc.

 

The orange tally lamp of death. The power light is on too, but no buttons are illuminated.

FSLwU7m.jpg

 

Google showed me a few posts about models displaying the same symptoms, and one or two people reported that the tech who fixed theirs said it was a power supply issue. At any rate no more sensible information seemed to be available. So I borrowed the other PVM1454 from the post above back from its new owner and swapped the power supplies over (the G-board). With this new G-board the set worked fine.

 

I swapped the faulty G-board back, and decided to recap it – hey, we’ve all done it. This produced exactly no change. The G-board has five connector plugs on it – AC in, AC to front-panel power switch and back, degaussing coil, and two smaller ones that take power to the A-board, the main board of the set. Most PCB’s of this vintage have nice silkscreens, and the two smaller connectors were labelled with helpful markings like 115V, -15V, GND, etc.

 

With the set powered-up all the voltages at the two connectors tested fine, except for one pin. There are two 5V lines on this set, labelled 5V A and 5V B. 5V B tested fine at 4.89V, but 5V A showed only 1.9V on my meter. Swapping the working G-board back in showed its 5V A line at 4.88V with 5V B at 4.98V. I turned the faulty G-board over and began tracing the 5V A line back from the connector, and then the 5V B line, and to my delight found that each went through an inductor, then a voltage regulator (IC603 or IC604 depending on which rail), then a resistor, but upstream of that became common. So the regulator for each rail was fed from the same supply. Given the 5V B rail on the faulty G-board was fine, the upstream supply probably was too. The problem was almost certainly going to lie in one of the three components that control the 5V A rail (given I'd already changed the filter caps).

 

G-board solder-side showing the components for the two 5V rails having a common supply. The painted red X was to identify the faulty board.

PhdRESo.jpg

 

The resistor was the same for each rail. But the inductors and voltage regulators were not, so I couldn’t just swap them between rails on the same board. Having a second board proved handy again because without desoldering anything I could meter known working components. The inductor tested fine, the same on both boards with a multimeter set to resistance. Not normally a way to test an inductor, just looking for differences between the two boards here. The resistor tested fine too. But the voltage regulator IC603, a New Japan Radio NJM78M05FA, tested differently each time. I didn’t do any fancy testing, again just a multimeter set to ohms, but the readings for the regulator on the faulty board kept jumping, or giving a totally different value each time I tested, both out of circuit and in.

 

I swapped the suspect regulator for the known working one, and problem solved - no orange light, line A button illuminated, and after a few seconds I can see the OSD come up nice and stable when I push the button!

 

The culprit.

90aUsMK.jpg

 

It’s really an FA not an A model as the package is totally encased in plastic. It's clamped to a heatsink regardless, so perhaps poor thermal dissipation killed it. I have some replacements on order, but might look for a substitute in the TO-220 rather than TO-220F package, so it has the exposed metal tab.

 

NOTE: the service manual I have for the 1454QM has a supplement at the bottom which contains information about the G-board in the sets I have. The main body of the manual contains a completely different power supply, or a revision different enough it made my head spin for a short time. The supplement contains no schematics for this different G-board, only a bad B&W scanned photo of the PCB that seems to be missing most of the silkscreen markings.

Edited by buttersoft
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Pursuant to the subject above, apparently there’s a green tally lamp of death as well. @Dochartaigh reports having this on one of his Olympus OEV’s, which are a rebadge of the PVM-xxM2MD medical models. The light clearly has a fault-indicating function as well as it’s normal purpose, but whether it can come up in different colours on the one set, and what it might signify in any case, is information we’ve not been able to find. It might be that the medical models have a green led not an orange one, or just that newer models do, or even that it's reporting a different kind of fault, but if anyone knows more please let us know! Edited by buttersoft
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  • 2 months later...

There's a nice PVM-20M4A power supply repair log by Evan Weston at this link

 

Describing a set that was working and then suddenly wasn't, and didn't show any signs of life afterwards. It seems this problem is not unique, and is a combination of IC601 & IC602 on the power supply board, and Q501 on the main board.

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  • 1 year later...

Welcome to AA :)

 

https://ia800101.us.archive.org/8/items/SonyPVM1450QMPVM1454QM1354ServiceMaintenanceManual/Sony%20PVM-1450QM%20PVM-1454QM%201354%20Service%20Maintenance%20Manual.pdf

and

https://ia803109.us.archive.org/14/items/SonyPVM135013511354ServiceManual/Sony%20PVM%201350-1351-1354%20service%20manual.pdf

 

Just make sure you look at the right schematic diagram, as those cover a few models. And make sure to check against what you're seeing inside the 2054 as well, because sometimes the manuals are not correct!

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Welcome to AA :)

 

https://ia800101.us.archive.org/8/items/SonyPVM1450QMPVM1454QM1354ServiceMaintenanceManual/Sony%20PVM-1450QM%20PVM-1454QM%201354%20Service%20Maintenance%20Manual.pdf

and

https://ia803109.us.archive.org/14/items/SonyPVM135013511354ServiceManual/Sony%20PVM%201350-1351-1354%20service%20manual.pdf

 

Just make sure you look at the right schematic diagram, as those cover a few models. And make sure to check against what you're seeing inside the 2054 as well, because sometimes the manuals are not correct!

 

I really appreciate that you ...�

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