L.G. 42PC1D, dark flickering pic.

[Alastair E]

Re: L.G. 42PC1D, dark flickering pic.

Yes--Once Great Makers de-evolved into re-badging utter crap--Very sad really!

I used to work at Hitachi dealers in early 80's the sets were good. We used to service the likes of the CNP190, these things Barely ever went wrong--only mechanical wear of the push-button tuner, --after 20 years--then, still good.
Picked an earlier one up a year back--a CSP-470 from 1974, Its Still Working today!

Sorry to go o/t, Normal service will be resumed tomorrow eve when I dig the scope out!

[Clydeuk]

Re: L.G. 42PC1D, dark flickering pic.

I worked for Comet service until the hammer fell on that company, they sold a huge number of JVC badged sets right up to 42 inch, made by Vestel. While I'll agree it's cheap crap they are at least pretty consistent with failures, which seem to have been worse the newer the chassis. Power supply as always with Vestel is a weak point, and can damage other areas when it fails.

I have to say due to the hectic nature of that job I never had any chance to delve in deep, I have since leaving discovered a whole lot more about them.

They can give a decent display despite the poor quality design, 32 inch and below anyway.

[Alastair E]

Re: L.G. 42PC1D, dark flickering pic.

OK, Ive dug the scope out and checked the waveforms.

Y-sus appears a fair facsimile of whats in the manual, but the sharp spike downwards of the positive going ramp has a flat bottom of approx 10us.
Its approx 250V at its peak from the '0' v line.

the wave is fairly stable and constant.

The Z-sus wave is rather similar in shape, but the positive ramp doesnt climb to a peak then return sharply to 0v, but has a rounded off part after the downward spike (neg going square-wave block) climbing again and a flat top, of 90V in relation to '0'V.

There's a lot of messing round going on with the Z-sus waveform, not stable or constant--'stuff' going on in the background is the best I can say....

Z-sus IPM is stone cold after half-hour while Y-sus is warm.

Does the above confirm Z-sus IPM failure?

My old scope absolutely Hates these waveforms and its rather difficult to see/sync on them--Let alone take any pics of 'em!

[Alastair E]

Re: L.G. 42PC1D, dark flickering pic.

If you reckon it is the IPM--where would be the best place to get one? --Seem to be a lot around of dubious origin!

[tom66]

Re: L.G. 42PC1D, dark flickering pic.

Does your scope have a line trigger? Feed the set with ~50Hz video and sync off 50Hz mains. It's not perfect, but it's good enough to have a quick look.
(Panel refresh is about 10 x input frame rate, no frame conversion is done.)

[Alastair E]

Re: L.G. 42PC1D, dark flickering pic.

Better still--I could sync off the video sync from external source....

Cant remember--set is put away at the mo, but I think there's a video O/P, could sync off that, or as you say--feed off a SCART etc....

Didn't think of that (Doh--What a dumbo!)--Cheers Tom!

[Alastair E]

Re: L.G. 42PC1D, dark flickering pic.

OK then--I'm fairly convinced its the IPM what with the readings and scope-checks, plus the fact its stone-cold......

Ive got a 50PDPX3 chassis at work--but this uses two IPM per board, a J015C and a J016C.

The 42 uses a single J018C....

I'm wondering if either of the above would be suitable as a replacement. I cant find any datasheets or anything on any of them though....

Anyone got a spare good YPPD-J018C (Or even a complete working Z-Sus) want to swap some parts/boards for? Ive got lots of different make/model etc to choose from--Probably more than those iffy sellers on fleagay!

[tom66]

Re: L.G. 42PC1D, dark flickering pic.

AFAIK, the IPMs are not compatible. On 50" chassis, one is ERC, other is SUS. On 42" chassis, one IPM does both ERC and SUS.

[Alastair E]

Re: L.G. 42PC1D, dark flickering pic.

Ah--Aint That typical!

[Alastair E]

Re: L.G. 42PC1D, dark flickering pic.

Well--I've got two sets now--One at work a 50" (50PC1DA) and the set I have here--Both have much the same flicker in the screen and similar voltages etc. Ive yet to check to 50" waveforms, it was getting late, had to shut the shop--and the ever present distraction of customers stopped me checking waveforms today....

This thread, Tom had a tussle with a 50" with the grey flickering screen--

https://www.badcaps.net/forum/showth...hlight=50pc1da

In the end, it was his ERC IPM and buffer-chips causing problems.....
--I'm hoping the buffers are OK on my 42" but looks more and more like the IPM's are my troubles with that one.

Guess I'll have to stump up and buy a couple, unless anyone can suggest anything more to test.
--Not sure what to do with the 50", Guess I'll shove it back in my tin-shed at work--with all the other sets Ive got spares issues with!

[Alastair E]

Re: L.G. 42PC1D, dark flickering pic.

For the record--I repaired the IPM in a thread here--

https://www.badcaps.net/forum/showthread.php?t=34766

Buffers were OK thankfully.

[Alastair E]

Re: L.G. 42PC1D, dark flickering pic.

The set now has 25 hours on its repaired IPM, with a computer case (quiet) fan added over each IPM heatsink for cooling.

Firmware has been updated to remove the Mal-Discharge or red-dots it had a severe case of.
So far--so good.....

[adamp91gvm]

Re: L.G. 42PC1D, dark flickering pic.

Sorry to jump in on your post but I have the same tv that has no pic at all would it be easier to start a new post ?

[Alastair E]

Re: L.G. 42PC1D, dark flickering pic.

Well--Seeing same set, you could carry on this one if you want....

What tests have you done? Anything on the screen at all--in darkened room?

[adamp91gvm]

Re: L.G. 42PC1D, dark flickering pic.

Nothing I have narrowed it down to the y sustain the voltage is up and down when it's plugged in but when disconnected voltage from the power board is level

[Alastair E]

Re: L.G. 42PC1D, dark flickering pic.

Have you tried it with the Vs fuse Out on first, Y-Sus, then Z-Sus...?

Set will trip out if there's no 5V to the Y-Sus board--as in pulling the plug, I think the Control-board sources 5v from there....

[adamp91gvm]

Re: L.G. 42PC1D, dark flickering pic.

In fact it seems to be when the t con is connected to the y sustain just taken the ribbon out of it and everything is level and constant

[Alastair E]

Re: L.G. 42PC1D, dark flickering pic.

Are the three or four temp LED's lit on the Control-Board?--Usually three if its cool, two if very cold

[adamp91gvm]

Re: L.G. 42PC1D, dark flickering pic.

Yer there is only 2 on

[Alastair E]

Re: L.G. 42PC1D, dark flickering pic.

Ok--Thats fine, control-board active, doing something anyway!

Have you a scope?