1084ST Won't power on.

Bit of an odd one this.

Old Commodore 1084ST. Left running all day, generally showing signs of being a bit knackered (flyback whine, blurry corners) but fully working. But just now when I've had my back turned, died!

Now it just shows a vertical white line, which once a second collapses into a white dot, then expands to a line again. Monitor power LED turns on and off with this, and it also makes noise like it's powering on and off.

I know this is a rare variant, but I guess CRTs are all similar enough... I can't find any manuals online. What part failure is this, normally?

you have vertical and horizontal collapse,maybe even flyback failure...


you might have bad solder joints,but dont get your hopes up.

Well I think the most important symptom is rapid powering on/off at 1 second intervals. Is that the flyback?

Kindof bummed out because I just bought this with an A500. A500 was DOA but I thought the monitor would at least be nice.

i wouldnt know what the exact problem was unless it was siting on my bench right in front of me.:)

the power light going on and off would be an overload somewhere probably on the high voltage rail.
could very well be the flyback possibly other parts as well.

i wouldnt turn it on again if i was you,it wont get any better.


EDIT: there is a way to find out if its the flyback but suggesting it to people who may have no electrical knowledge can be a danger in itself.

I know enough not to blow myself up, I can solder and do work on things myself.

lol,ok you discharge the flyback remove it then check the voltages on all the rails.

if they look good and the power light stays on with the flyback removed its most likely the flyback.
i dont have a service manual for this monitor though,but i would imagine the main rail is around 125 volts dc when stable.
i think the tube itself is a philips but the chassis isent.

you dont want to messing around in the back anywhere near the flyback itll generate around 25k volts when working.

Taking it all apart now. How do you remove the small board on the back of the tube? I would leave it in place, but there are some wires directly soldered to the main board so I need to take them both out together.

I tried pulling - firm but gently - and it did not move. I don't want to break the glass.

EDIT: Gave it a firmer yank after wiggling it about. There was hotglue where I couldn't see. All unplugged now.

Oh now I'm reassembling it (minus flyback) and I realize I've done something incredibly dumb...

The board on the tube neck has two identical 4 pin connectors. One goes to the video in socket, the other goes to a small pcb which plugs in the far corner (right hand side closest to you from the back) of the main board.

I've only gone and unplugged both without marking which is which!

Looking at each plug, one is R,G,B, Ground.

The other is white, red, blue, Ground. white and ground use the same insulation.

neck board ports, each have one pin go to ground. But the interesting port's traces have only two wires go directly to an IC, the third to wherever. So that one must be for the second cable...

This is not as hard as it seems! I could get back into this.


_________

1:36AM update:

SUCCESS! after a snack break I finished reassembling the monitor, without the flyback transformer. Turned it on, and it stayed on!

Of course I turned it off after a couple of seconds because I have no idea what running it without such a vital part could do to it. But now we know flyback is kaput, time to find a replacement. I'll be happy to be rid of that horrible whining sound it makes.

It's identifying marks are:

top of flyback : 26 18 R
above focus control: CMP-15A

and a sticker:

SAMPO 9241
FEA188
42-025-01
MADE IN TAIWAN

Ten pins underneath in a horse shoe shape, and an eleventh in the middle.

Feeling positive about this! I'll also need a HOT right? How do I identify that?

it wont hurt it to run it without the flyback.

the hot usually will be a large transistor on a large heatsink near the flyback


was that what was written on the flyback? the sticker you mention.

if you can,take a clear picture of the underneath of the flyback directly into he pins and label please.

EDIT:i did quite a bit of searching and investigation,the replacement for the flyback(LOPT) is a HR7495
one down,now if you can tell me whats written on the hot transistor...

Sorry no can do on photos today, the weather is too bad.

Can't find a HR7495 anywhere online... This flyback has the same FEA188 on it: http://www.donberg.co.uk/catalogue/l...mat_33135.html

HOT is labeled:

T
S2000A
*2A