1084s-P problem

[Loedown]

Originally Posted by Impakt

I took the BU508A out again and here are my measurements, they're different depending on the orientation of the probes. The component is on my desk, not on the heatsink.

| + | - |  Ohms  |
| B | C | ~0.85M |
| C | B |Infinity|
| C | E |Infinity|
| E | C | ~31.9M |

Edit: Just now i powered up the monitor without the BU508A, sound went away, and speakers are working again. Looks more and more like it's this part. I have a CM8833 and a CM8833-II too (which are set up elsewhere), so if I was desperate I could swap the part out just to help isolate it.

You should do a diode check on the transistor, but it certainly points heavily towards it, or the flyback transformer, pray it's the transistor, far cheaper.

Diode check should read either around 30 - 47 or 550 for E-B and around 550 for B-C.

I would still lean towards a short, as the power supply is being dragged down, most likely the flyback, you still need to check the remainder of the circuit after TS467, that's where your short will be.

Paul

[Impakt]

0.534v when testing + on B, - on E.

0.494v when testing + on B, - on C.

Nothing when i try the other combinations...

[Loedown]

You have a short AFTER the collector, check components

C467, C468, C469, D467, D468, C471, C473, C479 ( 470pF 2kV ), shorted deflection coil, flyback transformer. Usually you can disconnect the deflection coils, they have a separate plug onto the main board, if it powers up normally after that, then the coils are shorted ( horizontal ), but don't do it for long, otherwise it will phosphor burn a dot into the centre of your screen and it isn't really good for anything not driving the coils either.

Paul

[Impakt]

Will do. I think I checked some of those already but I'll have another look. If it is the flyback transfomer, are they still available? How much are they?

[Loedown]

Originally Posted by Impakt

Will do. I think I checked some of those already but I'll have another look. If it is the flyback transfomer, are they still available? How much are they?

http://groups.google.com/group/sci.e...49f6761fae47c7

http://www.amiga-hardware.com/showha...cgi?HARDID=849

Look at those two sites, read what it says, if you need a LOPT after that, I would go to www.hrdiemen.com

If you give me the EXACT number on the side of the flyback transformer, I will try to give you the equivalent.

Paul

[Impakt]

haven't had a chance to test the components but the flyback is labelled as such

E39144
TYPE AT2079
30101TY (looks like 8845 is stamped after the TY).

[Loedown]

http://www.hrshop.es/index.php?comma...930101&x=0&y=0

[Impakt]

Awesome, local mob here in Sydney sells them for $18, BU508A for around $4.
I'll probably go in this weekend and get 2 of each regardless of how the tests go with the other components.

Will keep you posted though loedown, thanks for your help so far!

[Loedown]

Originally Posted by Impakt

Awesome, local mob here in Sydney sells them for $18, BU508A for around $4.
I'll probably go in this weekend and get 2 of each regardless of how the tests go with the other components.

Will keep you posted though loedown, thanks for your help so far!

You won't need two of each, it's far more likely to be the flyback, you only need one. I would suggest Warner Electronics / Wes Components over in Ashfield, but I think that's who you already are going to.

Paul

[Impakt]

Yeah I meant WES. I put the HOT back in and desoldered the pin on the flyback that connects to the transistor, sound went away again.

I was going to get 2 because I don't want to get caught out in the future with a need for a part that isn't available anymore!

[Matt020]

May I please jump in here and comment that back in the day when CRT monitors were the in thing, I was always heavily cautioned to be very, very carefull when playing with the insides of a CRT monitor. I beleive it was due to the amount of energy that can be stored inside, even after being switched off. Is this worth mentioning before Impakt gets a shock of his life (excuse the pun)...

[Impakt]

Of course. Already discharged the old flyback and changed it. Doesn't short anymore but now there's no picture. I'm wondering if I still need to change the HOT or whether then2 knobs on the flyback need adjusting.

[Anemos]

i have socked 2-3 times from dam TV,s from then i have lost some data from my head..
my best way for discharge.. > [ Show youtube player ]

[Loedown]

Originally Posted by Impakt

Of course. Already discharged the old flyback and changed it. Doesn't short anymore but now there's no picture. I'm wondering if I still need to change the HOT or whether then2 knobs on the flyback need adjusting.

One is marked focus, the other is marked screen.

Oddly enough, focus is for the screen focus, screen is for screen voltage, or equating basically to brightness, yes, you need to adjust screen, if you see a series of lines on the CRT when you turn screen up, then it's too high. Turn it slowly!

Paul

[Impakt]

Hi Paul,
I adjusted the screen and focus (the guy at WES said I didn't need to worry about them). When tweaking them I noticed that they were turned all the way down.

Anyway, all adjusted and it's 100% working now!

Thanks heaps for your help. Sorry if I was a pain!

Impakt

[Loedown]

Originally Posted by Impakt

Hi Paul,
I adjusted the screen and focus (the guy at WES said I didn't need to worry about them). When tweaking them I noticed that they were turned all the way down.

Anyway, all adjusted and it's 100% working now!

Thanks heaps for your help. Sorry if I was a pain!

Impakt

I think you owe me a beer.

Paul

[cosmicfrog]

wow you got it working, great news Impakt and well done Loedown

[Loedown]

Originally Posted by cosmicfrog

wow you got it working, great news Impakt and well done Loedown

Repairs by proxy today, repairs by telekinesis tomorrow

Cheers Cosmicfrog

[Impakt]

Indeed I do. Thanks again mate