Commodore 1084s-p1 fault with video.

[kadird]

Hi all, i have a 1084s and that was working fine until yesterday. But yesterday monitor is suddenly stopped and faulty now.

I want simply upload a video about problem, which parts and areas should i check, can anyone help?

Thanks.


https://youtu.be/qiizl8iJRLM

[stj]

Re: Commodore 1084s-p1 fault with video.

it looks like a philips chassis, so it could be the line output transformer failed.

[R_J]

Re: Commodore 1084s-p1 fault with video.

I would first check for a shorted horizontal output transistor or maybe a shorted diode in the power supply secondary. Are you getting any secondary voltages? there is a service manual for this monitor
Being an old monitor I would I would check the small caps in the primary switching circuit and it could also be a bad cap for one if the secodary voltages. This power supply has a triac for over voltage protection and that "might" be the sound you are hearing

[kadird]

Re: Commodore 1084s-p1 fault with video.

it looks like a philips chassis, so it could be the line output transformer failed.

Yes, it is Philips one. What's the line output transformer, you mean flyback transformer?

[kadird]

Re: Commodore 1084s-p1 fault with video.

I would first check for a shorted horizontal output transistor or maybe a shorted diode in the power supply secondary. Are you getting any secondary voltages? there is a service manual for this monitor
Being an old monitor I would I would check the small caps in the primary switching circuit and it could also be a bad cap for one if the secodary voltages. This power supply has a triac for over voltage protection and that "might" be the sound you are hearing

Thanks for advices. I dont measure any voltages yet. Only visually controlled around pcb and dont noticed any bad looking caps or transistors. I have service manual, will check soon. Thanks again.

[stj]

Re: Commodore 1084s-p1 fault with video.

yes,
there is a way to test for this.
but first:

remove the flyback transistor and test it.
while it's out, put a 40w lamp ( a traditional one, not led) across the B+ capacitor
it should light up.

[kadird]

Re: Commodore 1084s-p1 fault with video.

yes,
there is a way to test for this.
but first:

remove the flyback transistor and test it.
while it's out, put a 40w lamp ( a traditional one, not led) across the B+ capacitor
it should light up.

Okay ill try it thanks

[kadird]

Re: Commodore 1084s-p1 fault with video.

@stj, I cant spot these points in the pcb, is there any detailed schematics or guide somewhere?

[stj]

Re: Commodore 1084s-p1 fault with video.

manuals

[kadird]

Re: Commodore 1084s-p1 fault with video.

thx again, can u give me part numbers in schematics? for example, which one is flyback transistor, 7512?

https://imgur.com/a/KKkkpEw

[R_J]

Re: Commodore 1084s-p1 fault with video.

Yes, 7512 is the horizontal output (flyback) transistor

[kadird]

Re: Commodore 1084s-p1 fault with video.

Yes, 7512 is the horizontal output (flyback) transistor

okay, which one is B+ cap then?

[stj]

Re: Commodore 1084s-p1 fault with video.

2520 10uf - you should see 128v across it.

[kadird]

Re: Commodore 1084s-p1 fault with video.

Hello again. I replaced EHT transformer with new one, picture partly came back but another issue appeared now. Here is the video about new situation:

https://youtu.be/GIYkvtMsf28

Where should i check now? Caps maybe or?

Thanks.

[kadird]

Re: Commodore 1084s-p1 fault with video.

I just configure brightness potentiometer on the EHT and problem solved.

[stj]

Re: Commodore 1084s-p1 fault with video.

you must adjust focus and brightness on the transformer.
brightness is often labeled "screen"

you need to do focus first, then brightness, then focus again - because they slightly effect each other.

[kadird]

Re: Commodore 1084s-p1 fault with video.

you must adjust focus and brightness on the transformer.
brightness is often labeled "screen"

you need to do focus first, then brightness, then focus again - because they slightly effect each other.

thanks man, i'll do it again this way.