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Old 08-06-2019, 03:33 PM   #1
kadird
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Default Commodore 1084s-p1 fault with video.

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
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Old 08-06-2019, 05:43 PM   #2
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Default Re: Commodore 1084s-p1 fault with video.

it looks like a philips chassis, so it could be the line output transformer failed.
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Old 08-06-2019, 06:37 PM   #3
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Default 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

Last edited by R_J; 08-06-2019 at 06:50 PM..
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Old 08-07-2019, 06:41 AM   #4
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Default Re: Commodore 1084s-p1 fault with video.

Quote:
Originally Posted by stj View Post
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?
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Old 08-07-2019, 06:43 AM   #5
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Default Re: Commodore 1084s-p1 fault with video.

Quote:
Originally Posted by R_J View Post
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.
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Old 08-07-2019, 06:43 AM   #6
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Default 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.
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Old 08-07-2019, 07:16 AM   #7
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Default Re: Commodore 1084s-p1 fault with video.

Quote:
Originally Posted by stj View Post
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
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Old 08-09-2019, 01:15 PM   #8
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Default Re: Commodore 1084s-p1 fault with video.

@stj, I cant spot these points in the pcb, is there any detailed schematics or guide somewhere?
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Old 08-11-2019, 04:49 AM   #9
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Default Re: Commodore 1084s-p1 fault with video.

manuals
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Old 08-12-2019, 06:58 PM   #10
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Default 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

Last edited by kadird; 08-12-2019 at 07:03 PM.. Reason: adding picture
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Old 08-12-2019, 09:54 PM   #11
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Default Re: Commodore 1084s-p1 fault with video.

Yes, 7512 is the horizontal output (flyback) transistor
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Old 08-13-2019, 03:55 AM   #12
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Default Re: Commodore 1084s-p1 fault with video.

Quote:
Originally Posted by R_J View Post
Yes, 7512 is the horizontal output (flyback) transistor
okay, which one is B+ cap then?
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Old 08-13-2019, 07:25 AM   #13
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Default Re: Commodore 1084s-p1 fault with video.

2520 10uf - you should see 128v across it.
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Old 10-19-2019, 03:08 PM   #14
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Default 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.
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Old 10-20-2019, 10:30 AM   #15
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Default Re: Commodore 1084s-p1 fault with video.

I just configure brightness potentiometer on the EHT and problem solved.
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Old 10-20-2019, 04:07 PM   #16
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Default 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.
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Old 10-21-2019, 01:31 PM   #17
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Default Re: Commodore 1084s-p1 fault with video.

Quote:
Originally Posted by stj View Post
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.
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