Help with dead Commodore 1802

[R_J]

Re: Help with dead Commodore 1802

Just wondering what is this B+ adjustment and I cannot see anything in the manual about it. The manual only mention static & dynamic convergence.

There is no B+ adjustment, just check if it is close to the 121vdc as indicated on the schematic, if it's off a couple volts either way, thats not an issue.

[roadrash]

Re: Help with dead Commodore 1802

https://www.rapidonline.com/power-pcb

found one on ebay. i will just have to swap over LED.

https://www.ebay.co.uk/itm/RVFM-PT-M...MAAOSwgARa58oX

[roadrash]

Re: Help with dead Commodore 1802

you should check the B+ voltage and compare it to the manual - it can be ajusted.
it's DC btw.

Just wondering what is this B+ adjustment and I cannot see anything in the manual about it. The manual only mention static & dynamic convergence.

[stj]

Re: Help with dead Commodore 1802

there is no standby trigger on the CBM monitors, just DPST mains switching.

[R_J]

Re: Help with dead Commodore 1802

If the small spst part of the switch is not used, this might work: https://www.conrad.com/p/pwl-2p1tl-6...h-1-pcs-701606

There is also the ALPS SDGA3P

[roadrash]

Re: Help with dead Commodore 1802

I want to thanks both of you guys STJ & RJ for helping me finally get this commodore monitor fixed. I put the Wire wound resistor back it and it doesnt blow now and the display fills the screen and i can hear audio too. I will give it a test with a video signal when I more time but I am glad its finally fixed and I doubt I could have done that without the
help from you two.
I have learned loads and just hope I don't forget it all as I have big Issues with memory problems caused by my Multiple Sclerosis which is most difficult as I find it hard to learn new things and make them stay in my memory although I can remember all my past history.
I've got it all stored on my hard drive so if i ever need to use it again I can. RJ that Schematic that you did for me showing where it changed from to DC was brilliant and made it all a lot easier for me to understand.
Thanks again guys your brilliant and cant thank you enough.

cheers!
Jon

[roadrash]

Re: Help with dead Commodore 1802

https://www.rapidonline.com/power-pcb

Thanks for that STJ that's a great help. Ive got quite a few Commodore and Phillips CM monitors for all the Amiga kit I have here. I sold My Original Amiga A1000 and Amiga branded matching 1081 monitor last year. I still have a few A500's, a A1200 and my big A2000 with hard drive and IBM XT bridgeboard inside. I've got tons of software too. If your looking for anything Commodore just ask.

[stj]

Re: Help with dead Commodore 1802

https://www.rapidonline.com/power-pcb

[roadrash]

Re: Help with dead Commodore 1802

does that switch normally solder to the board, or have wires on it?
if it's wires then a replacement wouldnt be hard.

on the 8833-II i removed the pushbutton from the case and fitted a rocker switch instead.
i'll get photo's over the weekend if you want.
not exactly original, but on the 8833-II the switch is at the back out of sight.

Yes it has wired connections and the switch assembly is screwed onto the plastic casing.

[stj]

Re: Help with dead Commodore 1802

does that switch normally solder to the board, or have wires on it?
if it's wires then a replacement wouldnt be hard.

on the 8833-II i removed the pushbutton from the case and fitted a rocker switch instead.
i'll get photo's over the weekend if you want.
not exactly original, but on the 8833-II the switch is at the back out of sight.

[roadrash]

Re: Help with dead Commodore 1802

If the lamp is in place of this inductor then it will still pass the voltage to that part of the circuit, It might be slightly low, likely around 100vdc. You can remove the lamp from the 121 volt line and reconnect the coil, I suspect you will then get a full width screen also.

Ok I found I had put it back in when you asked me to earlier put everything back. I am begining to think it might be safe now to put the resistor R801 back in now.
I currently have 2 bulbs in place of this resistor.
I am still a bit unsure as we still never found what was causing that short.
What do you think?

[roadrash]

Re: Help with dead Commodore 1802

btw, can you take a picture of the power switch?
i want to see if it's like the one on the phillips CM8833-II (commodore 1084-s)

These switches are a nuisance and I can't find replacements anywhere and end up bridging the contacts and turning it on/off at the mains wall plug.

[stj]

Re: Help with dead Commodore 1802

btw, can you take a picture of the power switch?
i want to see if it's like the one on the phillips CM8833-II (commodore 1084-s)

[R_J]

Re: Help with dead Commodore 1802

If the lamp is in place of this inductor then it will still pass the voltage to that part of the circuit, It might be slightly low, likely around 100vdc. You can remove the lamp from the 121 volt line and reconnect the coil, I suspect you will then get a full width screen also.

[roadrash]

Re: Help with dead Commodore 1802

I still have the light bulb in place of the resistor and I still have that other bulb in place of the indictor which was done to isolate the psu from everything else except audio so I dont get it how is the screen powering up?

[R_J]

Re: Help with dead Commodore 1802

you should check the B+ voltage and compare it to the manual - it can be ajusted.
it's DC btw.

The voltage is regulated by ic801 but there is no adjustment, I agree on checking that the 121vdc is ok across C813

[stj]

Re: Help with dead Commodore 1802

you should check the B+ voltage and compare it to the manual - it can be ajusted.
it's DC btw.

[R_J]

Re: Help with dead Commodore 1802

Good to see it's working. Feed it some signal and see what it looks like, One capacitor I have changed a lot is tv's and monitors it the drive transformer filter cap. C430 (1µf/160v) If you have one I would replace it.

[roadrash]

Re: Help with dead Commodore 1802

So what is the voltage across C803?

I have got it back to where we were now and i have the psu working and audio section now working again.
I replaced the IC801 and now its back working and i have a display now look.

What now?

[roadrash]

Re: Help with dead Commodore 1802

Ive removed IC801 to be sure and there is no short.

There is a resistance between the pads 3 & 4 of IC801 that changes value like its connected to a cap or something which the Schematic seems to suggest and I think you mentioned before 27 ohm.
am I right? could this short we are looking for be in this area?