Help with dead Commodore 1802

[R_J]

Re: Help with dead Commodore 1802

Its fluctuating between 50 & 69v DC.

That is likely too low for the power supply to start.

[roadrash]

Re: Help with dead Commodore 1802

What is the voltage across C803, If this voltage is too low the circuit won't start
Did you check that C806 did measure different with your meter ?

Its fluctuating between 50 & 69v DC.

[R_J]

Re: Help with dead Commodore 1802

Ok soldered in and still the monitor is tickimg and lilght bulb is flashing. So no change

What is the voltage across C803, If this voltage is too low the circuit won't start
Did you check that C806 did measure different with your meter ?

[roadrash]

Re: Help with dead Commodore 1802

Just a thoght and i think STJ mentioned it before, it couldn't be a transformer could it? Running out of things to test now. We could just replace all caps in psu.

[roadrash]

Re: Help with dead Commodore 1802

They will be fine

Ok soldered in and still the monitor is tickimg and lilght bulb is flashing. So no change

[R_J]

Re: Help with dead Commodore 1802

They will be fine

[roadrash]

Re: Help with dead Commodore 1802

Hold them up to the monitor so I can see them I'm sure they will be fine, With newer technology they can make them smaller as long as the capacity and voltage is correct they will work.
Check the new 2.2/160v capacitor [C806] on your meter just to see what it displays.

Ok here is comparison picture. They are about half the original size.

[R_J]

Re: Help with dead Commodore 1802

I'm guessing there isn't one, but that wasn't my point. Just figured I'd add the information as it may help someone in the future.

I made an edit after you quoted me.

[Agent24]

Re: Help with dead Commodore 1802

Can you point out the Optoisolator in THIS circuit?

I'm guessing there isn't one, but that wasn't my point. Just figured I'd add the information as it may help someone in the future.

[R_J]

Re: Help with dead Commodore 1802

Optoisolators can degrade over time too, with the LED inside becoming dimmer like any LED does.

I was talking about THIS ciruit ONLY it was not a ment to be a general comment, This monitors power supply does'nt us an optoisolator. Since the monitor worked befor it was stored, components like transistors, ic's, resistors, normally won't deterorate, but electrolytic capacitors can dry out.
The crt will degrade over time also.

[Agent24]

Re: Help with dead Commodore 1802

I would replace the caps, They are about the only parts that will deteriorate overtime, This is a crude switching circuit and if it doesn't operate properly it won't work.

Optoisolators can degrade over time too, with the LED inside becoming dimmer like any LED does.

[R_J]

Re: Help with dead Commodore 1802

Hold them up to the monitor so I can see them I'm sure they will be fine, With newer technology they can make them smaller as long as the capacity and voltage is correct they will work.
Check the new 2.2/160v capacitor [C806] on your meter just to see what it displays.

[roadrash]

Re: Help with dead Commodore 1802

I would replace the caps, They are about the only parts that will deteriorate overtime, This is a crude switching circuit and if it doesn't operate properly it won't work.

I just repaired a monitor power supply that would turn on and off about 10 times before it would stay on. The power supply startup cap was a 22µf/50v. It's capacity checked 21.5µf. However the scope showed about 3~5v of high frequency ripple on it. replaced it and the power supply was working fine.

C806: c=223nf = 0.22µf. On the schematic it looks like 2.2µf/160v

I ordered the two caps as suggested and they arrived today. However I was shocked at how much smaller they are than the originals. WIll this be OK or should I find some others a similar or nearer size.

[R_J]

Re: Help with dead Commodore 1802

I would replace the caps, They are about the only parts that will deteriorate overtime, This is a crude switching circuit and if it doesn't operate properly it won't work.

I just repaired a monitor power supply that would turn on and off about 10 times before it would stay on. The power supply startup cap was a 22µf/50v. It's capacity checked 21.5µf. However the scope showed about 3~5v of high frequency ripple on it. replaced it and the power supply was working fine.

C806: c=223nf = 0.22µf. On the schematic it looks like 2.2µf/160v

[roadrash]

Re: Help with dead Commodore 1802

Check if you have ANY voltage on C814 or C812, if the power supply is ticking, it is trying to start but can't, either due to a short in the secondary or the primary can't start properly. I would start by replacing C806 and C825 and see if it makes a difference.

Check if you have ANY voltage on C814 or C812, if the power supply is ticking, it is trying to start but can't, either due to a short in the secondary or the primary can't start properly. I would start by replacing C806 and C825 and see if it makes a difference.

C806 & C825 when tested give the following results:

C806: c=233nf vloss=1.5% ESR=1.6 ohms
C825 c=12.25uf vloss=0.7% ESR= 3.0 ohms.

Will need to get some 10uf 160v if its no good as I only have 50v.ones.

[roadrash]

Re: Help with dead Commodore 1802

what AC voltage at L802 ??
input AND output side?

I get 237v AC.

[R_J]

Re: Help with dead Commodore 1802

Check if you have ANY voltage on C814 or C812, if the power supply is ticking, it is trying to start but can't, either due to a short in the secondary or the primary can't start properly. I would start by replacing C806 and C825 and see if it makes a difference.

[stj]

Re: Help with dead Commodore 1802

what AC voltage at L802 ??
input AND output side?

[roadrash]

Re: Help with dead Commodore 1802

I would just use the 60watt lamp in place of the resistor R801.

Ok i put the smaller bulb on L805 and when i power it up i still get the ticking noise and the 60w lamp flickering.

[R_J]

Re: Help with dead Commodore 1802

I would just use the 60watt lamp in place of the resistor R801.