Help with dead Commodore 1802

[stj]

Re: Help with dead Commodore 1802

https://uk.rs-online.com/web/p/throu...stors/6661718/
£7.90 inc free postage.

https://www.tme.eu/gb/details/crl10w...s/sr-passives/
55p + about £6 postage

https://www.reichelt.com/gb/en/wirew...?&trstct=pol_0
87p + postage

[stj]

Re: Help with dead Commodore 1802

where the fuck are you shopping?????

RS is free delivery,
germany and poland only cost about £6

[roadrash]

Re: Help with dead Commodore 1802

It will be a wirewound, this from digikey should work A137101-ND Mfg # SQZW103R3J which seems to be like the original. TYPE SQZ horizontal, pluggable.
They go open after time, the wire gets a weak spot and thats it, If there was any other problem it would have blown the fuse and not the resistor.
If you just want to try the monitor, replace it with a piece of wire, if there is a short anywhere the fuse will blow. or if you want to get fancy replace it with a incandescent lamp to test

wow thats expensive..

Subtotal: £2.07
Shipping: £12.00
VAT: £2.81
Total: £16.88

ive got a few ceramic wire wound ones coming from Ebay and yesterday after lots of searching I also found and purchased a MOX one as well. Is the MOX a better one to use?

[R_J]

Re: Help with dead Commodore 1802

It will be a wirewound, this from digikey should work A137101-ND Mfg # SQZW103R3J which seems to be like the original. TYPE SQZ horizontal, pluggable.
They go open after time, the wire gets a weak spot and thats it, If there was any other problem it would have blown the fuse and not the resistor.
If you just want to try the monitor, replace it with a piece of wire, if there is a short anywhere the fuse will blow. or if you want to get fancy replace it with a incandescent lamp to test

[stj]

Re: Help with dead Commodore 1802

you cant tell without breaking it, but you rarely get wirewounds used on ac because the coil radiates interference.

btw, the replacement needs airflow under it, what we used to do is solder the new one on top of the dead one so it still stands high off the board.
that or use ceramic spacers.

[roadrash]

Re: Help with dead Commodore 1802

This is it. Is it. What type is it?

[roadrash]

Re: Help with dead Commodore 1802

R801 is probably metal oxide, not wirewound.
a wirewound will get glowy hot instead of going open-circuit.
smash the old one to check the insides.

so now you need to see what made it burn!

Its a large white oblong ceramic type.
Could it be just age and maybe being left turned on for hours because I accidently did that when I left it on overnight one night by accident. It was after that I found it dead.

[stj]

Re: Help with dead Commodore 1802

R801 is probably metal oxide, not wirewound.
a wirewound will get glowy hot instead of going open-circuit.
smash the old one to check the insides.

so now you need to see what made it burn!

[R_J]

Re: Help with dead Commodore 1802

3.3Ω 10 watt not, 10 amp, the 4.7Ω would work to test if it is around 10watt

[roadrash]

Re: Help with dead Commodore 1802

I only had a 4.7ohm wire wound resistor here and ordered some I thought were 10A 3 Ohms that were actualy 3.3ohms. Ive got another 10A 3ohm one comming and be here in a few days or so.

[roadrash]

Re: Help with dead Commodore 1802

So you have 0 voltage the main filter capacitor, that does'nt leave much, Check the large 3.3Ω 10 watt resistor R801, it must be open or has cold solder connections

R801 is open circuit and registers nothing on any scale.

[R_J]

Re: Help with dead Commodore 1802

So you have 0 voltage the main filter capacitor, that does'nt leave much, Check the large 3.3Ω 10 watt resistor R801, it must be open or has cold solder connections

[roadrash]

Re: Help with dead Commodore 1802

The sound (bong noise) is the degausing coil, mesure the DC voltage across the filter caps, C814 (12v) and C813 (121V) the heatsinks may not be grounded. If there are no voltages, then its time to start checking on the primary side.
What voltage do you measure ACROSS C803? If you have voltage across C803, leave your negative meter lead on C803 negative and with the red probe check the voltage on T801 pin 4 and pin 2

Couldnt find C814 anywhere until i noticed it was a cap labeled as R814. Anyway no voltage across C813 & C814 and no voltage between C803 and pins 4 & 2 of T801

[R_J]

Re: Help with dead Commodore 1802

The sound (bong noise) is the degausing coil, mesure the DC voltage across the filter caps, C814 (12v) and C813 (121V) the heatsinks may not be grounded. If there are no voltages, then its time to start checking on the primary side.
What voltage do you measure ACROSS C803? If you have voltage across C803, leave your negative meter lead on C803 negative and with the red probe check the voltage on T801 pin 4 and pin 2

[roadrash]

Re: Help with dead Commodore 1802

I cant get any voltage from D807 or D806. Thats using both AC & DC and connecting black proble to a heatsink which should be a good ground. Or should I have reversed the probes as well with it being on a diode.Something interesting when I powered it up this time It made a slight bong noise and and you could hear it power up. Dont remember if it was doing that before.

[R_J]

Re: Help with dead Commodore 1802

I just asked to check Q402 to see if it was shorted, you checked it and measured a short between b-e which is normal, you were measuring the horizontal drive transformer secondary. I assumed there was no short e-c since you did'nt say.
There are two (2) secondary voltages produced by the power supply.
One is 12 volts from D807, the other is the B+ 121 volts from D806
Check if they are there or not.
Pin 3 of T461 (horizontal output transformer) will have B+ 121VDC, Caution measuring pin 1, it will have ~120 VDC, BUT if the horizontal circuit is working it will also have 1~1.5KV of 15khz AC

[roadrash]

Re: Help with dead Commodore 1802

I think I read the pins wrong on the transformer, It should have been pins 4 & 2 (the primary winding) Do you get any other voltages on the str54041 Pins 1, 2 and 4 ?
You could also check those resistors in that primary circuit, maybe one of them is open.

sorry I had to go away for a while and I was waiting for a new Q402 2SD1397 Transistor to arrive after I thought we had established it might have been faulty but I cant find here now for some reason. Anyway I soldered in the new transistor and I couldnt get the monitor to power up at all and there was no 240vAV bgoing in. Ironically it was the latching on/off switch decided to fail just at that moment. Ive jumped the connections so now have 240vAC going in again and just want to check that I am now looking for voltage on pins 1 & 2 of the LOPT is that AC or DC volts?

[stj]

Re: Help with dead Commodore 1802

the lopt is the one with the big red wire to the crt.
all voltages on it are high frequency ac so you didnt meter it - and you shouldnt try.

[R_J]

Re: Help with dead Commodore 1802

I think I read the pins wrong on the transformer, It should have been pins 4 & 2 (the primary winding) Do you get any other voltages on the str54041 Pins 1, 2 and 4 ?
You could also check those resistors in that primary circuit, maybe one of them is open.

[roadrash]

Re: Help with dead Commodore 1802

RJ there is voltage at the filter cap and on pins 4 & 5 of the LOPT. No voltage anywhere else like 12v or 5v. I can only get 240v AC.