Computer boots, no video output????

[MIRKOSOFT]

Hi!

I have big problem - I was using my C128DCR correctly... but at one time it boots and has no video output, no VIC no VDC...

Can anybody help?

Many many thanks.

Miro

[bacon]

As always, Ray Carlsen's repair articles to the rescue, specifically "C128: chips vs symptoms and diagnostics".

[MIRKOSOFT]

All what I did:
replaced JiddyDOS KERNAL128D with standard C128D KERNAL
tried all monitors...
disconnected all devices, only LED indicates power.

I had look at all chips in sockets / no one has moved...

REALLY MISSED HOPES..

[Hydrophilic]

Check the 9VAC from the PSU.  The red LED will come on if 5VDC is working, but will not tell you if 9VAC is working.  Without 9VAC, the Z80 will not run and none of the video chips will get initialized.  If the voltage is good, consult the above mentioned chips & symptoms guide.

If the voltage is bad, then obviously fix/replace the PSU.  But before you connect good PSU to C128 to try again, look inside your C128 again to make sure did not short-circuit anything. 

[MIRKOSOFT]

Have no volt meter...


But I forgot to write that the GREEN (1571CR) LED indicates boot.
RED diode only one time blink and no lights... is it that problem about you wrote?

[Hydrophilic]

Well if the green LED is power, yes that is what I am talking about.  If you don't have a voltage meter, you can open the PSU and check the fuse.  Other than that, you need a voltage meter. 

... or if you have another PSU, you can try it, but be sure to check for any short-circuits in your C128 before you connect another PSU...

[MIRKOSOFT]

I have else one C128 - but it has externally PSU - and this ?damaged? C128 is DCR, so internal PSU... and don't have other PSU.


I can lent any voltmeter. But when I will have one - I need advice and following any steps.
Now is connected only PSU, VIC monitor and VDC monitor and keyboard, I give back JiffyDOS 128D KERNAL and in free socket I have BASIC8 / GEOS2.0 desktop.
Screens are both black, no CTRL+G (bell) sound output...

[MIRKOSOFT]

you can open the PSU and check the fuse.

OK, how to do it? - maybe stupid but important Q