help me my picture !!

[moger4]

i have recently got back into the mighty QL and bought one
the problem i have is
the picture flashes' so to speak when i boot up
it also judders a bit
im not an expert so any pointers to a possible cause from one of the big brains here would be great
i replaced the voltage regulator at IC 36 as it barely outputs 3 v with my tester so hopefully that's a problem solved but the picture still judders and flashes
thank you
delboy

[Chr$]

How is it connected to the TV/display? RF lead, RGB output?

What is shown on the screen, is it the normal F1/F2 prompt? (if so, it might just be a modern TV not liking the QL video output, especially if it's over RF)

Or is it not getting as far as showing the F1/F2 prompt at all, i.e. not fully booting? If so, what exactly do you see?

[moger4]

How is it connected to the TV/display? RF lead, RGB output?

What is shown on the screen, is it the normal F1/F2 prompt? (if so, it might just be a modern TV not liking the QL video output, especially if it's over RF)

Or is it not getting as far as showing the F1/F2 prompt at all, i.e. not fully booting? If so, what exactly do you see?

Firstly thanks for replying
It's the F1F2 screen I can't go any further as the membrane has gone and I am using a RGB in a modern TV the zx8302 seems to have been modified and I'm reading up on that at the moment
Could I try a composite mod on the rf and see if that works any better ? And go on from there to see if it's the video chip ?

[moger4]

How is it connected to the TV/display? RF lead, RGB output?

What is shown on the screen, is it the normal F1/F2 prompt? (if so, it might just be a modern TV not liking the QL video output, especially if it's over RF)

Or is it not getting as far as showing the F1/F2 prompt at all, i.e. not fully booting? If so, what exactly do you see?

Also the svart lead is from retro computer shack so I assume it's correct for the purpose

[Derek_Stewart]

Hi,

I use a Retro Shack RGB SCART cable, it works well.

There is no benefit of modifying the RF outpurpt to get Composite Video, therd is a compositd vispdeo available on the QL RGB Socket, details in the Concepts section - Monitor Section of tge QL Used Guide:

QL Monitor QL User Guide

The mod on the 8302 is probably 2 resistors solderd in a Y configuration, fying wire, going a IC Chip near the 8302. This supposed to improve the reliability of the Microdrive, see thread: viewtopic.php?p=28960#p28960

This does not affect the video, likely, the 8301, next to the CPU is at fault or logic chips on tge video circuit.

Do you have logic probe or Oscilloscope to test the actvity on each chip?

If possible post a picture of the fault,

[moger4]

Hi,

I use a Retro Shack RGB SCART cable, it works well.

There is no benefit of modifying the RF outpurpt to get Composite Video, therd is a compositd vispdeo available on the QL RGB Socket, details in the Concepts section - Monitor Section of tge QL Used Guide:
Screenshot_20240812_211136_ReadEra.jpg


The mod on the 8302 is probably 2 resistors solderd in a Y configuration, fying wire, going a IC Chip near the 8302. This supposed to improve the reliability of the Microdrive, see thread: viewtopic.php?p=28960#p28960

This does not affect the video, likely, the 8301, next to the CPU is at fault or logic chips on tge video circuit.

Do you have logic probe or Oscilloscope to test the actvity on each chip?

If possible post a picture of the fault,

I will give it a go with an oscilloscope over the next few days I will use the manual to test the pins see what I get
Thanks for pointing me in a direction
I am busting to get back to my youth and being the dogs danglers because I had a QL

[Chr$]

Getting the F1/F2 screen is a very good sign.

I'd say test with another TV and see how that looks. Test with more TVs if you have them handy. I think some simply don't get along well with the QL video.

I happen to have a made up VGA converter sitting on my desk if that's any good to you. It outputs a perfect VGA signal to any VGA monitor. But you've already paid for the scart lead so no doubt you'll want to try and get the most out of that first. viewtopic.php?t=4437

[stevepoole]

Hi Folks,

I too had a QL monitor image which juddered for years from time to time.

It turned out to be a problem in the QL mains plug... cured by soldering. Not a QL or monitor fault at all !

Rock solid image since. ( The mains plug was under the table, and had got kicked occasionally...). Regards, Steve.

[moger4]

i have discovered its either the din socket or the scart lead as i DID composite mod the rf and get a great picture
so in effect problem solved for now until i get all up and running that is as i am waiting for a keyboard membrane
thanks for all your suggestions and help
i am contacting retro computer shack to see if they will do an exchange

[Martin_Head]

I may be completely misremembering this. But I've got a vague recollection of having a din socket with tarnished/loose connectors.
So that the plug made bad connections.

You could try removing the QL's top case, and use a meter to measure the continuity from the scart plug pins to the back of the QL's socket.
Bear in mind that there will be some resistors in some of the lines.