Sinclair QL with garbled mess.

I got real excited picking up a QL today at the local car-boot sale (just missed a nice Lynx for sod all too but oh well. :roll:). Got it home and gave her a clean but all i get is either a white screen, black and white vertical bars (with more garbled crap each time I retry power) and sometimes no picture at all. :(

Any ideas? I could get some pictures up if necessary?

[EDIT] Tried re-seating the socketed chips with no joy. :(

Hi

Can you see the memory test on bootup? A lot of blck and white spots on screen for about 5 seconds.

If you can´t see then, try to replace the 68008 processor, next the ULA chips anf finally the ROM Chip, but you need a working QL to do these test.

Regards

Hi

I copied this from the QL service manual which can be down loaded from the WOS wed site. Looks a bit like the problem you’re having.

John

If the screen is not quite pure white or green and has either very
narrow vertical stripes, or a vertical pattern of dots, this indicates
that one bit in the system is faulty, either as a result of a fault
within one of the RAM chips or of a short-circuit across a
data/address line. In order to pin-point the faulty RAM chip, proceed
as follows:
(a) Take a probe and connect one end to ground.
(b) Touch the probe on the data pin of each RAM in turn and observe
the screen.
(c) As the probe short-circuits a data line, a vertical black line or
series of black lines appears on the screen. When this black
line coincides with whatever pattern is on the screen, dots or
stripe(s), then the offending chip has been found. In fact,
since the two banks of RAM are connected together via the data
bus it could be an 1C from either bank (e.g. either IC1 or IC9).
With this example, IC1 would need to be changed since this is
part of the memory mapped area of the store. In general, a long
vertical stripe suggests a data line short-circuit, and dots
suggest a RAM fault.
2.2.13 If RESET is pressed and a 'tweed' pattern is seen on the screen for a
certain time and it then reverts to white, this suggests that some
failure has been found in the second bank of RAM.
2.2.14 To summarise, if on power up a white or green screen is displayed, it
indicates that the RAMs are in general working, and that the machine
is very close to being fully operational. It suggests a data or
address line short-circuit or a faulty RAM chip.

4.6

Thanks guys, sounds likes is probably a ram issue. I don't have anything like a probe to test them with but I suppose I can be on the lookout for the CPU. Theres a few on feeBay so might give it a try...

Tokyoracer,

I might have a spare QL if interested, I know I have one with a faulty microdrive on it but I know it powers up OK and runs mdv1_ without issue.

Has the manual and power supply etc. Let me know if interested :D

regards

Bagpuss22

PM sending!

Quote:

---

Originally Posted by Jomor58

Hi
...In order to pin-point the faulty RAM chip, proceed

as follows:
(a) Take a probe and connect one end to ground.
(b) Touch the probe on the data pin of each RAM in turn and observe
the screen.
(c) As the probe short-circuits a data line, a vertical black line or
series of black lines appears on the screen. When this black
line coincides with whatever pattern is on the screen, dots or
stripe(s), then the offending chip has been found...

---

What a great way to check for Ram problems :) I love the way it actually the indication of the state of the RAM on screen. Excellent! :)

Could this method be used on a rubber key'd speccy??

Quote:

---

Originally Posted by ptp170

Could this method be used on a rubber key'd speccy??

---

I can definately say no...don't try this on a 16K/48K speccy:Doh::oops:

This can now be closed, bagpuss22 VERY kindly donated a working QL, just needs a membrane, made a thread about that already.

Thanks for all the responses. :)

P.s. Sorry I can't seem to give FB, says the URL is invalid. :(