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CBM PET 3032 STRANGE BOOT

Not sure.

Try it and see what you get.

If you start off with a stable screen and you get the 'screen jitters' when it warms up - then yes you can do it this way.

We are looking for the jitters to go away after you freeze one specific chip; and then it coming back as the machine warms up again. But, of course, it will take it longer to warm up from -20 or -30 degrees than room temperature. After the 'jitters' have come back, you freeze the ONE device and they should go away again. If so, then you need to look around the identified device and/or replace it.

Dave
 
Lets not get the bunting out just yet shall we :).

The problem needs to come back when the device warms up again and needs to go away when this (and only this) device is sprayed with freezer.

If you wave your hands, feet, etc. around the same area as you did previously (when the device is frozen) you now shouldn't observe any problems. It this true.

Part of the 'scientific process' is repeatability.

Dave
 
daver2 said:
The problem needs to come back when the device warms up again and needs to go away when this (and only this) device is sprayed with freezer.
Click to expand...
Yes! After some minute, problem come back but if i spray again, it disappear!

daver2 said:
If you wave your hands, feet, etc. around the same area as you did previously (when the device is frozen) you now shouldn't observe any problems. It this true.
Click to expand...
Yes, after spray, i can't see noise if i touch board near uf10!
What I'm wondering is why does this happen with E11??? :(
 
Because the data output lines from UF10 go to the shift register UE11 via PCB tracks...

There are other PCB tracks that will go to UE11.

Touching the board near UF10 could/will be inducing additional noise into UE11 - which is (a) faulty and (b) subjected to enhanced noise.

One thing you need to discount next - does the problem go away because of the cold (temperature related) or because of the 'wetness' sprayed on by the can of freezer?

Get a thin piece of plastic film and make a little 'boat' out of it. Put the 'film boat' on top of UE11. Perhaps some bluetack or adhesive tape to keep it in place. Spray the freezer can into the film boat in the direction of device UE11. This should cool down UE11 without spraying wetness anywhere.

Does the screen corruption go away then?

If so, you have a faulty UE11 and I would replace it.

I would also order a spare UG5 just in case that is faulty.

What I would propose (when you have removed UE11 (!)) is that you clean the PCB up etc. and then power the machine up. You won't get any display (you have removed the parallel to serial video shift register of course) but you should now be able to probe UE11 pin 2 (CLK8) with your oscilloscope and you should get an 8 MHz clock this time without the monitor complaining with the noise it made. If you still get the horrible noise, I would replace UG5 as well as UE11.

Dave
 
daver2 said:
Get a thin piece of plastic film and make a little 'boat' out of it. Put the 'film boat' on top of UE11. Perhaps some bluetack or adhesive tape to keep it in place. Spray the freezer can into the film boat in the direction of device UE11. This should cool down UE11 without spraying wetness anywhere.
Click to expand...
I did this with some film and the defect disappeared but it took longer...so I removed E11 but there my despair started again!! I tested E11 with logic tester and it told me that the ic is good :(
 
I would forget the logic tester results.

Think about it... The PET works when it is cold. It only malfunctions when it warms up.

At room temperature, the device works - and that is the ambient temperature that you live at and you are operating the logic tester at...

You could get the hair dryer out and warm the device up whilst it is being tested in the logic tester to see if that provokes a failure...

Dave
 
I am desperate again! This morning it's arrived the 74ls191....i tried on Logic tester but it give me error!!! the legs are a little oxidized :(
I'm waiting for the other supplements that I ordered in the meantime to arrive...
 
>>> This morning it's arrived the 74ls191....i tried on Logic tester but it give me error!!! the legs are a little oxidized

Well, we can't do anything about that...

Either clean the oxide off and try again, or return it for a replacement.

>>> I'm waiting for the other supplements that I ordered in the meantime to arrive...

Like alcohol?

Dave
 
I assume you have removed E11 now?

Have you tried to measure E11 pin 2 with your oscilloscope again without E11 fitted?

Dave
 
Which Logic Tester do you have? Only a very very fancy one would be able to detect a marginal part. Most cheap testers don't check voltage levels nor do they operate that a representative frequency; even worse some assume CMOS levels when testing TTL parts.
 
I changed the ls191 but i have again same noise and same waveform...time to waiting for new ls165...
 
Hmm, you shouldn't be getting that noise, especially if you have replaced the 191. But why did you replace the 191 in the first place?

Putting a chip in E11 is not going to help either...

Dave
 
daver2 said:
Hmm, you shouldn't be getting that noise, especially if you have replaced the 191. But why did you replace the 191 in the first place?

Putting a chip in E11 is not going to help either...

Dave
Click to expand...
you told me in post 635 to replace G5...
 
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