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Re: Lambda 8300 - screen goes black after a while
Posted: Fri Jun 16, 2023 11:54 am
by kolbeck
Will the internal 2kb RAM be disabled if you attach external 16K Ram - as with the ZX81?
/Thomas
Re: Lambda 8300 - screen goes black after a while
Posted: Fri Jun 16, 2023 12:07 pm
by mrtinb
Yes, the internal RAM will be disabled.
Re: Lambda 8300 - screen goes black after a while
Posted: Fri Jun 16, 2023 12:31 pm
by 1024MAK
I don’t think I’ve asked this, but apart from a multimeter, what test gear do you have?
Also, excluding the keyboard connections, did you do any soldering or desoldering work on this board?
Mark
Re: Lambda 8300 - screen goes black after a while
Posted: Sun Jun 18, 2023 9:23 pm
by kolbeck
1024MAK wrote: ↑Fri Jun 16, 2023 12:31 pm
I don’t think I’ve asked this, but apart from a multimeter, what test gear do you have?
Also, excluding the keyboard connections, did you do any soldering or desoldering work on this board?
Mark
Only have a multimeter- but strongly considering an osciliscope.
I have replaced the 7805 and added a ZX8-CCB composite module.
/Thomas
Re: Lambda 8300 - screen goes black after a while
Posted: Mon Jun 19, 2023 2:52 am
by Flatulentia
A long shot I know...
If you used the modulator can as the ground connection for the composite video mod, try giving the can a wiggle.
I only mention this as 2 of the 3 ZX81s I've played with had dry joints on both of the modulator can legs that solder through the PCB. This could lead to an intermittent ground to your video mod.
Re: Lambda 8300 - screen goes black after a while
Posted: Fri Aug 11, 2023 10:14 am
by kolbeck
Update: kind of solved... and it points to the worst case scenario, a dying ULA
I managed to source a working Lambda with a working ULA - loaded a few games without any problems. Switched the ULAs and now the "working" got unstable, and the machine in discussion got stable...
With working ULA, both machine now works perfectly - tested with 16K, 32K RAM pack as well as 16K ZX81 RAM pack. So, my conclusion for now is that one of the ULAs are dying (i still can work for a few minutes before going out).
I also noticed that with the dying ULA, only half of the keyboard works
/T
Re: Lambda 8300 - screen goes black after a while
Posted: Fri Aug 11, 2023 12:26 pm
by mrtinb
There is still no Lambda 8300 ULA replica.
However Tynemouth Software tried to play around with a Minstrel 3 board, and got it to work as a Lambda 8300.
Their findings could be used to create a Lambda 8300 ULA replica.
However I think my hobby electronic knowledge is not suitable for the task.
http://blog.tynemouthsoftware.co.uk/201 ... clone.html
Re: Lambda 8300 - screen goes black after a while
Posted: Fri Aug 11, 2023 1:23 pm
by Paul
Interesting read indeed