Lambda 8300 - screen goes black after a while

[kolbeck]

Will the internal 2kb RAM be disabled if you attach external 16K Ram - as with the ZX81?

/Thomas

[mrtinb]

Yes, the internal RAM will be disabled.

[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

[kolbeck]

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

[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.

[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

[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

[Paul]

Interesting read indeed