Sinclair ZX80 / ZX81 / Z88 Forums

It has been a few months since I last powered up my TS, but today it is showing no signs of life. Was functioning just fine the last time used.

Voltage from the power supply is good, and got 4.7 and 9 volts when checked at the Traco. and connection is good to the ZX8-CCB.
It had previously been fitted with a working heat-sinked ULA by Ian.

Suggestions on what to try next will welcomed!

Mike

When you say, ‘lifeless’, it would be helpful if you give a description of the screen.

The output voltage from the Traco should be between 4.9V and 5.1V (although the digital circuitry should work between 4.75V and 5.25V).

Does your machine have any chips in sockets? If yes press firmly on each chip that is in a socket.

Apart from the ULA (which runs warm anyway), are any of the other chips running warn or hot?

Mark

By "lifeless" I meant that "No Signal" was displayed on the monitor. Sorry for the lack of clarity. The ULA and and Z80 are socketed. I gave each a good push into the socket and they seemed fine.

After my posting I realized I had two spare ULAs to try, one a reclaim and the other from Andy. I pulled the resident ULA and replaced with the reclaim and it roared back to life.

What is puzzling is that this would happen after just a few months of sitting on the shelf.

Thanks for the reply, Mark!

Mike

It always seems odd when something fails after not being used. But keep in mind that in normal use, electronics and electric items experience the greatest amount of stress when they are actually turned on / powered up.

So now that it’s working again, just to confirm that the ‘old’ ULA is indeed dead, remove the working ULA and try the ‘old’ one again. I say this, because it is still possible it was a poor connection on one or more of the pins.

I maintain and fault find Industrial equipment, and it’s normally powered up all the time. We experience the most problems when it’s powered up from cold after being left off for any length of time, or when there are power blips where there is a loss of power, immediately followed a few seconds later by the power coming back...

Mark

When I went to the Commodore 64 it became a monthly routine to pop the case and re-seat all the chips as they would gradually "walk" themselves out of their sockets.

Although the "old" ULA seemed to be firmly in its socket, I may just have to take a shot at giving it another try.

As always, thanks for your quick and informative reply!

Mike