Digikit Reaction Tennis

[elwro07]

The alternative would be a programmed 22V10 GAL.

Yes, but why complicating a fairly simple logic circuit? ;-)
Going this direction the whole game could be remade using one microcontroller...

Not sure if you found this, but one guy already designed a 74198 replacement using two 74LS194s
Will this work here?

 

[daver2]

Good spot - no I missed that device.

I was thinking of a use for my MC14500 single bit CPU processor !

The 74LS194s (in a DIL package) are available in the UK for £2 each from a local electronics store... I will get a couple ordered. It should be possible to parallel up the control signals and cascade the shift left/right inputs to the opposite device to make an 8-bit device from two 4-bit devices.

Dave

 

[falter]

Sorry for the massively delayed response! Had my bench tied up with other things but finally got back to this! Almost kind of want to get an old DYMO labeler.. I think half my problem is forgetting which side is which for the different players.

We didn't actually test out U5. U5 pin 5 was a convenient place to set the two reset buttons S2 and S5. Do these buttons both work OK then?

I think we have an issue with s6 not being reliable.

The next test would be U2 pin 11. This pin should be LOW. Pressing S1 (serve player A) should cause this U2 pin 11 to go HIGH. Releasing S1 should cause U2 pin 11 to go HIGH once again.

U2 Pin 11 is LOW on power up. Pressing S1 makes it go HIGH. Releasing S1 returns kt to LOW which is what I think you meant above?

The next test would be U2 pin 3. This pin should be LOW. Pressing S6 (serve player B) should cause this U2 pin 3 to go HIGH. Releasing S6 should cause U2 pin 3 to go HIGH once again.

U2 pin 3 is LOW on power up. It requires a fair bit of force and repeated pushing on S6 before you get it to go HIGH but it does go LOW after release.

Alternately pressing S1 (serve player A) and S6 (serve player B) should cause the serve LEDs (L1 and L10) to alternately illuminate and extinguish (i.e. one of L1 and L10 should be illuminated and the other LED extinguished).

Yes this seems to work.

S4 is the speed - but it is a 3-way switch with the centre way OFF. If you put your oscilloscope on U4 pin 11 - there should be a lower frequency with S4 one way than the other. The centre position is OFF (the positive power supply is disconnected).

Yes this seems to behave correctly.

We will get to S3 later...

The reset buttons do not work as you think...

Changing S4 causes the power to be killed to the ICs - thus causing them to 'reset' to some undefined power-up condition.

You probably need to clean the flux off with IPA and reflow any dubious solder joints. If the buttons are 'hesitant' then you may have dirty contacts and need replacing. But my above tests will identify this...

Dave

I definitely think S6 has an issue now although it seems to test fine with a continuity meter. I notice with flexing the board it sometimes works more reliably. So I'm thinking you were on the right track here with possible switch problems or dry solder joints. Going to reflow some suspect ones and see where it goes from there.

 

[elwro07]

I would replace all those push button and slider switches just to be sure. They aren't expensive.

 

[falter]

I would replace all those push button and slider switches just to be sure. They aren't expensive.

I'm going to try some contact solution on them first.. just to see if I can preserve the thing in its original state. But failing that, I think I can see markings on the switches that might let me find exact replacements.