Our PCS100 card is not working anymore.
The software says the parallel port is defective, but this is not the case, since we have already tried this with different PC’s. Moreover, all parallel ports on these PC’s have been tested and are ok.
Now, we’ve checked the optocouplers on the PCS100 board and there fine.
When we start up the software and choose calibration, we clearly measure communication in both directions. Only after a while the software says the port has failed. Sometimes we even get a scope trace, but not at the correct levels.
It’s a pity we don’t have a circuit diagram. Is there one available so we can have a look at it?
Are there any suggestions to solve this kind of problem?
Best regards, and thanks in advance,
Patrick Van Torre
Assistant Professor
Hogeschool Gent, dept. INWE
Schoonmeersstraat 52
B-9000 Gent
This is either a communication problem or there is something wrong with the scope. Check with the users if there is a possiblility that the input section has received a signal which exceeded 100Vp. Did you test on a desktop or laptop PC ? Are these equipped with ‘real’ parallel ports (not USB to parallel converters or similar ? The diagram can be found on the CD rom that came with the unit.
Thanks; we tested on desktop PC’s with real parallel ports.
The card has not been used with anything that can provide more than 100Vp. The Pc’s are all the same type and it used to work on them.
I’m nearly sure some part of the card is defective, suppose that the ADC was blown; could this cause a “LPT comm error” in the software?
When I measure on the ADC data out, I see only the LSB moving (with anolog sinusoid input of sufficient amplitude).
The analog input for the DAC itself seems strange too, a kind of “rectified” looking sinusoid signal.
Thanks for informing me about the schematic, I’ll have a look if I can find the CD here.
Strange problem. Semiconductors usually don’t go bad overnight, there must be a reason. Check the DAC reference. Check the databus. The DAC is not necessarely defective. Some other part could cause a problem on the databus (e.g. the RAM).
If you cannot get it to work, you can return it to the address you can find in the manual.
Ok, thanks again for your quick reply.
Well, I noticed the RAM IC feels just a little bit hot, like 40 degrees or so.
Should it stay really cold on a normal working board?
I located 2 defective analog switches 74HC1G66.
My card works more or less with the switches removed, but of course I can’t do the range switching properly.
I ordered the components and will see if I can fix it completely.
The switches were probably blown because of a ground problem.
The PCS100 card was supplied from the same power supply as the measured circuit, which is a problem since the “gnd” of the BNC on the PCS 100 is at 2,5 volts DC.