Funny VIC-20 hardware mystery

[ral-clan]

I posted this on VCF but think it should be posted here as well.

Today I went to log onto a BBS using my beloved VIC-20 with a WiModem modem in its user port. I booted up my terminal software and typed ADTS=1, but got no local echo on screen. Uh oh. So I looked at the WiModem and its OLED screen and power LED was dark. Double Uh oh. Dead WiModem or bad user port on the VIC-20?

I disconnected the VIC-20 from monitor, disk drive, joystick, datasette and swapped in a spare VIC-20. This time I only plugged in the WiModem. Turned the VIC on. Power to the WiModem, Great! The WiModem works...but does that mean my original VIC-20 has a bad user port?

One more test. Put the original VIC-20 back, but this time only plug in the WiModem. Power it up....WiModem works! Super! I guess that means it was only making a bad connection. Whew! Time to set everything up again. Plugged datasette, disk drive, monitor back into the VIC-20.

Turn the system on. Everything works! So grateful! But oh...I see I forgot to plug my joystick back in. Turn the system off. Reconnect the joystick. Power everything up. WiModem is dark again. What? I've heard about the user port and joystick sharing the same lines on the VIC-20, and indeed, with the WiModem plugged in, sometimes games think the joystick is being pressed down down and the fire button is being pressed...but a power issue?

I look over at the joystick (a WICO bat model), which is sitting a few feet away and see the problem. When I had first sat down to BBS, I had removed the thick vinyl dust cover from the VIC-20 and draped it over the joystick. The weight of it was causing the button on the shaft of the joystick to become depressed, causing the conflict!

Shut the system down. Removed the dust cover from the joystick. Powered the system up. Everything worked as it should!

The darnedest things....

[srowe]

Someone reported this before. I'm sure I followed up with an explanation but I can't find it at the moment.

It's because the support for faster baud rates uses pins that the VIC uses for the joystick (but the C64 doesn't)

[Edit: ha, it was your post] http://www.sleepingelephant.com/ipw-web ... 2&p=103926