Did I fry my PIC ???

[ohmstudiste]

I just started mounting the core and my SID and it all went very smooth:soldering core,SID, LCD, uploading MIOS and Midibox and I heard it scream for the first time yesterday.

However today  I had some short circuit(probably when  I moved the different modules some cables must have interferred with some other) and since nothign appears on the LCD(it lights but I got this first range of 'full square' caracter). And when I plug in the Midi cables there is no incoming message either.

I used the C64 PSU and when the problem occured, it blew the PSU fuse. I designed the PSU using the mbhp_sid_c64_psu.pdf.

I checked the voltage on the core, and I get 5V where I should get them (I didn't tested all the connections, just the main ones, IC1 and IC2)and 12V on the SID.

I noticed when I turn the unit on again, the PIC and the 7805 voltage regulator are getting very hot. I don't remember if it was the case prior to the incident. And if I keep the unit on for some time, it goes off by itself...

Can anyone help me trace the problem ? Is there anyway to tell if a PIC is fried ? if the voltages are OK, does it mean the other component are safe ?

I would really appreciate some help on that one...

[Skunk]

Hi,

it sounds like you have blown your PIC by a shortcut in your wiring to +5V. The fact that your PSU fuse was also blown leads to the same direction. The PIC normally doesn't get that hot. It might have died, and now it pulls a big current out of the 7805 regulator -- which works, by the way when you see clean 5V on the corresponding pins without the PIC.

My proposal: change the PIC, but before you insert it in the socket, measure all PIC socket pins against GND and +5V -- just to be sure there is no shortcut anymore. AND: measure the 5V current from the PSU to the CORE board. Should be in the range of a few mA without the PIC.

Your display might have been not affected by this "accident". The first row with black characters is nothing unusual. I think if the display is damaged, you don't see anything changing.

Optocoupler died? Don't know, this is hard to say just according to one post. The only reccon: action in the same way as for the PIC: first measurement of all pins with 5V switched on, then insert the coupler if all pins show a regular voltage. If it does not work, try a new coupler.

Cheers & good luck,

Skunk

[ohmstudiste]

Thanx for the answer...

I'm gonna check the voltage and current everywhere to be sure.

I ordered a new PIC (I intended to buy second core and SID modules to build a dual SID anyway , so it just hurried the process... and added some bucks to the budget for the PIC replacement  :( )

Gonna be more carefull next time. Still don't know what happened.