Input question from a newbe

[Bdlhome]

This project is determined to drive me mad..

Seeing that you are on a roll, I have another question if you don't mind.

Testing was going well until the circuit stopped working all together. On checking the PIC was getting power etc so I tried reflowing the solder on a few points and it started working again. It would work for a few minutes out say 5-10 minutes later I would power on and nothing. This appears to be repeatable, could the 22pf caps or 4Mhz Oscillator be working due to the heat caused by resoldering? I only ask that because there doesn't appear to be anything wrong with solder joints, so I wondered if it is the heat that is causing the circuit to work? I'm going to try swapping out those components and see what happens.

[Demon]

If improper solder is the problem, put the board through some simple tests: freezer for a minute, test, under halogen lamp for a minute, test.

I'd start by melting all the joints with the solder tip (or reflow oven if you have that). It does sound like you have a bad solder. Heat makes metal expand and bridge small gaps.

Robert

[Demon]

... On checking the PIC was getting power etc so I tried reflowing the solder on a few points and it started working again. It would work for a few minutes out say 5-10 minutes later I would power on and nothing. ...

After rereading your post, I wonder if the PIC could be damaged internally? Since you appear to have a heat gun, try applying a little heat just to the center of the PIC.

Is it possible that you abused the chip somehow, maybe a little too much current on a pin?

I've messed up PICs before by forgetting little things like current limitting resistors, short circuits mishandling test leads, etc. LOL The PIC would sometimes keep on working, but not reliably.

In some cases the damage would be limitted to just that port, everything else would work fine. They really are tough little buggers but there's only so much abuse they can handle from people like me.

[Bdlhome]

After rereading your post, I wonder if the PIC could be damaged internally? Since you appear to have a heat gun, try applying a little heat just to the center of the PIC.

Is it possible that you abused the chip somehow, maybe a little too much current on a pin?

I've messed up PICs before by forgetting little things like current limitting resistors, short circuits mishandling test leads, etc. LOL The PIC would sometimes keep on working, but not reliably.

In some cases the damage would be limitted to just that port, everything else would work fine. They really are tough little buggers but there's only so much abuse they can handle from people like me.

I don't think it is the PIC but I've been wrong before - you only have to read this thread for examples

When using the soldering iron on just the oscillator pins I don't think there would be enough heat transfer through the tracks and PIC socket to have an effect on the PIC itself. By the way I'm using through hole components and not surface mount.

I've just replaced the OSC and everything now appears to be working, so either a bad solder joint as you suggested or the component itself. I'm going to try the OSC I removed in another circuit to see if I have the same problem.

[Demon]

I had a similar problem on a breadboard; the oscillator pins weren't making perfect contact.

I had another one on the Lab X1; it would work fine if I lightly touched the oscillator with my fingertip. Resoldering fixed that one.

Robert