Topic: Heathkit ID 5001 - intermittent problem

[HCMP]

Hi All,

After sitting in storage for roughly 30 years I got my ID 5001 going again. I made some improvements such as LED backlighting (which, incidentally, I did without making any non-reversible modifications to the unit). I  posted a year or so ago about fixing a badly weathered and non-functioning humidity sensor. All has been going well and the unit has been running essentially continuously for about 10 months. However...

Three times this year I have noticed that the barometer goes crazy and it reports rapid changes up and down. then after some hours or days it appears to settle again. The behaviour seems very similar to that described in the manual when a temperature sensor goes bad or is disconnected. However, when I measure the voltage on those inputs at the back of the unit as per the manual, all seems fine. My question is: before I really have to go to town trying to find the source of this intermittent problem, can anyone suggest (or know of) the most likely culprits (components)? Many apologies if this has been covered previously - I searched but could find nothing.

Second, I was very surprised that none of the electrolytics was bad. Is this because the components were of high quality or have they, in fact, likely gone bad but  not obviously so and would need to be removed to test?

Thanks for any help,
Hugh

[WA7FWF]

Hi Hugh,
   After 30 years capacitors can dry out and will look fine from the outside, they can also start shorting and swell up and then leak ( those are easy to find) you have to look at the supply lines with a scope to see if there is excessive ripple. The weather alert beeping makes the barometer shift a little but massive changes can be many things. A common problem is the sockets Heathkit used for the IC's were not the best and can corrode and since we are working with miliivolts it matters, the fix is to take it apart and pull and carefully reseat the analog IC's. I repaired one 5001 that had a shifting Baro that turned out to be one of the ground lugs on the rear terminal strip for temps was flakey, flexing the chassis or light taps on the back would make it jump.
If it was me I would just change the main power supply filter caps, reset the analog IC's and while its apart look for cold solder joints or loose ground points and then go from there.
Kevin