HP 34C turning on but Error 0, zeros, frozen

[goncal]

I have owned a 34C since I was very kindly given it by my grandfather back in 1980. It was a prized possession back then and I have always looked after it well. It was the first programmable device I owned and I actually learnt to code with it.

After I got my 41C I put the 34C back in its case and box. I did remember to take the batteries out before putting it away thankfully.

The calculator survived several house moves and now belongs to my collection.

I took it out of its drawer a couple of weeks ago and purchased new batteries from Waterhosko on eBay:

https://www.ebay.com/itm/Hewlett-Packard...3312936986

However when I put the batteries on the calculator it would randomly not turn on, or alternatively show all zeros, or Errors 0 and 4, and appear to be frozen no matter what keys I pressed. (Actually when Error 0 came up the display would go blank after pressing any key)

I decided to take the calculator apart to look at the contacts. I used the great instructions in this article:

http://www.hpmuseum.org/cgi-sys/cgiwrap/...i?read=925

I must have been doing something wrong as it took me longer but did manage to open the case without breaking anything.

However there did not seem to be anything wrong. There was a bit of dust and some light brown goo on the board where the on-off and prgm-run switches are which I removed although I later realised this might have been contact grease applied by the Singapore assembly line staff on purpose.

I used a custom power supply set at exactly 2.4V to test the calculator before putting it back together and unfortunately all had been to no avail - same problem.

I would love to fix my beloved 34C but have as yet been unable to find any information on fixing this particular error.

Any help would be greatly appreciated.

PS Thought I would post a few photos. The light brown goo can be seen on the board contacts, it is now gone.