[Heathkit] GD-1290 Metal Detector

[Ron Bussiere via Heathkit]

Hi. Just wondering if anyone out there has one and if they have luck servicing it.
I built one when they first came out, and it worked perfect. Had a lot of fun with it and even took it to Hawaii. 
Lost that one in a divorce, but kept the manual. Just bought a mint one on eBay. However it doesn't work. The previous owner had put the wrong battery pack in it (12 V) versus the 9 V one as designed.

I honestly have not had time to look at it, but the schematic is nice with voltage test points and even 'scope patterns.
Just kind of concerned about the parts availability.......

ron
N4UE