Friday, 20 May 2016

Racal 836 Repair

Racal 836 

I picked up an old Racal 836 32MHz Universal Counter-Timer (circa 1972) at a radio rally last year. The unit looked good, powered up and all the digits worked. However having carried out some of the preliminary tests as outlined in the technical manual the unit would not perform the self-check function.   

Top side showing the various plug-in assemblies


I found this thread on the UK Vintage Radio Repair and Restoration forum and posted a reply for some help, I also posted on the Yahoo Racal Dana group.   Various helpful things were suggested to check which I did. All of the supply rails were correct, the 1MHz frequency standard was running and I replaced several tantalum capacitors. I finally discovered that motherboard was plagued with dry joints and that there was a dry joint on the gating control board connector so the signal wasn't getting to the high speed decade counter board. Having re-soldered these dry joints all of the functions now work correctly.

Overall I'm very happy with the unit, it is beautifully made though it can still be a bit temperamental. Usually re-seating the plug-in modules fixes the problem.  I have recently acquired a OCXO 10MHz frequency standard to check my counter with, it seems to be pretty much in calibration still after all these years.