Racal-Dana 1992 Repair

[RCL]

Gentle Readers:

I purchased a defective Racal-Dana 1992 on eBay last week ($145).  I came here and read everything I could find and then I watched some You Tube videos.  Sure enough, every one of the front panel push-buttons were defective.  So, thanks to the member that posted specific replacement push-button information.  They fit perfectly without any modification.

When I examined the bottom of the main PC board there was a big black hole burned through the board.  It appears that a bad solder joint (at the fuse) developed enough heat to put a 1/4" hole in the board.  I reworked that area and restored power.

I remembered reading a comment about excessive heat at the custom ceramic counter IC.  I added two paste-on aluminum heat sinks to this IC and dropped the temperature from 130° F to 111° F.

Just now read about a trick to get an extra digit of resolution!

So...............thanks everyone!

[bdunham7]

So, thanks to the member that posted specific replacement push-button information.  They fit perfectly without any modification.

Could you repost that information and where you got the parts from?

[RCL]

The front panel switch information follows:

Supplier:  onlinecomponents.com
Manuf.      Alps
Model#:   SKEGACA010
Cost:        $29.00 / 100

I did add a small dab of school-poster-putty to each cap.  This was to enhance retention to the switch stem.

[coromonadalix]

and for canada  they charge almost 30$ shipping  to get them ....  but i have 2x 1992 ....  mmmmmmmm

[Swainster]

Haha, I bid in that auction, too. I have a 1991 but it was misbehaving (randomly switching to external reference mode). Losing the auction persuaded me to track down the problem - turned out to be a broken SMD resistor.

Must admit that the instrument runs uncomfortably hot for my preference. That ceramic DIP is really toasty... I tried a heatsink but with the whole interior being so warm, I'm not sure that it will be doing much 'sinking'. I'm strongly considering drilling some vent holes in the case, and adding a fan.

[wn1fju]

I did the same, namely replace all the switches and add a stick-on heat sink to the main IC.  I haven't had any issues with the 1992 since I did that a few years ago.  I like the nice bright display and I especially like the small compact size.  It is easy to move around the lab.

[RCL]

one post-script..........

I did remove the IEEE-488 GPIB board.  Speaking for myself, I don't believe I will have a need to operate this thing remotely and it may reduce some internal heat generation.

[coromonadalix]

indeed the gpib board is huge, and venting the internals would help in a way,  but i dont know if it could bring drift

And ba careful,  the regulators legs sometime broke  due to mechanical stress