I am now the owner of a Datron 4700 Multifunction Calibrator.
The unit is in very nice "cosmetic" condition.
It had power supply problems due to a shorted ( and burnt, see attachment ) dipped tantalum capacitor.
For the time beeing i replaced it with a similar value aluminum electrolytic that i had.
Inguard Power Supply unplugged from motherboard measured okay, but the unit still complained after power on. Low +15V/-15V rails.
Now my lack of experience caused a bit of smoke...
Since the PS was okay when unplugged from board i thought the voltage regulator LM7815 was broken. So i desoldered the regulator and attched my bench supply with 15V set.
After switching th unit on the failure was still present.
Now i was just stupidly watching that display of the bench supply ...
... 1,5 V --> 1,5 A ( limited ).
And just could not imagine what was going on.
... until smoke started to appear on the ac assembly board and gave me the nice hint!!!
I switched the unit off but the tantalum capacitor was kind of burning already and did continue so for some scary 30 seconds...
Okay, lesson learned! If the regulator output voltage drops there is some probabilty of a component eating to much current!
I replaced this one with an aluminum as well and the unit is working 100 percent now.
I read a lot of information here and elsewhere about problematic tantalum capacitors and especially with problems in Datron equipment.
Which makes me thinking i should replace all of them.
On the other hand there are roughly 100 of them in this unit.
So that would be a lot of work ( and Dollars ).
But i dont want to have one of those light up in my precious machine again
Right now my plan is to do a complete renovation of the power supply boards.
About the rest of the boards i am unsure.
Should i try to measure them in circuit and find the shorted/leaking ones?
Thanks for your thoughts
regards
Joerg