Author Topic: Burster digistant 6425 T (current source) teardown and repair.  (Read 1172 times)

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Offline The SoulmanTopic starter

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This little current source has been acting up for some time, occasionally it would produce lower current with tremendous amounts of noise, a little mechanical persuasion would usually fix it but now I have enough of it and had a proper look at it.
From the outside I could narrow it down to the external/internal v-ref switch on the back.
After opening up the digistant I spotted the culprit, can you?
It have been like this for forty years.  :-DD

Apart from the defect and one of the resistors on the second decade being out of spec, it is a handy little thing.

Pics attached for your entertainment.  :)
 
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Offline The SoulmanTopic starter

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Re: Burster digistant 6425 T (current source) teardown and repair.
« Reply #1 on: June 19, 2019, 06:57:43 pm »
Some more info:

Output range: 0,001 mA to 110mA (first dial goes up to ten, others up to nine)
Maximum output voltage: 20 V
Maximum error: 0,03%

Op-amps: 3) ua741, 1) LH0042
Zener: unknown
Precision resistors: Burster in various grades
 
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Online Dr. Frank

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Re: Burster digistant 6425 T (current source) teardown and repair.
« Reply #2 on: June 19, 2019, 09:33:22 pm »
 ;) thank you for these pictures!
Always loved Burster resistors, built many CC sources out of them...

That lead coming from the switch, left under that 100M resistor did never see a solder joint, for as much as 42 years, obviously.

Frank
« Last Edit: June 19, 2019, 09:39:00 pm by Dr. Frank »
 
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Offline Vgkid

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Re: Burster digistant 6425 T (current source) teardown and repair.
« Reply #3 on: June 20, 2019, 10:42:02 am »
Thanks for the teardown. It is always interesting to see inside various precision current sources. They are always aimple.
Did you find a schematic for it.
If you own any North Hills Electronics gear, message me. L&N Fan
 

Offline The SoulmanTopic starter

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Re: Burster digistant 6425 T (current source) teardown and repair.
« Reply #4 on: July 21, 2019, 11:33:55 am »
One of these days it is coming apart again, the rear switch is still a bit dickey, anyone want
some pics of anything specific?
 
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