Electronics > Repair


(1/15) > >>

Hi Folks  :)
In the true spirit of the great Dave's Dumpster Youtube videos, which brought me to this great forum  :-+
I found a great bit of old 1991 pro kit (regarded by some as probably the best 4 gas analyser made) that was in a skip for the great crusher  :-- and i had to save it.
Being a gentleman  :) , I gave the owner a beer token and now it's my challenge to get it working again.
He told me 'it booted up last week to try, but when i turned it on yesterday....it went "woof".  :palm:
After a 'lets look in side' ;D and blow the dust out session.....nothing nasty visible.....i plugged her in....BANG! FLASH!!   :wtf:  :-BROKE
5amp plug fuse blown....and my reactions tested  ;D
It has a toroidal transformer with a power supply pc board, containing 5 reasonable size electrolytic caps....and this was where the flash came from. As a relative newbie (but keen to learn!) i'd like some advice on whats the best way to test/repair and wake up these Caps(and the ones on the infrared gas bench), that probably have been unused for about 10 to 15 years?
Caps image attached(how do i insert it here, or is it best to attach?)
will post more pics when i get the pcb out and my phone charged.
I have a china ESR meter, solder station etc. i did read that its possible/best to apply the rated cap voltage to old caps via a resistor to wake them from there dormant state, do you do this first before testing them? I dont have a 35v dc source but could link some 12v car batteries if this would work?
Any help/advice welcome  :-+

I know nothing about this unit but if something is flashing over and going bang then you should be seeing physical damage, where is this damage located? Normally when electrolytic capacitors go bad the cases bulge on the top and/or the bottom and it's easy to spot but from your picture they look OK.

Just take care around the high voltages please.

Yes i was expecting visible damage too, maybe 1 cap looks at a raised angle from the others?
I'll wear my wellie boots  :D
Maybe the 5amp fuse saved some damage?, not sure what the mains plug rating should be, info for this gas analyser was pre internet days and hard to find, tho i did speak with a guy today that was taught at college in Kings Lynn. U.K. by the guy that was the chief engineer on this Tool (sadly, he too is suffering old age  :( )
I look forward to more replies  :-+

Picture of the Gas analyser for people to see attached, and also the other Caps, visible on the side of the heated NDIR gas bench that detects the gas makeup

I would start by replacing the fuse and connecting the unit to a dim bulb tester (a light bulb in series with the plug lead) using a 40W bulb as a start.  If there is a major short in the primary section of the transformer the bulb will glow brightly but the fuse will not blow.  If the unit draws more then 80 or so watts use a light bulb that is roughly half of the units wattage for the test.  If the bulb glows medium or dim then the primary side of the transformer is most likely fine.  Use a multimeter on volts to see if there is any voltage on the various capacitors in the power supply when it is unpluged and if there is not set the meter to ohms mode and check the capacitors for shorts.  If there is voltage across the capacitors then there is probably no short but they could have become leaky at higher voltages (hard to test unless you have a high voltage capable capacitor tester).  I do not think that you will have to worry about refreshing the capacitors due to the unit been from 1991 or so.  I have used a dim bulb tester to power up tube radios from the 40s that the capacitors still worked fine (no reforming necessary)!


[0] Message Index

[#] Next page

There was an error while thanking
Go to full version