HUNTS CRB Analyser.

[davebms]

thanks
with the balance control full clockwise (open) -.2 volts dc

ant clock (short) -75 volts dc

the strange thing it does this with NO RESISTOR ? (same readings)with or without DUT

no need to apologise small mix up on pin numbers

dave

[ronbryan]

With my instrument, if the 2k2 D.U.T. resistor is fitted to the terminals on the R1 range, the Y63 grid voltage goes from zero at balance, to -18V DC at OPEN to -28V DC at SHORT.

If the D.U.T. resistor is disconnected, the grid voltage goes from 0V DC at OPEN to -67 at SHORT. Because you are getting this condition if the D.U.T. is present or not, it seems that there is actually no current flowing through the D.U.T. even when it is fitted. Try putting a meter on AC current range across the measurement terminals in series with the 2k2 and see if any current is flowing. My instrument measures 20mA AC (AVO 8) under this test.

If you find no current flows, then try continuity checks from the terminals back to the balance pot with the instrument off.

Ron

[ronbryan]

A correction to post #42 second paragraph.

My instrument measures 10mA AC (AVO 8) under this test (with the 2k2 in series) and 20mA AC with the meter directly between the measurement terminals.

Ron

[davebms]

Thank you will have a look when I get home and

[davebms]

WELL I tried to measure ma/ac zero !!. so I removed the plus/ neg terminals
and put fibre washers behind the originals (they looked a bit crazed)
still zero,, but, balance .5 volt -24 open -34 short the widest shadow
dial reads 200.2 is that 2k2 in mega ohms ? I put a 1meg DUT on R that reads 1, I think that correct .back 2k2 avo 8, 10ma and 20 ma ac
it still does not measure capacitors,, and I have resistors and meters all over the table !!! best tidy up re check things

my fluke 25 does not read M/A !!

THANKS dave

[ronbryan]

Originally Posted by davebms

the widest shadow dial reads 200.2 is that 2k2 in mega ohms ?

If you are on the R1 (divide by 100) range with a 2k2 ohms (2,200 ohms) resistor as the D.U.T. and the scale reads two small divisions past 200 at balance, then the resistance reading is 220 kilohms divided by 100, which is 2,200 ohms.

If the AC current reading across the terminals is still an intermittent or unreliable 20mA, now that you have replaced the insulating washers, the switch wafer contacts may need cleaning with a small amount of switch cleaner.

You did not say if you did the (power off) check of the resistance back to the balance pot end tags from the terminals, but on the R1 range you should read 1.5k from the - terminal to one pot end tag and zero ohms from the + terminal to the other end tag.

With regard to capacitor range tests, the silvered mica reference capacitors would normally be ok, but the C2 range 2uF reference cap in the rectangular metal can is likely to be leaky or lossy unless it has been changed or restuffed already. I think the C1 range 200pF silvered mica reference cap is soldered direct to the switch wafers and is hard to spot.

Ron

[davebms]

sorry for the slow replys !!

If you are on the R1 (divide by 100) range with a 2k2 ohms (2,200 ohms) resistor as the D.U.T. and the scale reads two small divisions past 200 at balance, then the resistance reading is 220 kilohms divided by 100, which is 2,200 ohms.

This is the first time that the tester has worked, so just looking for conformation that I had worked it out

If the AC current reading across the terminals is still an intermittent or unreliable 20mA, now that you have replaced the insulating washers, the switch wafer contacts may need cleaning with a small amount of switch cleaner. (my fluke had a blown fuse 20ma is present

I have striped the machine down and cleaned contacts with isopropyl achohol
cotton buds and small brush (the switch is/was covered in nicotine)

You did not say if you did the (power off) check of the resistance back to the balance pot end tags from the terminals, but on the R1 range you should read 1.5k from the - terminal to one pot end tag and zero ohms from the + terminal to the other end tag.

yes 1.59 -.01 ohms

With regard to capacitor range tests, the silvered mica reference capacitors would normally be ok, but the C2 range 2uF reference cap in the rectangular metal can is likely to be leaky or lossy unless it has been changed or restuffed already. I think the C1 range 200pF silvered mica reference cap is soldered direct to the switch wafers and is hard to spot.

I have replaced all the caps

the resistance readings are good, it seems not to be able to measure any capacitor bigger than 10uf (the eye only opens, in the open position)
the eye also opens with the tester set to open, in all positions ie r1 r c2 c1 and c
as the switch was so dirty can it short out or electrically leaky

thanks dave
I have also re soldered a few bad solder joints

[davebms]

Just to clarify the eye opens, in the OPEN position. with NO DUT fitted

dave