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Old 14th Nov 2017, 12:09 am   #1
ronbryan
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Default Hunts CRB C & R Analyser updated circuit diagram

The Hunts CRB Capacitance and Resistance Analyser circuit diagram shown in the Operating Manual on the web has component values written on the drawing which have scanned badly. I have also identified a few differences in the circuit when compared to production unit s/n 1670.

I've marked up the original manual circuit with the correct component values and the voltage readings taken from my unit. I have also corrected the selenium rectifier polarity and the position of the 2k2 bridge resistor and have added the cathode resistor to the Y63 magic eye.

Ron
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Old 14th Nov 2017, 12:42 am   #2
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Default Re: Hunts CRB C & R Analyser updated circuit diagram

Hi,
this is very good of you to take the time to do. I have one of these units to have a go at refurbishing ( repairing ? ) , but it has got put on the " round tuit pile "
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Old 14th Nov 2017, 8:57 am   #3
ms660
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Default Re: Hunts CRB C & R Analyser updated circuit diagram

Excellent.

Lawrence.
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Old 14th Nov 2017, 12:03 pm   #4
David G4EBT
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Default Re: Hunts CRB C & R Analyser updated circuit diagram

Fantastic job Ron!

To illustrate just how helpful this is, until now, all that anyone wishing to repair or restore a Hunts CRB Analyser had to go on was the circuit from the manual, which is completely devoid of any values or voltages, and doesn't identify the type of neon indicator, as show below. It must have been quite a task for Ron to have checked everything out and to neatly annotate the circuit. I dare say that until now, many will have opened up a CRB with a view to restoring it, but just put it back together, for the lack on information.

No excuses now!
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Old 14th Nov 2017, 6:15 pm   #5
Andrewausfa
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Default Re: Hunts CRB C & R Analyser updated circuit diagram

Very helpful Ron, thank you.

On the circuit you've noted 159k2 ohm, am I reading that correct as 159,002R? I just wondered about the precision

Mine is serial 925 so I will see if there are any 'original' differences in mine.

Andrew
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Old 14th Nov 2017, 6:24 pm   #6
ronbryan
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Default Re: Hunts CRB C & R Analyser updated circuit diagram

The precision resistor labelled as 159k2 is 159200 ohms 1%. I believe I have the notation correct, (e.g 1k2 is 1200 ohms, not 1002 ohms), but I did wonder whether I might cause confusion.

I will be interested to hear if your earlier unit has more differences.

Ron
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Old 14th Nov 2017, 7:15 pm   #7
Andrewausfa
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Default Re: Hunts CRB C & R Analyser updated circuit diagram

Hi Ron,

You're quite correct I was just reading it incorrectly. Now I've had mine apart I see what was meant. Here's the inside of mine and proof they were using Vishay MKT1813 in the 1940s..... There was a reason I didn't finish this a few years ago, possibly pondering what to do with the rectifier. I don't recall. I do note the original soldering isn't great.

Andrew
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