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Old 19th Sep 2020, 6:23 pm   #1
Bufo Bill
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Default Hunts CRB: how practical for modern use?

Hi, Re my ongoing collection of vintage test gear, I have come across the famous Hunts CRB. Would a working example be worth restoring so as to use it in active service, or will I be better off using one for shelf dressing and buying something modern? I know which i would like but I guess I want to know if a restoration would have any major sticking points, such as "unobtainium" components or the device just being too darn worn out to work?
Cheers from Bill.
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Old 20th Sep 2020, 1:21 pm   #2
Andrewausfa
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Default Re: Hunts CRB: how practical for modern use

Hi Bill,

Which Hunts CRB do you have? There were three versions.

Andrew
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Old 20th Sep 2020, 2:32 pm   #3
MrBungle
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Default Re: Hunts CRB: how practical for modern use

I'm not sure it has any practical use compared to a lot of modern kit. For example I have a nice Peak LCR45 that does most of the required functions. If I want to measure leakage of a capacitor I tend to stack some bench power supplies up to the desired voltage (I can hit 200v with three of mine) and use a Fluke DMM in series.

Shelf dressing definitely worth it!
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Old 20th Sep 2020, 2:41 pm   #4
AC/HL
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Default Re: Hunts CRB: how practical for modern use

I've got one of the early metal ones. Seems reasonably accurate, but the eye is very dim making it awkward to use. Unless you're keen on end - end authenticity, like much equipment it's of its time.
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Old 20th Sep 2020, 5:21 pm   #5
Bufo Bill
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Default Re: Hunts CRB: how practical for modern use

Many thanks guys. I have been shown a picture of an original version, local to me (we head into a new lockdown here on Tuesday). The guy plugged it in to show the magic eye in action. This worries me in case things start to sizzle in there, no Variac or anything used to bring the power up slowly. It's owned by a contact who is a dealer in decorative antiques, he has no experience of vintage electronics.
Well guys, worth a punt if under £50, or leave well alone?
Cheers from Bill.
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Old 20th Sep 2020, 10:08 pm   #6
factory
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Default Re: Hunts CRB: how practical for modern use

Shango066 on youtube sometimes uses a couple of different "eye" based capacitor testers to either spot check capacitors for value & leakage, or to confirm they were the cause of the diagnosed fault.

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Originally Posted by MrBungle View Post
snip... If I want to measure leakage of a capacitor I tend to stack some bench power supplies up to the desired voltage (I can hit 200v with three of mine) and use a Fluke DMM in series.
If using bench power supplies beware if they aren't current limited, wouldn't want anyone to blow any expensive DMM fuses if the capacitor under test decides to go short-circuit when measuring leakage current.

David
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Old 21st Sep 2020, 9:03 am   #7
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Default Re: Hunts CRB: how practical for modern use

Excellent advice.
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Old 21st Sep 2020, 12:11 pm   #8
Leon Crampin
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Default Re: Hunts CRB: how practical for modern use?

The trick is to use the DVM on a voltage range (an autoranging meter is better), in series with the device under test.

So if your DVM has an input resistance of 10 Meg Ohms, and after your capacitor under test has charged (and is leaking) you can easily estimate its leakage resistance by just reading the voltage in relation to the power supply voltage.

For example, if you apply 200V to the series combination, and the DVM reads 100V, you have 10 Meg Ohms leakage. Use potential divider arithmetic for other results.

Leon.
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Old 21st Sep 2020, 4:53 pm   #9
Andrewausfa
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Default Re: Hunts CRB: how practical for modern use

Quote:
Originally Posted by Bufo Bill View Post
Many thanks guys. I have been shown a picture of an original version,
The original one was this Solar one branded up for Hunts. Nice looking thing, wanted one myself.

Andrew
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Old 21st Sep 2020, 8:09 pm   #10
factory
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Default Re: Hunts CRB: how practical for modern use?

One of those branded Hunts sold a few months ago, I did wonder about the connection with the Solar version I've seen in the US.

Quote:
Originally Posted by Leon Crampin View Post
The trick is to use the DVM on a voltage range (an autoranging meter is better), in series with the device under test.

So if your DVM has an input resistance of 10 Meg Ohms, and after your capacitor under test has charged (and is leaking) you can easily estimate its leakage resistance by just reading the voltage in relation to the power supply voltage.

For example, if you apply 200V to the series combination, and the DVM reads 100V, you have 10 Meg Ohms leakage. Use potential divider arithmetic for other results.

Leon.
I usually use an LCR meter (analog or digital) to check the value, then check leakage with a Megger (someone on the forum recommended one that has ranges from 50V to 1kV some time ago).
With more modern LCR meters you have to be careful to discharge capacitors before testing, as they don't usually have any input protection against high voltages.

David
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