Author Topic: 55 kg multimeter calibrator '171' by G & E Bradley, England  (Read 2399 times)

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Offline baltersice

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55 kg multimeter calibrator '171' by G & E Bradley, England
« on: February 01, 2018, 01:28:58 pm »





Pretty horrible to troubleshoot unless somebody has a schematic? ::)
Probably no LTZ1000 in there, but a ton of .02% resistors and other cool parts ...
Could it be from around 1970?
I don't have a lot of time now, but if there's any interest I'll post some more detailed photos on Sunday.
« Last Edit: February 01, 2018, 01:32:01 pm by baltersice »
 
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Offline Vgkid

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #1 on: February 01, 2018, 02:10:04 pm »
I will gladly wait for then  :)
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Offline Edwin G. Pettis

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #2 on: February 01, 2018, 07:26:15 pm »
Three power resistors in upper left corner has date code of 7040 on them....what a boat anchor!
 

Online tautech

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #3 on: February 01, 2018, 07:36:52 pm »
Years back I bought a broken Bradley 100 MHz CRO only because it came with a decent manual that of course included schematics. Quite nicely made but yes a bit of a shite to work on. Fixed and sold of course.  ;)
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Offline vindoline

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #4 on: February 01, 2018, 08:14:43 pm »
Looks amazing! More pics please!
 

Offline anymouse

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #5 on: February 01, 2018, 11:32:53 pm »
Ah, it was you who got the ebay.de item ;) I watched the auction because I have a similar one, but that was Buy-it-now for ~100€. I just wanted to know a hint for the "normal" price.

Did you note the fuse rating on the back of the device? ;)

The similar one I have ist the Bradley 171 B. The obvious difference is the "% deviation" part. On yours one can set the switch to 1%, 3% or 10%, and than adjust the output voltage or current up to that amount. Means: Dial "100" and adjust the output till the multimeter to calibrate also reads "100" -- then one can read by the small meter how much the multimeter is off. On the 171 one can also switch to partials of "Full Scale Deflection".

Don't get to exited -- accuracy is only about 0,1% -- so it is comparable with the Hewlett Packard 6920B or Fluke Meter Calibrator 760A . The reference is a temperature compensated zener diode (1N825 or 1N829 or the like) low TC diode BXZ49, divided down to 4V.

I got the paper manual from http://www.telford-electronics.co.uk , but they only have the 171B, not the 171-blank. I don't know how much they differ.

For more pictures, just remove the bottom ;)
« Last Edit: February 01, 2018, 11:59:41 pm by anymouse »
 
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Offline baltersice

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #6 on: February 02, 2018, 12:45:36 am »
Did you note the fuse rating on the back of the device? ;)

Yes, I hope it never draws that kind of current ... Although with those huge power resistors directly behind the fan I could imagine that it does?
Thank you for the operation details, it wasn't clear to me (in my defense I haven't thought about it very hard :)
If you have any other interesting facts, I'd love to hear them because there is literally nothing on the internet.
Nah, I am only slightly excited that I got it relatively cheaply, but I am not planning to keep this huge beast for long. There have been some repair attempts before apparently and I don't think I'll spend a lot of time trying to figure out what's wrong. Your paper manual doesn't happen to have a schematic, does it? :-//
 

Offline anymouse

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #7 on: February 02, 2018, 08:50:38 am »
There have been some repair attempts before apparently and I don't think I'll spend a lot of time trying to figure out what's wrong. Your paper manual doesn't happen to have a schematic, does it? :-//

It does (service manual, about 1cm thick): three-DIN-A4-pages sized fold out with schematic, BOM, layout for the bottom PCB, calibration instructions, mode of operation, etc. But it's paper, and not that simple to scan, lying here in Castrop-Rauxel ;)

For the power rating:

For Voltage and Current the allowed output seams to be 10W (!) , so 10mA for '1000V', 1A for '10V', 1V for '10A'. This would  explain, why it seam to be based on transformers instead of resistors. And that is the reason for the weight ;)


 

Offline hscade

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #8 on: February 02, 2018, 08:55:30 am »
baltersice, that a thing for a "free" vacuum cleaner  >:D
 

Offline baltersice

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #9 on: February 02, 2018, 10:44:12 am »
Nah this thing is beyond vacuuming, there seems to be a uniform crusty coating of all components ...
Few days in the rain? Magic smoke deposit by one of its own components? We may find out on sunday :scared:
« Last Edit: February 02, 2018, 10:55:33 am by baltersice »
 

Offline EEVblog

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #10 on: February 02, 2018, 10:53:35 am »
Woah, gorgeous!
 

Offline baltersice

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #11 on: February 02, 2018, 11:01:37 am »
Woah, gorgeous!

Would love to hear your professional opinion on the smell of that thing ... it is unusual and not unpleasant :)
 

Online Kleinstein

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #12 on: February 02, 2018, 11:53:36 am »
....
For the power rating:

For Voltage and Current the allowed output seams to be 10W (!) , so 10mA for '1000V', 1A for '10V', 1V for '10A'. This would  explain, why it seam to be based on transformers instead of resistors. And that is the reason for the weight ;)

The switches still seem to use resistors. So you are not that lucky getting a calibrator with a precision inductive (transformers) divider. That would be if they need to go beyond the KV divider. Still this would be only the precision (AC) divider and there would be still a conventional amplifier.

They likely just use different taps from the mains transformer and this way get the approximately constant power limit for the ranges, but likely
 

Offline John Heath

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #13 on: February 05, 2018, 04:01:06 pm »
You know with a good shoulder harness it could be a portable calibrator. The Bradley shirt pocket calibrator.
 

Offline Hrozba7777

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #14 on: June 16, 2019, 08:13:34 pm »
Hello guys. Two days ago I bought the Bradley 171B calibrator. I am searching for service manual, if someone could send it to my e-mail, it will be super. My e-mail is: cernansky.peter1@gmail.com
 

Offline Hrozba7777

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Re: 55 kg multimeter calibrator '171' by G & E Bradley, England
« Reply #15 on: October 13, 2019, 06:52:12 am »
Thank you so much for NO help. I bought the manual for about hundred euros and scanned for you, here it is

https://elektrotanya.com/showresult?what=Bradley%20171B%20calibrator%20SM

Please help each other and scan manuals...
 
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