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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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28th Jun 2020, 9:20 pm | #81 |
Triode
Join Date: May 2017
Location: Suffolk, UK.
Posts: 15
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Re: Hunts CRB3
Many thanks
I will try that method, yes, suck it and see appears to be the method, and interpretation of the results is interesting too! |
29th Jun 2020, 12:58 am | #82 | |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,867
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Re: Hunts CRB3
Hi!
Quote:
The price of these indicator valves is rocketing alarmingly every year because of their scarcity, but you can get a much cheaper Soviet–made 6E5S type that will do the job adequately enough without impairing the appearance of the instrument. EM34 characteristics:– Heater 6.3V 0.2A, Target Anode pin 5, 250V, Anode Resistors, pins 3 and 6, 1M, Grid volts for shadow–closure, –5V (1) & –16V (2). Pin 1:– i.c., pin 2:– h, pin 3:– a', d', pin 4:– g, pin 5:– t, pin 6:– a", d", pin 7:– h, pin 8:– k, g' 6E5S characteristics:– Heater 6.3V 0.3A, Target Anode Pin 6, 250V, Anode Resistor, 1M, pin 3, Grid Volts for shadow–closure, pin 4, –22V. Pin 1:– Not used, pin 2:– h, pin 3:– a, d, Pin 4:– not used, pin 5:– g, pin 6:– t, pin 7:– h, pin 8:– k, g' To rewire an EM34 holder to suit a Soviet 6E5S, disconnect the 1 megohm resistor between pins 5 and 6 and discard it. Disconnect the h.t. lead from pin 5 and reconnect it to pin 6, and also disconnect the 1 megohm resistor connected to pin 3 from pin 5 at it's other end, and reconnect the free end to pin 6 along with the h.t. lead. Also transfer the 4M7 resistor and 0u01 capacitor from pin 4 to pin 5, or simply connect pins 4 & 5 with a short piece of wire. No other wiring alterations are needed. Chris Williams
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! Last edited by Chris55000; 29th Jun 2020 at 1:05 am. |
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29th Jun 2020, 9:27 am | #83 |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,867
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Re: Hunts CRB3
Hi!
It's normal for the eye balance indicators on bridges to open fully at one end of the balance (and sometimes the "power factor" control) this is because, with the usual wiring arrangements, (see my circuit diagram and others in this thread) the wiper of the balance control is directly earthed along with the cathode of the indicator, so when you turn the wiper towards the end connected to the grid circuit of the indicator, you're short–circuiting it's input and therefore the eye will open fully! Chris Williams
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! |
29th Jun 2020, 12:33 pm | #84 |
Hexode
Join Date: Mar 2020
Location: Rochdale, Greater Manchester, UK.
Posts: 452
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Re: Hunts CRB3
Hi Chris Williams,
that's a really helpful description of how to substitute the cheaper Russian magic-eye tube for an EM34 - I shall save it for future reference. I wonder if you have seen the adaptors which claim to fulfill this task without any circuit alterations to the original equipment? I have attached a photo of a Chinese adaptor from EBay as a random example of the species. There may be some issues in finding the extra inch or so of space where the tube is a tight fit in the original equipment. Cheers Chris King |
29th Jun 2020, 9:25 pm | #85 |
Triode
Join Date: May 2017
Location: Suffolk, UK.
Posts: 15
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Re: Hunts CRB3
When I get chance I will post a picture of the magic eye, which, after looking at more images of how it should look seems to be ok.
It is more the neon with has splodges of colour inside the halo rather than the clean ring in the photographs above. My suspicion is that the rectifer may not be up to snuff so I will pull the chassis and check the voltages are as I expect form the very helpful diagram V4. Cheers |
29th Jun 2020, 10:54 pm | #86 |
Hexode
Join Date: Mar 2020
Location: Rochdale, Greater Manchester, UK.
Posts: 452
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Re: Hunts CRB3
Hi - in case you haven't already figured things out, the method I used to test the neon was short out the capacitor terminals, set the selector to "Ins" or "Leak" and increase the right hand switch through the fixed voltage levels. The neon should illuminate sequentially more quadrants as the volts go up.
Of course it's possible the neon may have been replaced with a less sofisticated type and just light up when it's strike voltage is reached.Good luck with it. Cheers Chris |
14th Jul 2020, 11:01 am | #87 |
Nonode
Join Date: Jan 2010
Location: Edinburgh, UK.
Posts: 2,008
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Re: Hunts CRB3
More than one person has commented that the schematic is difficult to understand and I agree. To help understand what is going on I have prepared some simplified diagrams for the basic functions of the instrument.
As a result of seeing the diagram of the insulation and leakage functions I am now wondering what setting users use for reforming electrolytics. Al
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8th Sep 2020, 2:02 pm | #88 | |
Nonode
Join Date: Jan 2010
Location: Edinburgh, UK.
Posts: 2,008
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Re: Hunts CRB3
Quote:
The first thing I noticed after opening it up is that it also has a 5pF 600volt capacitor across the leak terminals. The serial number on my unit is 246 so it may be that this cap was deleted on later production. I am going to do one last update to the manual so I will include this component. Al
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8th Sep 2020, 3:55 pm | #89 |
Dekatron
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 8,932
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Re: Hunts CRB3
Joy of joy it is a Hunts! Must check mine and see serial number.
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19th Sep 2020, 4:23 pm | #90 |
Nonode
Join Date: Jan 2010
Location: Edinburgh, UK.
Posts: 2,008
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Re: Hunts CRB3
There is an easy way to measure the leakage in that capacitor or any externally connected cap.
This is a draft of an entry in an updated manual I am slowly compiling. It explains the method CAPACITOR REFORMING The CRB3 can also be used to reform electrolytic capacitors.Select the voltage you want to start the reforming process at and INS. As the reforming progresses the neon should flash less and less often. Repeat the process at higher voltages until the capacitor’s maximum voltage is achieved. Due to there being a neon in the current path the actual voltage applied to the capacitor will be less than selected. As a final stage of reforming select LEAK or LEAK HIGH CAP for a short period of time. Connecting a high impedance voltmeter between the CAPACITY negative and EARTH terminals will give an indication of the leakage current. In the LEAK setting 1 volt equates to approximately 15uA leakage current. In LEAK HIGH CAP 1 volt equates to approximately 30uA. Stubborn capacitors may benefit from short spells on the LEAK or LEAK HIGH CAP settings at the start of reforming. Figure 16 shows the active circuitry for these processes. Al
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25th Sep 2020, 12:25 pm | #91 | |
No Longer a Member
Join Date: Nov 2015
Location: Kilkenny, Ireland
Posts: 138
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Re: Hunts CRB3
Hello Alistair
I saw your updated manual on http://golbornevintageradio.co.uk/ posted 13 Jun 2020. Will you be updating this further? Thanks for your hard work. Quote:
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26th Sep 2020, 4:06 pm | #92 |
Nonode
Join Date: Jan 2010
Location: Edinburgh, UK.
Posts: 2,008
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Re: Hunts CRB3
I do have quite a bit more in the next version of the manual. Currently the whole document is in draft form.
When I do get round to tidying up and completing it I will post a copy. Al
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18th Jan 2022, 12:48 pm | #93 | ||
Nonode
Join Date: Jan 2010
Location: Edinburgh, UK.
Posts: 2,008
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"Hunts CRB3" by Alistair D - reported by Alistair D
Alistair D has reported a post.
Reason: Quote:
Forum: Vintage Test Gear and Workshop Equipment Assigned Moderators: N/A Posted by: Alistair D Original Content: Quote:
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18th Jan 2022, 12:52 pm | #94 |
Moderator
Join Date: Dec 2010
Location: Exeter, Devon and Poole, Dorset UK.
Posts: 6,864
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Re: Hunts CRB3
Opened as requested.
Cheers Mike T
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18th Jan 2022, 1:04 pm | #95 |
Nonode
Join Date: Jan 2010
Location: Edinburgh, UK.
Posts: 2,008
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Re: Hunts CRB3
Well it took long enough but I have now managed to complete the full version of the manual.
A big thank you to everyone who provided information, pictures etc. Al
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