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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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22nd Feb 2021, 5:49 pm | #21 |
Rest in Peace
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
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Re: Output Valve bias meter? how to wire in correctly?
David: Thanks for your post 19.
As for a metal zero-adjusting screw, hazard arising as a consequence, that is something I've never considered. As I sit here and write this, that is a consideration that I do not know to be applicable to my stock of meters: something I will have to check-out and bear in mind from this moment on. Al. |
23rd Feb 2021, 10:52 am | #22 |
Heptode
Join Date: May 2017
Location: Konongo, Ghana
Posts: 510
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Re: Output Valve bias meter? how to wire in correctly?
The earthing of the filament supplies puzzles me a bit. Both the supply for the 71-A filaments and the 6F5 filaments are earthed. Probably this does not create big problems anyway because of the relative high value of the two 50 Ohm resistors. But still I wonder what will be going on current-wise.
The schematic from post #17: https://www.vintage-radio.net/forum/...7&d=1613918787 Addition: If this is too much off-topic, just ignore this post.
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Robert Last edited by Robert Gribnau; 23rd Feb 2021 at 11:13 am. Reason: Addition |
24th Feb 2021, 6:09 pm | #23 | |
Heptode
Join Date: Mar 2017
Location: Cedar Grove, Wisconsin, USA.
Posts: 823
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Re: Output Valve bias meter? how to wire in correctly?
Quote:
I know that the valves on the left are voltage regulators but the center black coated one is? The large one on the right is maybe a 807? Dave, USradcoll1 interested! |
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25th Feb 2021, 10:58 am | #24 |
Hexode
Join Date: Feb 2007
Location: Luton, Bedfordshire, UK.
Posts: 454
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Re: Output Valve bias meter? how to wire in correctly?
To be honest Dave I can't recall...I asked at the time on the forum (several years ago) and it was deemed to most probably be a power supply from perhaps an old telephone exchange. That was as far as we got...there were a couple of variable pots and lots of tappings....one was an 807 and as you say voltage regulators x 2 ....I still have all the spare parts in the loft ...one day the mammoth 400-0-400v power TX will power maybe a 300B amp or something similar as it has 6.3/5 and 4 volt heater taps. It was a v cheap ebay purchase.
Best Mike |
25th Feb 2021, 1:24 pm | #25 | |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
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Re: Output Valve bias meter? how to wire in correctly?
Quote:
I found out about it as a schoolkid when I asked about the perspex plates mounted on extensions of the screws holding classic round meters in the panels of a walloping big broadcast transmitter. Our guide knew the reason and explained it well. I think he was rather pleased to get asked. David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
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25th Feb 2021, 1:28 pm | #26 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Output Valve bias meter? how to wire in correctly?
The shaft of the meter set zero pot in the HRO receiver can give a kick, amongst other adjustments.
Lawrence. |
25th Feb 2021, 6:26 pm | #27 | |
Heptode
Join Date: Mar 2017
Location: Cedar Grove, Wisconsin, USA.
Posts: 823
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Re: Output Valve bias meter? how to wire in correctly?
Quote:
Fully knowing this is slightly OOT, but it's worth looking into. I'd be lost without the excellent Heath schematic website. Dave, USradcoll1, retired but, seldom bored. |
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