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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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6th Jun 2022, 3:46 am | #1 |
Heptode
Join Date: Oct 2005
Location: Olympia, Washington, USA.
Posts: 663
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Home brew adaptor to test battery draw
Not sure if this has been posted before.
Just take a rectangular piece of very thin double sided PC board and solder a wire to each side. Hook wires to your ammeter and slide board in between battery and contact in radio. I used this simple piece of "high tech" equipment for servicing any radio that uses AA, AAA, C,D and coin cells. I had acquired a small piece of very thin & flexible PC board from Boeing Surplus in Seattle WA USA to make it from. (Sure miss that place). Any thin PC board should work, or use 2 strips of wide copper foil for making stained glass windows, and adhere it to either side of a piece of "fish paper" electrical insulation. Same result, but just not as rugged. I used it for servicing xistor radios and remote controls primarily. |
6th Jun 2022, 8:49 am | #2 | |
Dekatron
Join Date: Dec 2004
Location: East Yorkshire, UK.
Posts: 3,958
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Re: Home brew adaptor to test battery draw
Quote:
John.
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My favourite text message "I'll be there in five minutes, if not read again" Last edited by 60 oldjohn; 6th Jun 2022 at 9:07 am. |
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6th Jun 2022, 10:33 am | #3 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,189
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Re: Home brew adaptor to test battery draw
I remember seeing this idea in an electronics magazine (probably a tip sent in by a reader) about 50 years ago. But yes it's worth remnding people about it as it is simple and works very well.
I also rememebr an Archer kit project (Radio Shack/Tandy brand) for some kind of remote control. The output was a relay contact. Included in the kit was a small piece of double sided PCb, the idea was you could connect it to the relay contacts and insert it between the cells in a radio/cassette recorder/other device to as to turn said device on/off remotely |
6th Jun 2022, 12:29 pm | #4 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
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Re: Home brew adaptor to test battery draw
I wrote a thread on this which I though was in the last couple of years. I'm shocked to find that it was actually seven years ago, all but a few days.
Not sure where those years went, or why the years seem to be getting shorter and shorter! https://www.vintage-radio.net/forum/...d.php?t=117709 On Roberts (R505 etc) and Bush radios, before I even switch on, I always put a meter in series with the battery supply, ready to compare the current drawn with that in the spec. Invariably excess current is caused by failing electrolytics (such as the blue Philips ones) which morph into low vale resistors, and depending on the design of the output stage, can damage the output transistors, analogous to audio coupling capacitors on valve radios becoming 'leaky' and passing DC to the grid of the output valve. It's not that the capacitors are unreliable as such - after all, we can hardly complain about something which has lasted for six or seven decades.
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David. BVWS Member. G-QRP Club member 1339. |
6th Jun 2022, 12:57 pm | #5 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Home brew adaptor to test battery draw
Another trick back in the day with battery powered receivers was to connect the meter probes across the on/off switch.
Lawrence. |
6th Jun 2022, 5:43 pm | #6 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,482
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Re: Home brew adaptor to test battery draw
I too can remember seeing this as a reader contributed suggestion in a hobby electronics magazine decades ago but it was such a useful idea that it stuck in my head. My version is usually two bits of copper foil closely matched to the size of a piece of double sided tape.
I like Lawrence's across-the-switch idea too, the kind of slap-hand-to-forehead idea which is so simple that I probably never would have thought of it. |
6th Jun 2022, 6:09 pm | #7 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,951
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Re: Home brew adaptor to test battery draw
That was illustrated back in Pat Hawker's "Technical topics" RadCom column back in the early-1970s, using a 'wafer' of double-sided PCB back when double-sided [and multilayer] PCBs were somewhat of a novelty outside professional/military circles.
It's still a good kludge. As is the use of double-sided PCB to engineer quick-and-dirty capacitances in low-power low/high-pass filtere. Though you need to be careful with these; a friend built one and then shoved 50 Watts of RF into it.... Oh Dear....
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6th Jun 2022, 8:25 pm | #8 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
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Re: Home brew adaptor to test battery draw
Neat. Like it.
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Al |
6th Jun 2022, 10:14 pm | #9 | |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
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Re: Home brew adaptor to test battery draw
Quote:
So simple too - like all the best ideas.
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David. BVWS Member. G-QRP Club member 1339. |
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7th Jun 2022, 9:59 am | #10 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,081
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Re: Home brew adaptor to test battery draw
-As i found out as a kid, remote switching LV DC using an interrupter adaptor either needs short cables or fat cables, to avoid losing 2 or 3 volts in transit!
Dave |
7th Jun 2022, 11:24 am | #11 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Home brew adaptor to test battery draw
S.P.S.T only for the switch trick.
Lawrence. |