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Old 6th Jun 2022, 3:46 am   #1
FrankB
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Default 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.
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Old 6th Jun 2022, 8:49 am   #2
60 oldjohn
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Default Re: Home brew adaptor to test battery draw

Quote:
Originally Posted by FrankB View Post
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.
Hi Frank, it has been covered a long time since, possibly by my friend David G4EBT. Well worth the reminder as it is very useful when needed. This is one I made earlier as the BP phrase goes, the PCB is 0.25mm thick and I did tin it at the time.

John.
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Last edited by 60 oldjohn; 6th Jun 2022 at 9:07 am.
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Old 6th Jun 2022, 10:33 am   #3
TonyDuell
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Default 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
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Old 6th Jun 2022, 12:29 pm   #4
David G4EBT
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Default 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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Old 6th Jun 2022, 12:57 pm   #5
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Default 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.
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Old 6th Jun 2022, 5:43 pm   #6
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Default 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.
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Old 6th Jun 2022, 6:09 pm   #7
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Default 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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Old 6th Jun 2022, 8:25 pm   #8
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Default Re: Home brew adaptor to test battery draw

Quote:
Originally Posted by ms660 View Post
Another trick back in the day with battery powered receivers was to connect the meter probes across the on/off switch.
Neat. Like it.
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Old 6th Jun 2022, 10:14 pm   #9
David G4EBT
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Default Re: Home brew adaptor to test battery draw

Quote:
Originally Posted by ms660 View Post
Another trick back in the day with battery powered receivers was to connect the meter probes across the on/off switch.

Lawrence.
That’s a real ‘light bulb’ moment Lawrence!

So simple too - like all the best ideas.
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Old 7th Jun 2022, 9:59 am   #10
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Default 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!
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Old 7th Jun 2022, 11:24 am   #11
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Default Re: Home brew adaptor to test battery draw

S.P.S.T only for the switch trick.

Lawrence.
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