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 Post subject: General Electric Model 7-2826
PostPosted: Sep Fri 04, 2020 5:05 pm 
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Joined: Sep Fri 04, 2020 4:55 pm
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This radio has worked fine on battery or house current for many years. purchased used at a flea market.
A few months back, it quit working on battery power. Still works when plugged in. There is no physical switch
to toggle between DC/AC. The unit has an internal something that does that.
Question: Any ideas why this unit quit working on batter power?


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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Sat 05, 2020 1:38 am 
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Joined: Jan Tue 31, 2012 1:55 am
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Location: Mountains of Mourne. Ireland.
Battery connections (soldered wires) can often become "broken" due to many changes of batteries.

Their terminals can also become oxidized with the passage of time. You can clean them with some 70% IPA, electrical Contact Cleaner, Zippo lighter fluid or a pencil eraser.

You can also use the pencil eraser on the batteries.


Greg.


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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Sat 05, 2020 1:43 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 8691
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
Does anyone have access to a schematic?


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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Sat 05, 2020 5:16 am 
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Sams didn't cover it John. I guess there may be a 1980s factory service sheet somewhere. This model is often seen on eBay for less than 20 bucks, shipped.

Maybe the OP could open 'er up. lol
:) Greg.


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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Sat 05, 2020 1:55 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
egg wrote:
Maybe the OP could open 'er up. lol
:) Greg.


Yup, many of those sets had the schematic pasted on the inside. A good clear, sharp, hi-res photo would work as well as anything else.


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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Sat 05, 2020 3:39 pm 
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Joined: Sep Fri 04, 2020 4:55 pm
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Leads all well soldered. I see no oxidation. Just in case, I did use an oxidation cleaner, but to no avail.
I am wondering if there is an internal electronic power supply switch on this device that simply went out of specs?
I did not see the schematics. Picture of inside below.
Thanks to all for input so far.

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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Sat 05, 2020 4:33 pm 
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Location: Mountains of Mourne. Ireland.
It's best to use a table lamp or photograph your set outside on a bright overcast day... :)


The AC cord is fixed. - - so no mechanical battery-disconnect!


As the batteries appear to be in a detachable cradle, there is every likelihood of a short in one of the connecting wire, snap-connectors or a dry solder joint on the holder or at either end of the connecting wires.

As I have stated above...
repetitive handling of the removable battery holder often causes problems.

With a less than $7.00 Harbor Freight multimeter (if you haven't got one) confirm the integrity of the wires with the continuity function. Reflow any "sketchy" solder joints with a soldering iron.

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Large image: https://i.ebayimg.com/images/g/-GoAAOSw ... -l1600.jpg

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Large image: https://i.ebayimg.com/images/g/POkAAOSw ... -l1600.jpg

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Large image: https://i.ebayimg.com/images/g/dWAAAOSw ... -l1600.jpg


Greg.


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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Sat 05, 2020 4:45 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 8691
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
The battery / AC isolation can be as simple as a diode in one of the wires leading to the battery. Are you able to trace the wiring form the battery POS and NEG to see where they connect to the power supply circuitry?


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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Sat 05, 2020 11:16 pm 
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Joined: Apr Wed 21, 2010 12:01 am
Posts: 360
I have that same radio and there is simple setup on the battery connections. First off, and forgive me for mentioning this, but are
The batteries OK? Are they in the holder OK? The snap connector connecting the battery holder should be checked next. With the radio switch on and with the snap connector disconnected from the holder, check for continuity both ways on the connector terminals. It should read a resistance one way, if open both ways then a connection is open in the snap connector or the wiring from the snap connector to the board. That would boil it down. There is nothing else to that battery interface. Ken


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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Mon 07, 2020 5:17 pm 
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Thanks Ken. I am going to trace the leads into the circuit board in depth. Gotta be a bad lead problem(I hope).
I will post a report when I accomplish the next task.


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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Mon 07, 2020 6:14 pm 
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Success!
In my parts department I found a new battery connector. So I replaced that, and the radio now works on battery and AC. All the solder connections looked OK on the battery connector leads. But apparently were not.
Thanks to you all for your input and my successful repair.


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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Mon 07, 2020 6:28 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 8691
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
compengsls wrote:
There is nothing else to that battery interface. Ken


I am curious to know, if there is no switch to change between AC and battery, what it there in the circuit to isolate the batteries from the AC power supply? My thought would have been a diode in one of the battery supply routes, probably soldered into the circuit board just where the wires from the battery holder are connected. Without a schematic or a set to look at it's impossible to say.

Any ideas?


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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Tue 08, 2020 2:17 pm 
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Joined: Apr Wed 21, 2010 12:01 am
Posts: 360
Yes, there is a diode in line with the batteries. I didn't mention the diode because typically when diodes fail, they fail shorted. The leads connection to the board, battery holder, connector system is the most troublesome. 99% of the time that's the cause. So to minimize further probing, etc. I steered the problem to that interface only. I've had it happened to me and other sets I looked at. Ken


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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Tue 08, 2020 3:51 pm 
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Joined: Sep Fri 04, 2020 4:55 pm
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I steered the problem to that interface only.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
And once again, that was the problem. :)


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 Post subject: Re: General Electric Model 7-2826
PostPosted: Sep Tue 08, 2020 4:24 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 8691
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
compengsls wrote:
Yes, there is a diode in line with the batteries. I didn't mention the diode because typically when diodes fail, they fail shorted. The leads connection to the board, battery holder, connector system is the most troublesome. 99% of the time that's the cause. So to minimize further probing, etc. I steered the problem to that interface only. I've had it happened to me and other sets I looked at. Ken


Super, thank you. I understand the battery holders/connectors/corrosion/poor solder joints issue, but I was curious about the isolation technique and you have answered that for me.
cheers


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