[aprssig] Kenwood TR-7730 backup battery?

Greg D ko6th.greg at gmail.com
Sat Apr 20 14:20:47 CDT 2013


Thanks for the link to the schematic; Google wasn't quite so friendly to 
me this time.  I had found the operating manual, and the battery part 
number, but no details like voltage or pinout.

I see the mod you are referring to.  The battery appears to get charged 
from the mains, through a diode and resistor.  1.2v x 6, it says, so 
7.2v.  That's pretty high for a memory backup battery, no?

I'm guessing the box to the left is probably the 3-pin connector, though 
it looks to have spots for 4 pins.  One pin for ground, one to the mains 
for charging, and one out to the circuitry.  So, the charge limiting and 
such was originally in the battery product?  Odd.  But if so, then the 
big question is the black smudge above.  What is it?  What is it covering?

If I follow what appears to be the output wire, it looks like it goes to 
some sort of adjustable voltage regulator.  Again, odd.  Why have an 
adjustable regulator for a processor memory backup?  There's another mod 
there ("4k", presumably a resistor), so it's probably related to the 
other battery mod.

The final odd thing is that I don't see where that the backup battery 
supply would be replaced with mains power in the original design, if as 
I have it, the battery is removed.  That regulator circuit isn't 
diode-driven by mains, for example.  Unless it's under that smudge.

Still searching...

Thanks for the help,

Greg  KO6TH



Steve Noskowicz wrote:
>
> The link in the upper left of the page below has a slightly better schematic.  It is in the upper right of the schematic right at the power input, but someone added a mod and the otiginal is obscured.  However, it appears you may be able to ohm it out.
> One pin is ground and it may be that the other three are plus, but it's hard to tell.  A better schenatic will tell.
>
> http://elektronicsstock.blogspot.com/search/label/TR%207730#!/2011/04/schema-kenwood-tr-7730.html
>
>
> 73, Steve, K9DCI  USN (Vet)  MOT (Ret)  Ham (Yet)
>
> --- On Sat, 4/20/13, Steve Noskowicz<noskosteve at yahoo.com>  wrote:
>
>> From: Steve Noskowicz<noskosteve at yahoo.com>
>> Subject: Re: [aprssig] Kenwood TR-7730 backup battery?
>> To: "TAPR APRS Mailing List"<aprssig at tapr.org>
>> Date: Saturday, April 20, 2013, 10:43 AM
>>
>>
>> Mods.dk probably has it.
>> Also...
>> Please remember that Google is your friend:
>>
>>    try Google "kenwood tr-7730 service manual"
>>
>> BUT BE CAREFUL.  On some sites the big, obvious
>> "DOWNLOAD" buttion is for something else.  The real
>> download is in "fine print" somewhere else:
>> e.g. this operator's manual:  http://elektrotanya.com/kenwood_tr-7730_sm.pdf/download.html
>>
>> Poor resolution Schematic:
>> http://elektronicsstock.blogspot.com/2011/04/schema-kenwood-tr-7730.html#!/2011/04/schema-kenwood-tr-7730.html
>>
>>
>>
>>
>>
>> 73, Steve, K9DCI  USN (Vet)  MOT (Ret)  Ham
>> (Yet)
>>
>> Up to date APRS Beginner Guide - updated Oct-2011
>>    http://K9DCI.home.comcast.net
>>      Click 'APRS Beginner INFO' under Contact
>>
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>>
>> --- On Fri, 4/19/13, Greg D<ko6th.greg at gmail.com>
>> wrote:
>>
>>> From: Greg D<ko6th.greg at gmail.com>
>>> Subject: [aprssig] Kenwood TR-7730 backup battery?
>>> To: "TAPR APRS Mailing List"<aprssig at tapr.org>
>>> Date: Friday, April 19, 2013, 10:54 PM
>>> Hi folks,
>>>
>>> My packet station and iGate runs on an old but quite
>>> serviceable Kenwood TR-7730.  The rig has a connector
>>> in the back for a backup battery, but none is present,
>> so
>>> any momentary glitch in power send it back to
>>> defaults.  I have not been able to find a battery,
>> nor
>>> the pin-out and specs to fashion one of my own.
>>>
>>> There appear to be 3 pins in a triangle formation. 
>>> Anybody know what the spec is?
>>>
>>> Thanks,
>>>
>>> Greg  KO6TH
>>>
>>> _______________________________________________
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