[aprssig] Kenwood TR-7730 backup battery?

Steve Noskowicz noskosteve at yahoo.com
Sat Apr 20 18:14:29 CDT 2013



I think that stuff is all poart of the ham's mod. 

1 -  I can't resolve why it looks like a 4 pin connector. 

   I suspect:

2 -  the original circuit had nothing to do with the main power input.  He did that mod so he could use some batteries instead of the external TK-1 power widgit and wanted the main power to keep it charged.  Nice idea.
  I think there is another path from the DC power input to the micro processor memory supply, but am too lazy too try to trace it out.  This is becauese that schematic looks like the lines are all hand drawn going between DC input and the memory backup connector..  Dunno.


3 - He added the 4k resistor deeper in the schematic along that backup input line .  Don't know why because it appears to say 6V by the backup connector.  Perhaps the TK-1 is a 12 volt wall wart and he wants to frop more, so increased that resistance......?

Gud Luk.


73, Steve, K9DCI 


--- On Sat, 4/20/13, Greg D <ko6th.greg at gmail.com> wrote:


> 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
> >>
> >> Manage Radio Memories with an Excel Spreadsheet !
> >> Click to tune. Click to capture Radio freq.
> >> All Memories on one page. Cut, Copy, Paste, Print
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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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