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Kenwood TM-741A



 
 
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  #1  
Old December 17th 03, 12:24 AM
Carl Domanico
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Default Kenwood TM-741A

Need Help with my Kenwood TM-741A Triband FM Mobile Radio.....I purchased
the radio new some 12 years ago, with the 220MHz. Module Installed....The
Radio Has 144 Mhz / 220Mhz / 440 Mhz.....For years the radio worked
excellent....Then about 5 years ago I had lost the out put on 144 (two
meters)... However , the other two bands functioned fine...220/440mhz... I
sent the radio back to kenwood...and they indicated that the Driver
Transistor Q23 2SD1902R on the two meter module was defective. This
transistor is an inexpensive part...$ 3.05 ea. Anyway...It seems like the
same problem occured the other day...all the symptoms seem the same...Can
anyone shed some light on why this seems to happen often?? Also is it
possible to replace this 2SD1902R transister with something capable of
handling some what more power dissapation?? What ever happened to those
motorola hep sustatutes?? Any and all info supplied here will be greatly
appreciated....

Thanks
Carl
N2MFW


  #2  
Old December 18th 03, 02:30 AM
Thomas C. Sefranek
Guest
 
Posts: n/a
Default

The 741 classic failure....

The output module in the 2 meter section was NOT heat greased!
ALL the 741s I know of failed by cracking the alumna substrate on the power
module,
due to over heating. The fix usually was to just bridge the cracks with
solder.
After you remove the module, the cover pops off so you can get to the
substrate.
Else, spend the cash for a new module and heat grease!

"Carl Domanico" wrote in message
...
Need Help with my Kenwood TM-741A Triband FM Mobile Radio.....I purchased
the radio new some 12 years ago, with the 220MHz. Module Installed....The
Radio Has 144 Mhz / 220Mhz / 440 Mhz.....For years the radio worked
excellent....Then about 5 years ago I had lost the out put on 144 (two
meters)... However , the other two bands functioned fine...220/440mhz... I
sent the radio back to kenwood...and they indicated that the Driver
Transistor Q23 2SD1902R on the two meter module was defective. This
transistor is an inexpensive part...$ 3.05 ea. Anyway...It seems like the
same problem occured the other day...all the symptoms seem the same...Can
anyone shed some light on why this seems to happen often?? Also is it
possible to replace this 2SD1902R transister with something capable of
handling some what more power dissapation?? What ever happened to those
motorola hep sustatutes?? Any and all info supplied here will be greatly
appreciated....

Thanks
Carl
N2MFW


--
*
| __O Thomas C. Sefranek
|_-\,_ Amateur Radio Operator: WA1RHP
(*)/ (*) Bicycle mobile on 145.41, 448.625 MHz

http://hamradio.cmcorp.com/inventory/Inventory.html
http://www.harvardrepeater.org


 




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