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Old Aug 14, 2010, 06:49 AM
Martin - AKA mr.sneezy
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Adelaide, Australia
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Question
JR MAX-44 radio repair help needed

I have a JR MAX-44 transmitter that I'm repairing for a fellow club member.
He unfortunately reverse powered the TX when fitting up a brand new battery pack.

Two components have popped, IC2 & D2. I could guess that IC is a regulator, and guess again it's a 5V regulator (but there is a small but real chance it's lower than that). However, I'd rather not guess if somebody has the right information at hand.
So if somebody has or knows where I could find a MAX-44 schematic, or if they can measure the voltage on pin1 of IC2 on their own MAX-44 radio for me it would be a great help to us. Pin3 has 12V and pin2 is Ground.
See the images if you know about this radio (please, no wild guesses, I can do that myself).
Thanks all.
Martin
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Old Aug 14, 2010, 11:35 AM
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It is a 78L05F 5V reg, D2 is a 1SS352 diode.
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Old Aug 14, 2010, 08:19 PM
Martin - AKA mr.sneezy
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Originally Posted by mac_man View Post
It is a 78L05F 5V reg, D2 is a 1SS352 diode.
Thanks mac_man, just the concise info I need. Off to warm up the soldering station....
Many thanks,
Martin
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Old Apr 29, 2011, 12:43 AM
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Originally Posted by PLMS View Post
Thanks mac_man, just the concise info I need. Off to warm up the soldering station....
Many thanks,
Martin
Were you able to repair your radio?

I have about the same issue with a XF421EX. I haven't used the radio for about 8 years and I've just fired it back up recently whenever I turned the radio on everything on the LCD was active. I took it apart and noticed that IC2 and D1 are blown. The IC is split in half and has the same markings (AE with a 041 in the circle).
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Old Apr 29, 2011, 04:13 AM
Martin - AKA mr.sneezy
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Adelaide, Australia
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Originally Posted by whatelse_is_new View Post
Were you able to repair your radio?
No, I replaced the parts and tested it. No response from the radio. I think the MCU was destroyed by the reversal and excess current. The radio is scrapped now.

If you know how to do it, it would still be worth spending a few minutes fitting up a TO92 size 5V regulator and see if yours fairs better...

These radios are still useful when fitted up with a 2.4Ghz hack module like the one FrSky makes. I've done a few of them now.

Martin
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Old Apr 29, 2011, 08:21 PM
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I just ordered the 5V regulator and a diode as well as a 3 volt battery today from mouser.com. We'll see if it fixes the problem.
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Old May 01, 2011, 05:53 PM
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PLMS, you should have PM'd me... chances are the CPU needed a hard reset by shorting out the reset pins on the pcb. Or I could have given you further test data as another transistor in the supply chain may have blown.
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Old May 02, 2011, 03:56 AM
Martin - AKA mr.sneezy
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Adelaide, Australia
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Originally Posted by theaton56 View Post
PLMS, you should have PM'd me... chances are the CPU needed a hard reset by shorting out the reset pins on the pcb. Or I could have given you further test data as another transistor in the supply chain may have blown.
I can still get it back from the club member who owns it and do that, but I did check that 5V was on the MCU power pins, and looked for MCU clock with my scope. It had the 5V, but no clock or other digital activity.
Given that info do you think it's worth trying further ?
Martin
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