OpenGD77

Hi everybody. I need a little help. By mistake I powered my dm 860 (through a battery eliminator) with higher voltage. As a result the unit stopped transmitting. I opened it and looked at the circuitry and located a burned out component.
https://ibb.co/1bz9DP0
https://ibb.co/NVzhQwK
Since I wish to attemp to replace it, can anyone help me identify the component? With any luck I might be able to make my baofeng work again.

Thank you

Mike IK7VXC

Wow that got hot enough to desolder itself; impressive. I'll be surprized if that's the only issue given how much current that would have taken.

How much voltage are we talking here?

Believe it or not only 9 volts!!!

Hi,

If part of the final released the magic smoke (as the picture demonstrate), I'm afraid there are more damage than that.



Cheers.
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Daniel

not sure, but i think only final stage of RF power amp is getting unregulated voltage from battery, so there is big chance that only this PA mosfet got smoked ...

Thanks guys. I think it's worth trying to replace the mosfet and see what happens. The point is, I don't know what type. If some of you has a Baofeng dm 860 (or the 1801 which "should" have the same hardware) and would be willing to look inside ... it would be really helpful. Disassembling is not a big deal. Thanks

Mike IK7VXC

http://members.optuszoo.com.au/jason.re ... ainPCB.jpg

LY1RF

Thanks Rolandas for the picture. Hope the component is easily findable online.

Mike IK7VXC

The VHF and UHF bands use separate driver and PA stages, so if that device is the only failure your radio should still transmit OK on the opposite band. The devices are the same for both bands, the failed one will be the same as the one in the opposite band marked H3 324. I can’t identify the device from those markings but the GD77 schematic shows it as a 2SK3078.

The manufacturer uses different devices in different batches of radios (probably using the cheapest available at the time) so the part numbers will vary, any of them should work OK.

Colin G4EML

Thanks Colin for your input. I already sent for a RQA0009SXAQS. I hope I didn't make any mistakes. I'll keep my fingers crossed.

Mike IK7VXC