9xr pro rf deck

Hardware Support for the 9XR Pro
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AndreL
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9xr pro rf deck

Post by AndreL »

would anyone have any information on the smd transistors located on the rf deck - especially Q2 (to start with) - i would like to guess that it is a fet but what would be a good replacement. I was messing with the radio trying out some mods and accidentally shorted the feed to the the 5v reg input (fat fingers). The fuse did not go but i lost the resistor that is across that switching smd (the resistor would go because if the fet/transistor is not switching on leaving the resistor to supply all the current). I dont think that i will find a replacement rf deck hence it would be nice to fix it. Thanx for your help and info. The deck of the pro is totally different from the straight xr or it would have been fixed by now.

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MikeB
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Re: 9xr pro rf deck

Post by MikeB »

Q2 is a SI2319CDS-T1-GE3
R9, that may be blown, is a 0.1R 1% 1/4W.
R9, which is a current sense resistor, usually goes before anything else. It is safe to simply replace it with a wire, you only lose the radio current measurment. It is in series with Q2, so Q2 may be OK.

Mike
erskyTx/er9x developer
The difficult we do immediately,
The impossible takes a little longer!
AndreL
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Re: 9xr pro rf deck

Post by AndreL »

that 1 i replaced but assumptions had me largely out of tolerance - R100 - thought it was 100 ohms not 0.1. Although if i short out R9, Q2 becomes irrelevant anyway since it parallels the drain to source of the mosfet anyway. Thank you for your info !!
AndreL
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Re: 9xr pro rf deck

Post by AndreL »

how would that work anyway - considering that the resistor is 1/4 if not an 1/8 watt in line with a regulator capable of 1.5 amps. Even if you draw 0.5 amps you still smoke the resistor unless the mosfet is being pwm at a rate which allows a very small time for the resistor to be in cct by itself for such a measurement.
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MikeB
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Re: 9xr pro rf deck

Post by MikeB »

R9 is definitely in series with the MOSFET (Q2) not in parallel. U1 is the measurement IC that is in parallel with R9.
The resistor will handle 1.5A. THe power in the resistor would then be 1.5*1.5*0.1 (I squared R) = .225W, which is less that 1/4 W.

Mike
erskyTx/er9x developer
The difficult we do immediately,
The impossible takes a little longer!

AndreL
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Re: 9xr pro rf deck

Post by AndreL »

maybe i was looking at another resistor - the one i replaced was across the fet from (source to drain), but i will revisit it soon, determined to make it work. I wish i could find a schematic of it, would definitely ease the troubleshooting. Thanks again.
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MikeB
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Re: 9xr pro rf deck

Post by MikeB »

Does this bit help?
Image2.jpg
Image2.jpg (17.76 KiB) Viewed 6360 times
The 9XR-PRO is basically the same circuit as the SKY board for the 9X. The schematic of the SKY board is in this post: http://openrcforums.com/forum/viewtopic ... pdf#p28055.

Mike
erskyTx/er9x developer
The difficult we do immediately,
The impossible takes a little longer!
AndreL
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Re: 9xr pro rf deck

Post by AndreL »

you are absolutely right Mike - i looked at the wrong trace

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