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  #21 (permalink)  
Old 06-01-2017, 5:49 AM
G7HID's Avatar
Join Date: Nov 2015
Location: Box 500 Slough UK
Posts: 373

If you don't mind sharing, who is the seller ?

Connect Systems CS750 and CS800, Hytera PD-365, Motorola DP4600.
Raspberry Pi 2 and DV4Mini HotSpot
AOR AR-DV1 Digital Voice Receiver / eSPY on ARD
WS1088 / TRX-1 / Whistler Q / UBCD3600XLT..
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  #22 (permalink)  
Old 06-14-2017, 6:45 PM
Join Date: Dec 2002
Location: madison, WI
Posts: 17

Ok, First of all; I missed messages from F5HPE, the author of DV1 Manager. Looks like he may be able to help out in a contact to return this for servicing. Hopefully he doesn't think I was intentionally ignoring him; looks like my email was just filtering out RR Forum replies. Sorry about that sir!

The seller is a Latvian seller on Amazon, but he had the radio drop-shipped from "Wealthy Electronics" in Hong Kong. ..

Information I've found:

The small 5-pin voltage regulator labeled "836120" supplies Vcc to the LA4425A. This voltage regulator is a New Japan Radio NJM2836DL3; (the '836' part), and it's a 12v output version (the '120' part.) Pin 1 is enable, pin 2 is input (in this case, from the wall wart), pin 3 is GND, Pin 4 is output (12v) and Pin 5 is NC.

Both the LA4425A Pin 5 Vcc is showing short to ground, as is the NJM2836/836120's output pin.

The NJM2836/836120 heats up immediately according to my thermal camera, right when power is applied (even if off.) This is not true in other radios, so there's some kind of short from the wall wart to GND being presented immediately without 'Enable' high. This leads me to believe the short is inside the NJM2836.

The NJM2836 (NJM2836DL3-12) is not available for distribution anywhere, apparently. Its package is TO252-5;

I've found a very close equivalent LDO VRM from Rohm at DigiKey; which has the same pinout except for the middle Pin 3 GND is not connected/present. This should be OK as it's simply continuous with the ground/heatsink tab on the device. Enable voltage and input voltage tolerances are within range; it may get a bit hotter though since it handles 1A vs the 500mA of the NJM2836. It also doesn't appear to require the 2.2uF bypass cap that the NJM2836 does; which i'm actually concerned may be causing the short or contributing to it.

The close-equivalent Rohm part number is a mouthful: BAJ2CC0WFP-E2CT-ND.

Disconnecting the NJM2836 and bypass cap temporarily, and feeding it a current-limited 100mA 12V ... got me audio! And I was receiving signals as I held my Rigol's +V lead to the VRM's Vo pad...

So at this point I'm going to try to correspond with the AOR contact leads - or if that doesn't work, replacing that VRM with the Rohm may get me up and running...

Posting all this info here though so that anyone else who has this problem or has a unit that goes out, has a lead on this information. I've figured out much of the audio circuit and how it travels in the unit, so hopefully I can help out if others run into this problem.
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