Device Marking of the "Unidentified RF amplifier"...

[dl9sec]

Hi,

yesterday I got an ATS-20+ from Amazon (brand "Yunxwd").
The RF amps device marking here is "C1R". This could be a UPC2746TB from HUABAN (formerly this amp was from NEC).
The pinning seems to be turned by 180° and there is a little discrepancy at the connections:
The VCC pin of the "DKHE" is marked as "GND" at the "C1R" and the pin which seems to be some bias (with the series 10k resistor) at the "DKHE" is marked as VCC at the "C1R".
So either this isn't a UPC2746TB or it works by chance...

Regards, Thorsten

[m4rc0d1]

I also have one unit with the RF amplifier marked "C1R" and this seems to be a uPC2746TB from CEL or other manufacturers. Looking at the datasheet (https://www.mouser.it/datasheet/2/286/upc2745tb-36504.pdf or https://www.renesas.com/us/en/document/dst/upc2745tbupc2746tb-ds-pu10443ej01v0ds) the pins seem arranged in a different way than the "usual". Looking at the marking in a natural reading orientation, pin 1 is top-left and then the numbers go up in a clockwise direction (C1Q and C1R are the same chip with different gain and NF):

The pin numbering is standard when looking at the package from the bottom, something impossible with the chip soldered on the board.

This makes sense looking at the datasheet's pins list:

1 INPUT
2 GND
3 GND
4 OUTPUT
5 GND
6 VCC

The only strange connection is at pin 3 that the datasheet specifies as GND, but in the circuit it is connected to 3.3V, with a bypass cap to ground. Looking at the internal connections pin 3 is not directly connected to pins 2, 5 and the only reason I can think to do this is to reduce the overall gain of the amp and not saturate the receiver with the strong FM signal, but I haven't tested that.

According to these info, the schematic could be modified in the following way: