FET silk-screening on pcb, proper position. Cobra 29 ltd

[LeapFrog]

I decided I wasn't going to give up on my parts radio.
Here are 2 cobra 29's side-by-side (have the service manual and the schematic).

Could someone explain what direction the FET1/FET2 should face on the pc board.
The symbol is a circle with one "side" cut off, what side should the printing on the Transistor face?
[photo="large"]4086[/photo] [photo="large"]4085[/photo] I don't trust these parts radios, before I start powering them up I want to make sure the parts are not in backwards then I can take some voltage readings and see where the faults are.
I know the legs of the component can be in different locations dending on the transistor in question.
The picture above has FET1 facing a different direction than it is in the other radio, which one is correct?.

Thank You, while searching FET Cobra 29 i couldnt find anything using the search bar.
The three cans with one crystal inbetween have FET1 above them, and FET2 below. The picture is rough but someone knows these and could explain the silkscreened part symbol on the pcb, I tried to describe it the picture does not really show the symbol well, you can see it in the first photo under fet2.

 

[LeapFrog]

BUMP, the 29 LTD Taiwan R.O.C. (pre-dates philli) has the silk screen for FET2
printed reverse compared to the 29 LTD Classic (China).

Has anyone else noticed this? Also does the schematic differentiate between two models, I will have to go back on the inter-webs and see if there are two different schematics, both radios use the same audio chip, not the same pll and are about 7 years apart.

 

[ExitThirteen]

Actually, on the new China made ones, the audio chip is different as well. As far as the FET's go, the LARGE flat side of the FET installs to the flat side of the screening on the PCB.

~Cheers~

 

[LeapFrog]

Actually, on the new China made ones, the audio chip is different as well. As far as the FET's go, the LARGE flat side of the FET installs to the flat side of the screening on the PCB.

~Cheers~

Very Good on you Kind Sir Cheers, & Thank You.
I'm going to plug in the solder iron now and make the corrections.

Later on tonight I may research the data sheets. Discover the pinouts for each fet, Google image search for the schematic symbol of a Field Effect transistor and study the DC path and Signal path on my schematics and use the voltage table found in the service manual as a reference point to have a greater understanding of how the radio functions.

I was getting frustrated, and the straight up answer you gave me is going to help me troubleshoot for now. Would you happen to know from prior experience if I installed the Field Effect transistor in reverse that perhaps it is blown? I don't have a dedicated tester yet and would have to use my digital multimeter to test these components.

73 Thank You ExitThirteen once again for the tip on the new China Cobra audio chip. This one is from 1995 though so no worries there LoL. The humble Toshiba TA7222AP is still doing the business and gettin'-on-down. (PA works great, TX works great, radio does not rx and no meter movement. I might just start a thread if I can't knick this one after trying at it for a bit more)

 

[ExitThirteen]

Oh ok, yes, that one will have the same audio chip. I think the newer ones made after about 2008 or so have a different one than the standard TA7222(A)P.


I don't think you damaged the FET any... it passes low current so doubtful it'll be bad. Just re-install it the other way and you should be fine. Good luck.

~Cheers~