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Many thanks (it was: TS790 "anoying" mute)



Hi 

I got what I wanted. Many thanks to all who helped me.
For those who might be interested in the solution, 
here it is the sugested mod:

> 
>                           Modification Procedure
>                           ======================
> Preface:
> =======
> Because of the extremely delicate nature of part of this procedure, it
> should be performed only by an electronics technician experienced in
> working with micro-miniature components and who is equipped with the
> required precision tools and work environment.
> 
> Part 1: Eliminating the blanking circuit.
> ======
> a. Loosen IF board (X48-3050-00) by removing 13 screws. Then stand the
> board up and carefully fold back while avoiding damaging attached cables.
> Work will proceed on the "back" or previously concealed side of the PCB.
> 
> b. Locate Q5 and Q4 and R15.  They are on the "back" side of the PCB
> adjacent to L2 and L3 which are visible on the "front" side of the PCB.
> 
> NOTE: R15 is a 470 ohm chip resistor marker "471".
>       Q4 is a chip transistor with 3 legs. It is located just beside R15.
>       Q5 is a chip transistor with 4 legs marked "V11" and is located next
>       to R15.
> 
> c. Using an Exacto knife and magnifying glass, carefully slice the track
> between the collector of Q4 and R15.
> 
> d. Using a very small (approx 32 gauge) wire, connect a jumper
> approximately 4 mm long between the end of R15 (which was separated from
> Q4) and the nearby ground island. Use extreme care. Use a low wattage,
> needle soldering iron, tweezers, magnifying glass, high intensity lamp and
> razor blade or scalpel to effect jumper installation.
> 
> e. Carefully inspect with magnifying glass to insure no solder bridges have
> resulted and that the free end of R15 is now grounded.
> 
> f. Carefully replace IF PCB using the 13 screws previously removed.

==================================================================================

> Additional Notes from JR1EDE and JA6FTL.
> 
> 1. Cut the line between Q4 collector and R15 (470 ohm) and ground the end of 
> R15. JA6FTL made the mod by removing Q4 entirely and grounding the end of 
> R15. Q4 is located to the left of Q5 and they are located roughly opposite 
> side of L2 and L3. You need a magnifying glass!
> 
> 2. This modification is to disable the blocking line for the IF amplifier. The 
> audio muting function remains unchanged but the audio muting is no problem 
> if using the rear data port. (The audio muting circuit consists of D20 and 
> Q12).
> 
> a. Put the front side of the radio towards you and remove the bottom 
>    cover.
> b. Remove the 13 screws that fix the IF board. Lift the board up towards 
>    you.
> c. Q5 and Q4 are located just opposite the side of L2 and L3. Chip Q5 
>    (printed 'V11') has four soldered legs and is located next to R15 (a 
>    470 ohm surface mount resistor printed as '471'). Q4 is located just 
>    beside R15 and has 3 legs.

73 F.Costa, CT1EAT

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