[ICOM] Re Xmit problem with IC-745

[Milton Taylor]

I just realized I never followed-up on this:  The transmit issue I had was
due (entirely) to the RF LEVEL pot being very dirty.  I actually found some
small openings on that pot which allowed me to spray contact cleaner
isside.  No more erratic pot!

On Thu, Dec 8, 2016 at 8:52 PM, M. J. Taylor <wa3mds at comcast.net> wrote:

> My 745 has a similar issue:  Output is erratic (into a 50 ohm load) as I
> increase the RF Level.  The  meter juumps around, like I am turning a
> 'dirty pot.'  If  I do get it to full power, when I go to transmit it has
> been either hit or miss, output or nothing.  This is true in either CW or
> SSB,  I hear a noise that I thought could be an erratic relay or even
> arcing, but I don't smell anythig.
> Anyone have similar experience?
>
> Regards,
>
> Milt, WA3MDS
>
>
> ----- Original Message ----- From: "GGLL" <nagato at speedy.com.ar>
> To: <icom at mailman.qth.net>
> Sent: Saturday, November 05, 2016 8:00 PM
> Subject: Re: [ICOM] Re Xmit problem with IC-745
>
>
>
> R64 is 47 ohms. If you have 13.8V when in TX mode, at the source side of
> it and 3.6V at the load side, circulating current is approx. 200 mA
> through R64, so it should be very hot (almost 2 W dissipation).
>
> Check its value, if not so hot.
>
> Regards
> Guillermo - LU5WE.
>
> El 05/11/16 a las 19:56, Fern Rivard escribió:
>
>> I have an IC-745 which has a no transmit issue on all modes.
>> I know that the problem is in the RF board as I proved it by
>> substitution of rf  board from another IC-745 which has no issues.
>> I'm not getting proper dc voltage to Q16.
>> There's only 3.5 volts dc on the load side of R64 so there's  something
>> loading the dc voltage down that feeds Q16 but it's difficult to probe
>> that board while installed in the radio.
>> I initially replaced Q16 with a new 2SC2053 with no change.
>> Any help or suggestions as to what to look for would be greatly
>> appreciated.
>> I'm sure that somebody else must have had the same issue at one time.
>> I'd like to donate this rig to a new ham as their first rig but have to
>> get it operational first.
>> 73 from Fern  VE7GZ
>>
>> ----
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>>
>> ----
> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
> Icom Users Net: Sundays, 1700Z, 14.316 MHz
> Icom FAQ: http://www.qsl.net/icom/
> To support QSL/QTH.net: http://www.qsl.net/donate.html
> ----
> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
> Icom Users Net: Sundays, 1700Z, 14.316 MHz
> Icom FAQ: http://www.qsl.net/icom/
> To support QSL/QTH.net: http://www.qsl.net/donate.html
>