[ICOM] 765 freq problem

Sat Feb 28 12:28:44 EST 2015

Tony,

Sounds like the best plan.
On Feb 28, 2015 9:18 AM, "Tony Hwang" <dragon40 at shaw.ca> wrote:

> Hi,
> If I were you I'd start replacing them all since it is well known problem.
> Even if they are good now,
> sooner or later you'll have to deal with it if you plan to keep the radio
> quite a while. I did all the mods. and
> trimmer replacement B4 the problem started. Also I installed CW tone mod
> as well.  I replaced PA driver
> transistor with heavier one too.  If you want to heat the trimmers for
> testing, you can use hair dryer.
> Have fun.
> Tony, VE6CGX
>
> Marc & Tricia Niebergall wrote:
>
>> Carmine,
>>
>> We will investigate further.  Thanks.
>>
>> Marc
>>
>> On Sat, Feb 28, 2015 at 8:23 AM, Carmine Caira <iz8azz at tiscali.it> wrote:
>>
>>  You should perform the operation after at least an hour the rig was
>>> powered up,
>>> a good warm-up is always mandatory.
>>> I don't know if deviance after an half our could mean bad trimmers in pll
>>> board, but if
>>> the frequency shift you have happens only in usb mode it is sure related
>>> to usb bfo trimmer.
>>> I had to replace it in my ic-751a  because  of same problem (usb only).
>>>
>>> 73 Carmine
>>>
>>>
>>>
>>> Il 28/02/2015 16:45, Marc & Tricia Niebergall ha scritto:
>>>
>>>   I have begun the troubleshooting and started with the infamous PLL
>>> trimmer
>>>
>>>> capacitors.  I measured the voltages on the four trimmers according to
>>>> the
>>>> service manual and each trimmer was high by about 0.3 or 0.4 vdc.  I
>>>> re-trimmed to exactly 6.5vdc on the precise freqs and checked about 1/2
>>>> hour later.  The voltages had drifted about 0.3 volts high.  My
>>>> question:
>>>>    Is this normal or is this an indication that the plastic trimmers
>>>> are in
>>>> fact in need of replacement?  I would think the voltages should stay
>>>> constant at the freqs listed once re-adjusted.
>>>>
>>>> Marc
>>>>
>>>> On Thu, Feb 26, 2015 at 12:43 PM, Marc & Tricia Niebergall <
>>>> mtniebs at gmail.com> wrote:
>>>>
>>>>   Tnx to all the contributors for the wealth of knowledge. My suspicions
>>>>
>>>>> are
>>>>> that the solution lies therein.
>>>>>
>>>>> I'll post my results for others to benefit as I have.
>>>>>
>>>>> Marc-k7wxk
>>>>> On Feb 26, 2015 9:28 AM, "D. Jones" <djoneses at verizon.net> wrote:
>>>>>
>>>>>   Mouser has the Sprague GKG10015 in stock for 60 cents each.
>>>>> Comparing
>>>>>
>>>>>> specs with the GKG10024 it seems these should work although they are
>>>>>> 2.3 mm
>>>>>> taller. I don't know if that is an issue.  The Mouser part number is:
>>>>>> 659-GKG10015.
>>>>>>
>>>>>> David
>>>>>>
>>>>>> <div>-------- Original message --------</div><div>From: Marc & Tricia
>>>>>> Niebergall <mtniebs at gmail.com> </div><div>Date:02/26/2015  10:52 AM
>>>>>> (GMT-05:00) </div><div>To: ICOM Reflector <icom at mailman.qth.net>
>>>>>> </div><div>Subject: Re: [ICOM] 765 freq problem </div><div>
>>>>>> </div>Rich,
>>>>>>
>>>>>> Thanks for the additional info. It seems that the part numbers are
>>>>>> pretty
>>>>>> scarce, so I would welcome any new info regarding availability of
>>>>>> ceramic
>>>>>> trimmers.
>>>>>>
>>>>>> Marc
>>>>>> On Feb 26, 2015 7:42 AM, "Rich Dailey" <redailey1 at gmail.com> wrote:
>>>>>>
>>>>>>   I'm the author of that page. I need to mention that I'm not sure of
>>>>>> the
>>>>>>
>>>>>>> availablility of the replacement trimmers that are mentioned in the
>>>>>>> article. If someone has a good link to a supplier of substitutes,
>>>>>>> I'll
>>>>>>> update the page to add those links. Been a lot of years.
>>>>>>>
>>>>>>> Also, I'll throw in that I recall having one on the bench that had a
>>>>>>> sililar drift situation. I replaced the trimmers, AND
>>>>>>> 10uf bypass caps coming off a 5 volt regulator. They were pulling
>>>>>>> hard
>>>>>>>
>>>>>>>  on
>>>>>>
>>>>>>  that supply voltage. Seems
>>>>>>> it was on the board under the power supply, on a long, shared heat
>>>>>>> sink
>>>>>>> with other regulators. Like I said,
>>>>>>> it's been many years, my brain is foggy, but that's what I remember.
>>>>>>>
>>>>>>> Rich, N8UX
>>>>>>>
>>>>>>> On Thu, Feb 26, 2015 at 4:57 AM, rrocket88 at netzero.net <
>>>>>>> rrocket88 at netzero.net> wrote:
>>>>>>>
>>>>>>>   here is an old descriptive i've had filed away, was going to
>>>>>>> perform
>>>>>>> but
>>>>>>> health went south  good luck K4IMZ
>>>>>>>
>>>>>>>> http://home.windstream.net/ferncity/icom.htm
>>>>>>>>
>>>>>>>>
>>>>>>>>   ----
>>>>>>>>
>>>>>>> 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
>>>>>> ----
>>>>>> 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
>>>>
>>>>  ----
>>> 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
>>
>>
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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
>