[ICOM] 765 freq problem

Sat Feb 28 12:17:04 EST 2015

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
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2015.0.5645 / Virus Database: 4299/9199 - Release Date: 02/28/15
>
>