[ICOM] Techs repair...

[Ham Op]

Wonderful info Gary, this can help us all in the future. I have 2 781s and 
an R9000 and they just keep trucking along.  The R9000 is late, 2001 and 
before the L model, coming from Hong Kong and SN 5323. Latest USA sold unit 
I have heard of is about #2800 (1997 maybe?)... I have used Kuni and he is 
very knowledgable and fair on pricing and quick to get it back to you.. Do 
not know the other gentleman, Scott, but can you give his ham call, if he 
had one? Thanks..
San K5YY

----- Original Message ----- 
From: "Gary P. Fiber" <gfiber at comcast.net>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Thursday, October 23, 2008 12:12 PM
Subject: Re: [ICOM] 751A Main RF Board


> Eddy,
>
> PBT means Pass Band Tuning. Its a nice method of applying a variable 
> bandpass filter to the incoming receiver signal. Its done in the RF 
> stages.
>
> On the now older removed Main Board with J-17 removed the PBT function was 
> restored, the IF shift control became the PBT control. Icom in later years 
> restored the PBT in the IC-751A. During the unsettled patent  issue all 
> PBT was removed from Icom products except for the IC-735 and the IC-781. 
> The IC-781 was Icom's own PBT design. Some say the patent issue was with 
> the Collins Radio company, I never actually found out though.
>
> I have never tried a different main board in the NON PBT 751A versions but 
> I think it should work.
> You might give a local repair person Scott Malcom   mts at trip.net   an 
> email.  He is very responsive and you can tell him I asked you to write if 
> you want to.
> I worked with Scott for several years and he is knowledgeable on the 
> IC-751A and may have actually swapped main units like your situation.
> Kuni Okuma is also a good tech,  w7jv at aol.com   You might email him too 
> and see if he has done a board swap.
>
> Kuni,  Scott and I worked for Icom America, Inc. I was in the Technical 
> Customer Service group and  Kuni and Scott were bench techs. They may tell 
> you I always grabbed the hot end of the soldering iron ;)  I had some 
> limited time on the bench too but we almost never swapped entire circuit 
> boards, they went to componet level repairs there.
>
> Gary Fiber K8IZ
>
>
>
> EP Swynar wrote:
>> Hi Gary,
>>
>> Bingo...! Yes...!
>>
>> There is, indeed, a "J17" marked on the pc board, right next to the pin
>> terminal...
>>
>> What does it all mean, then...? Can I safely install the board into my
>> existing rig --- minus the black wire / J17 connection --- and expect it 
>> to
>> work OK...?
>>
>> I assume PBT refers to "push button tuning"...? If I hook-up the board 
>> LESS
>> the wire, will some button on the face of the rig allow me this option, 
>> vs.
>> my simply spinning the dial...?
>>
>> ...And how'd you get so smart about these things, anyway, Gary...?! Hi 
>> Hi.
>> Seriously, it's great to have the knowledge & experience of guys like you
>> available to aid & abet dunderheads like me...I sincerely do appreciate 
>> it.
>>
>> ~73!~ Eddy VE3CUI - VE3XZ
>>
>> ****************************************
>>
>>
>> ----- Original Message ----- 
>> From: "Gary P. Fiber" <gfiber at comcast.net>
>> To: "ICOM Reflector" <icom at mailman.qth.net>
>> Sent: Thursday, October 23, 2008 12:04 PM
>> Subject: Re: [ICOM] 751A Main RF Board
>>
>>
>>
>>> On the original board was that post labeled J-17? If do that was the
>>> defeat for the PBT. You may have a board that PBT is enabled on where
>>> your original one PBT was disabled from the factory due to a patent
>>> infringement that was settled years ago now.
>>>
>>> Gary K8IZ
>>>
>>> EP Swynar wrote:
>>>
>>>> Hi Guys,
>>>>
>>>> Here's a good one...
>>>>
>>>> A year ago, my venerable back-up rig --- the Icom 751A --- suddenly 
>>>> went
>>>>
>> belly-up in the transmitting department. A tekky friend of mine, who is 
>> in
>> the business of consumer electronics repairs, had a good long look at it, 
>> &
>> determined that a 9-MHz crystal-controlled stage on the main RF circuit
>> board wouldn't oscillate in transmit...no idea why, either (all the 
>> parts,
>> voltages, etc. therein apparently checked A-OK).
>>
>>>> Anyway, last summer I bought a complete 751A board (less filters) from 
>>>> a
>>>>
>> fellow who was parting-out his rig. Great! I'll just swap out the "bad"
>> board, & replace it with the new one...
>>
>>>> Well, to-day I proceeded to carefully dismantle my board from the rig,
>>>>
>> recording which connector goes where, etc. etc. etc. ... and all went 
>> well,
>> too, until the end, when I finished-up with a black wire that pulls out 
>> of a
>> post at the juncture of diodes D-161 & D162 in my 751A...
>>
>>>> The problem is, there is no such post on the board that I
>>>>
>> purchased...and no diodes D161 or D162, either.
>>
>>>> I examined my 751A service manual schematics, circuit board outlines,
>>>>
>> and parts list --- and learned, to my complete & utter dismay, that these
>> diodes aren't listed in the manual, either!!!
>>
>>>> I must have a newer-vintage transceiver which was manufactured AFTER 
>>>> the
>>>>
>> manual was printed, or an older transceiver & a new manual --- with a 
>> brief
>> history of any & all engineering revisions made to the rig being NOT duly
>> noted therein...(sigh!).
>>
>>>> The black wire goes from the afforementioned post, and plugs into the
>>>>
>> Matrix board.
>>
>>>> I am debating whether, or not, I should simply proceed with the swap &
>>>>
>> tape the wire off to one side (the same way automobile manufacturers do 
>> with
>> redundant underhood wires in the face of upgrades) & hope for the best, 
>> or
>> do as my friend did last summer, & simply part this sucker out to the 
>> world,
>> piece by miserable piece...
>>
>>>> ~73!~ Eddy VE3CUI - VE3XZ
>>>>
>>>> PS: How come I never have this problem fixing-up my old Drake &
>>>>
>> Hallicrafters rigs...?!
>>
>>>> ----
>>>> 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/
>>>>
>>>>
>>>>
>>> ----
>>> 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/
>>>
>>
>> ----
>> 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/
>>
>>
>
> ----
> 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/
>