[ICOM] IC 756 Pro III fuse over-heating?

Tue Dec 16 21:45:10 EST 2008

    I've used a TL922 but apparently the supplied cable got separated 
for the the amp a few owners ago and we used whatever was the proper 
length available to get the amp and rig connected. I'm not sure the 
length is critical if you have a good quality jumper.
    Phil N0KE

Dan Cotsirilos K9DTC wrote:
> The Kenwood TL-992A provides a jumper with their amp and it measures 
> 57 1/2 inches.
>
>
> Dan K9DTC
>
>
>
> ----- Original Message ----- From: "Jim Hargrave" <w5ifp at gvtc.com>
> To: "ICOM Reflector" <icom at mailman.qth.net>
> Sent: Tuesday, December 16, 2008 8:40 AM
> Subject: RE: [ICOM] IC 756 Pro III fuse over-heating?
>
>
>> There is some merit to the length of the coax.
>>
>> Years ago I had a Collins KWM-1 and there was a note that recommended 
>> a 21
>> ft length of coax between the KWM-1 and the 30L-1 linear. I don't 
>> know the
>> theory on how they arrived at the 21ft. But it does make some sense. 
>> I just
>> coil the excess up behind the desk and it makes a good RF choke 
>> between my
>> FT-920/IC-735 and the Clipperton-L.amp.
>>
>>   * 73's Jim W5IFP *
>>
>>
>>
>>
>>   >-----Original Message-----
>>   >From: icom-bounces at mailman.qth.net
>>   >[mailto:icom-bounces at mailman.qth.net]On Behalf Of Julio Peralta
>>   >Sent: Tuesday, December 16, 2008 1:02 PM
>>   >To: 'ICOM Reflector'
>>   >Subject: RE: [ICOM] IC 756 Pro III fuse over-heating?
>>   >
>>   >
>>   >Try changing the length of the coax between the rig and the input 
>> to the
>>   >amp. Sometimes the length of that cable will cause the rig to
>>   >reduce power
>>   >out until it determines the match is OK. I've experienced this 
>> myself.
>>   >
>>   >Julio, W4HY
>>   >
>>   >-----Original Message-----
>>   >From: icom-bounces at mailman.qth.net
>>   >[mailto:icom-bounces at mailman.qth.net] On
>>   >Behalf Of Phil Krichbaum
>>   >Sent: Tuesday, December 16, 2008 5:49 AM
>>   >To: ICOM Reflector
>>   >Subject: Re: [ICOM] IC 756 Pro III fuse over-heating?
>>   >
>>   >    On Saturday night I had been running along working a bit on 
>> 10m CW
>>   >and then got a phone call. When I came back on the air some 15 
>> minutes
>>   >later the Alpha 91B grid safety feature would trip after about two
>>   >seconds. I'd not had this problem previously in this contest
>>   >during some
>>   >good runs or ever before. I have two antennas and one is about
>>   >1.3:1 and
>>   >the other 1:1 and it didn't mater which antenna I used. I was running
>>   >the 756PROIII at less than 50w output. A little further checking  
>> and I
>>   >noticed when I first started to transmit I was getting less than QRP
>>   >output for 2-3 seconds before going to the set power level. This in
>>   >itself is a very undesirable feature for contesting not to mention 
>> not
>>   >having the amp available as it would trip as the power came up!  Just
>>   >for the heck of it I tried loading on 20m and everything seemed OK. I
>>   >went back to 10m and same problem. I bypassed the Alpha and same
>>   >problem. I tried a different amp, same problem! I removed the
>>   >PROIII and
>>   >no problem with another rig and finished the rest of the
>>   >contest with it.
>>   >    I'm using the Icom PS125 that came with my PROII "free" as a
>>   >closeout sales promotion (I certainly would not pay that much
>>   >for a 25 A
>>   >switcher). The PROII got taken out of service permanently with a
>>   >lightening surge that apparently came in the neutral side of the 
>> power
>>   >line. My PROII was off but this PS125 was left on (I've changed that
>>   >practice with the PROIII). I assume the PS125 means it is rated at 25
>>   >amps and there is a short power cord of about 12 inches with no fuses
>>   >and the 6 connector Jones type plug on the end. I suspect if there 
>> are
>>   >fuses, they are inside the PS125. I need to do some further 
>> checking of
>>   >the problem as to what bands are affected and at what power levels. A
>>   >friend had a similar problem on 6m last summer and it eventually went
>>   >way by itself. It seems I should try a different PS if the problem
>>   >persists and also take a look at the fuses in the PS125. Perhaps the
>>   >PS125 was damaged somehow when the surge came thru it. Damage
>>   >to the rig
>>   >also came in the rig control cable and CW keying jack from my desktop
>>   >that was connected but off. The HD in the desktop was toast. I
>>   >have also
>>   >picked up some 3 wire 250V 30A knife switches they use in Costa 
>> Rica at
>>   >the main house feed to shut off power to the house and will
>>   >install then
>>   >on my 120 and 240 lines into the shack prior to spring so there 
>> will be
>>   >no connection to the house wiring when I leave the shack assuming I
>>   >remember to throw the switch! I've also had my power provider 
>> install a
>>   >"Meter Treater" at my meter which has some big  MOVs in it.
>>   >    Anyways it seems like I need to check the PROIII with a
>>   >different PS
>>   >if this problem doesn't fix itself!
>>   >    73 Phil N0KE
>>   >
>>   >Jim Reisert AD1C wrote:
>>   >> I've had problems the last couple of weeks with my IC756 Pro III
>>   >> shutting down in the middle of transmitting.  This weekend I 
>> traced it
>>   >> to the fuses (which were getting warm to the touch).  I  notice 
>> that
>>   >> my SS-30 power supply reports ~ 20 amps being drawn on transmit, 
>> and
>>   >> the fuses are rated at 20 amps.
>>   >>
>>   >> **  Is 20 amp draw during full-power transmit normal?
>>   >>
>>   >> **  Are the fuses supposed to be 20A?
>>   >>
>>   >> **  Should I replace with 25A fuses, or 20A slow-blow, or is 
>> there a
>>   >> bigger problem here?
>>   >>
>>   >> Thanks & 73 - Jim AD1C
>>   >>
>>   >>
>>   >>
>>
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>>
>>   >>
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>>   >12/15/2008 5:04 PM
>>   >>
>>   >>
>>   >----
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>>   >
>>   >----
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>> Icom Users Net: Sundays, 1700Z, 14.316 MHz
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