Icom IC-718 Low Power

[KT4WO]

Yes ---I have checked the pwr supply/connector,,etc

Into a dummy load I get 100 watts on 10 meters and as I go down to 160 meters
the power drops to 30 watts ---

I have reset the radio,,,,changed pwr supply, pwr cable, jumpers...all that stuff.
(It IS in the radio)

I'm thinking I may have a stuck/open/closed relay on the low pass filter board.

Has anyone had this issue with the 718 or other Icoms in this class?

Trip - KT4WO
kt4wo67@gmail.com

[KT4WO]

Yes--- In all modes.

KT4WO

[WB2WIK]

Did you try using a different coax patch cable from rig to dummy load?

Not as nutty as it sounds: A cable with a bad shield connection may still transfer a lot of power at 28 MHz, which it just cannot do at 1.8 MHz.

If that's not the problem, then your guess is the same as my guess, which is a LPF relay isn't switching properly.  This is likely controlled by firmware; have you tried a global reset?

[KT4WO]

From my 1st post:

"I have reset the radio,,,,changed pwr supply, pwr cable, jumpers...all that stuff.
(It IS in the radio)"

I will pull the LPF board this weekend and start checking relays....

KT4WO

[KA5IPF]

Observe the current draw. If it's a LPF relay the current draw will go up as the radio tries to maintain 100w out. If the current draw goes down it's before the final unit.

Clif

[KT4WO]

RE:
"Observe the current draw. If it's a LPF relay the current draw will go up as the radio tries to maintain 100w out. If the current draw goes down it's before the final unit."


Didn't even think of that! ... Tnx Clif  ....I will do that now.

Trip - KT4WO

[KT4WO]

About 16-17 amps on most bands but not all --- one band was down to ~9 amps....
a few others in the 12-15 range.(meter is maybe 10%) ....
I didn't make a list yet.

I'm wondering if its a driver...I have seen some post about failures
of one or both of them... but the amp draw makes me wonder.

My TS-50S is in the 17-18 amp range at ~100 watts ... so I guess it could
still be on the filter board --- need to make a jumper straight from power
deck to meter/dummy load and see what that shows -- That should narrow it
down.

KT4WO

[KT4WO]

Think I have nailed it down to the drivers...per voltage checks and power out.

Drivers came in today..will update this weekend.

I guess after 7+ years it been worth the 550 I paid new for it!!

KT4WO

[WA8MEA]

Why couldn't it be the dummy load?

I was one of those that thought all dummy loads were the same, UNTIL I ran across one that gave me a 3.5:1 SWR on certain bands.

I didn't see it in your original post, BUT....do you show 30 watts into a dipole or antenna with approx. 1.5:1 (or better) SWR on 160 meters?

I use a 160 meter dipole on my 718 and it QUICKLY drops down to 35 watts and a 3 to 1 match about 80 KHz away from minimum SWR of 1.2:1.

73, Bill

[KT4WO]

Re:Dummy Load

Its the same into the dummy load or  thru the match to my antenna(or real close).
(or into the resonate((spelling?)) parts of the bands on my antennas)

The "import" 2SC3133 drivers "were not" .... I should have known better...

I will reorder from RF Parts and try again....

KT4WO

[W5WSS]

My 718 I had to replace the drivers pair stupid to have a pair that needs biasing IMHO.

when 1 can be done easily.

The symptom when progressing to failure was 1 went bad.

Normally one would expect an instantaneous failure with a single componenet but in tandem was a progression.

The output power everywhere all bands would be 100 watts then suddenly power would drop to 10watts.

Changed the drivers.

works fine now.

Wonder if a better and reliable driver is seekable

We are all relying on device that can be potentially poor quality from Asia.

Just sayin

[KT4WO]

As I run 25 watts (or less)on digi modes 99% of the time, this could have been
a issue for a month or more and I didn't see it.

I did see that RF Parts sells a 2SC19?? as the replacement for the 2SC3133...
Maybe that would be better?...who knows...Like you said..all from Asia.

Trip - KT4WO