modding the Driver board , so it does not fry,


davebb123456
 

modding the Driver board  ?
i see that icom did mod the driver board with an added resister to stop it self oscillating, and burning it self out,  does this work ?
I have seen on youtube TRX Bench that he is still getting some 7000 with badly blown driver boards that already have this mod,
i am thinking of doing the modes by SV8YM, and i am going to fit a self re-settable 1.5amp fuse, for the driver board power supply, Doing these mods is no problem for my skills ,
Thanks Dave 2e0dmb


Joe Krout
 

The driver board is a definite weak spot. I've blown a couple up over the years.  The best solution I have found is to always use a good auto tuner like the LDG IT-100, even when using a resonate antenna. Not a perfect solution, but some added insurance. 

Joe KR0UT


davebb123456
 

Hi Joe
the only thing is with a auto tuner, when tuning you are putting the radio into high vswr when it is tuning, 
i will be using my radio with a  screw driver antenna ,
My driver board is still good, i do not know what revision it is , until i lift the PA board, i will do this today or tomorrow ,
as i can see that there is no heat sink compound on the driver board, and i will re-grease the other PA if dry like the uhf output was,
Thanks Dave


Joe Krout
 

The IT-100 when connected via the tuning cable sets the output power to 10 watts while tuning via the tune button. 

Granted, it is possible to tune at full power manually.

While not a perfect solution,  its the best I have found. 
Good luck on disassembly.


On Tue, May 10, 2022, 10:18 AM davebb123456 <davidbrowne76@...> wrote:
Hi Joe
the only thing is with a auto tuner, when tuning you are putting the radio into high vswr when it is tuning, 
i will be using my radio with a  screw driver antenna ,
My driver board is still good, i do not know what revision it is , until i lift the PA board, i will do this today or tomorrow ,
as i can see that there is no heat sink compound on the driver board, and i will re-grease the other PA if dry like the uhf output was,
Thanks Dave


Steve W3AHL
 

I haven't seen many driver board failures personally (I typically only repair 7K's for local hams over the past 15 years, so I don't see a lot of units).  I have looked into the driver's design and signal levels at various drive levels and on all bands, while using an auto-tuner into various mismatches.  I do feel that antenna tuners and perhaps operation at LOW power seem to be a somewhat common thread for units that have multiple driver failures, but haven't seen direct evidence of it on units I've worked on. 

Many operators use antenna tuners to try to match antennnas well beyond the tuner's design spec.  This often damages the tuner, which then damages the radio.  Poor connections in the feed line and antenna are often intrmittent problems that lead to voltage/current transients that can damage the radio.  I feel that poor installations damage more radios than design flaws in the radio itself.

The added resistor change issued by icom was only for certain countries that had a different frequency range or band -- I forget the details.  Several postings indicated it was not effective.

Thermal measurements of the driver case don't indicate that the lack of thermal compound is a problem, but I always apply it when reinstalling the device. 

In short, I haven't encountered enough driver failures on rigs that I knew how they were being used at the time, to have an opinion about what the root cause of the failure is and what the proper fixes are.  

I doubt that a resettable circuit breaker will trip fast enough to protect the circuit, but haven't looked at their spec's for years, so maybe some exist.

The HF and VHF PA's will have factory-applied thermal compound.

My two 7K's are about 12 & 16 years old and had fairly heavy use (until the past few years), mainly mobile and portable, HF-UHF.  I've only fixed my radios 3 times and all of the failures were due to problems external to the radio.  I've also replaced the HM-151 mic switches with similar better-sealed switched when the original ones failed and replaced the poorly designed ATC style fuse holders used on some power cables with automotive style holders that bite through oxidation on the fuse blades.  

Steve, W3AHL


davebb123456
 

Thanks Steve
its a smd Self recovery fuse i am going to fit
on trx bench on youtube had some that the driver was badly burnt, but he did not know how it was used,
Thanks again,
Thanks Dave


 

Per the tuner statement, I lost a driver when I had an auto tuner go crazy when an antenna was connected incorrectly (wrong antenna!).
This is the only time I had a driver issue on one of my IC-7000