Re: in the adjustment menu i can not get the driver idle current down to the 1 amp setting


Hi Steve
Yes I have just realised what I was doing was incorrect, I have just done it correctly,
I could not get the 430m final ideal current to 2.5a above the 00 , reading, I could only get it 400ma above, all the other bands adjusted at per the manual and I am now getting the 35w at 13.8v on UHF ,it is also more stable
It's good to see that you are still about on all of the forums, I still have my Kenwood ts2000 ,I got this to put in my car,
I will fit a 15v TVS diode as I do have some,
Thanks Dave 2E0DMB

On Sun, 24 Apr 2022, 17:52 Steve W3AHL, <w3ahl@...> wrote:

Set the Driver Idle Current adjustment reading to "00", then note the current draw.  Rotate the  dial to INCREASE the current draw by 1.0 amp above the previous reading.  That establishes the proper Driver Idle Current, assuming the adjustment circuits are working correctly.

This only sets the Class A Driver idle current -- it has nothing to do with the output FET's operating points, which are fixed.

The UHF PA FET is often weakened by excessive (>35 VDC) voltage spikes on the 12 VDC power input when operating mobile, due to counter EMF spikes from the engine's starter motor.  In my experience though this usually results in the UHF power output dropping to 5-10 watts or zero.

I would do the complete Transmitter adjustment procedures before attempting any troubleshooting of varying transmitter power output by band.   It may bring all the bands close to specification.  If not, it may lend more insight to where the problem is.  If multiple bands are below the specified output level after correct adjustments, then the Driver (Q504) may be at fault.

It is important to verify that the "12 VDC" input supply is 13.8 volts at full TX PO output and capable of supplying 25+ amps before doing TX adjustments.  More importantly, verify that the supply voltage seen by the circuits inside the unit are > 13.3 VDC under full load by measuring across the TUNER port pins 3-4.  A common problem is excessive voltage drop across the factory supplied fuse holders on the input power cable.  These fuse holders are a poor design and should be replaced with 30 amp automotive style fuse holders.

Steve, W3AHL

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