[Kenwood] TS950 help

[Martin Sole]

Dave,

Can't help with the 950 I'm afraid.

For the 940. I would take a step by step approach. Confirm the off load 
collector voltage is not more than 29 volts. With the RF drive removed, 
(pull the plug on the RF board underneath) check for bias voltage and 
current. Start with the bias pot at minimum volts and increase slowly 
until you get the correct amount of current, 1.3A. I would also check 
the driver bias and set it as per the book too, 50mA.

With drive connected but in SSB you should have no output and no blown 
devices. In CW with the power at minimum and the carrier level at 
minimum you should have no output. Increase carrier and you should see 
about 5 watts with ALC action. Then increase power to 110 watts maximum. 
If you are getting more than this then turn it down at VR2 on the 
control board.

Though I have never seen it happen I understand there can be a problem 
with high gain drivers. If the original low gain MRF485 drivers have 
been replaced with high gain types (different spot colour) it is 
necessary to do some mods to the driver bias. I suppose if these mods 
were not done the excess gain, as well as putting the drivers at risk 
might try to overdrive the final transistors.

We need some more info I think to see what might be happening.

Cheers
Martin


Busbar827 at aol.com wrote:
> I have a TS950 that will go into tx on am but produce no rf and on fmit  
> starts of ok but rapidly
> drops 20-30watts and then abit more gradually,it is fine on SSB,any ideas  on 
> the prob?I am also looking for a cure for my TS940 which is eating MRF422's  
> on key up,can find nothing obvious,even rebuilt the board,can anybody 
> help?Would  also like to know of a good source of 940 parts,especially a PA board.
>  
> Dave
> G6CNW 
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