Need Help: Kenwood TS-930S Receiving Erratically

A fellow HAM dropped off a later serial numbered TS-930S he acquired. After bringing it up on a variac, I noticed the receiver performs erratically. It will drift in and out or it will cut out all together. After a few seconds, it will come back. The meter would reflect that. I tested the power supply, which is mostly original, and the voltages look OK. I was going through the voltage adjustments from pg 64 of the service manual, and most of the voltages checked out fine except for Jumper wire J13 on the signal board. It should be 2.2V but I'm getting 18V. Adjusting VR25 has no affect on the J13 voltage. I'm not sure if this reading is related to this specific problem.

With a HP signal generator, I was able to check the receiver across the entire band using 0.5mhz increment and I hear the 1khz tone just fine. Any suggestions?

 

Can you be a bit more specific about what is happening?

And does the frequency display look all OK?

(and by the way, the TS-930S is a synthesized and all solid state rig . . . so you shouldn't be posting for advice in the Boat Anchor section !)

Roger G3YRO

 

And yet, here we are with several 930/940 threads in the BA section.

It qualifies in stock form due to its weight!

 

Roger, this Kenwood weighs like an old Collins just smaller, but seriously my decision to post in Boat Anchors was due to the number of TS-930S posts as N8YX observed. I do agree in principle so future posts about this transceiver will be in the appropriate section.

I don't know if I can be anymore specific. I can post a video on youtube to show the behavior of the receiver next time I'm in the shop.

The frequency display/counter was frozen but after cleaning VR1 and VR2 and giving it a back and forth twist it is working well. Hmmm, I need to check to see if a received signal becomes erratic. What I hear is the rf noise cutting in and out. I haven't tested the receiver for a constant signal. Well, let's see what happens next time I'm in the shop.

 

You can just use the Calibrator to see if it's receiving OK

Roger G3YRO

 

I'd double check the rig settings defined in the service manual just prior to the alignment section to make sure all mode settings are correct and then re-measure the voltage on J13. If everything is set correctly to support that test and you still see such a dramatic variation in expected voltage then spend some time figuring out what that's happening.

FWIW, it's a good idea to troubleshoot the problem right in front of you rather than ignoring it and moving on. Maybe it's just some setting of the rig wasn't correct to support that test but if that's not the case figure out what's happening with the problem you've already identified before moving on to look for other problems.

 

Interesting, I've never used the calibrator for that purpose other than to line up the dial on a Drake. I'll look into that. Thanks.

 

I had the rig settings set per page 63 of the service manual under Preparation.

I agree.

 

Do you realize there are 3 different versions of the 930 and some checkpoints changed.

 

No, I was only aware of the two version with the change after S/N 309xxxx. This unit is 401xxxx and the previous owner(s) has marked up the later versions of the schematic from earlier repairs.

When was the third version produced? Thanks.