Heathkit HW-101 troubles

[KA9MOT]

My loaner HW-101 has an oscillation problem on USB on all bands. Info I found online suggested loose board screws t the chassis. I checked and found a bunch of loose ones and all are tight now. My diagnostic skills aren't what they should be. I usually build stuff based on an idea or somebody else's design and I am good at modifying and repairing electronic stuff (based on others published information).

Anybody have any ideas?

[WØTKX]

Dunno. But here's some linkies...

http://www.ki6yfq.com/projects/heathkit_hw-101_hf_transceiver.html

http://nrwilliamson.tripod.com/Hw101.pdf

http://www.davemorris.com/dave/wb8jkr.jpg

http://www.qsl.net/k5bcq/102/102.html

http://ww_heco.home.mindspring.com/heco_fix.html

http://m0msx.webs.com/heathkitequipment.htm

[W1GUH]

Does the oscillation happen with the mic gain all the way down?

[KA9MOT]

Does the oscillation happen with the mic gain all the way down?

Yes, with the mic gain all the way down, with mic and with-out. When keyed she oscillates and only on USB.

[KA9MOT]

Dunno. But here's some linkies...

http://www.ki6yfq.com/projects/heathkit_hw-101_hf_transceiver.html

http://nrwilliamson.tripod.com/Hw101.pdf

http://www.davemorris.com/dave/wb8jkr.jpg

http://www.qsl.net/k5bcq/102/102.html

http://ww_heco.home.mindspring.com/heco_fix.html

http://m0msx.webs.com/heathkitequipment.htm

Some of this I've all ready seen. All helpful and all a good read! Thanks!

[ka4dpo]

Is the carrier balance adjusted?

[W1GUH]

Yes, with the mic gain all the way down, with mic and with-out. When keyed she oscillates and only on USB.

Hmmm...only USB? Not LSB? Interesting. Gotta be a clue there, somewhere. Will be thinking about it.

Oh, and has it been determined if it's oscillation or just too much carrier? Sorry if I'm suggesting things that you'ver already tried...just thinking off the top of my head. Or maybe off the bottom of my....

Or does that mean only when it's plugged into your computer? Just coudn't resist! Sorry about that!

[W1GUH]

I'm looking at the schematic, on the left, about half way down around a mode switch wafer that switches between two crystals. Have you checked that the USB crystal is there, is good, and the connections are in good shape? The schematic I'm looking at is not so good, can't read which xtal is USB. Looks like the only RF difference between USB and LSB. The wafer above might be suspect, too.

No, but wait...this is only on the upper bands? Do I remember that correctly?

Does USB work on the lower bands?

Sorry about my OF memory!

Good luck & have fun!

[W1GUH]

Just bumping this up so 'MOT can see it. Cheers!

BTW...re: only upper bands....yea, even then. Could be if there's something funky in that sideband selection scheme, the feed back could only be strong enough at the upper frequencies? In any event, it's easy to check. What happens on the lower freqs. on USB?

[KA9MOT]

Thanks all! I haven't had the time to work with this rig for a while (needed to take a break anyway). Paul, I really appreciate the time and thought you've put inot this. My problem is on all Bands and only in USB Mode.

The guy who owns the rig said it worked FB at his place, and I have ruled out RF in the shack, Mic problems and all of the basic stuff. I running on the assumption that FedEx may have been less than careful with it, and have been looking at solders and grounds.

John, the carrier balance does seem to be adjusted, but I am not sure how to test it. There are some modifications to the circuit (regular shaft style pot soldered directly to the board replaces the stock board mounted pot) and all of the solders on this thing look really poor.

[W1GUH]

"My problem is on all Bands and only in USB Mode."

That may just nail it, hope it does, because that really seems to localize the problem. The only difference in the RF path between USB and LSB is what I described above...the stuff where the sideband is selected. That it works everywhere on LSB implies very strongly that the rest of the path, including the balanced mod. is just fine.

OTOH, anything can happen and there's always that "weird" bug that makes unexpected results!

Have fun!

[K7SGJ]

You're right on checking the soldering. The older Kenwoods were notorious for bad solder joints, and intermittent pb switches as well as rotary switches. Deoxit can be a real buddy. A Good luck.


(Try cold swaping the knobs. :-D}