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 Post subject: Heathkit sb 102- no receive on 20 meters
PostPosted: Nov Mon 16, 2020 6:11 pm 
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Joined: Sep Sat 28, 2019 2:05 pm
Posts: 185
HI everyone working on another 102 here and i looking for a few pointer`s on where to start looking. The one symptom i have is that it receives on 20 meter`s when i first power it on ,but after it warms up it does not receive on that band anymore . And when i turn the driver pre selector no change in audio happen`s except a popping type noise occasionally. But the pre selectors works before warm up ?. I haven`t done to much to the unit yet i did some contact cleaning and changed out the cap`s. Tube testing is going to be my next item on the agenda .

The last 102 i worked on had the same issue and i found some bad solder joints for the ground`s on a few of the shield`s in the band switch area. This one had the same thing ,but i wasn`t so lucky this time with it being that issue . Any pointer`s on where to start looking will be greatly appreciated thanks again.


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 Post subject: Re: Heathkit sb 102- no receive on 20 meters
PostPosted: Nov Mon 16, 2020 6:21 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 7694
Very possible that the hetrodyne oscillator coil is out of adjustment for the 20 meter band. The conversion oscillator for that band is 22.895 Mhz (Heathkit HFO operates 8.895 mhz above the low end of the band in the SB and 5 band HW series rigs).

If the coil adjustment is marginal, then the crystal starting will be unreliable and it will drop out as the set warms up. Adjustment instructions are in the manual.

Rodger WQ9E


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 Post subject: Re: Heathkit sb 102- no receive on 20 meters
PostPosted: Nov Mon 16, 2020 7:27 pm 
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Joined: Sep Sat 28, 2019 2:05 pm
Posts: 185
I will have to take a look at the alignment the next time i work on it .


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 Post subject: Re: Heathkit sb 102- no receive on 20 meters
PostPosted: Nov Tue 17, 2020 2:24 pm 
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Joined: Sep Sat 28, 2019 2:05 pm
Posts: 185
Rsingl I have been working on the 102 and i got 20 meter`s to come back to life . ! :D Not to sure what i did but I hooked up my vtvm on the test point by v19 and had it set for 20 meter`s and when i touched the test point spot on the board 20 meters starting working again so all i did was picked out a strong signal and adjusted the coils a tad and watched for a max reading on the s meter . Not sure if that`s the correct way to do it but it seemed to work so i just roled with it lol . and for now the 20 meter band is working again .


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 Post subject: Re: Heathkit sb 102- no receive on 20 meters
PostPosted: Nov Tue 17, 2020 2:45 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
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The critical adjustment is the hetrodyne oscillator coil which I am confident is the reason for the intermittent operation. It is an easy adjustment from the top side of the board. If the rig is operational on 20 meters, you can make the precise adjustment so that it stays that way via the S meter.

Tune in the calibrator signal anywhere on 20 meters and peak it with the preselector control. Use an alignment tool to adjust the 20 meter "het" coil for a peak and note that as you align the coil on either side of peak it falls off rapidly on one side and slowly on the other. The correct setting is a little past the peak to the side where the output falls slowly. This ensures reliable and stable oscillation. You don't want this coil on the absolute peak or it is likely to cause the oscillator to be intermittent and unstable and adjusting to the fast falling side will have the same result.

NOTE: Several of the hetrodyne coils have two coils on the same form with two slugs so make sure that when adjusting you insert the alignment tool in the end closest to the marking for that band. And if the core sticks, don't twist it to break it free because the coil form will break loose and break the attaching wires.

Rodger WQ9E


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 Post subject: Re: Heathkit sb 102- no receive on 20 meters
PostPosted: Nov Wed 18, 2020 2:04 pm 
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Joined: Sep Sat 28, 2019 2:05 pm
Posts: 185
Rsingle I did what you suggested with the calibrator and peeked it a little more and i think we are back in action on 20 and receive`s nicely again and i tested rf output as well tunes up to a 100 watts easily . Thank`s again for the tip i will have to remember this for future heath projects :D


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