[Heathkit] SB 101 xmit problems

[Kenneth G. Gordon]

On 6 May 2007 at 19:10, Richard Franzson wrote:

> I just had my rig serviced by a fellow ham that resolved many problems
> with my rig. Which had poor receive and no output. A choke in the
> final area was burned out. Well I went to use the rig this weekend and
> all was fine on 20 M. So I went to use the other bands and found
> transmit problems
> 
> 80 meters-5 watts out
> 40 meters 10 watts out w/carrier (adjusted the carrier null, no
> difference)
> 20 meters 100 watts out
> 15 meters 100 watts out
> 10 meters (28.0 thru 29.5) 5 to 10 watts out.
> 
> The service manual does not list this problem. Is this low output and
> 40 meter carrier problem be resolved by following the transmitter
> alignment procedures? Or are there possible other transmit problems.

Your results are a classic example of improper alignment of the 
driver/preselector coils, although there may be OTHER problems at 
work here, i.e. the heterodyne oscillator coils may not be set at the 
correct peak.

FIRST, the heterodyne oscillator coils must be properly set.

THEN, the driver/preselector coils MUST be aligned in the proper 
sequence, with the driver/preselector tuning knob set in the proper 
places.

Then this must be repeated until there is no further improvement.

Those driver/preselector coils are in a series-parallel arrangement so 
that, except for 80 meters, misalignment of one coil will effect other 
bands.

OK. First the heterodyne oscillator coils:

There are several ways of getting these in the correct place, assuming 
they were physically installed correctly to begin with.

First, look in your manual and find the heterodyne oscillator test point. 
Connect an high-impedance voltmeter to that point. It should read at 
least 1 VDC or higher on every band.

Step through the bandswitch.

If any of those show less than 1 VDC, there could be a problem there. 
As you go higher in frequency (i.e. 80 to 10meters) the voltage can be 
lower, but should not go below 1VDC.

Using the proper sized tuning tool, adjust each heterodyne oscillator 
coil for a maximum voltage. Be careful here. On ONE side of the peak, 
the voltage will drop off very rapidly, while on the other side of the peak, 
it will rise or fall more slowly. After finding the peak, adjust the slug 
down a little bit on the SLOW side.

Remember that three of these adjustments, 80, 20, and 28.5 are on 
TOP, the rest on the bottom.

Try to set each one to at least 2 VDC, or as close as you can get.

If any of these do not adjust to 2 VDC, it is possible that the crystal is 
bad.

If any of the heterodyne oscillator crystals are not working, of if the 
associate coil is bad, you will NOT get any output on that particular 
band.

Let's now assume you have been able to successfully adjust the 
heterodyne oscillator coils.

The next step is to adjust the driver/preselector grid and plate coils.

The manual suggests that you use the crystal calibrator, set the VFO to 
the 200 Khz setting, and adjust each coil, in the proper sequence, for 
maximum "S" meter reading. This is fine to start with, but I prefer a 
different method.

OK. Now the sequence is as follows:

First, make certain that your driver belts to the driver/preselector tuning 
caps are working properly, not slipping, and that the knob is set so that 
you get an accurate setting, lock-to-lock. Many times, the 
driver/preselector tuning caps are so stiff that they slip. Make sure they 
aren't slipping and are moving together all the time.

Set the driver/selector knob to exact center, and adjust the 80 meter 
coils, first grid, then plate, then repeat as many times as necessary.

Switch to the 29 Mhz band. Set the driver/preselector knob at the 4th 
mark from the bottom right (4:00 oclock). Adjust the coils.

Switch to 21 Mhz, set the D/P knob at the 5th mark from the right 
bottom. Adjust the coils.

Switch to 14 Mhz, set the D/P knob at the exact center. Adjust the coils.

Switch to 7 Mhz, set the D/P knob at 1:00 Oclock. Adjust the coils.

Switch to 3.5 Mhz, set the D/P knob in the exact center. Adjust the coils.

Repeat the entire process.

Now, I prefer to connect the transmitter to a dummy load with a 
wattmetter in the line, and adjust those coils while in the transmit 
condition, adjusting the CW/MIC gain enough to get about 1/2 scale 
reading on the relative power output position of the meter, and keeping 
the final properly dipped.

I set the VFO in the exact center of each band. I.e. 250 on 80, and 10, 
225 on 15, 175 on 20, and 150 on 40, with the D/P knob set as above.

Your power outputs should be as follows, 110+ on 80, 100+ on 40, 
100+ on 20, 100 on 15, and 90+ on 10.

If you have gotten this, then you are in fat city and can button the rig up 
and operate.

If a problem has shown up, then it has to be something other than 
alignment.

Ken Gordon W7EKB