What better way to celebrate Father's Day than to have lunch with my favorite daughter (my only daughter) and enjoy a great meal and to get some valuable presents.
A T Shirt from the Viper Room (LA), some plastic parts storage bins and coffee mugs to replace the one I recently broke. Hey I scored!
That said (and a most enjoyable time) I made some real progress on the HW-32A. Throwing caution to the wind, I made two small holes in the tops of the sealed cans (L2, L3) and a tweak or two significantly raised the output.
The HW-32A uses a fixed load capacitor on the Pi Network, a 290pF, 3% Silver Mica. I read on one of the Heathkit forums that a low power output was traced to this cap. I popped it of the circuit and installed a 330pF, 2KV Polyester unit. Shazam -- 30 watts on Tune. So we had a banner day.
This morning, I wanted to follow up on something I observed yesterday. I note that on voice peaks, that I hardly hit the 30 watts. By design, the HW-32A on Tune is intended to give a quite good bit of RF for tune up and SWR adjust but NOT full output as with voice peaks.
I also noted that there is one critical setting on the mic gain control where you get the 30 watts on Voice Peaks. The mic gain has no impact during the Tune process. In fact opening up the mic gain reduces the output. Yep, it has got to be the ALC circuit is limiting the output.
A quick look at the audio input to the balanced modulator shows a clean waveform and the mic gain control is fully adjustable from 0 to Full Open. So, it is not the mic gain stage.
The ALC looks similar to the AGC and upon a sensing of overdrive at the 6GE5's generates a negative voltage applied to several lower-level stages to reduce the gain including the transmit IF amp V2A and the Driver V5.
The ALC circuitry is located in the upper left-hand corner of the chassis facing front. Regrettably there are many under chassis parts that prevent easy access to this area (Power Plug wiring and the Audio Transformer). So, I might have to resort to clipping out the part and installing new parts on the stubs sticking out from the top of the circuit board. Certainly not aesthetic but may be required.
That is on the work list for today, to first see if it is a simple fix to the ALC or the more drastic part removal.
Them that know can make it go.
73's
Pete N6QW
Any one feel concerned that $45M of US Tax Dollars were spent so 20,000 of your fellow citizens could watch a parade. Anyone disagree that such a sum could have been directed to more significant uses?