[TenTec] The Argonaut 509 From HELL!

[Richard Arland]

Hi Gang:

Many thanks for all the support that came in off-list. Don't worry, I have not given up.....yet.

Todate I have over 20 hours in on troubleshooting this rig. Here are the latest developments:

1. The 20M oscillator stopped oscillating while I was fine tuning it! I removed the coil, desoldered all the pins on the coil, redsoldered the  pins and wires, perfomred a continuity check. All is as it should be. I resoldered the coil and the 20M section took off just like "Downtown"! OK, one problem fixed.

2. 10M was still inop. I removed the 10M coil, performed the same "magic" on it as I did the 20M Coil, and replaced it. 10M still won't come up.

3. In an attempt to isolate the problem to one stage, I hooked the 100 MHz Tectronix scope to the junction of R2 (1.5K) and R1 (220 ohm) resistors on the emitter of Q1, the oscillator. All bands showed the fundamental frequency (T-T calls this the "basic frequency") except on 10 meters, which had no output. The oscillator will not fire up on 10M at all. I got the following P-P readings: 80M 1.0 V, 40M 1.1 V, 20M 1.1V, 15M 1.1V, 10M 0.0V. All the waveforms looked nice and pretty; fine examples of sine waves.

4. I moved the scope to the output on the back of the PTO/Osc board and everything except 10M had an output there (T-T calls this the "injection frequency"). Some of the waveforms (namely the 20M output) looked a little "funkie" (non-sinusoidal), but the all had an output somewhere between 3.5 and 5.0 Volts P-P. 

5. I measured the DC voltages on the pins of Q1, the oscillator: on all bands except 10M the voltages were: Emitter 2.03 VDC, Base 2.13 VDC & Collector- 7.45 VDC, which were well within the parameters specified in the manual. On 10M I got the following DC voltages: E- 1.56 V, B- 2.2 V, C-7.56 V, indicating that the oscillator was not functioning. 

6. Then the multiplier transformer, T-1, started giving me fits. In an attempt to verify the operation of the multiplier stage and fine tune the outputs per the instrucitons in the manual, I set up the 15 M band and then the 80M band per instructions. I went to 40M, where T-1 and Q4 function as a tripler (on 80 & 15M they function as a doubler and on 20 it is straight through without any frequency multiplicaiton at all), and was setting up the output for a peak on 16.1 MHz, when Q4/T1 stopped trippling! All I could get out of the stage was doubling, which was NOT a good thing. 

7. At this point, I became EXTREMELY frustrated and removed the entire oscillator board subassembly, P/N 80233! I heated EVERY connection on the baord, removed T-1 and found that the bottom slug had broken, so I chipped it out, moved the top slug to the bottom position, and then found another slug that looked similar and put it into the top of T1. I then desoldered both wafers of S-1A  & B and cleaned up the joints and resoldered all the wafer connections, in the event that the problem with 10M was a cold solder joint on the bandswitch. I then reassembled the oscillator subassembly and PTO, powered the rig up and found that 10M still would not come up, and the T1 coil was tuneable but the results on the Injedction Frequency was not correct. I tried several other slugs in the top of T1 and finally found one that would allow the 40M basice freq to triple to the required 16.1 MHz Injection Freq. 

This where I left everything. I am still not satisified with T1/Q4, as I don't feel confident that this stage will triple as needed, and that it could be erratic. Still no output on 10M, and I have done everything I can think of, and recomeded by Garland Jenkins at T-T, to make this oscillator take off and fly. To no avail. 

Does anyone have any ideas? I am rapidly running out of ides and patience. At his point does anyone have a 509 they are parting out and can I PLEASE get the 83233 oscillator subassembly from you? Failing that, does anyone have a 509 that they will sell me for parts? At this point I am about ready to procure another 509 that actually works properly and use this one I'm working on for parts. 

Help!

73 Rich K7SZ