Hi Everyone,
I thought I might find a bad tube by swapping both tubes in and out one at a time.?? Only thing I confirmed is that what ever the problem is, it hasn't healed itself.?? FWIW I checked both tubes with a DMM and found no evidence of any shorts.? Below is the results of my testing.? I am probably done with this kind of testing as the SWR spikes make me fear for my transceiver. ? I'll be away from this for a while, but reading about grounded grid amps in my spare time, but if you see any clues here, please share.??
73?? John W7SWB
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| Socket |
Tube? |
Watts In |
Plate I |
Grid I |
Watts Out |
? |
| Rear |
Rear |
0 |
40 |
10 |
? |
? |
| Rear |
Rear |
0.7 |
50 |
18 |
9 |
? |
| Rear |
Rear |
9.8 |
130 |
40 |
90 |
? |
| Rear |
Rear |
20 |
180 |
60 |
100 |
? |
| Rear |
Rear |
30 |
180 |
60 |
170 |
After key down Starts to glow and output power drops |
| Front |
Rear |
0 |
40 |
10 |
? |
? |
| Front |
Rear |
0.7 |
60 |
20 |
10 |
? |
| Front |
Rear |
9.8 |
140 |
45 |
80 |
? |
| Front |
Rear |
20 |
200 |
60 |
170 |
Starts to glow when keyed but fades key up.? High SWR on Transceiver |
| Front |
Front |
0 |
? |
? |
? |
? |
| Front |
Front |
0.7 |
? |
? |
? |
? |
| Front |
Front |
9.8 |
? |
? |
? |
? |
| Front |
Front |
20 |
200 |
70 |
170 |
Started to glow red and power dropped? SWR pegged for an instant on keyup.? 2 hours later tube glowed immediately and SWR spiked.? |
| Front |
Front |
30 |
? |
? |
? |
? |
| Rear |
Front |
0 |
? |
? |
? |
? |
| Rear |
Front |
0.7 |
? |
? |
? |
? |
| Rear |
Front |
9.8 |
? |
? |
? |
? |
| Rear |
Front |
20 |
240 |
80 |
250 |
After key down, starts to glow red and power drops. |
| Rear |
Front |
30 |
? |
? |
? |
? |
| ? |
? |
? |
? |
? |
? |
? |
| Transmitter repeatedly keyed in RTTY mode for 5 count |
? |
| Watts in measured with MFJ 993B |
? |
? |
? |
| Watts out measured with Heathkit HM-2140 (ballpark) |
? |
| IC-7300 Output Set |
0% |
11% |
25% |
33% |
? |
? |
| Watts out |
0.7 |
9.8 |
20 |
30 |
? |
? |
| ? |
? |
? |
? |
? |
? |
? |
?
