Sudden Loss of Amp Keying
My station has been on most of the day…just “reading the mail”. Late this evening, as I was getting ready to turn everything off, I noticed that I had lost amp keying. Neither rig keys up any amplifier.
It may be related to my experience last night. I checked into the Collins net about 2200 last night. I used the Orion II driving the Drake L7 amplifier. It keyed the amp normally. However, as soon as I gave it any power by modulation or by just hitting the TUNE button, the T/R relay in the L7 began to chatter like crazy. Before I knew it, the L7 lost plate current while the plate voltage was normal. I think it blew the HV “fuse” resistor in the power supply. I don’t recall transmitting at all today. So it is possible that my amp keying problem started last night.
Can someone help me think what is going on here. The POD amp key lines from both the K3 and the Orion II are connected. The amp key lines are all plugged into the back of the SPII. Do you think my L7 relay chatter could have caused SPII damage? I doubt a component in the SPII could have caused the relay chatter, because last night (after the Drake L7 died) I was able to key the Alpha amp and the Elecraft KPA-500 amp normally from the Orion II and the Elecraft K3. At least that is my memory of last night. So why is there no amp keying this evening?
My SPII is modified with an interrupt in the keying line which goes to an N8LP SteppIR Tuning Relay box. I measured the resistance between the (2) RCA jacks that are connected to the N8LP relay box. With the transmitter not keyed I get 7.76 kilo ohms (shouldn’t it be zero ohms?). With the transmitter keyed, I get 16.6 meg ohms. A jumper between the two RCA jacks does not restore amp keying.
Usually the explanation for weird behavior in the station can eventually be explained by some cable or plug pulling loose. Can someone think of some cable disconnection that could explain this? Or do you think a keying component in the SPII was damaged?
Thank you for your thoughts.
Best 73 Torrey N9PY
It sounds like you are not running the audio output from all three transceivers through the StationPro into a common speaker. When you select a transceiver, the audio and antenna connections from the other transceivers are automatically disconnected. If you have separate speakers on any of your I selected transceivers, then you are likely to hear the signal from your selected transceiver. The StationPro shorts to ground the antenna input on unselected transceivers, so the signal that bleeds through to them is not strong.
73, Jim W8ZR
Sent from my iPad
Hi Group. I have yet another problem in that the audio or RF signal from Transceiver 1 is heard when I switch to Transceiver positions 2 and 3. The converse is not true. The RF signal of Transceiver 2 is isolated and cannot be heard when I switch to either TX1 or TX3. There is no attenuation odf the signal from TX1 in TX2 or TX3 positions. Any help is appreciated.
Yes, you should be showing zero ohms across your N8LP SteppIR protector, so if you're getting 7.76K, then your N8LP box isn't working properly. That would certainly explain (partly) your amp keying problem. I don't remember if the N8LP unit requires a separate 12V power supply, but if it does, then one possibility is a 12V power supply problem. More likely, however, is that a fault in the L7 somehow zapped the N8LP unit and also the solid state keying relay in the StationPro controller. If the latter, then it's an easy job to swap out the solid state relay. The relay is opto-isolated from the other StationPro circuitry, so there's unlikely to be any collateral damage to other StationPro components.
If you've blown the HV use in your L7, then that means you had a short in the HV line to ground. An internal arc in one of the 3-500Zs is the most likely cause, though a failed component in the L7 power supply could also be the cause, though that is unlikely because the fuse resistor in the circuit is downstream from the diode bank and power supply capacitors (if I recall correctly). A short to ground can cause damage to other components, because the short circuit to ground has to work its way back into the power supply B- lead. That can damage meters and also cause other problems, including the amp keying circuit in the N8LP box and the StationPro solid state relay.For now, though, I'd disconnect the L7 completely from your station and focus on the N8LP unit, including its power supply.