The other day I took the TS-850 apart, once again. For whatever reason (more about that later), I was only getting about 50W output on any band in CW mode. I did the ALC adjustments and got it stable at 100W where it should be… and along the way, figured out that it may have been “operator headspace” all along. There’s a CAR (carrier) control that I was suing to set the power, and also a “PWR” (power level) control that, honestly, I’d forgotten was there. I may have had it set to a lower level. Who knows? It’s working now.
I’d had to disassemble a substantial part of the “shack” to get the TS-850 set up on the bench. I had to un-cable the radio, pull the power supply, then unhook the Heathkit HM-102 power/SWR meter and the dummy load. In order to do that, I had to de-cable and move the Heathkit SB-101 and its companion SB-600 speaker cabinet with the speaker and power supply. Those sit on a shelf that I built that sits over the top of the TS-850 and some other gear. It really is kind of a major operation to take something out of the operating position desk, which is something I hope to remedy sooner or later with a bigger, roomier desk.
I got everything done – the power output back up to 100W and I re-installed the TCXO that I’d pulled for some reason a few months ago. I buttoned everything back up and spent the better part of an hour getting all of the gear re-installed and cabled. While I had it all apart, I decided to re-do the cabling. I have the antenna and the dummy load on an A/B coax switch, the input of which is connected to the HM-102, which is itself connected to the SB-610 station monitor. In order to switch from one rig to another I had to un-screw that rig’s antenna coax at the input of the SB-610, and connect the other’s coax. I decided to install the MFJ 6-way coax switch to all of the radios, and connect that tot he SB-610 to make it quick and easy to switch rigs. I wall mounted both coax switches and got everything cabled up, double-checking the connections as I went.
That evening I wanted to try some CW contacts with the SB-101. After tuning into the dummy load, I switched to the antenna and called CQ several times. I could hear a few other stations up and down a couple kHz from where I was, but I had no replies. I decided to switch to the TS-850, so just flipped the 6-way switch to position 1 and tried transmitting. The Kenwood showed no RF out – none. Even with the CAR and PWR turned to the max settings, nothing at all. Somewhat discouraged and more than a little irritated, I shut everything off and went upstairs.
The more I thought about it, the less convinced I was that both rigs had failed at the same time. I decided that I must have messed up the coax cabling, or had a bad cable. I went back down and did some troubleshooting. Starting with just the dummy load on a short coax jumper, I tested the TS-850 – full power out, no problem at all. I then went through the whole chain, connecting the dummy load at each junction and testing for power output. The 6-way coax switch tested good. Then the SB-600 – good. Then the HM-102 – good. Then the 2-way coax switch – Nope! No output.
That switch, an old MFJ-1702 that I’d picked up use years ago, has failed. THere’s nothing apparently wrong with it mechanically, I took it apart and checked for broken, corroded, or misaligned parts. It tests fine with an Ohm meter, no shorts or opens in either position. It does not, however, work with either radio in position A (the antenna) and intermittently fails in position B (dummy load).
Given its age and all, I decided not to try and troubleshoot or fix it. It’s going into the trash, and I’ll replace it with a good quality Diamond CX210A. It’s more expensive than the many options I see from Diamond, Opek, and many others including a slew of no-name Chinesium garbage that all look identical to the MFJ I’m replacing. In the mean time, I’ve connected the antenna coax directly to the HM-102.
Oh, and the reason for the low output on the TS-850? I’m honestly not sure. I suspect, however, that I simply forgot that there is both a CAR control for the carrier level in CW, AM, and FM modes, and a PWR control that is global in nature – it works in all modes, regardless of the MIC or CAR settings. Given that the most I’ve been able to get out of the rig while working FT8 without the ALC kicking in has been between 50 and 75 W, I suspect I may have just inadvertently had the PWR control set to the point where it limited CW output to 50 W. I really don’t know for sure, but I suspect that’s the root cause. Hey, at least I discovered the failed switch now rather than having it intermittently fail over some period of time and potentially cause more problems.