Working on electronics, that is. At least for today.
Spend 10 straight hours un-fscking a TS-940S which I recently picked up; rig had the (in)famous 'PLL dots' problem.
That was the easy part.
Seems Kenwood put some foam on the bottom side of the PLL board, presumably to prevent microphonics in one of several VCOs that are present on said board. Unfortunately, the stuff is hygroscopic (surprise!) and will eventually deteriorate, becoming contaminated to the point that the VCO overtop the foam won't operate.
Once I cleaned that mess off...I started testing the rest of the PLL. Board had to come back out once again for a resolder job of several components that are associated with another of the VCOs. Biggest time consumer was the remaining diagnostics and adjustment procedure: With a 5-loop synthesizer, a 'scope is an absolute must-have.
Upon getting good waveforms (and a lock of the PLL across the entire HF spectrum), I turned my attention to the receiver. Sucker was deaf as a post. Little bit of signal tracing showed adequate gain in the 3rd and 4th IF stages...then I spotted something which made me go
Someone had reversed the HET and RIF (Receiver IF) coaxes on the IF board. Apparently, I wasn't the only one who has been into this 'gem'.
But wait! There's more(ons)!
At some point in the rig's life, persons unknown modded the Narrow filter switch on the front panel switch board so that it could select a wide or narrow SSB filter while in receive. Of course, none of the filters were present....and half of the wiring for the "mod" was also missing. Upon restoring the switch board and a logic unit on the IF board, we have a working receiver - all modes.
I bought this neato YK88-A1 'plug-in' AM filter from a guy on QTH; opened the package and noticed it (you guessed it) a solder-in type.
Not to worry - eBay's yer buddy. I need a narrow CW filter for my second R-5000 - and since those are a solder-in type, I was weighing some options when I found a plug-in YK-88C1. When it arrives I'll swap filters around on the little plug-in board then I'll be good to go.
No more. I'm done tonight. If subsequent posts this evening fail to make sense, it's because I'm getting likkered up.
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Originally Posted by N9FE
