The transmit side of the transverter continued to work fine, but the receive side had gone rather deaf. The ever useful Finningley beacon GB3FNY had become very hard to hear.
I took the dish down & retrieved the DB6NT transverter from the protective box.
I wondered whether I had accidentally blown up the schottky diode pair which protects the receiver output, so I removed it, but it tested OK.
I didn’t feel confident to delve further, so I sent the transverter back to Kuhne Electronics, asking for a quote for a repair.
A week later I had it back, fixed and no charge. It was fixed “under guarantee”. Perhaps this is a German type of guarantee that I am not familiar with? I think I had had the transverter about 3 years. Also I had modified it to give me an output to indicate reference oscillator lock. And removed the schottky diode pair! Anyway, this is excellent customer service.
Apparently a helical filter had lost a connection. Perhaps a dry joint? I don’t understand the cause of the fault, really. I’ve replaced the schottky diode pair.
I’ll take the opportunity to put up a sturdier, manually-turnable pole for the dish and add a linear amplifier, so I may be off 3cm for a while.