I was *very* lucky. The 11801 cost $100 + $85 shipping. It had been in storage in Arizona, so minimal risk of corrosion and the seller furnished a photo of the extended diagnostic screen showing an E5622 (NVRAM) error. I got two SD-22 heads for $150 delivered and an extension cable for $100 from other sources.
When the 11801 arrived it was DOA and failed the Kernel diagnostics. I opened it up and after reseating all the boards in the main card cage and all the connectors I could reach a couple of times it finally booted.
However, at that point I was dead in the water. Moving the jumpers on the I/O board did not let me get out of the diagnostics. Then Tom Miller on the TekScopes list suggested I remove the DS1213 "smart sockets" and plug the SRAM directly into the board. That did the trick, it skipped the self test and worked. When I shifted the jumpers back to the default position, it halted in the Extended Diagnostics with a T1331 error, but now I could exit by pressing "Exit" twice. With the E5622 error I could not exit the diagnostics.
When my replacement NVRAM arrived I installed them and after 3 reboots it works like a charm. At least so far as I can tell. I still need to read the user manual.
An 11801 that had been stored in a humid climate would require a complete disassembly to address corrosion of the sockets. and cable connectors. That would be a full day's work. With no component level data, board swapping is about the only viable repair. If you can get multiple units for what I paid or boards from a reliable source (e.g. the TekScopes list) they can be maintained.
But this is an issue with all newer instruments.
Leo, were you using 3% silver solder when you ran into the gold soldering problems? Also what are sensible price ranges for SD-24, SD-30 & SD-32 heads? Most of the asking prices on eBay are ridiculous. And then there are sellers who don't allow returns for DOA and are insulted if you offer less than what they are asking.
Fortunately, I don't need any of this, I just had to have one after getting the pulser plots from you. So I can wait to get additional heads at sensible prices.