Good news! I found a dodgy cracked tant on the board and have desoldered it. Seems to have come back again with some measurements a bit jumpy and consuming a hell of a lot less current. I'll order some replacements tants and refurb it properly I think.
That's a relief. The reports of her demise were greatly exaggerated. (What Mark Twain would've said if he had a Fluke 8050A.)
Looking at GW Instek GDM-8341 at the moment which seems to do the job and is a reasonable price (compared to Keysight and Fluke anyway)
The earlier GDM-8251 that were being liquidated en masse seemed to be well liked. I still see some at a reasonable price from time to time.
does anyone know what the deal with modern DMMs is? NONE of them have any decent AC bandwidth. Need around 50KHz.
The Instek meters have 100kHz AC bandwidth. Sounds like it'd be OK for you, though you'd want to confirm the accuracy is sufficient at your desired frequency. The venerable HP/Agilent 34401A is 300kHz and 6.5-digit, but only single display.