Normally I prefer the 'Dark Mode' for my operations, not in this instance...
Stepping into the back room the other evening after an all-day online session, I found my Icom IC-251 (pre-A) was dark... Cycled the power switch, checked the AC cable connection, checked the rear apron fuse holder... Fuse tested good, still no joy...
Checked the eCopy of the manual I have for the A/E version, read that there are TWO values of fuses; 2A for DC ops, 5A for AC ops.
Only see one fuse holder listed in the docs, is there an additional board or inline mounted one internally ?
Removed the top and bottom covers, pulled the PS chassis, no more fuses evident. Consulted the Schematic, see no other fuse symbols other than the one located on the rear panel.
I have not pulled the main chassis or any of the sub-boards, and hope I won't have to.
There is no physical evidence of damaged components, no burn marks, exploded parts, acrid odor, etc... As far as I can tell, no components have been 'leaking smoke'.
The rig has been operating on receive acceptably for the last two weeks on a tabletop using AC power, and no power has been applied to the TX circuits. Been waiting for a mic and resonant antenna...
I have not done any voltage measurements yet.
That will be my next task, to re-install the internal PS, get ye ol'DVM out, decipher some pinouts - and take some readings.
Any constructive/positive input welcomed...
It will be about a month before I can get my hands on a 12vDC PS and I can supply power to the 12v rear panel connector then, and see if it comes back to life - pointing then to a failure of the internal AC PS.