this channel's sel-rep head seems to be malfunctioning. audio recorded on this channel does not playback when in sel-rep mode. if in input mode or repro mode everything seems fine. any suggestions on where to begin trouble shooting?

first try swapping cards [make sure machine is turned off when doing this] to see if the problem follows the card or not - i'd suspect it's the card not the head. also check that simply reseating the card doesn't fix it - in which case you can just re-wet the joints on the connector...

if determined it's in the card, then, get the manual and look for the IC that controls the switching logic - you should be able to follow the schematic to that. as i recall, there are like 4 or so ICs vaguely similarly sized - hopefully socketed (not the big ass IC in the middle) - it's one of those smaller 16pin ones if i recall correctly. i had a similar problem w/mine - but it's been a few years and i don't own the machine anymore. parts are easy to get from mouser (a few bucks i believe), and it's a good idea to socket it if it isn't already so the next fool this happens to has an easier time switching dead ICs.

looking through my notes, looks like i replaced a lot of IC29 and IC30s, and an IC6... so take a look at those on the schematic...

i have notes that say:

IC29 -> tape delay/record stuck selection
IC30 -> not commit to tape

LF oscillation fixed by replacing IC6

for some reason i replaced a lot of C126, C154, C152s

and i definitely replaced all relays with gas sealed relays to address the wind-on-microphone/ocean problem.

C152: end of bias string(?)
C126: back filtering of b-(?)

i also replaced some I-0500s

and another note says

middle relay by I0056 flips btw input/sel-rep

sorry, kinda hard to decipher my own notes from 2003 esp w/o the schematics here but that may help a bit. look into IC29/30/the relays/I0056