I see your schadow p-p switches and raise you insert jacks with intermittent switching contacts. I recall some drama after a purchasing puke approved changing the plating spec for the switch contacts on hundreds of thousands of (Switchcraft) TRS insert jacks. Silver was generally reliable but looked bad because it turned dark when oxidized. Some better looking contact treatments didn't work as well.mediatechnology wrote: ↑Tue Jan 26, 2021 2:29 pmAs someone who has replaced thousands of ITT Schadow switches in MCI consoles I know the heartbreak of on/off rectification at line level signals.
FWIW one of my two recent TS-1 repairs was a faulty (open) P-P switch.
Spoken like someone who has experienced that.
And I've also replaced a lot of unsealed P&B and Omron relays in MCI and Otari recorders.
I can't recall however ever having to replace a sealed relay except an occasional gas-filled Aromat "ice cube" style and that was rare.
That includes low signal, tape head level, cue relays.
The concern here may be MC levels and currents.
I'm really curious to see if there's anything to measure.
The beauty of the null test is that you can also use music and listen to the residual.
Open that contact however and you'll lose your hearing.
It might be a good idea to add a diode clamp to the output of the diff amp....