Re: GReg-Electrical Tech Journal Redux

101
Neotek Elite-

Channel 13 wasn't sending to the busses or direct out with the large fader set as the source (fader REV button up).

One of the legs on the REV switch (6P2T) wasn't soldered. This wasn't discovered until recently because the channel spends almost all of its time in the reversed mode, with the large fader feeding the 2-mix and the small fader feeding the busses/direct out. All good now.

Channel 47 mic preamp phantom power not working.

Via in the C108 pad, carrying the 48 volts from bottom to top side of the pcb was torn out when the capacitor was removed. Replaced that cap again with one lying down so the top and bottom side could be jumper-ed with its leg easily. All good.

Installed tested and calibrated 2 re-switched stereo channels-

Stereo channel 5 has distortion on the input of the insert return (right side).


The polarity reverse switch is meant to have one leg lifted from the pcb. There was contact still.
This caused an irregular direct connection back to the insert return point from the input section.



Jon replaced the rest of the Edac panel connectors in control room A with DL ones. We're just about finished with that big project.

Re: GReg-Electrical Tech Journal Redux

103
Lomo 19a18 noisy

Tried cleaning, swapping capsules and cables to narrow down the noisy element. The head amplifier was causing the noise. I resoldered an iffy looking joint near the capsule connector. It looked like a resistor and/or capacitor leg was floating in solder on an eyelet terminal. This is in the sensitive, ultra high impedance part of the circuit. That might have been it, but I decided to redo a few more joints while I was in there. When the weather changes, these kind of things pop up more.
Tested for a long day, and all was silent.


Omnipressor


AKG D112- Dead

Capsule winding "opened up" This is an older version of the mic which AKG/Harman doesn't support anymore. It is now a turd-burger, as they say.
Looking for a replacement capsule from somewhere.



Finished 10 more EApreqs

Re: GReg-Electrical Tech Journal Redux

104
Studio B-

Phantom powered mics not working with mic input 21, no matter what preamp.

Checked the pin-1 ground connection at the mic panel downstairs and saw it was open. Both patch points for mic channel and console input were correctly grounded at the sleeve contact. I re-punched the shield of the mic snake, channel 21 at the patch bay punch block (that's a mouthful).
All is good again. Maybe it's time to freshen up all the sensitive punch block connections?

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