Re: GReg-Electrical Tech Journal Redux

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Studio A

10/21-25/19

Elite ch.22 intermittent distortion in input/channel path. Very dirty. Changed to another input channel and all is well.

Channel replaced with reswitched one.


11/1/19

Neotech 17 no mic preamp output.

Dirty "monitor" insert switch – worked after exercised.




Studio B

11/9/19

ProTools input 17 wasn't getting signal.

"PT in" EDAC was making bad contact. (since replaced with Cannon DL connector).

11/13/19

Ch.11 pan pot very dirty/distorted at full "left" position – tried exercising, to no avail.

This ended up being control room monitor source select switch (TAPE 1-4, etc). The stereo mix goes through all of these switches on the way to the CR monitor output amp. If any are intermittent, or dirty, it affects the CR monitor. It cleared up with a little bit of exercise.

11/14/19

"Booth mic" input #1 was rife with RF interference; moved to #3 and it cleared up.
Suspect shield is disconnected/open somewhere.



Was crappy patch connection, breaking shield.

Re: GReg-Electrical Tech Journal Redux

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Neotek Elite
Trouble-shooting the last 8 re-switched channels installed in one throw.

Chan 12, 42, 47 - No send to bus 3

Bad solder joints on the bus select switch between the top (component side) trace, and new switch. The through hole plating was apparently damaged when the old switch was removed. Curious how this was consistently on Bus 3.
Re-flowed the joint from above.


Chan 42 - No bus sends to odd numbered busses between 1-16. 17-26 busses are ok. This suggests something is up with the subgroup assignment switch.

No connection between the track pan pot wiper (to odd busses) and "SUB16" subgroup switch. Suspect another torn plated through hole, buried under the 4P2T switch. Soldered a jumper in place.

Chan 44 no fader PFL solo signal, solo logic engages, however.

No connection between the output of U16 (pin7) and solo switch. Probably, another torn via. Soldered a jumper.

Re: GReg-Electrical Tech Journal Redux

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From the tech log book, Studio A
XX/XX/19

GML preamp ch1 fizzy distorted with Josephson 617 on cello.
GML preamp #2 at full gain got some hf oscillation with josephson c715.
GML mic pre ch. 1 oscillation changes freq with gain but gain switch works mic was C48 sonny no pad set to "V"


Replaced channels with those serviced by GML (new gain switches, general checkup).


11/19/19

Gain Brain II no compression.
Side chain might be missing normal.


Busted phenolic wafers on two pots, likely from whacking the knobs or something. Replaced pots.

2/16/20

Neotek Elite Channel 13 L-2 (line 2 input) switch is very scratchy? Fader section, actually "line" switch is gooped as well

2021
Channel replaced with re-switched channel.

2/17/20

Studio loudspeakers pop and crackle on big transients, but no audio is routed to the SLS – just talkback.
Happened in January but I forgot to mention. Noticed during playback, but happened during tracking as well. Shutting off SLS during takes as a quick fix.


*Eventually, this was discovered to be crosstalk from the clipping talkback mic preamp on the Elite. When speakers were at a louder level in the control room the talkback mic preamp would be distorting, and that would spit through the muting FETs to the studio loudspeaker send.

2/18/20

Neotek elite channel 12 "L-2" (line 2 input) switch is scratchy. (no mention of which path, fader or monitor)

2021
Channel replaced with re-switched channel.

3/5/20

Maxi-Q module out of phase with input. Using solo mode with lowest band.

7/20
That is the correct polarity in solo mode (as designed), not a fault. The normal output is correct polarity.

5/30/20

Neotek Ch.12 Large fader not passing audio. Swap to small fader works. PFL shows no signal on large fader path.

Exercised EQ to fader switch.
Eventually replaced with a re-switched channel

Re: GReg-Electrical Tech Journal Redux

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Studio B's tech logbook-

12/1/19

Studer ch.12 shows -1dB relative to other channels with external inputs. Internal oscillator shows normal. Demonstrated to Greg.

Problem follows line amplifier board.
C8 (electrolytic) was not replaced. Done now, tests correctly.


12/19

Studer "remote shuttle value invalid" error message on start up, and occasionally causing problems during sessions – when mach stopped, a machingun-like shuddering of the roller solenoids would occur. When this starts it overrides normal operation, actions similar to nudging the shuttle a tiny bit.


Opened auto locator – cleaned, recapped repositioned shuttle wheel pot for even resistance at rest (as per manual) – reseated I.C.S as well.

Re: GReg-Electrical Tech Journal Redux

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-Elsewhere-

Studer C37 1/4” 2-track-

Noisy channel, constant wind and sputtering noise.

Found noisy V3 on the repro amplifier. Replaced with an expensive period-correct E188CC tube. The noise is gone.
Tweaked braking forces for smoother winding at the ends of the reel. Did a full calibration using another 1/4" Studer A820 as its meter bridge.
Pretty crazy seeing the start and end of production history.
Image
.

Studer B67-
B67 stops after a second after play, or wind mode engaged. Behaves in a controlled manner.

After a lot of digging, I found a bad C2 (10uF tantalum cap) on the move sensor board, which corrupted the YBI - MOVE signal, leaving the logic in the not moving-state. The machine is designed to stop automatically if that happens or the tape load sensor doesn’t sense opaque tape.
Replaced all the motor phase and suppression capacitors with a kit from Nagravox. The old ones were leaking black death. I got some of it in an open scratch on my finger, felt a little sick. When I went to the bathroom my urine changed from amber to black, somehow darker than ink. I looked in the mirror and saw the black beginning to flood the whites of my eyes. I can now see perfectly in pitch darkness. I have a strong sense of imminent change and can no longer empathize with the most tragic of hardships.
Checked and performed basic alignment of the transport. All seems smooth...
Later-
Did full audio calibration, discovered the erase current was way too weak to completely erase the tones I was recording over.
Heads need a relapping anyway. I’ll check the erasure afterwards.

MCI Jh-24 -
Transport, cleaning, checkup and alignment. Full audio calibration for ATR tape. Repaired channel 17 (not recording because of stressed molex pin on sync head cable).
Checkup and calibration of the newest Studer A820 mkII 1/2” 2-track I've seen. Serial number suggests mid to late '90s, which is virtually "new".
Cleaned decomposed pinch roller goop off the deck and parts beneath.
Kids, if you see your pinch roller is getting soft and mushy, remove it immediately. When this stuff goes, it goes fast and it sucks to clean.

Evaluated MCI MJ-24 8-track for rehabilitation. This machine was used as a parts machine for the 24 track, but there's interest in putting things back together. It would be a real project.

Re: GReg-Electrical Tech Journal Redux

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Greg wrote: The old ones were leaking black death. I got some of it in an open scratch on my finger, felt a little sick. When I went to the bathroom my urine changed from amber to black, somehow darker than ink. I looked in the mirror and saw the black beginning to flood the whites of my eyes. I can now see perfectly in pitch darkness. I have a strong sense of imminent change and can no longer empathize with the most tragic of hardships.
Keep us posted on how this progresses. If my years of comic books reading has properly trained me for this moment, it won't be clear if this is a one-dose=permanency or if you'll be required to keep dosing yourself as needed.

If you're looking for a handler, I could probably be available. My superiors have provided me with a 32-page list of other questions for you if you have some time. Just the usual stuff like if you are able to commune with owls now or does food taste metallic (or does metal taste like food) or does your touch kill green plants...but maybe that'd best be saved for PM.

Re: GReg-Electrical Tech Journal Redux

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All Clear!

Studio B Echoplate II noisy output on one channel.

Replaced noisy pickup amp (LF356).
Replaced all the original electrolytics, which were bulging slightly. Tested them out of curiosity, and a few were as low as 1/4 value.


Studio A, Studer A820MCH 1" 8/16-track machine-

On some mornings, the meterbridge display does not progress past "audio self test" after the machine is powered on, does not respond to key commands.

Recapped the 5.6v switching regulator and "Basis Board VU Panel" (carries the MP Unit VU Panel and handles the serial communication to it), inside the meterbridge.
Modified the MPU board as per the service bulletin "A812-A820-A827 uP PCB Modification" (deals with reset routine errors).
What I think was the solution -- C16 on the "Basis Board VU Panel" is the power bypass cap for the transformer primary center tap in the bi-phase communication output amp. It's similar to a filter cap of a HT supply to a push pull tube amp. It was supposed to be 100uF, but measured about 200nF, out of circuit. I replaced a similarly bad capacitor on the Communications Controller board (C3). This is the companion amp for that bi-phase signal housed in the lower transport.
I wrote about this happening before in the lost tech log, I believe.
I didn't bother testing between these steps, because the problem was intermittently happening, and it all needed to be done eventually.

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