Flying Faders-
Replaced a broken pulley cable.

Searching for new replacement pan pots for the Neotek Series II. The part I spec'd out years ago is not possible anymore.
Looking to get a decently matched dual log/antilog 10K-50KΩ pot with ≤ 3/8" bushing, round 1/4"-ish shaft. Asking TDK/Tokyo KO-ON. Fingers crossed we get something good.

-Elsewhere-

Work on a Neotek Elite

1. Channels 13 and 16 intermittently cutting out (to the 2-mix).

Iffy connections on the ribbon cable exercised, as well as the "sub to 16" button (which is blank on this console).


2. Channel 3 (original module pulled for repair)-

Evidence of burned out logic supply in the mute solo section. Replaced incorrect resistor for R52 (50kΩ in place of a 10Ω). This fixed the failing mute function, and frozen mute LED (always on). Cleaned up sloppy soldering, which included one solder bridge.
Fully tested functions. Some dirty EQ pots...


3. Channel 3 Fader not going completely silent at the bottom of its travel.

Wiring to the Fader molex connector was frayed with exposed wire stands which could've easily come in contact with other parts of the PCB.
Tidied the wiring. These are replacement P&G faders. They're nicer than the OG Alps, but whoever did the job half-assed the connectors.


4. Aux A solo button shorts out power supply rail when actuated (flexing the board).

Found that this nudged the Aux Master PCB into the neighboring 2-mix balanced output amp daughter board, shorting one of the 18 volt rails.
Completely covered daughter board with electrical tape, as well as the Cue source assignment daughter board. Both of these had a cardboard insulator covering the boards originally.


5. Channel 28 (disconnected for repair).

Found another torched mute/solo logic section. Replaced burned out resistors R52, and R53, cleaned char off the pcb and neighboring parts. Made sure the carbonized spot of PCB wasn't conducting.
Replaced mismatched phantom power blocking capacitors at the mic preamp input with proper parts.
Replaced dead, poorly wired Mute LED, cannibalizing one from a spare channel.
Needed to make slack for the bottom ribbon cable to reach the channel. This apparently is tight because the Motherboard moved to accommodate an API summing bus modification. You need to dismount the neighboring master section modules to gain access to plug that connector in.
Fully tested channel


Moved unterminated "unbalanced mix output" wires away from where they might short against something (under master section).


Inspected mic panel to console preamp patchbay.
The patchbay is 1/2 normalled. This should change to fully normalled whenever it’s possible. In the meantime, the bottom row needs to be "dead patched" when using outboard preamps. If not, the mic is connected to both the console input (normal) and the preamp it's patched to. In addition to loading the mic with a lower impedance, this acts as a voltage divider for the phantom power, when one preamp's is on, and the other is off. This is unfortunately not totally rare with hasty retrofit mic preamp patchbays, and is the reason why a lot of condenser microphones can be noisy through them.

-Elsewhere-

Work on Neotek Series I "Theater" console, and patchbay.

1. Mic preamps 9-13 showing odd behavior, crosstalk.

Pin 3 and pin 1 reversed at the punch block, grounding the negative leg of the mic line. Re-punched all 16 mic snake pairs, and added better strain relief.
Inspected and re-punched other iffy joints.

2. Repaired many frayed or broken E3 terminations on wires connected to various places on the patchbay.


3. Channel 9 had no output to the patchbay, sending signal to mic or line input.

Traced the signal all the way up to the input module, which seemed to be working.
Channel positions 9-16 don't have inserts. I discovered those modules need a jumper installed (J101) to work properly. The module in chan 9's position didn't have one, implying it was originally mounted in the 1-8 section. Testing around, I found the module it got mixed up with, returned the proper modules to the proper sections, and everything works again.

Various patchbay and rack snake rewiring, and arranging.

Tested all 16 mic inputs, 16 line inputs, inserts, and stereo mix outputs on the Neotek. Confirmed the native Neotek master section functions properly, and could be used for a future monitor section. Currently, used as just a front-end for recording, everything else ITB.

AKG C24
Noise related to the cable connector.

Swapped the modern tuchel part for an original spare. The size of the socket pins is a much better match for the pin size on the mic.

Neotek Series II-

Experimented with an Elma switch replacement for the pan pot (thanks to Mike Stucker for the sample switch). Unfortunately, it won't fit in the spot, though the feel was perfect and I love the idea of switched pans... switched everything really. I'm tired of pots, their noise and distortion.


Yamaha NS-10-

Blew a tweeter. Ordered a pair of NOS replacements.


Some EApreq500 work (our 500 series preamp).

Ordered a Fredenstein 2-channel 500 series 19" rack to do final calibration and testing of our pres. The little switcher power supply inside was squealing relatively loudly in the room. It was also present on the audio outputs of the modules I was testing it with (ours and others).
I bought the cheapest rack thinking there would be problems, kind of counting on it to check the robustness of what I make, and how it deals with adversity. There's no way this is normal, however. Waiting to hear back from the company about it.

RCA 74 Jr Velocity #2
Blown ribbon, replaced.

RCA 74 Jr Velocity #3
Blown ribbon to be replaced

RCA 74 Jr Velocity #1

No or low output.

Ribbon in good shape. Re cinched the screws that held down the bottom edge of the ribbon, apparently renewing a fresh connection, bringing the mic back to life.
This is the same mic that gave me trouble before, which I attributed to a defective transformer winding. I wonder if that was a red herring after all.
Update 4.9.24
Sound drifted away again in-session. I added a starwasher beneath one of the oxidized screws as a temporary test. When the ribbon goes, I'll see about cleaning the metalwork thoroughly. Right now, I don't want to mess up the tension.


Yamaha NS-10

Tweeter blew, when the amp powering it failed (apparently).

Replaced tweeter with a NOS one. Might do the same to the accompanying speaker after comparing the pair in a test.


Studer A820MCH in the A position of Studio A-

When I was gone, reel motors became unresponsive, while the rest of the machine looked to be in normal shape. This change apparently happened overnight.

Tried swapping transport related cards, and exercising internal connections to trouble-shoot. Not it.

I hoped this was a repeat of an earlier problem with another studio's machine and immediately upgraded the Power Fail Sense board to the .81 version (allowing for a higher threshold for failure), then calibrated the ±15 volt rails more precisely. No luck.

Looking around more, I found a burned out trace on the supply motor drive amplifier (MDA) (1.830.875.81). This was on the circuit side of the inductor (L4), in series with the unregulated power supply rail (+STABIN). Looking at the take up MDA, the same trace looked burned up. I measured around and found two power MOSFETs, a push-pull pair that were shorting the +STABIN TO ØSTABIN (50+ volts DC high current). Presumably, this should have blown the 16A fuse in the power supply specifically there for the reel motors, but maybe the inductor slowed things down enough to burn up just the trace?
More on this as I rebuild the MDAs.
After making sure nothing else looked burned out on the actual motor, and spooling motor driver board, I made a leap of faith and I installed a pair of MDAs from our parts machine. All good. Did a quick check of the tensions, and did some stress tests to be sure.


Low input on channel 17.

The strain relief on the new DL connector was loose, causing some tugging and pulling on the individual wires. Channel 17's input connection lost its positive leg. I re-pinned it.

Schoeps 221b -

No output.

Problem eventually narrowed down to one of our N20B power supplies through a process of swapping cables, mics and supplies.
Opened up the PSU and checked the voltages unloaded. There are drain resistors for the filament and B+ rails, so I could see if things were basically functioning without having the mic, and (now 2024) $3k tube at risk. With the mic connected, the voltages were safely in range, but no audio... I heard a loud crackle when I wiggled the tuchel to xlr umbilical and then felt dumb. There was a busted wire in the xlr connector. I replaced the ancient xlr since it was a bit janky.

I used the opportunity to check out another Schoeps 221 left in the shop for probably a misattributed noise comp;aint. All good after 60 minutes.

Upgraded the remaining Lomo 19a9 with the reskinned capsule. Replaced the tube because of some quiet sputtering noise.

Replaced both 19a9 cable connectors (XLRs), which had bent pins.

Built and tested a newer version of the EApreq500 module, with a new faceplate. About to order 100 of everything!


-Elsewhere-

Lomo 20B-35 power supply (for19a9) -
Installed NOS power transformer, C7 (transformer coupling capactior), homebrew replacement output transformer. Replaced the power connector with an IEC, and audio connectors with XLRs.
Calibrated the filament and HT voltages.

Ampex ATR #4 -

Tape played off the end of the reel, and the tension rollers froze in the innermost position, causing the reel motors to spin full speed, and then the capstan motor took off at full speed. After powering down, Taylor discovered some blown up parts on the capstan servo board. Tried a spare, and things didn't work quite right still.

Not sure what the sequence of events is, but on the Capstan Servo card, the +12 volt regulator fried passing the "20 volt" rail on through to the +12 volt path. The TO-220 transistor blew apart! As did a 2n3904 and 2n3906. A22, a MC1458 dual op amp had a bulge and crack in it.
Replaced the following busted parts; Q, 8, Q16, Q17, A22, and VR1. The board will power up on the bench with no other obvious issues. I'll test in the machine later.

For now, I calibrated the tachometer gains in the spare board, and the capstan runs smoothly. This can be tested discretely, without the need to load tape by simply removing the Reel Servo board.

Discovered little shiny orange bits in the card cage, and found two tantalum capacitors on the Reel Servo board had detonated. These were bypass capacitors C40, C41, for the ±12 volt rails coming from the destroyed Capstan Servo board, suggesting the -12 volt rail was high for a moment. Replaced those. That board, with the spare capstan servo board is working well in the machine today.