AKG D112 -
Capsule winding upen circuit.

Tried and failed to solder the 2mm nub end of the busted winding to its post. Oh well. These aren't expensive enough to get too upset. Right???

Neve B002-

Problematic channel had its gain switch replaced by Brian.
The "AM" section of amp board (B183) wasn't working properly. Cleaned a couple iffy looking solder joints, and posable solder flux grunge between traces. Reflowed some joints. No clear explanation, but the thing works now, on the bench. I'll confirm later if everything's good in the mixer.

Tested in the mixer, and it rolled off all the lows when loaded by 600Ω. Pulled the amp card, and found that the electrolytic cap on the output was measuring 1/1000th it's intended value. I recapped these in 2007. Lifted the legs of the other elecrolytics to see if this was a sign of things, but they all measured correct. I'm a little unsettled to learn I've been at this long enough that caps I installed are now going bad!
Cap replaced, all is good.


Mid Side Matrix work.

Studer A820MCH MkII-

Slow recap beginning.
Recapping the control related boards above the audio drawers.


Studer A820MCH 1" machine-

Recapped the Tape Deck Display Driver board, Tape Lifter Cont boards, Pinch Roller Gate.

Mid Side Matrix buildin'

Neumann U67 #5714

Occasional 5k-ish whistle, and rumble noise.

This was the one with the fancy Mullard tube installed.
Looked for causes to the noise. Checked power supply, touched up some component solder joints, replaced the tube. The whistle went away, but still had a slightly higher wind rumble noise, compared to the other U67 (after about an hour for the tube to get a bit settled). Swapped power supplies with the same outcome. Swapped capsules, and the noise seemed to follow the capsule, but gradually declined. With all parts returned, no remarkable noise difference between the two mics. Suspect the capsule might have some dirt conducting with humidity. We'll see. Not a satisfying conclusion.

Finished and packed 2 Mid Side Matrixes for sale.

Neotek Elite-

Channel 45 intermittently sending weak level to busses from small "monitor" fader, works fine when fader swapped with large fader. .

The small "monitor" fader's output was distorting randomly. I narrowed the source down to the actual wiper of the fader with the oscilloscope. The riveted solder stud was making a bad contact with the wiper track. I could cause or remove the distortion by gently pushing on that wire and location. I pressed down on the rivet with a screwdriver while supporting the underside of the fader's pcb. The signal stayed strong after that with a bunch of wiggling. Let's see how long that lasts..

Finished another batch of DIs and chased down a Studer Meterbridge blackout issue that's been randomly happening lately on studio A's machine.. .

Silkscreened the last of the Mid Side Matrix Boxes with our pal Jay Ryan, using the jig I built during the Bush admin. The screen was still good. He has a full grown adult working for him who lived in Steve's old house as a baby sometime after we moved to the current building, almost 30 years ago. I feel old writing about something that I vividly remember happening almost 30 years ago.

Ampex ATR has a lose reel turntable post.

Dan Labrie of Myriad Magnetic was nice enough to hook me up with a replacement turntable, and handy height setting jig. Replaced and set.


UREI 1176 in studio B-
Weak/thin sound.

Brian pulled it and checked it out, ok.
One of the spade connectors on the rack snake had a horrible solder joint (done by yours truly long ago). Reflowed all of the spade connectors. Sounds good now.


-Elsewhere-

Rebuilt Ampex ATR power supply.

Studer A820MCH MkII -

Recap list for this beast. There's slight differences between this and the other versions, so I had to recheck things.

Broke in new pace desoldering guy.

Recapped an A820 power supply switching stabilizer, and fancy repro board...

-Elsewhere-

Various trouble-shooting and work on another person's A820MCH.
Noise/partial erasing of tracks 17-18, via a defective repro preamp board???!!! I know...
Recapped a bunch of things...
Updated the Power Fail Sense Board to the .81 schecmatic, something I've been into lately.

Sphere eclipse C -

Noisy channel-
Traced down to the "boost" amplifier, which also is the polarity reverse circuit, and buried for some reason in the eq module.
The 1014 eqs' boost amps are more noisy than the graphic eqs, interestingly.

This console used to have a lot of troubles with the psu regulators on the 301 modules oscillating (above hearing), causing noise and other issues.. The power distribution to the 'buckets' was radically improved, reducing impedance to the source. A lot of the noise is gone now, and things are much more predictable.

What a crazy beast...

Orange County Stressor - Dynamic Range Processor (compressor/limiter/expander module)-

Peak lamp was full on, and meter pinned, in full reduction. Peak and Compression lamps eventually burned out.

Module was recapped in the '00s, I believe by Tim Isler when he was filling in for me during my splenectomy.
The peak limiter sidechain circuit, compressor and expander sidechains are also their own daughter boards, which all bus to a FET for gain tomfoolery. The limiter was the source of the problem. The other features worked with it removed. It comprises of a simple, discrete transistor circuit. Should be no sweat, right? Since the board was recapped, I focused on the 7 BJTs and the two trim pots. Fortunately, we have an OC parts carcass chassis, and parts compressor, so I could bench test in place and swap things. The spare chassis is great since there's external control and some system routing that would need to be harnessed-in to work correctly.
Anywho, the AC, audio signal was immediately being loaded down at the input transistor (just after a gain pot and coupling electrolytic. The transistor didn't show signs of failure doing simple diode and short checks, though I was testing in circuit. None of the other transistors showed signs of complete failure at first pass. Progressing through the circuit signal path, there's a phase splitter, buffer stages after the split, then a transistor pair used as a rectifier, cathodes tied together at +24v, and collectors tied together as the rectified output. It was here I saw something weird, full 24v DC on the collector output. This should be 0vDC when nothing's going on. I swapped in the spare peak board to see if it worked, and it did, so at least I have a reference point to compare. After making my own voltage test point notes on the schematic, I started swapping out transistors with the working board. Working my way from the input stages to the output, nothing changed the performance. I was still getting full supply voltge at the rectifier output, where it should've been a version of the signal rectified (above the threshold level). I isolated the timing circuit (the rectifier fed a diode, then a pair RC filters, then an output buffer transistor). I did a quick check of the resistors to see if any of them were wildly out of spec. It's unlikely that they fail without any visual evidence in such a low current circuit. All of them are at a value which would easily handle a dead short, with 24v across them if another part failed.
While feeding a sine wave to the input, I lifted the two output diodes (one to the timed BJT output buffer, the other straight from the rectifier BJT pair (to the indicator lamp circuit)) and saw that the rectifier acted appropriately, as well as saw a healthy signal throughout the input stages. This confused me a bit and lead to some red herrings. I noticed the signal quality on one half of the phase split signal paths was a little distorted, while on the working example board, they both looked relatively heathy. Because I ran out of things to swap, I replaced the two, relatively new, coupling electrolytic capacitors feeding the rectifier from the phase splitter, and voila. Everything was functioning correctly.
Out of circuit, the troublesome 10uF 50v 105º BC 138 AML capacitor tested close, about 8-9uF, with no odd DC leakage. Perhaps when charged, it acts differently? The solder joints and traces looked clean.
Anyways,
I replaced the blown obsolete indicator lamps. One with a resistor coupled amber LED, which is dimly on, then brightens when active. The other, I cannibalized a lamp from a "slide base" bulb, used in the EAO switches we have around the studio.

Happy New Year!

Neumann U67 standmount cable-

The male end (connects to the PSU) was deformed, wouldn't allow a good connection. The threaded shell looked like it was stomped on by a cow. The molded part holding the pins was also worn down, not able to be held in place securely.

Replaced with a brand new connector from Neumann. The newer Tuchel part I used to know isn't easily available, at least I couldn't find it. Anyways, it's fitting perfectly.

Altec P-525-a power supply (for M20/M30 mics) needed a new lamp. I'm using an 1819 lamp, which has a higher voltage rating than needed for longevity. The O.G. was 1813.