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Film Industries M8 ribbon mic-
Needs an output adaptor.

FM Roddy was nice enough to send me one of the proprietary connector/mount assembly. Trying it out now, in-session. Thanks Roddy!

Fender Twin (the disembodied head amp)-
Low output.

Before turning it on for a test, I noticed something felt rattly about the power cable. Turns out, the neutral lead was loose in the power connector's screw terminal. Then I noticed the amp had mismatched power tubes. It looks like someone grabbed two pairs instead of a set of four matched tubes. I later found out this is a thing you were supposed to be able to do on this version of the amp with help from the "bias balance" circuit. However, the tube pairs were not in the right sockets to work like this. Anyway, the balance circuit doesn't really allow you to bias the tubes to a desired current, rather lets you equal the current between the two different pairs.

I cut the power cable down, and installed an IEC connector. Installed a new set of 6L6GCs. Modified the bias "balance" circuit so it works as a normal adjustable bias, then discovered one of the tubes wasn't working correctly. Measured the screen resistors (looked slightly baked), and one was open. Replaced them all, biased, and we're back up.

Schoeps M934 B capsule with a "tent" in the membrane (spare from a while ago).

Disassembled capsule housing and sprayed the rear of the backplate (through pattern vents) with compressed air at low pressure, until the dirt worked out. Cleaned all the metal parts that were meant to contact each other. I'll test in a mic when the studio's free.Cleaned a Gefell M62 and M58 capsules

Neotek Elite Channel 27 has no signal on the large fader.

Polarity reverse switch dirty. Exercised it vigorously, and life came back. If it happens again, I'll pull the channel and deep-clean it.

Sony C-38-
Stud mount for the "Y" stand is broken. Ordering that part (thanks for still making them Sony).

Neotek Elite Flying Fader channel 6-

Pulley string on the motorized fader broken.

Replaced with a fresh new one from our fishing kit. It took a few tries, but everything's together and tested in the console.

Gefell 563-
Crackle and hum on output.

Female cable connectors (on two cables) have poor tensioning. You can push gently back and forth on the connector (unthreaded, but seated) and get it to work. Used a needle to push in the tabs on the female pins (roughly trifurcated) closer together. This isn't a permanent solution. We'll need new connectors soon.

Bassman 6G6B (blond)-
Occasional hum on output today, post preamp stage. Seemingly responds to moving or tapping the power tubes.

One leg of the bias filter capacitor (newish) lifted off of it's post. I could nudge it a bit and cause the hum to come and go. Resoldered, wrapped around the leg of the resistor it's in parallel with.

"Modernizing a Neumann N-61v mic power supply with XLR connectors, IEC power inlet, 120V transformer (from 240v), and recap.
This will work with the Gefell/Neumann 582s and 563s."

I know you did this a while back, do you remember the model number for the 120V replacement transformer that you used? I'm getting 200VAC and 24VAC on the secondaries when the primary reads exactly 220VAC. Just can't find a transformer with those voltages. Been looking for months!

drpat wrote:
"Modernizing a Neumann N-61v mic power supply with XLR connectors, IEC power inlet, 120V transformer (from 240v), and recap. This will work with the Gefell/Neumann 582s and 563s.
"I know you did this a while back, do you remember the model number for the 120V replacement transformer that you used? I'm getting 200VAC and 24VAC on the secondaries when the primary reads exactly 220VAC. Just can't find a transformer with those voltages. Been looking for months!"

That was probably a custom toroid transformer that we bought for this purpose. I've had good luck with the Hammond 262D6 in other PSU projects. It doesn't have a dual primary, which is too bad, but the price is right...
Are those voltages read off the transformer connected to the circuit, and mic, or lifted from the rest of the power supply? You're feeding it 220VAC?

Greg wrote "Are those voltages read off the transformer connected to the circuit, and mic, or lifted from the rest of the power supply? You're feeding it 220VAC?"

Yes, the voltages were read directly off the transformer fully loaded with mic. Being fed from a 220V variac. With the above conditions:
Node1 measured 217.74VDC (supposed to be 220VDC)
Node4 measured 14.15VDC (supposed to be 14VDC)

Greg wrote: "That was probably a custom toroid transformer that we bought for this purpose. I've had good luck with the Hammond 262D6 in other PSU projects. It doesn't have a dual primary, which is too bad, but the price is right... "

I'll probably end up with a custom part too... I've got a query in to Edcor for a custom EI core jobbie.

drpat wrote:
"greg wrote: Are those voltages read off the transformer connected to the circuit, and mic, or lifted from the rest of the power supply? You're feeding it 220VAC?"
Yes, the voltages were read directly off the transformer fully loaded with mic. Being fed from a 220V variac.With the above conditions:
Node1 measured 217.74VDC (supposed to be 220VDC)
Node4 measured 14.15VDC (supposed to be 14VDC)

That's pretty spot-on for unregulated voltages. The 262D6 won't be a drop-in replacement, I see. I tend to rebuild supplies when the caps are dead, and make them fully regulated w/ solid state parts.I'll probably delete these posts to keep the log clean, btw. Feel free to start a new topic on this.