Dec 2021-
This is the remnant of the tech log I kept on the old Electrical website. Last year, a large chunk of the entries were lost inexplicably when transferring the site to a new server.
2020 will forever be remembered as the year Greg lost some of his tech forum posts.
I'm in the midst of rebuilding from notes, and cleaning up some of the corrupted entries. You may notice some posts are out of sequence, referring to things that happen later. This is a glitch of the salvage. If there were multiple posts from the same day, they might have been rearranged incorrectly. Just read through to add context.

From the original 1st post from 2003,

Hello there,
My name is Greg Norman.
This is a journal of the techwork that I do at Electrical. Anytime I do work in the shop, I'll try to write it down here. This will be an "e" version of a repair log I've been keeping for a couple of years. If I come up with something somewhere else that's useful, I'll include that as well.
I'm going to start this for a few reasons. One being it might help some people out with mundane studio tech problems, another is that you guys might help me out sometimes. It's handy to look back on a tech problem for hints. Either way, I am really in to recording/documenting things (anyone who has recorded with me knows I keep a recording journal for notes, drawings and other garbage). This journal will be more technical, and very boring. Inevitably I'm going to make mistakes. I'll point them out as I find them. Please feel free to do so as well.

I probably wont go at length describing a problem/solution because of time. When I can, I'll add the methodology I used. Sometimes this will be done retroactive to the initial post (instead of making a new one).

If you have a problem not related to what I am posting, please start a new topic

Red text is describing something not working.
Blue text is attempts to find the problem, and not succeeding.
Green text usually is the solution.
Black text is mundane maintainance or other comments.

10/29/03

Problem-
Altec 175 (mic) has no output. When used on snare it sounded like a thump instead of a snare.

Solution-
Mic connector (at the end of the cable permanently attached to the mic) wiring was falling apart. The crusty old 22k resistor mounted in connector housing was shorting against other pins. Found this out by wiggling cable near the conn. while under test.
I rewired the connector, installed a new resistor, and heat-shrinked all the posts except the shield one.
I brought it up to the shop and turned it on to trouble-shoot. It worked fine.
This happens a lot. When you have a lot of things (money, time, and pressure) riding on the piece of equipment that will be when it fails. When you're testing it, it will work fine.
After being on for several hours (plugged in to a mackie mixer for headphone monitoring) it started to make a fizzling sound. This is the rare moment when you can start poking and prodding.

-Hunted down some parts for the Elite. Ended up ordering a new monitor pot.

-packed and sent off broken mic part for repair

Problem-
Ampex 351 preamp #6 cutting out.

Solution-
The pad switch is defective. Must be replaced

10/30/03

I showed up pretty late today and worked on getting the 351 info together for the forum. Had two coffees.

10/31/03

Today Andrew and I installed the Furman headphone system into Studio B. This entailed cutting rectangle holes in our mic panels, pulling, and punching down Cat 5 wire. Mounting the Cat 5 jacks on the mic panel took a little more time than I expected because the jacks were built for thinner faceplates. This just meant we had to get creative and file parts off of the plastic connectors. Andrew helped out by wiring up the main control box in the control room.
Russ should be surprised tomorrow.
I guess there is nothing to be lernt from this but what ever.
Time for Halloween to start.

11/4/03

Problem-
Line 2 on our phone is out, and the phone co. thinks it's our fault.

Solution-
I went to the main punch-block to check the line with my home made headphone/alligator clip thingamajigger. I found out we were getting a poor signal from them. This means they have to pay to fix it.

Solution-
Installed BSS DPR 402 that came back from BSS service refurbished. We had a distortion problem with it and sent it off.

Problem-
Eventide Instant Phaser: "Oscillation" mode not working, but other modes do.

Solution-
Bought a schematic from Eventide (great new website!) for $25. I found the oscillator circuit (2 op-amps MLM301s) and started testing the caps diodes and resistors around it. I didn't have a replacement op-amp so I was first looking for other culprits. I found out that the -15 volt rail measured at -19.5 volts. This could have made a DC offset that would screw with the oscillator. It was a old style emitter follower regulator that I replaced with a modern regulator chip (I made sure nothing would be over-taxed current wise). The voltage rail was right as the rain outside, but still no oscillation.
Now I need an op-amp. I looked through all the cross-reference books to link this op-amp with one we had here to no avail. I then started looking at the unit to see if I could cannibalize one to just see if it was the op-amp. I wish I were smarter and knew exactly how they were supposed to act in-circuit so that I could cut to the chase, but swapping out components will get me my answer just the same. In the schematic I saw an "aux" output. This was identical to the main output, we weren't using it, and it had my chip. So I cannibalized away and the thing works now.
Next.

Greg:

Did you check for any leaking/malfunctioning componets before or after the opamp where you had the -5VDC overpowering?

It's obvious, but there might have been some damage from the power differential over time that could still be malfunctoning.

Good point. I looked up the max power supply voltages for the 301 amps and they were +-18volts.
All the op-amps in the box were seeing the -19/+15 volt rails. No other problems were apparent however. I checked the components in the oscillator circuit and along the power rails. The caps and diodes were well within their max ratings in this condition.

11/5/03

Problem-
Altec 175 (different one) has no output.

Solution-
Tube popped out of its socket. Unfortunately, rough handling is to blame. Put tube back in, tested it over several hours. Done and done. I have to find a widget that keeps the thing in place for the future.

Problem-
Neotek Series II talkback works intermittently (I hate these).

Solution-
Hopefully

Bad cable connecting the talkback signal from the 2-mix master module (where the talkback mic is), to the monitor module. The cable was a solid core cable that worked its way loose on both the soldered-in side (cold solder joint on the 2-mix mod.) and the molex connector side (monitor mod.). It was easy to slip the wire out of the connector.
I replaced it with a more flexible stranded cable fattening up the wires crimped to the molex, then glueing the wires in place for support.
This has been a problem for a while. Every time I tried to find the problem, it would be working. So I would do preventative maintenance like cleaning connectors, reseating components and the like. In session, when the talkback would cut-out, wiggling the master module would bring it back. I guess the wiggling action would move the cable enough to make a temporary contact.
We'll see.

Problem-
Neotek Series II Buss #7 normal to 24-tk channel 23 input broken.

Solution-
Bad connection at the patchbay punchblock.
Replaced stressed jumper wires with new ones.

Problem-
Lexicon PCM 41s input and output levels wacked.

Solution-
Steve and I decided on a calibration scheme then I calibrated them.
They now have a "0" mark on the input pot noting unity gain.

Lexicon PCM 41s input and output levels wacked.

Solution-
Steve and I decided on a calibration scheme then I calibrated them.
They now have a "0" mark on the input pot noting unity gain

I'm curious what was decided for this calibration scheme.

Thanks.

Greg:

You can also use plastic snap ties to hold yr talkback cabling in place, instead of glue. It keeps them in place, and sustains tension, etc.

Just in case there is another prob in the future, and you have to fuck with the glue.