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All your geeky questions about electronics, microphones, tape machines, etc.

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Postby greg on Mon Dec 01, 2003 8:28 pm

gcbv wrote:Greg:

do you have any schematics/signal flow/napkins to follow the path?

You may have already tried, but trace the input (or output, whichever) with an oscilloscope pen to see where the the signal dies.

I would also venture a guess that yr D/A converters are fucking up somewhere. but why the dry signal when the pot is off?

Have you tested the resistance differential in the "effect level" pot itself?


I don't have any schematics. They are very protective of their special box.

I've followed the output signals back to a DA converter, and I only know that there is nothing coming out. The inputs (DA) are unreadable with my equipment.
I believe the pot is controlling a control voltage, but hmmm I'll check on that.
It is interesting that both left and right channels are screwed. Not knowing what the clock speed is supposed to be, or anything else makes it hard to test.
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Postby greg on Tue Dec 02, 2003 10:39 pm

12/2/03
Problem-
Altec 150 making a low rumbly noise after warming up


Solution-
Testing today
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Postby greg on Wed Dec 03, 2003 9:28 pm

12/3/03
Problem-
Elite's master stereo fader sketchy when pushed all the way up. It cuts one of the sides out.


Solution-
Replaced fader with a spare. I'll clean the old one if we ever need it in a pinch.


Fixed Neumann CMV 563/582 mic cable (was intermittent).
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Postby greg on Thu Dec 04, 2003 9:27 pm

12/4/03
Problem-
Flying Faders stereo fader mute light fluctuating in intensity. Mute function ok.


Solution-
Checked the mute switch. The connection was bad between the switch and its socket. Tested the switch after removing it - it was bad so I replaced it.


Problem-
Elite channel 3 wont mute all the way with the FFaders mute, but will with console mute.


Solution-
Pulled fader and exercised the connections to it. Worked after that. There must have been an under voltage supplied to the optical switches or something.


Problem-
Loose patch points on the patchbay in Studio A


Solution-
Big pain in the ass. Pulled the bays out as far as they could go (not far) and tightened the jacks.
If anyone out there is wiring up a studio, always give yourself extra cable slack!
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Postby justinc on Fri Dec 05, 2003 6:57 am

hey when yr REALLY bored next: how about an off the cuff estimate of the number of sauder points involved in the EA patchbays. both A panels, B panel, all mic/line/headphone patchpoints.

then if we can approximate Who did How Many we can stitch stripes or yr jumpsuits like military generals.
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Postby greg on Mon Dec 08, 2003 9:06 pm

12/5/03
In addition to the Neotek s2 talkback post above-
On the Neotek S2 I removed the "Pre Echo Mute" momentary push-button switch. This mutes the 2-mix and allows you to hear the echo return by itself. I did this because the 2-mix bus has to pass through it before the final o/p amp. It was a Shadow switch that had the whole show depending on it. It probably would have given us a problem later on. We also have used it a total of 2 times in the last 10 years. I put the appropriate jumpers in where the switch was. Phantom fix.
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Postby greg on Thu Dec 11, 2003 1:45 pm

12/9/03
-Fixed phone.
-Calibrated, put safety ground, and IEC connector on one of our Loftec test sets (tone generator/meter).
-
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Postby greg on Tue Dec 30, 2003 2:49 am

12/29/03
Problem-
Elite channel 17 line input 3 dB high (shows that on the meter as well)


Solution-
Replaced module with a spare so the session could go on.
None of the components around the input circuit look bad. I recalibrated the input trim. On my home made test jig everything's fine.


Lubed the capstan motor for the Studer 820 (black sides) upstairs.

Helped David of Neurosis resolder a fader, and fix a burned trace on an analog synth. I didn't catch the name of the brand.
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Postby greg on Mon Jan 05, 2004 7:34 pm

Problem-
Mic line 32 not working in studio B's dead room


Solution-
Broken strain relief post ripped the 32nd pair off its connector.


Problem-
"Solo Enable" switch on the Neotek Series II not disabling solo feature when turned off.


Solution-
A leg from a debouncing capacitor mounted on the switch was shorting the 12V logic rail to the buss (keeping it permanently on). This probably happened when I was working on the talk back nightmare. Oops.


Put a local bypass cap on the phantom power switch of Ampex 351 #4
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Postby bomberz1qr20 on Mon Jan 05, 2004 7:56 pm

greg wrote:12/29/03




Helped David of Neurosis resolder a fader, and fix a burned trace on an analog synth. I didn't catch the name of the brand.


Moog?
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Postby greg on Wed Jan 14, 2004 9:23 pm

Yes it was a moog

1/14/4
-The last few days Chad and I have been fixing up the new mellotron. I checked and recapped boards, cleaned pots, built a new power cable. Chad gave it the complete one over, cleaned, lubed, bought parts. We are getting new tapes soon.
-More work on the Quantec see above

Does anyone out there have any spare Phillips TDA 1541A Digital to Audio converters?

-Went to my bother's house in North Carolina to see my him, his wife, and their new daughter. Came back on Sunday night to a flood in my basement. No studio equipment busted. One pipe busted. It's all dry now thanks to some help from Josh. Arrg!
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Postby sybd on Thu Jan 15, 2004 9:40 pm

Which model of Mellotron are you fixing? M400, Mk2 or 4?
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Postby greg on Thu Jan 15, 2004 11:54 pm

M400
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Postby greg on Fri Jan 16, 2004 7:31 pm

1/16/4
-replaced the neotek series II talkback button. This is not related to the earlier problems with the talkback.
-Russ and I replaced all the mellotron tapes. Now we know how to do that.
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Postby greg on Mon Jan 19, 2004 8:55 pm

1/19/4
Problem-
We had a new Twin Reverb from the band that had some noises on it.


Solution-
Replaced preamp tube, seems fine now.


Problem-
Steve wants 14" 1/2" reels for mixdown. No one sells them anymore.


Solution-
After long search we contacted the manufacturer for a quote. We might have to order a large number so if anyone wants any let us know.
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Postby greg on Mon Jan 26, 2004 8:16 pm

1/26/4
Problem-
Neve 3118 had intermittent and sometimes distorted signal because of dirty phase and eq switches.

Solution-
Cleaned the switches for both channels. Ordered replacement gold plated switches.

Also replaced solder contacts to the modules with gold connectors for easy disconnection.
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Postby greg on Tue Jan 27, 2004 8:25 pm

1/27/4

Problem-
Neumann CMV 563 mic making wind noise.
I found out that the filament supply to the mic was about 2.3v (should be 4.5 to 6v). This was with one of our two Neumann N52a cassette power supplies (Nr.017).


Solution-
When I increased the filament voltage the noise went away. So I built a new filament regulator to supply 5v to the tube. This was already done for the other one.
I recapped both N52a PSUs. They had the original caps from 60 years ago.

Testing so far - there hasn't been a problem.
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Postby greg on Mon Feb 02, 2004 8:16 pm

2/2/4
Problem-
Sony c-57 mode indicator not indicating,


Solution-
Display disc broke off the rotating switch. Super glued it back on.


Problem-
Band's OLD! big muff has no output when it is switched on.


Solution-
Partially stripped audio wire was leaning on ground. I put a bit of heat shrink tubing over it.


Ampex ATR #4 (non ATR Serviced) -
I stripped the pubic hair-like filter off the bottom vent. This was decomposing and becoming the problem it was made to prevent. This is something Mike Spitz recommended. I scrubbed the metal clean then sealed it with oil.

Problem-
Flying Faders occasionally... well I'll tell you tomorrow.
Last edited by greg on Tue Feb 03, 2004 7:56 pm, edited 1 time in total.
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Postby MTAR on Tue Feb 03, 2004 9:47 am

I stripped the public hair-like filter off the bottom vent.


Did you mean pubic hair?
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Postby greg on Tue Feb 03, 2004 7:56 pm

I don't know what you mean Mike.
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