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

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Postby greg on Tue Feb 03, 2004 11:38 pm

2/3/4 to 2/4/4
Problem-
capps mic does not work


Solution-
fixed broken wire between the capsule and tube amp


Problem-
DAT machine's transport not moving tape and giving error messages.


Solution-
I took it to a shop in the 'burbs for repair and alignment. I'll let you know how that goes.


ATR #4 -
I calibrated the I/Os (in, out, meter, DC offsets) and replaced lamps
Glued a card rail back on.
Replaced a dead fan. The machine, she is running very cool now.

Dealt with sync'ing the pro tools HD up to the tape machine for a band. They did not have a sync i/o with their HD so we borrowed an equivalent from a friend (who helped me hook it all up).

Researched a replacement switch assembly for the neve phase and eq switch. I found the part numbers but no one is selling them in a quantity less than 500 pcs. Fuckers.
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Postby greg on Tue Feb 10, 2004 12:20 am

2/9-10/4
Problem-
Console channel strips line in and bus sends were out of cal.


Solution-
Replaced two channels that wouldn't fall into line with spares. One had to have its Line gain pot replaced, the other I cleaned the pot and now they both work.


Problem-
Flying Faders not in run mode would occasionally "glitch" overnight. You would come in the next day and a couple select, and record leds would be activated.


Solution-
Ran through Fiber Optics calibration procedure, and found that the positive pulse width of the fiber optic signal was not as specified (should be 50-55 nanoseconds). Ours was shorter.
Shut up.
I made sure there were no bends in the cable and checked the connectors to see if the fibers were flush to the ends.
So far so good.
Last edited by greg on Wed Feb 11, 2004 8:51 pm, edited 1 time in total.
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Postby greg on Tue Feb 10, 2004 8:08 pm

2/10/04
Replaced Line in pot on Elite channel 5

Built hanger for Melotron tape cage.
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Postby greg on Wed Feb 11, 2004 9:03 pm

2/11/4
Checked out the remaining Elite channel (Spare #3) which had a problem with the bus output being too high. All is good.

Quantec - Finally got the TDA 1541A DAC chip from a company in Ireland and stuck it in to the Quantec. That thing works now! Installed the unit back in to studio A

Ampex 351 preamp- I tested a new logarithmic pot for replacing the gain pot. The pot sucked and the gain/rotation relationship was irregular. I'm leaning towards the switched gain option.
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Postby greg on Fri Feb 13, 2004 8:39 pm

2/13/4
Fixed MXR Gate pedal
Checked out the Capps mic sysem.
other stuff. godda go
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Postby greg on Tue Feb 17, 2004 7:49 pm

2/17/4
Problem-
Micro Lynx machine A not reading timecode.


Solution-
Off to Bill McMeekin at T.L. Services for repair. Sometimes you just got to chose your battles.


Installed Machine #3 or C card and tested it out.
Last edited by greg on Tue Mar 02, 2004 11:03 pm, edited 1 time in total.
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Postby greg on Thu Feb 26, 2004 6:45 pm

2/26/4
Problem-
Our Space Echo has problems.
Some of the switch positions are faulty and the O/P level can be unpredictable (pots).
chassis was not grounded.



Solution-
Upgraded it with a safety ground which got rid of motor noise, and hum. It's also needed in a balanced power situation. I cleaned some pots and the main selector switch
Last edited by greg on Tue Mar 02, 2004 11:01 pm, edited 1 time in total.
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Postby greg on Tue Mar 02, 2004 2:52 pm

3/1/4

More Space echo noodling. Speed is irregular.
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Postby greg on Tue Mar 02, 2004 11:00 pm

3/2/4
Problem-
351 #8 had low headroom (distorting at around +4dBu) and had incorrect polarity.


Solution-
Found out that the input wires were reversed at the polarity switch. Corrected it.
Found out that the gain trimmer, the one right after the 1st 12ax7 was turned down too far.
I re-adjusted it for 65dB max gain.
Unfortunately this was found after an hour of over estimating the complexity of the problem.


Problem-
Altec 150 cokebottle has a lot of 60Hz hum on it when plugged directly into the stereo power supply (with out a cable).


Solution-
Use a cable. The new multipin connectors on the PSU require a fatter case on the connector for good contact. The body of the microphone is too slender, and works as a loose connector. This provides an intermittent connection from the case of the mic to the case of the PSU.
The case of the mic is a solid ground reference, but the case of the PSU connector is connected through the chassis to ground. because of this there is a potential for a ground loop.


Problem-
Space Echo not keeping a consistent speed.

Solution-
I cut the kinks out, shortened the length of the tape loop. This created less dragg and allowed the week little machine to move easier. It sounds cool but it's still a pice of shit.
I cleaned and re-adjusted the pinch roller also.
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Postby greg on Wed Mar 17, 2004 2:12 am

3/17/4
Studer A820 24-track (Czech one)-
Lubricated capstan motor.

ATR 102 #2 in Studio B-
Replaced noisey timer wheel berrings with help from IEM.
Last edited by greg on Mon Sep 27, 2004 4:46 pm, edited 2 times in total.
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Postby greg on Thu Mar 25, 2004 6:38 pm

3/24/04
Problem-
Studer 820MCH (blacksides) channel 2 sync output not there on two occasions


Solution-
Recapped all five audio cards after I found a bad bipolar cap on the NRS control card. That card is where the output signals are switched and routed to output amp.
Any time I recap a card I'll also carefully remove all the ICs and clean their sockets with alcohol.
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Postby matthieu on Thu Apr 01, 2004 2:53 am

damn EA sucks ! all machines are messed up ! I'll never ever record anything there !

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Postby greg on Mon Apr 05, 2004 12:49 am

Upkeep schmupkeep!
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Postby greg on Wed Apr 07, 2004 5:56 pm

4/7/4
Is been a while. How's everybody?

Problem-
Lexicon Prime Time has noisy faders. I need to find replacements. I can't retro-fit another fader because there is no room.


Recapped a more studer cards.
Looked for parts.
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Postby cgarges on Wed Apr 07, 2004 6:29 pm

greg wrote:Problem-
Lexicon Prime Time has noisy faders. I need to find replacements. I can't retro-fit another fader because there is no room.


Hey Greg,

You're probably already aware of this guy, but in case you're not, try http://www.jimfabiano.com. He specializes in older Lexicon pieces.

Chris Garges
Charlotte, NC
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Postby greg on Fri Apr 09, 2004 6:53 pm

4/8-9/4
Repaired cables and snakes.
Worked on my compressor project.
Tracked down some 14"reel flanges.

Problem-
Sytek mic preamps occasionally have a DC charge on the input with the phantom power off. This caused a "snap" noise on a ribbon mic when I pugged it in.


Solution-
I talked to Mike Stoica who told me that the electrolytic bypass capacitors that appears on each channel after the phantom switch and before the 6.81k drop resistors were probably still charged. When I patched it in at the patch bay the voltage was discharged through the mic. There isn't much current there so the mic doesn't get zingged to bad. However the way to keep this from happening is to switch off the phantom power a few minutes before disconnecting the mics. This will discharge the caps through the mic's electronics.


Problem-
Neumann SM-2 to GML mic preamp channel 4 to M-S Decoder To channel 22 Elite input out the 2-mix caused and oscillation at around 30K to appear.


Solution-
I recreated this arrangement and played with the settings to try to cause this problem. No luck.


Problem-
GML channel 4 set to 55dB gain or higher being "unstable" with the Sony c37p. I will ask what "unstable" means exactly.


Solution-
I recreated this arrangement as well with no problem.
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Postby greg on Tue Apr 13, 2004 6:28 pm

4/12-13/04
Lexicon Prime Time- Cleaned faders and connectors, and looked for replacement faders. I called Jim Fabiano but have not got though to him yet. Thanks for the recommendation Chris. I seem to remember him not having parts for the Prime Time when I talked to him last though.

Problem-
Drawmer 201 dual gate doesn't work on the left channel.


Solution-
Filter pots for the sidechian were dirty and intermittent. I cleaned them so they work now.


Yamaha 1010 delay- Ordered a new power transformer. We bought it from Europe so it had a 220 - 240V transformer, that couldn't be switched to U.S. voltage. I powered it up with our variable ac transformer to see what voltages we needed (+-18V and +8V).
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Postby cgarges on Tue Apr 13, 2004 8:54 pm

greg wrote:Thanks for the recommendation Chris.


No problem.

Chris
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Postby greg on Tue Apr 20, 2004 5:52 pm

Last few days

Problem-
Ampex 351 #8 has a high hum it's output.


Solution-
Hum located after the first gain stage. You could hear the hum at a consistent level with the gain pot in any position. The problem was in the power supply board. The filter cap C-16 was measured under spec. When I added a cap in parallel to raise the C-16 capacitance, the hum went down significantly. So I replaced the cap
.
There are some corrections that I need to do for the schematic. I'll post them on the 351 topic.
Problem-
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Postby greg on Sat Apr 24, 2004 9:44 pm

4/23/4

Problem-
Ampex 351 #s 8, 6 and 2 have intermittent pad switches. The signal would cut out when you wiggled the switch knob. These are a type of C&K rotary switches that were originally installed. They aren't reliable.


Solution-
Replaced them with the new Grayhill switch (as mentioned in the 351 modification posts).
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