Premier Rock Forum

7/27/4
Problem-
Sovtek Mig 50 input #2 not working.
Solution-
1Meg Ohm Log pot "Volume II" malfunctioned. It might have been bumped. I don't know. It's broken now. This was found by sending a signal to the input and following it (with my scope) past the preamp tube to its demise at the pot. I then measured the pot in circuit (power off) with a ohm meter and saw that the wiper pin did not change its resistance to the other pins over the rotation of the pot.
New Sensor is sending a replacement set for all the pots.
8/3/4- We got the pot, I replaced it, all good now.
Problem-
Royer 122 mic (the phantom powered one) S/N 1112 has "fuffling" noise after being used for a few hours. Sound quality of the mic seem good aside the noise. I'm thinking it has something to do with the head amp.
Solution-
Off to Royer.

Problem-
Coles 4038 has a blown ribbon.
Solution-
That makes three, so off to the labs with those.
I wait until we have 3 down to save on shipping to England.
10/4/04-They are back now.

any reason why you don't send them to Wes at AEA?

Jarrod

It's nothing personal to Wes.
Steve likes to send it to the company who made them. As long as they're in buisness. . .

8/4-5/4
M-S matrix box circuit board layout.

Problem-
Studer A820 MCH (Czech one)
Occasionally the machine will not go into play. After fast-forwarding or rewinding the machine wont go into play. The capstan will spin but the tape wont move (pinch roller has ok pressure). If you help either reel in the right direction, it will play properly.

Solution-
Unfortunately this problem was not there yesterday (4th), but I went ahead on checking/calibrating the tension sensors (dancer arms on either side of the head block). When Steve showed me the problem the reels felt chunky in their movement in edit mode. This seems like a constant tension servo problem. More to be checked.

The sensors were off a bit. I am going to order a metal jig made so I can do this ajustment without making my own jig out of a ruler and a razor. What jig? you ask. I'll tell you more later.

Last Week at home.
Problem-
My MCI JH-24 track
In "sync" mode, no tracks armed, an input signal on track 2 can be heard faintly on the outputs of tracks 1 and 3.

Solution-
Long story short. The problem followed the Record/Cue audio card.
The FET switch (Q3) that when turned off allows channel 2's input signal to go (out of phase) to the neighboring tracks for the crosstalk compensation wouldn't turn on.
This crosstalk signal cancels out the bleed magnetic field picked up by the other two tracks on the sync head. The signal in the manual is called "CFO." It should work only when in record mode. I found out that the Gate of this FET should be at roughly 24 volts when the crosstalk compensation shouldn't be on. On this channel I was measuring less than 1 volt. After checking for shorts and bad resistors. I found that at the Gate there was a relatively low resistance to ground (compared to a working channel). The culprit was a .01uF/50 volt ceramic cap (C47). This cap was bypassing the Gate input signal (filtering noise off of the DC signal). It was leaking DC to ground. This is the second ceramic cap that has failed on me in my brief experience. The other was on an audio card for my ATR. Other techs told me that this doesn't happen. Well, it does for me. I replaced it with an NPO rated cap. All works now.

your job looks like it must be so much fun. Not like Screaming with your arms in the air like a rollercoaster fun, but fun as in you get to do things that interest you, use your creative, and work with your brain a lot for solutions. Do you love your job?

I do love my job. A lot of work to be done and little time to do it.
8/12/4
Studer 820 MCH-
Recapped/Cleaned 2 NRS control cards
Recapped/Cleaned 2 Line Amplifier cards (one needed a 10 wire ribbon jumper replacement.
+
More PCB layout for the m-s box.

6/19/04
MS circuit board layout- finished the power supply

Last week or so.
Problem-
Eventide H-3000 w/ sampler board (studio A) has noise on the output of the right channel. THis would go away when in bypass (which would make sense because the relay shunts the input straight to the output). The noise would also go away when the input was disconnected. The noise sounded like someone saying "cat-cat-cat-cat-cat" really fast.
Solution-
I replaced it with the one from studio B (no one in there right now) and brought the f-ed one to the shop. It wouldn't make the same noise exactly but that channel would be generally noisier than the left one. Since the noise seemed to appear when the input was terminated I looked at the op-amps near the input. When I noticed a noise I would probe around the outputs of the TL072s looking for something wrong. Sometimes my probing would cause the noise to disappear. After a while sitting there on the bench. A noise resembling the sound of rain on a plastic tarp appeared. I swapped some op amps to see if the noise would follow and it disappeared. Today I noticed a special type of distortion on the output. With a 400Hz tone on the input, and the input level digitally set below "0" the sinewave was horribly disfigured. It looked like a jagged version of itself (little saw-teeth floating on the fundamental wave). The input tone far below clipping level. Listening to the output while in this state the distortion harmonics would change when I would raise or lower the "input level" (changing the "output level" had no unanticipated effect). Since that level is digitally controlled there is a possibility that the converter is f-ed. Right now it is working again. I'll let you know.
Problem-
Ibinez EQ pedal noisy
Solution-
Sprayed tuner cleaner into the faders and pots then exercised them to silence.
I forget what else.

9/3/4
Problem-
The band's Fet 47 mic was not working.

Solution-
The male XLR connector that fit within the collar of the mic's ass was loose. Its one retaining screw was not causing enough friction to hold the Switchcraft made connector in place. Consequently an RF suppressing cap broke when the connector was pushed back into something else. The cap was a 100pF cap between pin 1 (ground) and Pin 2. There was a clone of it between pin 1 and 3. Fortunately I had a bunch of good quality 100pF caps leftover from my MS-16 mod days so I matched a pair and replaced the old ones.
I should charge them $800 you say?
Maybe I will. Maybe I will. . . . . .. . .. . . . . .