home studios equipment staff/friends booking/rates for sale forum contact

Electrical's Old Repair List

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

Moderators: kerble, Electrical-Staff

Electrical's Old Repair List

Postby greg on Fri Apr 18, 2008 3:24 pm

I will be slowly transferring a log of service work I kept before starting the GReg/Electrical Tech Journal. It dates back to 2000. The info is pretty thin so I will try to flesh it out a bit. I'll omit redundant listings like mic re-ribboning, and fixing cables unless there is something unique about it.
I was learning a bunch as I went, so there might be some novice-minded solutions.
20/20 observations in different colors
Last edited by greg on Tue Apr 22, 2008 1:52 pm, edited 10 times in total.
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Fri Apr 18, 2008 3:27 pm

Sometime in 2000
Equipment: Neumann M-7 Capsule
In:
Out: to Dirk Brauner
Repaired:
Date:

Equipment: Altec 21B Capsule
In:
Out: to Dirk Brauner
Repaired:
Date:

Equipment: Schoeps Capsule
In:
Out: to Dirk Brauner
Repaired:
Date:

Equipment: Neumann M58 Cap
In:
Out: to Dirk Brauner
Repaired:
Date:
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Fri Apr 18, 2008 4:03 pm

Equipment: ATR 102 #3 (bought used, not working)
In: Take up tension sensor bounces causing the machine to unload anytime the transport is in forward motion.
Out:
Repaired: Blown trace on PWA motherboard, supplies +20V to reel servo board.
Date:2000
This was a very hard thing to find. The voltage appeared to be there when in stop mode, with the board on the extender, but drooped to nothing as soon as the machine went into action. I thought somewhere the current was being limited (which it was) and replaced the diodes and power transistors on the main deck plate, then swapped psu, then thought there must be something up with the motor, swapped that. Nothing had a positive effect. I pulled my hair out for a while. At some point I looked at the trace on the connector side of the card cage mother board, and saw a black dot on a trace. It looked like someone touched it with a fine tipped sharpie, no burn marks. It was feeding the +20v to the reel servo board. I think there was a rch of wire left, so I would see +20v when I measured around. As soon as the board needed more current, that dropped. After soldering in a jumper the machine operated normally.
Last edited by greg on Tue Apr 22, 2008 1:45 pm, edited 3 times in total.
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Fri Apr 18, 2008 4:16 pm

Equipment: NTI EQ 3 (studio B) intermittent
In:
Out:
Repaired: replaced crappy in/out (bypass) switches
Date: 3/20/00 + 3/24/00 (for studio A's nti)

Equipment: Elite CH 4
In: No monitor solo
Out:
Repaired: trace broken - jumper put in
Date:

Equipment: Elite CH 4
In: Noisy Mic Pre
Out:
Repaired: blown electrolytic cap C111 upper board
Date: 3/22/00
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Fri Apr 18, 2008 4:18 pm

Equipment: Ampex 351 #
In: Bad VU meter
Out:
Repaired: replaced
Date: 3/23/00

Equipment: Elite CH 46
In: Aux 7 pot bad
Out:
Repaired: replaced
Date: 4/3/00

Equipment: MCI ALII
In: not working well
Out:
Repaired:
Date:

Equipment: MCI ALIII
In: completely dead
Out:
Repaired:
Date:

Equipment: 2X Coles 4038
In:
Out: Coles
Repaired:
Date:

Equipment: Neve 6-pack
In: not working
Out:
Repaired: blown filter cap in the 24VDC power supply replaced
Date:
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Fri Apr 18, 2008 4:22 pm

Equipment: Altec capsule
In: needs reworking, already cleaned
Out:
Repaired: capsule works OK - problem located on base
Date: 4/20/00

Equipment: Studer (black)
In:???
Out:
Repaired: replaced 2 remaining bridge rectifiers. all 4 new now.
Date:
Must have been something wrong with the power supply? I don't remember.
Last edited by greg on Tue Apr 22, 2008 1:45 pm, edited 1 time in total.
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Fri Apr 18, 2008 4:26 pm

Equipment: MCI JH16
In: modification
Out:
Repaired: Modified the audio cards to be switchable between IEC+NAB 15IPS
Date:

Equipment: AKG 414 #2
In: sputtering noises
Out: AKG service
Repaired: back $7.00, cleaned switches
Date:

Equipment: AT4051
In: low output cap - spitting body
Out: AT
Repaired:
Date:
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Fri Apr 18, 2008 4:28 pm

Equipment: Altec 175
In: dead
Out:
Repaired: replaced tube
Date: 5/29/00

Equipment: Crown GLM 100
In:
Out: crown for repair
Repaired: returned. works well. $68
Date:2000

Equipment: Josephson 609 + sidefire (KA32 capsule)
In: check sensitivity
Out:
Repaired:works fine compared to others
Date:

Equipment: MXR delay
In: noisy
Out:
Repaired: cleaned chip/pin connections
Date:

Equipment: C-24
In: 60Hz hum,
Out:
Repaired: high voltage regulator zener diode failed (1st norman made psu)
Date: 7/17/00
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Fri Apr 18, 2008 4:29 pm

Equipment: U67
In: noise
Out:
Repaired: changed tube. ok
Date:

Equipment: Neumann SM-2 PSU
In: buzzing on mic
Out:
Repaired: rewired grounding scheme.
Date: 7/20

Equipment: Schoeps 21 Capsule M934C #5973
In: did not have any o/p
Out:
Repaired: cleaned connections, seems to work ok
Date: 7/28/00
Last edited by greg on Mon Apr 21, 2008 1:37 pm, edited 1 time in total.
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Fri Apr 18, 2008 4:39 pm

Equipment: MXR Delay
In: bad memory chips on expansion board
Out:
Repaired: got replacements, works ok now
Date:

Equipment: Geffel UM70
In: capsule does not work
Out:
Repaired: two contacts in capsule housing not touching
Date: 12/00

Equipment: Schoeps 221 Body
In: not working
Out:
Repaired: Broken transformer primary. When ordering a replacement one from Schoeps, I found out the mic was a eastern european copy, and not a real 221. The only difference being the metal body, and output transformer. The capsule (real Schoeps capsule), tube and passive components were the same however. Knowing this, Schoeps was still nice enough to send us a new output transformer.
Date: 8/25/00

Equipment: ATR capstan servo pwa
In: 5V rail short
Out:
Repaired: preformed 5V 'heat' test, replaced A6 (short) + C29 (leaky)
Date: 8/24/00
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Fri Apr 18, 2008 4:55 pm

Equipment: Neve 3115 Channel 2
In: EQ noise
Out:
Repaired: Cleaned eq 'in' switch
Date: 8/28/00

Equipment: Neotek Elite CH#1
In: No aux. 1 output
Out:
Repaired: wiper tap of pot not connected to trace
Date: 8/29/00

Equipment: AKG c-28
In: 9/12 suspicious writing (poyst cap)?, bad capsule, torn membrane
Out: #89 AKG service, to Dirk Brauner
Repaired: replaced capsule and gold ring
Date: 10/12/00

Equipment: Studer 820 (brown #2)
In: +/- 26V PS failed
Out:
Repaired: Tape lifter control board, internally shorted electrolytic cap 1000uf, 63V. replaced cap
Date: 11/7/00
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Sat Apr 19, 2008 6:09 pm

Equipment: Neve 3115 CH2
In: distortion complaints
Out:
Repaired: miss-wiring of fader pot
Date: 10/10

Equipment: furman HP mixer
In: submix #2 no o/p
Out:
Repaired: works, might have been poorly connected
Date: 10/10

Equipment: Studer brownsides
In:
Out:
Repaired:
Date: 10/11

Equipment: Studer A820 (blacksides)
In: ch 24 Internal NRS control board failure
Out:
Repaired: Short in one of the 393 op amp or fet sw. replaced op amp
Date: 10/11

Equipment: Studer A820 (blacksides)
In: Internal NRS control, ch 17, no level, calibration ability
Out:
Repaired: replaced MM74C374 Chip
Date: 10/11
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Mon Apr 21, 2008 1:35 pm

Equipment: Sennheiser 441
In: apparently dropped, loose diaphragm, horrible buzz on output
Out: 1/7 sennheiser for repair
Repaired: all good, new capsule and suspension
Date: 1/26

Equipment: Studer 820 (black)
In: +/- 15V +24V sw stabilizer
Out: studer for repair. squealing and fallout
Repaired: received studer +/- 15V PSU 1.820.873.81
Date: 11/7

Equipment: Neotek Elite monitor module
In: Bad talkback button and nonfunctioning rear deck speaker
Out:
Repaired: Rear deck speakers relay replaced, talkback button replaced
Date: 11/14

Equipment: oscilloscope 2120 studio B
In: blurred display
Out: B+K Precision
Repaired: like new now
Date: 11/xx/00
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Mon Apr 21, 2008 1:41 pm

Equipment: Crown GLM 100
In: no o/p
Out:
Repaired: Broken wiring between pcb and mic cable
Date: 11/27

Equipment: Studer 820 CH 8 (brown #2) record card
In: record card 820.841.00 couldn't conduct the bias signal properly
Out: $420 from studer new, $210 exchange
Repaired:
Date: 11/15

Equipment: Shure SM98
In: no o/p
Out:Shure
Repaired:
Date: 11/28

Equipment: Marshall JCM800
In: bad preamp tube
Out:
Repaired: replaced
Date: 11/30
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Mon Apr 21, 2008 1:44 pm

Equipment: Neotek Elite Rear Deck Speaker Faulty, board = 1.5'' X 1.5'' on mix master section
In: bad relay or 353 chip
Out:
Repaired: replaced relay and chip Not the final solution
Date: 12/3

Equipment: Altec 150 W/21D capsule SN 4610
In: high pitched RF squeal,
Out:
Repaired: new tube, ferrite bead installed between capsule and tube (long run from capsule connector to tube) under observation
Date: 12/10

Equipment: Studer Blacksides
In: capstan lubed
Out:
Repaired:
Date: 12/11
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Mon Apr 21, 2008 1:46 pm

Equipment: Studer Brownsides
In: capstan lube
Out:
Repaired:
Date: 12/19

Equipment: Altec 150 W/2 Cap SN 9363
In: noisy tube replaced
Out:
Repaired:
Date: 12/19

Equipment: Fender Showman
In: filament rails not making good contact w/ power tubes
Out:
Repaired: cleaned and tightened socket pins, works now
Date: 12/00

Equipment: Ampex ATR I/O Modual #2 right
In: meeter offset adjustment unstable
Out:
Repaired: replaced A1, R32
Date: 12/23
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Mon Apr 21, 2008 1:49 pm

Equipment: Sennheiser 441
In:Fell on its grill, smashed
Out: 1/7 Sean for repair
Repaired: All Good New capsule and suspension $250
Date: 1/26

Equipment: Altec 175 29A Capsule
In: occasional dropouts, small tear in diaphragm
Out:
Repaired: replaced tube
Date: 1/10

Equipment: Altec 175
In: Small tear in diaphragm and dimples
Out:
Repaired:
Date: 1/15

Equipment: Sennheiser Headphone
In: broken speaker wires
Out:
Repaired: dead
Date: 1/15
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Mon Apr 21, 2008 2:06 pm

Equipment: Studer black A820
In: Set/cue wheel not responding
Out:
Repaired: performed duty cycle adjustment
Date: 2/01

Equipment: Altec 150 s/n 4610
In: noise
Out:
Repaired: changed tube
Date: 2/01

Equipment: altec 150 s/n 4254
In: noise, capsule not mounting properly
Out:
Repaired: capsule mount springs
Date: 2/01

Equipment: Ampex 351 #7
In: noise preamp, pad problems
Out:
Repaired: Replaced switch
Date: 2/01
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Mon Apr 21, 2008 2:10 pm

Equipment: Ampex 100 audio card spare version -16 (we bought a spare set of cards that were from a machine which was destroyed in a grease fire)
In: no playback
Out:
Repaired: replaced C7 on main audio PWA
Date: 2/10

Equipment: Ampex 102 #3
In: 5V rail failing, fuse popping
Out:
Repaired: VR3 6.8 zener intermittent, Q11 (SCR) Poor. VR4 replaced
Date: 3/01

Equipment: Ampex main audio PWA #2 (greese)
In: no playback
Out:
Repaired: Q2 bad, replaced
Date: 3/01

Equipment: Ampex ATR #3
In:
Out:
Repaired: reel and capstan servo o/p transistors replaced with new ones
Date: 3/01
I don't remember why.
Last edited by greg on Mon Apr 21, 2008 3:41 pm, edited 1 time in total.
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Postby greg on Mon Apr 21, 2008 2:14 pm

Equipment: AT 4051
In: microphonic head amp
Out:
Repaired: rescated capsule - went away
Date: 3/01

Equipment: MS decoder
In: low headroom
Out:
Repaired: redesigned second amp stage
Date: 3/01

Equipment: Sontec EQ
In: noise
Out:
Repaired: found loose cap in one of the filter banks, re-soldered it
Date: 3/01

Equipment: Studer 820 (black)
In: noise - repro ch 17
Out:
Repaired: found noisy op amp on repro preamp card IC1 (ECG123AP Noiser than BC337), also replaced C8??
Date: 4/01
User avatar
greg
Man with Encyclopedic Knowledge
Man with Encyclopedic Knowledge
 
Posts: 5001
Joined: Wed May 14, 2003 7:26 pm
Location: Chicago

Next

Return to Tech Room

Who is online

Users browsing this forum: Google [Bot] and 7 guests