EA/Eventide custom dual delays -
No output on right channel using two different units.
Hard wired some unused internal option switches after discovering they were causing intermittent failures (through wiggling the actuator).
Building some last minute snakes.
Calibrating and testing a batch of EAPreq500 (500 series) preamps at home with the AP ATS.
Re: GReg-Electrical Tech Journal Redux
52Studio B-
9/1/20
Studer take-up hub lock screw feels grind/dry.
Disassembled part and cleaned with alcohol, then lubed with Renolit st-80.
9/xx/20
Neotek (SII) stereo bus distorting on left channel. Wiggled module to make it stop.
Tried to replicate, reseated module, , looked for cold/bad solder joints.
While in there...
Neotek phantom power supply wire to 2-mix module frayed.
Replaced connector (molex) + rewired.
Studio A-
6/4/20
Flying faders computer psu fan, too loud hum.
Was cpu heat sink fan, Taylor replaced with a slightly quieter one.
6/5/20
Neotek Elite psu voltages drooping.
PS-3 (#1) +18v= 16.2 -18 = 17.5
PS-4 (#2) +18v= 17.1 -18 = 17.4
6/x/20
#1 pass transistors overheated because the air conditioning for the equipment racks was off for days. The power supply and amp rack is a closed cell with doors to keep the dust out, and direct the AC past the equipment. Having no air circulation created an oven. Normally the fan is on always.
Replaced #1's pass transistors, heat sync pads, and compound. Checked for other damage. Calibrated both supplies.
9/1/20
Studer take-up hub lock screw feels grind/dry.
Disassembled part and cleaned with alcohol, then lubed with Renolit st-80.
9/xx/20
Neotek (SII) stereo bus distorting on left channel. Wiggled module to make it stop.
Tried to replicate, reseated module, , looked for cold/bad solder joints.
While in there...
Neotek phantom power supply wire to 2-mix module frayed.
Replaced connector (molex) + rewired.
Studio A-
6/4/20
Flying faders computer psu fan, too loud hum.
Was cpu heat sink fan, Taylor replaced with a slightly quieter one.
6/5/20
Neotek Elite psu voltages drooping.
PS-3 (#1) +18v= 16.2 -18 = 17.5
PS-4 (#2) +18v= 17.1 -18 = 17.4
6/x/20
#1 pass transistors overheated because the air conditioning for the equipment racks was off for days. The power supply and amp rack is a closed cell with doors to keep the dust out, and direct the AC past the equipment. Having no air circulation created an oven. Normally the fan is on always.
Replaced #1's pass transistors, heat sync pads, and compound. Checked for other damage. Calibrated both supplies.
Re: GReg-Electrical Tech Journal Redux
53Checked out 26 DI Boxes.
RCA 74 B no output
Primary winding shorted in the transformer. When I unbolt the transformer from the frame, the transformer passes audio. I can see a dent in the body, where it comes in contact with the grounding post (janky looking setup). I put the transformer on 1/4" standoffs, to relieve the pressure, then wiggled and poked around to try to cause problems. Things sound and appear to be working.
Delivered 8 EAPreq500s (API 500 series EApreq) to Shane Hochstetler in Milwaukee. He seemed Happy. Working on version C for wider production.
Old analog tech log posts-
12/1/20
Ch.26 Neotek monitor pot still doesn't send to buses or channel solo. Check U7.
3/12/21
U7 dead, replaced, tested.
2/10/21
Orange Country EQ not doing anything.
Yes it is.
2/26/21
Fader 26 super scratchy + intermittent.
3/12/21
Might be related to earlier issue. Not observed after U7 replaced.
3/21
ATR #1 background 120Hz hum on repro with head shield up. Wide band width noise higher on left channel. Was this the one that was re-appeared? Noise not on i/p mode so in the repro path.
Removed machine. Needs PSU rebuild.
8/9/21
Studer "rec " button on autolocator not working – can/have to use "rec" button on upper controller.
8/23/21
Exercised connectors + reseated cmos chips on switch board (switch was functioning passively) works now.
9/15/21
Studer ch.24 sync output huge spikes, not associated with audio recorded on track. Card was previously marked "sync noise" so that's probably the one.
Problem on repro bd. No further notes...
9/26/21
UREI LA-4 #1
Vu meter shows -1dB Vu at rest..
1/6/21
Calibrated.
9/26/21
Gain brain #2 no signal. (nothing showing @ input).
Gain brain #3 – check meter, seemed intermittent. Out put cuts out when faceplate flexed.
#2 works after reseating.
#3 no notes
10/5/21
Ch.21 SII (Neotek Series II) doesn't pan left. – Replace mute switch.
10/20/21
Replaced mute switch.
12/21
Ch. 10 mix pan distorts badly into R side when panned in 10 o'clock.
1/6/22
Sprayed "tuner cleaner" into bottom of pan pot (needs to be removed) - Let's see how long that lasts.
12/29/21
+4 dBu output from Loftech reading +1 dB on ATR VU meter (1K frequency)
Also reading +1dB VU on console meters.
1/6/22
ATR i/os 1/2dB off, now calibrated. Loftech is .4 - off. "+4dBu" = 3.6dBu
4/22/22
Neve #2 gain switch not "catching" or rolling between low and high gain.
9/29/23
All nuts and knobs have been tightened. Everything Seems to be working fine. BF
RCA 74 B no output
Primary winding shorted in the transformer. When I unbolt the transformer from the frame, the transformer passes audio. I can see a dent in the body, where it comes in contact with the grounding post (janky looking setup). I put the transformer on 1/4" standoffs, to relieve the pressure, then wiggled and poked around to try to cause problems. Things sound and appear to be working.
Delivered 8 EAPreq500s (API 500 series EApreq) to Shane Hochstetler in Milwaukee. He seemed Happy. Working on version C for wider production.
Old analog tech log posts-
12/1/20
Ch.26 Neotek monitor pot still doesn't send to buses or channel solo. Check U7.
3/12/21
U7 dead, replaced, tested.
2/10/21
Orange Country EQ not doing anything.
Yes it is.
2/26/21
Fader 26 super scratchy + intermittent.
3/12/21
Might be related to earlier issue. Not observed after U7 replaced.
3/21
ATR #1 background 120Hz hum on repro with head shield up. Wide band width noise higher on left channel. Was this the one that was re-appeared? Noise not on i/p mode so in the repro path.
Removed machine. Needs PSU rebuild.
8/9/21
Studer "rec " button on autolocator not working – can/have to use "rec" button on upper controller.
8/23/21
Exercised connectors + reseated cmos chips on switch board (switch was functioning passively) works now.
9/15/21
Studer ch.24 sync output huge spikes, not associated with audio recorded on track. Card was previously marked "sync noise" so that's probably the one.
Problem on repro bd. No further notes...
9/26/21
UREI LA-4 #1
Vu meter shows -1dB Vu at rest..
1/6/21
Calibrated.
9/26/21
Gain brain #2 no signal. (nothing showing @ input).
Gain brain #3 – check meter, seemed intermittent. Out put cuts out when faceplate flexed.
#2 works after reseating.
#3 no notes
10/5/21
Ch.21 SII (Neotek Series II) doesn't pan left. – Replace mute switch.
10/20/21
Replaced mute switch.
12/21
Ch. 10 mix pan distorts badly into R side when panned in 10 o'clock.
1/6/22
Sprayed "tuner cleaner" into bottom of pan pot (needs to be removed) - Let's see how long that lasts.
12/29/21
+4 dBu output from Loftech reading +1 dB on ATR VU meter (1K frequency)
Also reading +1dB VU on console meters.
1/6/22
ATR i/os 1/2dB off, now calibrated. Loftech is .4 - off. "+4dBu" = 3.6dBu
4/22/22
Neve #2 gain switch not "catching" or rolling between low and high gain.
9/29/23
All nuts and knobs have been tightened. Everything Seems to be working fine. BF
Re: GReg-Electrical Tech Journal Redux
54-Elsewhere-
Neve 8014 with a mix mash of modules from different production runs. This was apparently parted out at some point, sold, then parted-in with whatever the previous owner could find to make it whole again.
1883 routing module distorted signal-
Dead BC107 transistor on one of the two BA183 amplifier cards.
Another 1883 routing module with distorted signal-
Found 2n3055 transistor on the BA283 amp board which didn't look right with the diode tester, out of circuit. Replaced. Everything good.
Recapped and cleaned the switches on 16 1883 routing modules (with Brian Fox's help). Installed and tested.
Several lamp sockets had poor continuity between the threaded insert and solder lug due to corrosion at the contact point. Still looking for a good no-replace solution. One of the few times I wanted to reach for some deoxit, but didn't have any around.
ATR 102 1/2" machine checkout-
This was a 2000 ATR Service rebuild in amazing shape, awakened from storage. I exercised connections, especially to the power supply before powering up, and ran through a bunch of transport checks. Lubricated simple mechanical bits which were dried (head shield shaft, tape lifters). The scrape flutter idler was not moving freely and the repro head grounding wasn't great, so the headblock is off to JRF for inspection, lube and cleaning. The capstan motor drum was replaced in the field by the owner without adjusting, so I rant through that alignment.
The machine was incredibly solid for sitting around so long.
Neve 8014 with a mix mash of modules from different production runs. This was apparently parted out at some point, sold, then parted-in with whatever the previous owner could find to make it whole again.
1883 routing module distorted signal-
Dead BC107 transistor on one of the two BA183 amplifier cards.
Another 1883 routing module with distorted signal-
Found 2n3055 transistor on the BA283 amp board which didn't look right with the diode tester, out of circuit. Replaced. Everything good.
Recapped and cleaned the switches on 16 1883 routing modules (with Brian Fox's help). Installed and tested.
Several lamp sockets had poor continuity between the threaded insert and solder lug due to corrosion at the contact point. Still looking for a good no-replace solution. One of the few times I wanted to reach for some deoxit, but didn't have any around.
ATR 102 1/2" machine checkout-
This was a 2000 ATR Service rebuild in amazing shape, awakened from storage. I exercised connections, especially to the power supply before powering up, and ran through a bunch of transport checks. Lubricated simple mechanical bits which were dried (head shield shaft, tape lifters). The scrape flutter idler was not moving freely and the repro head grounding wasn't great, so the headblock is off to JRF for inspection, lube and cleaning. The capstan motor drum was replaced in the field by the owner without adjusting, so I rant through that alignment.
The machine was incredibly solid for sitting around so long.
Re: GReg-Electrical Tech Journal Redux
55Thank youGreg wrote: Fri Dec 01, 2023 5:27 pm 9/26/21
UREI LA-4 #1
Vu meter shows -1dB Vu as normal.
9/26/21
Gain brain #2 no signal. (nothing showing @ input).
Gain brain #3 – check meter, seemed intermittent. Out put cuts out when faceplate flexed.
#2 works after reseating.
#3 no notes
jason (he/him/his) from volo (illinois)
Re: GReg-Electrical Tech Journal Redux
56-Elsewhere-
More Neve 8014 work
1. Neve 1073 clone # "16" with a distorted output
- Found a short on the circuit by TR4 and C9 on the BA283AV board. Cleaned up the section. Boards are covered in some kind of greasy solvent, possibly from overspray from a cleaner, which might be interacting. Cleaned what I could.
- There were many iffy solder joints where transistor legs were floating in solder instead of making solid contact with the traces. I desoldered, bent pins down and re-soldered several of those points to improve contact.
- Discovered 220Hz and 110Hz, in the Low Frequency EQ band cut and boosted the same frequency (around 110Hz). Discovered 2 misplaced capacitors on the B205 Card (16nF and 47nF reversed, at pins D and E).
Other Notes -
- Mic input transformer isn't the expected 10468 type, but a 31267 line input transformer wired in reverse.
- Builder used larger than original styrene capacitors on the B284 amplifier board which are coming into contact with the neighboring filter board, flexing the connection and possibly causing shorts against the side of the module. This was causing unpredictable function in the last stage of gain for the preamp (-55--80db). I tried to flatten components to some degree and insulated contact areas. The board also seems to be from a photocopy slightly out of scale (little larger). The edge connector fingers barely meet with the socket pins.
All tested well finally on the Audio Precision.
2. Neve 1883 routing module sn 7888/k, no audio :
- Found a short between M and L pins on the B283 A amp (B+ and input). Fixed and tested.
3. Neve 1272 "Broken":
- Unit actually a 1288 "loudspeaker amp". It looks like someone tried to modify it to be a mic preamp. Line input transformer was wired backwards like the above 1073. I guess this is a thing people do. Interesting info on it here...
Unit has an overall gain of 35db, and the trim pot is bypassed. This won't work like a normal 1272 in the 8014.
Anyway, - Output is noisy. Noise discovered in the output stage of the B283 board. Replaced TR3 (2n3055), then TR2 (BC184C) which ended up being the noisy transistor. I put the original 2n3055 back in place to be sure.
A decision needs to be made as to what to do with this (return to a 1288, 1272 or something else).
Finished building two more stereo Altec 150/M11 power supplies and cables, and tested four 150s with them. I replaced two tubes because of noise and microphonics.
A couple of the mic's capsules looked tarnished. One was a blueish/gold, the other a reddish/gold. I've never seen that before on these mics, and wonder what's up.
More Neve 8014 work
1. Neve 1073 clone # "16" with a distorted output
- Found a short on the circuit by TR4 and C9 on the BA283AV board. Cleaned up the section. Boards are covered in some kind of greasy solvent, possibly from overspray from a cleaner, which might be interacting. Cleaned what I could.
- There were many iffy solder joints where transistor legs were floating in solder instead of making solid contact with the traces. I desoldered, bent pins down and re-soldered several of those points to improve contact.
- Discovered 220Hz and 110Hz, in the Low Frequency EQ band cut and boosted the same frequency (around 110Hz). Discovered 2 misplaced capacitors on the B205 Card (16nF and 47nF reversed, at pins D and E).
Other Notes -
- Mic input transformer isn't the expected 10468 type, but a 31267 line input transformer wired in reverse.
- Builder used larger than original styrene capacitors on the B284 amplifier board which are coming into contact with the neighboring filter board, flexing the connection and possibly causing shorts against the side of the module. This was causing unpredictable function in the last stage of gain for the preamp (-55--80db). I tried to flatten components to some degree and insulated contact areas. The board also seems to be from a photocopy slightly out of scale (little larger). The edge connector fingers barely meet with the socket pins.
All tested well finally on the Audio Precision.
2. Neve 1883 routing module sn 7888/k, no audio :
- Found a short between M and L pins on the B283 A amp (B+ and input). Fixed and tested.
3. Neve 1272 "Broken":
- Unit actually a 1288 "loudspeaker amp". It looks like someone tried to modify it to be a mic preamp. Line input transformer was wired backwards like the above 1073. I guess this is a thing people do. Interesting info on it here...
Unit has an overall gain of 35db, and the trim pot is bypassed. This won't work like a normal 1272 in the 8014.
Anyway, - Output is noisy. Noise discovered in the output stage of the B283 board. Replaced TR3 (2n3055), then TR2 (BC184C) which ended up being the noisy transistor. I put the original 2n3055 back in place to be sure.
A decision needs to be made as to what to do with this (return to a 1288, 1272 or something else).
Finished building two more stereo Altec 150/M11 power supplies and cables, and tested four 150s with them. I replaced two tubes because of noise and microphonics.
A couple of the mic's capsules looked tarnished. One was a blueish/gold, the other a reddish/gold. I've never seen that before on these mics, and wonder what's up.
Re: GReg-Electrical Tech Journal Redux
57DI box work.
Other random office stuffff.
From Studio A's faults log book -
6/19/20
(Neotek Elite) Ch.17 Mon input switch fucked in up position kills signal.
7/2/20
Replaced with spare. Now in ch.21 position (7/24) after cleaning with MS 738. (see below)
6/26/20
Can't get "speaker C" switch to pass signal to right output.
Can't reproduce, but AB amp fixed again.
7/1/20
Studer ch.6 output not getting through to patch point of "tape out", had to re-route using long xlr cable to ex. patch bay.
Signal -6dB on both multi points (line, L2)
Re-punched that point on punch block.
7/7/20
(Neotek Elite) channel 21 L2 input crackly/intermittent. Exercised every switch, still crackled. gave up & used insert return and carried on with session. similar to ch.15 persistent prob.
Replaced with former channel 17 which was cleaned with MS-738, all switches cleaned except bus
11/xx/20- Not a great success
7/8/20
Urei La 22 crackly/distorted in "narrow" mode both channels. controls generally unreliable.
Left channel 'auto" stuck on, function + LED.
7/xx/20
Switches fucked. Pulled compressor.
Replaced all switches + Broken/cold solder joint on "auto" switch pin reflowed. Tested, works. -
7/16/20
(Neotek Elite) Channel 20 does not send to bus 22, had to hard patch. Bus 21 no problem. 22, niente(?).
7/24/20
Can't reproduce
7/18/20
Please fix loft oscillator, or we need a new calibrated preference oscillator.
Fuck that thing.
7/19/20
Studio loudspeakers cracking, popping with nothing selected to els send but speakers on & knob at 1 o'clock.
Caused by talkback mic preamp clipping during loud control room playback. The clipping crosstalk'ed to SLS amp send. Solved later.
7/21/20
Alcatraz & Kentucky studio loudspeakers sound blown out.
None recorded
7/23/20
Apogee Symphony MkII o/p 1+2 merged during 4- tk transfer session.
Some combination of power cycling computer and converters fixed it.
7/28/20
UREI LA-12
Switches replaced prophylactically.
8/2/20
Tape machine output ch.6 not making it through end/ patch bay. Had to use xlr cable to aux patch bay. Tried X patching & exercising elcos & patch points. No dice.
Patchbay normal dirty. Inserted patch cable, withdrew, and signal returned.
8/20/20
Distresstor soft keys locked.
Spilled root beer gummed up the push buttons. Cleaned. Works.
8/27
Elite cue 2 solo switch fucked.
11/20/20
Replaced switch + cleaned cue 1 solo switch.
8/xx/20
Akg c-24 noisy when mic connector tightened too much. Noise on both channels so maybe B+ interference?
None recorded
(Later- Added a rubber gasket/grommet to limit the travel of the threaded collar. Noise didn't return.)
Neotek Elite ch.18 monitor insert switch dirty
11/30 21
Replaced with re-switched channel
Elite ch 21 monitor insert switch intermittent.
12/28/21
Replaced with re-switched channel.
9/x/20
B&Ws (805 matrix) distorting (noticed with loud piece)?
Nah
10/13/10
Neotek Elite ch. 19 signal very low through bus 13, had to direct patch from main out.
Never mind, some [socially unacceptable ca. '23 language] turned the buss gain down.
(the intern who helped me transcribe these scribblings from paper to a text document couldn't bring themselves to write the word and wrote "count" instead.)
10/22/20
K.T DN780 reverb, after being on for 2 days, peak light came on and wild digital hash started roaring out. Cycled power and it went away for a bit. Then shut down with an error message & wouldn't come back.
None recorded
10/26/20
Lexicon PCM- 41 delay select switches nf (nonfunctional).
Replaced switches - old ones badly oxidized .
11/6/20
Urei 1176 levels are jumping erratically. Attack + release set to fastest, 4:1 ratio.
11/24/20
Can't reproduce hours of testing, so I'll go with ghost.
11/6/20
RNC filter caps dead buzzing on o/p.
11/28/20
Electrolytics replaced. Operating great now. Dead quiet .
Neotek Elite ch.16 preamp has more noise than the other. Double check with pad + phantom on.
Channel replaced.
(N.B. Don't know ultimately what the fix was, but through the re-switching of the board, we also replaced all the DC blocking caps in the mic preamp path, meant to block the 48 volts. These were rated for 50 volts, which doesn't leave a lot of breathing room. Some of them bulged and were the source of noise. They were replaced with 105º 63 volt caps. I recommend doing this if you have an Elite or Elan.)
11/xx/20
Flying faders - ch 33 cable bust? NF
No motor control.
11/20/20
Cable snapped - restrung with new one.
Other random office stuffff.
From Studio A's faults log book -
6/19/20
(Neotek Elite) Ch.17 Mon input switch fucked in up position kills signal.
7/2/20
Replaced with spare. Now in ch.21 position (7/24) after cleaning with MS 738. (see below)
6/26/20
Can't get "speaker C" switch to pass signal to right output.
Can't reproduce, but AB amp fixed again.
7/1/20
Studer ch.6 output not getting through to patch point of "tape out", had to re-route using long xlr cable to ex. patch bay.
Signal -6dB on both multi points (line, L2)
Re-punched that point on punch block.
7/7/20
(Neotek Elite) channel 21 L2 input crackly/intermittent. Exercised every switch, still crackled. gave up & used insert return and carried on with session. similar to ch.15 persistent prob.
Replaced with former channel 17 which was cleaned with MS-738, all switches cleaned except bus
11/xx/20- Not a great success
7/8/20
Urei La 22 crackly/distorted in "narrow" mode both channels. controls generally unreliable.
Left channel 'auto" stuck on, function + LED.
7/xx/20
Switches fucked. Pulled compressor.
Replaced all switches + Broken/cold solder joint on "auto" switch pin reflowed. Tested, works. -
7/16/20
(Neotek Elite) Channel 20 does not send to bus 22, had to hard patch. Bus 21 no problem. 22, niente(?).
7/24/20
Can't reproduce
7/18/20
Please fix loft oscillator, or we need a new calibrated preference oscillator.
Fuck that thing.
7/19/20
Studio loudspeakers cracking, popping with nothing selected to els send but speakers on & knob at 1 o'clock.
Caused by talkback mic preamp clipping during loud control room playback. The clipping crosstalk'ed to SLS amp send. Solved later.
7/21/20
Alcatraz & Kentucky studio loudspeakers sound blown out.
None recorded
7/23/20
Apogee Symphony MkII o/p 1+2 merged during 4- tk transfer session.
Some combination of power cycling computer and converters fixed it.
7/28/20
UREI LA-12
Switches replaced prophylactically.
8/2/20
Tape machine output ch.6 not making it through end/ patch bay. Had to use xlr cable to aux patch bay. Tried X patching & exercising elcos & patch points. No dice.
Patchbay normal dirty. Inserted patch cable, withdrew, and signal returned.
8/20/20
Distresstor soft keys locked.
Spilled root beer gummed up the push buttons. Cleaned. Works.
8/27
Elite cue 2 solo switch fucked.
11/20/20
Replaced switch + cleaned cue 1 solo switch.
8/xx/20
Akg c-24 noisy when mic connector tightened too much. Noise on both channels so maybe B+ interference?
None recorded
(Later- Added a rubber gasket/grommet to limit the travel of the threaded collar. Noise didn't return.)
Neotek Elite ch.18 monitor insert switch dirty
11/30 21
Replaced with re-switched channel
Elite ch 21 monitor insert switch intermittent.
12/28/21
Replaced with re-switched channel.
9/x/20
B&Ws (805 matrix) distorting (noticed with loud piece)?
Nah
10/13/10
Neotek Elite ch. 19 signal very low through bus 13, had to direct patch from main out.
Never mind, some [socially unacceptable ca. '23 language] turned the buss gain down.
(the intern who helped me transcribe these scribblings from paper to a text document couldn't bring themselves to write the word and wrote "count" instead.)
10/22/20
K.T DN780 reverb, after being on for 2 days, peak light came on and wild digital hash started roaring out. Cycled power and it went away for a bit. Then shut down with an error message & wouldn't come back.
None recorded
10/26/20
Lexicon PCM- 41 delay select switches nf (nonfunctional).
Replaced switches - old ones badly oxidized .
11/6/20
Urei 1176 levels are jumping erratically. Attack + release set to fastest, 4:1 ratio.
11/24/20
Can't reproduce hours of testing, so I'll go with ghost.
11/6/20
RNC filter caps dead buzzing on o/p.
11/28/20
Electrolytics replaced. Operating great now. Dead quiet .
Neotek Elite ch.16 preamp has more noise than the other. Double check with pad + phantom on.
Channel replaced.
(N.B. Don't know ultimately what the fix was, but through the re-switching of the board, we also replaced all the DC blocking caps in the mic preamp path, meant to block the 48 volts. These were rated for 50 volts, which doesn't leave a lot of breathing room. Some of them bulged and were the source of noise. They were replaced with 105º 63 volt caps. I recommend doing this if you have an Elite or Elan.)
11/xx/20
Flying faders - ch 33 cable bust? NF
No motor control.
11/20/20
Cable snapped - restrung with new one.
Re: GReg-Electrical Tech Journal Redux
58
-Elsewhere-
LOMO extravaganza. Each item a different item.
Lomo 19a18 supply
"odd voltages measured. Mic not working right"
No 0 volt continuity between the B+ and filament supplies. These are normally brought together crudely through the chassis by way of solder eyelet washer tabs at 3 different connector screw points. I Jumpered the 0v points for both supply rails at the last filter cap negative connections. Added starwashers to oxidized chassis ground tabs (3). Good continuity, all around.
Calibrated voltages 5.6v Fil, 115v B+"
Lomo 19a9 20B-35 PSU
Power transformer gets scorching hot.
Found a shorted diode in the B+ bridge rectifier. Replaced all 4 diodes.
Added a jumper between 0v points of both power rails.
Set voltages to 55v B+, 5.5v fil
Lomo 19a9 20B-35 with tube diode
Mechanical hum in the Power transformer, which also gets scorching hot.
Dying bridge rectifier diodes- replaced. On had a series resistance of 1200 ohms
Added a jumper between 0v points of both power rails.
Calibrated voltages 55v B+, 5.5v fil
Lomo 19a9 20B-35 PSU
"Weak sound. Bad connection to output cable"
Male output connector has pins of a smaller diameter than all the other 20b-35 PSUs.
Replaced connector,
Added a jumper between 0v points of both power rails.
Calibrated voltages 55v B+, 5.5v fil
Lomo 19a4 20B-50 PSU
No power Connector, broken lamp holder
Installed a spare connector, new lampholder.
Replaced all rectifier diodes.
Added a jumper between 0v points of both power rails.
Calibrated power rails, but forget to what. The manual says 110v B+, and I probably did 5.5v for the filament.
Lomo 19a18 20B-50 PSU
Needs different I/o connections
Replaced new XLR with original 60-year old, shitty Russian 3-pin output connector (as per the owner's need that this specific PSU use all original Soviet garbage parts).
Checked voltages
Added a jumper between 0v points of both power rails.
Lomo 19a18 Cable
Intermittent contact on the mic end connector
Rebuilt cable with New connectors (yay).
Lomo 19a18
Low output thin sound. hum
Wire carying the polarizing voltage to capsule was severed.
Replaced this wire, and the filament wire, since it was pretty melted looking from some previous work, looked like it had some exposed wire.
Lomo 19a18
Mic had a .5uF coupling capacitor instead of 1uF.
Replaced with a NOS 1uF cap.
Lomo 19a4 20B-50 PSU
Replaced mic input connector
Added a jumper between 0v points of both power rails,
Replaced 1uF output transformer coupling capacitor.
Filament = 6v, B+ = 110v"
IRPA MK61 (cables)
Two cables, different sloppy soldering, shorting different pins together through exposed, frayed conductors.
One cheap, damaged DIN connector
Repaired cables. Replaced connector.
Sony c-37A
Destroyed mic umbilical output connector, partially held together by epoxy. Socket pins sitting a different depths.
Replaced connector.
Lomo 19a4
B+ and transformer coupling cap shorted to ground.
Output connector wired incorrectly (ref. schematic and 3 other 19a4 mics). Corrected, and built new cable
LOMO extravaganza. Each item a different item.
Lomo 19a18 supply
"odd voltages measured. Mic not working right"
No 0 volt continuity between the B+ and filament supplies. These are normally brought together crudely through the chassis by way of solder eyelet washer tabs at 3 different connector screw points. I Jumpered the 0v points for both supply rails at the last filter cap negative connections. Added starwashers to oxidized chassis ground tabs (3). Good continuity, all around.
Calibrated voltages 5.6v Fil, 115v B+"
Lomo 19a9 20B-35 PSU
Power transformer gets scorching hot.
Found a shorted diode in the B+ bridge rectifier. Replaced all 4 diodes.
Added a jumper between 0v points of both power rails.
Set voltages to 55v B+, 5.5v fil
Lomo 19a9 20B-35 with tube diode
Mechanical hum in the Power transformer, which also gets scorching hot.
Dying bridge rectifier diodes- replaced. On had a series resistance of 1200 ohms
Added a jumper between 0v points of both power rails.
Calibrated voltages 55v B+, 5.5v fil
Lomo 19a9 20B-35 PSU
"Weak sound. Bad connection to output cable"
Male output connector has pins of a smaller diameter than all the other 20b-35 PSUs.
Replaced connector,
Added a jumper between 0v points of both power rails.
Calibrated voltages 55v B+, 5.5v fil
Lomo 19a4 20B-50 PSU
No power Connector, broken lamp holder
Installed a spare connector, new lampholder.
Replaced all rectifier diodes.
Added a jumper between 0v points of both power rails.
Calibrated power rails, but forget to what. The manual says 110v B+, and I probably did 5.5v for the filament.
Lomo 19a18 20B-50 PSU
Needs different I/o connections
Replaced new XLR with original 60-year old, shitty Russian 3-pin output connector (as per the owner's need that this specific PSU use all original Soviet garbage parts).
Checked voltages
Added a jumper between 0v points of both power rails.
Lomo 19a18 Cable
Intermittent contact on the mic end connector
Rebuilt cable with New connectors (yay).
Lomo 19a18
Low output thin sound. hum
Wire carying the polarizing voltage to capsule was severed.
Replaced this wire, and the filament wire, since it was pretty melted looking from some previous work, looked like it had some exposed wire.
Lomo 19a18
Mic had a .5uF coupling capacitor instead of 1uF.
Replaced with a NOS 1uF cap.
Lomo 19a4 20B-50 PSU
Replaced mic input connector
Added a jumper between 0v points of both power rails,
Replaced 1uF output transformer coupling capacitor.
Filament = 6v, B+ = 110v"
IRPA MK61 (cables)
Two cables, different sloppy soldering, shorting different pins together through exposed, frayed conductors.
One cheap, damaged DIN connector
Repaired cables. Replaced connector.
Sony c-37A
Destroyed mic umbilical output connector, partially held together by epoxy. Socket pins sitting a different depths.
Replaced connector.
Lomo 19a4
B+ and transformer coupling cap shorted to ground.
Output connector wired incorrectly (ref. schematic and 3 other 19a4 mics). Corrected, and built new cable
Re: GReg-Electrical Tech Journal Redux
59These notes are great. Remind me of my old gig debugging software.Greg wrote: Thu Dec 07, 2023 5:55 pm 7/18/20
Please fix loft oscillator, or we need a new calibrated preference oscillator.
Fuck that thing.
jason (he/him/his) from volo (illinois)
Re: GReg-Electrical Tech Journal Redux
60Neotek SII
Talkback not going to CUE 2 buss
Found a busted solder joint with the ribbon cable jumping the Control Room Monitor to the Motherboard.
I had previously re-pinned the molex hood connecting the ribbon to the CR Monitor board.
Red herring- the board to board tin molex pins between CR Monitor and Studio Monitor boards are shedding their tin plating. One of these carries the CUE 1 and 2 send.
I naturally suspected a bad connection there. They need to be replaced ultimately, but that wasn't the source. Finding 1.2" long square gold molex headers (KK series .156" pitch (or equivalent)) is the thing now. I have the female sockets I want to use.
Talkback not going to CUE 2 buss
Found a busted solder joint with the ribbon cable jumping the Control Room Monitor to the Motherboard.
I had previously re-pinned the molex hood connecting the ribbon to the CR Monitor board.
Red herring- the board to board tin molex pins between CR Monitor and Studio Monitor boards are shedding their tin plating. One of these carries the CUE 1 and 2 send.
I naturally suspected a bad connection there. They need to be replaced ultimately, but that wasn't the source. Finding 1.2" long square gold molex headers (KK series .156" pitch (or equivalent)) is the thing now. I have the female sockets I want to use.