Lovetone Meatball
No input envelope related effects.
Switches are in bad shape. Wiggling them brings back functionality temporarily. Tried cleaning them, but couldn't get solid reliability. -Switches replaced, and everything is back up and running.
Studer updates above...

Ampex 351 (preamp #2 located in studio A, position 2)-
1. Signal cutting out when meter defeat switch messed with.2. Needs phase reverse relay mod, and upgraded phantom supply wiring.
1. Fixed.2. Done.

Audio Technica 4033 -
Noisy output
Loose ground connection on the xlr output. Tightened.

Working on a custom MS Matrix.

RNC Compressor #2 studio B-
High frequency "tzzzz" on output. Gone in bypass mode.
Noise found the -15vdc rail (ripple).Recapped the supply section. Noise went away. Recapped the remaining electrolytics.

Studer A820MCH studio A (older one)-
Taylor discovered the supply reel motor was spinning fast when he showed up today. The only thing that would stop it was shutting the power off. When I turned it back on, there was a quiet whine coming from the reel motors, motor drive amps (MDA) or both.
I removed the two motor drive amplifiers to check them out in the shop. Both needed to be recapped (4 electrolytics for the ±15v rails C6, 7, 8, 9). I replaced the 5532 op amps (IC2) since they looked like they've been warmed. I checked around for obvious failures in the semiconductors, transformers/inductors, and cleaned the contacts. There were a few hot looking solder joints that I reflowed as well.
When I reinstalled the MDAs, and switched the machine on, all was quiet. I ran through some stress tests and checked the tensions roughly with scrap tape. All seems good. I didn't expect this. I figured there was probably something up with the Spooling Motor Control, or Spooling Motor Driver boards. So far so good.

Replaced the phantom power supply unit that feeds the four Ampex 351s in Studio B with this module.
I was a little nervous about the low switching frequency. Only getting right on top of the shielded module with a pickup, I could hear the switching frequency, but much lower than the line frequency. Testing in the application with the preamps at max gain with various different loads and mics, I couldn't hear/see it anywhere. So far so good.
Cleared out a few suspect microphones that had little or no problems of note.

greg wrote:
-Eleswhere-
For Studer A827 savvy techs...I'm trouble-shooting the machine ("Gold Edition") in this video. "When Play is engaged, tape promptly races away at a faster speed, and pinch roller disengages.
When Stop is pressed the tape halts, but the capstan still spins at incorrect IPS speed (measured at the capstan MDA board).
From here, if I press Play again nothing happens.
Capstan still spins, as if it is in the capstan shaft cleaning mode, but the speed can't be changed as with that mode. Resetting the MPU boards, specifically the Tape Deck Control MPU or the Capstan Control Unit and the capstan motor stops. The process can be repeated.
Tensions were correctly adjusted before this condition was constant.
Capstan motor control adjustments and measurements are correct, while testing in the shaft cleaning mode (no tape loaded, play engaged, all speeds tested). Wind, and Edit modes functioning correctly.
Power supply voltages correct.Was able to confirm the checksum of all eproms except the ones on the Master MPU board (don't know those so can't confirm 16/97 software). All tape deck control boards have been replaced except the Master MPU (no spare) while trouble-shooting this problem with no change in behavior.
Swapped the capstan MDA board with a known working one ...This machine was built new in 1999.Any ideas?"

Finally, One or more wires in the loom between the capstan tachometer pcb and capstan drive amp was making intermittent contact. I was able to get the machine to act normal by pressing against the tachometer pcb end of the loom. The wires are crimped to pins that are then soldered to the tachometer pcb. I simply reflowed the solder joints, and tested. All was good. I think if I had to do it again, I'd cut the pins off, then strip and solder the wires directly to the board, removing the middle-man interconnect of the crimp, but the system was solid here, and they are back in business. I don't know why this caused the illustrated problem, all the downstream logic and control anomalies. Many signals between the 4 boards that deal with controlling and sensing the capstan were nonsensical during fault mode. Not knowing which of the signals was intermittent makes it more difficult to trace.
P.S. To find all the relevant, block diagrams, schematics, and circuit descriptions, one has to mine the various updated and old A820 2-track, A827, A820MCH manuals (all use roughly the same boards). None of them have everything.
P.P.S.I'm gathering a small list of unfortunate discoveries with the few "gold edition" A827s I've worked on that lead me to believe the QC wasn't in top form for the last run of tape machines. I'm wondering if it was a skeleton crew at the end. All these problems were from the factory shipped machines, and not wear/user dumb related.
1. 5v stabilizer cold solder joint.
2. Loose timer roller.
3. Headblock alignment pins missing.
4. Capstan MDA harness bad soldering.
5. Odd mechanical switching issues

Ampex 351 preamp #1 in studio A -
Signal cutting out when the meter defeat switch is used.
The meter switch assembly, which includes a panel that holds the "cal" pot was loose. It nudged the wiring going to the -20dB pad. After enough nudging, one of the wires broke off it's post.Rewired, working.

Studer A820 Studio A-
Channel x record treble calibration, this channel needs much more gain than others to get it to 0vu.

Swapped Record and HF Driver boards with another channel, problem followed. Later, the cards tested in another machine, worked perfectly. Either someone fixed these and put them back on my shelf exactly as they found it, or there's an intermittent problem. I suspect something went goofy with the NAB/CCIR logic switch on the record board, but won't know until it happens again.

Fender Pro Jr. Day-

Pro Jr. #1
Intermittent connections on the input jack.
The 1/4" switching jack module is pc board mounted. The pins had broken loose from their solder pads.
Resoldered, bending the legs over for a little better support.
Pro Jr. #2
Power tubes intermittently working.
A few solder pads for the power tube sockets have torn of their traces on the pc board. The pc board is cooked in that section. Hard wired jumpers in place to reinforce the connections. This is the second time I've had to do this (not on the same pins). If it happens again, I might just replace the pcb with chassis mounted sockets, and wire point to point.