Juno 60 Full Log

Really Nice Audio · Repair case records

Case record 001: Roland Juno-60 (serial 305451)

A fully documented repair, recorded as it happened.

This page is a structured record of one repair. It captures the diagnosis as it unfolded, including the dead ends, every decision taken, and what was kept, repaired or replaced, so that the work can be checked, repeated and learned from.

Hands-on time
4 hours
Documentation
about 8 hours
Diagnostic steps
27, including dead ends
Interventions
12
Parts
£10
Outcome
Complete, everything working

Record prepared 30 October 2026 · Version 1.0 · About this record · Download as JSON

The video

Video: Roland Juno 60 Repair and Demos, Really Nice Audio, 29:35. https://youtu.be/sDFHMipudyw

Chapters 29 Length 29:35

  1. Intro – unwanted modulation
  2. First look inside
  3. Probing the VCA outputs
  4. The VCA control voltage & a suspect multiplexer
  5. Opening up board A
  6. Scoping the multiplexers
  7. Suspecting a grounding fault
  8. Tracing the earth traces
  9. Found it: ripped-off traces
  10. Rewiring the earth
  11. Power-on test
  12. Fitting a backup battery holder
  13. Loading the factory patches from tape
  14. Demo
  15. The MIDI retrofit isn’t working
  16. Where is it getting its power from?
  17. Temperature checks
  18. MIDI arrives – a Groove Electronics board
  19. Heat sinking the regulator
  20. MIDI working
  21. Running too hot
  22. Swapping the 7805 for a DC-DC converter
  23. Adding an output cap
  24. Why the supply was overloaded
  25. Soak test
  26. Fixing a PAT test fault
  27. Sending MIDI out
  28. Wrap-up & a power supply warning
  29. Outro

The instrument

Identity and provenance

Make
Roland
Model
Juno-60
Serial number
305451 LOG. Published with the owner’s permission as proof of provenance Restorer.
Year or estimated year
Not recorded
Original mains voltage
Not recorded. The rear rating plate appears in the video (27:52) but its voltage isn’t read. UK-market unit (inferred, from the UK 13A-fused mains plug and the PAT test).
Stream
Private client Restorer

Signs of previous repairs and modifications

  1. Replacement power supply. A switch-mode module on an "OCP BOARD JU-6/60" carrier (silk-screen "JU-6/60_PSU_3e"), over-current trip about 0.59 A ±5% per rail (+15 V, +5 V, −15 V), with +10 V made by a regulator IC on the OCP board LOGVIDEO 00:25–00:40, 20:50.
  2. Replacement CPU on Panel Board B. NMOS D8049C-028 (marked "www.vintagesynthparts.com"), same firmware code as the original µPD80C49C-028 LOG.
  3. Groove Electronics MIDI retrofit. Pamphlet drawings dated 15/12/85, with its function button mounted below the CHORUS OFF switch LOGGROOVE.
  4. Pin headers fitted at test points. VIDEO 01:12
  5. MIDI board power wires taped off. By the previous technician LOGVIDEO 17:44.
  6. A multiplexer suspected. The previous technician had suspected a multiplexer VIDEO 02:21.
  7. Original backup battery still fitted. With a bent leg VIDEO 00:51, 08:59.
  8. 13A fuse in the mains plug. LOG

What was wrong

Reported fault

A wobble on every note even with no modulation dialled in. The previous technician suspected a multiplexer. MIDI not working. VIDEO description; 02:21; 17:44

Paraphrased.

Symptoms observed on arrival

  1. Warbly, "FM’d" sound on every voice, present even with chorus off LOGVIDEO 00:06–00:25.
  2. Envelope interference with DECAY at minimum LOG.
  3. One voice quieter than the others LOG.
  4. MIDI retrofit not working, its power wires taped off LOGVIDEO 17:44.
  5. Patch memory almost empty LOGVIDEO 09:23.
  6. Mains cable loose at the rear cable entry, found during the PAT test LOGVIDEO 27:51.
Cosmetic condition
Not recorded
Photos taken
Not recorded. No photo list exists in the log. Scope photos and board photos were taken during the work inferred, but they aren’t catalogued.

The diagnostic path

The order follows the video timeline. Where the order isn’t recorded, it’s marked inferred. Each step shows what was suspected, the test, the tool, the result and the conclusion. Dead ends and wrong guesses are kept: they are part of how the fault was found.

  • Main path
  • Dead end or wrong guess (steps 1, 7, 16)
  • Root cause found (step 13)
  1. The wobble on every note
  2. 1SuspectedDC offset at the C5/R14 junction (VCF input) on the even-numbered voicesConclusionDead end. Not a fault. (Position in the sequence: early, inferred)Dead end
    Test
    Voltage measurement at C5/R14
    Tool
    Not recorded
    Result
    Offset reading turned out to be a measurement error. All C5/R14/IR3109 pin 2 points correct on every voice LOG
  3. 2SuspectedUnwanted modulationConclusionConfirms reported fault
    Test
    Played and held notes with no modulation set
    Tool
    Ears
    Result
    Held note not steady; wobble audible VIDEO 00:06–00:25
  4. 3SuspectedFault in the voice VCAsConclusionFollow the signal to the chorus board
    Test
    Scoped the VCA outputs at the test-point pin headers
    Tool
    Rigol DS1054Z
    Result
    Sawtooth present but with jagged, unstable ramps VIDEO 01:01–01:37
  5. 4SuspectedFault in or after the chorus boardConclusionProblem is in what controls the chorus board’s master VCA
    Test
    Scoped the chorus board input and output
    Tool
    Rigol DS1054Z
    Result
    Input clean; output shows the modulation VIDEO 01:37–02:00
  6. 5SuspectedBad control voltageConclusionMultiplexed CV is corrupted. Suspect a multiplexer (agreeing with the previous technician)
    Test
    Scoped the VCA control CV at chorus board pin 14
    Tool
    Rigol DS1054Z
    Result
    Expected steady DC; found a noisy, stepped signal VIDEO 02:00–02:21LOG
  7. 6SuspectedFaulty multiplexer IC8ConclusionInvestigate IC8
    Test
    Traced the CV path back on the schematic: IC6 op-amp, then IC8 on Panel Board A. Removed Panel Board A for top-down access
    Tool
    Schematic SN; screwdriver
    Result
    Path identified VIDEO 02:31–03:29
  8. 7SuspectedIC8 chip faultyConclusionPartial dead end: no chip fault shownPartial dead end
    Test
    Compared IC8 with IC3 as a reference
    Tool
    Rigol DS1054Z
    Result
    Both broadly normal, apart from a "squiggly line" on the top edge VIDEO 03:29–03:56
  9. 8SuspectedBoth multiplexers enabled at onceConclusionSelect logic OK
    Test
    Scoped the two inhibit (INH) pins
    Tool
    Rigol DS1054Z (200 µs/div, 2 V/div)
    Result
    Never both selected at once VIDEO 03:49–03:56
  10. 9SuspectedAddress or output faultConclusionSuspect a grounding fault
    Test
    Four channels: control pins A and B, plus two buffered multiplexer outputs
    Tool
    Rigol DS1054Z (5 V/div, 500 µs/div)
    Result
    The two buffered outputs are identical, which is impossible for separately held values VIDEO 03:56–04:22LOG
  11. 10SuspectedSupply missingConclusionRails present
    Test
    Measured rails at a ground point
    Tool
    Fluke multimeter
    Result
    Speech says 5 V, −5 V, +15 V present. Meter on screen shows 0.002 and −0.044 (mismatch noted) VIDEO 04:22–04:43
  12. 11SuspectedMultiplexer ground missingConclusionGround path broken
    Test
    Power off: continuity from ground to 4051 pin 8
    Tool
    Fluke multimeter (continuity)
    Result
    OL, open circuit VIDEO 04:51–05:04LOG
  13. 12SuspectedBreak in the earth traceConclusionBreak located
    Test
    Printed the board layout, marked the earth traces in green, followed them with a magnifier
    Tool
    Printout, highlighter, magnifier
    Result
    Break found VIDEO 05:04–06:08
  14. 13SuspectedPhysical damageConclusionRoot cause foundRoot cause found
    Test
    Microscope inspection
    Tool
    Microscope
    Result
    Earth traces ripped off on both sides of the board; the area moves when prodded VIDEO 06:08–06:29LOG
  15. 14SuspectedRepair completeConclusionFault cleared. The quieter voice was also cured LOG
    Test
    Continuity check after the wire links, then power-on test
    Tool
    Fluke multimeter; bench power-up
    Result
    Pin 8 to ground OK on both 4051s; sound good VIDEO 06:37–07:34LOG
  16. Patch memory
  17. 15SuspectedMemory empty because of battery or RAM powerConclusionSuspected the previous technician disconnected the RAM’s power (not confirmed)
    Test
    Checked the memory before removing the battery
    Tool
    Front panel
    Result
    Nothing much in memory VIDEO 09:23
  18. 16SuspectedTape load procedureConclusionWrong guess about the procedureWrong guess
    Test
    Loaded factory patches from a WAV, pressing LOAD before the tone
    Tool
    Logic Pro, audio interface
    Result
    Load error VIDEO 10:05
  19. 17SuspectedTiming of the LOAD buttonConclusionProcedure found
    Test
    Pressed LOAD just after the steady leader tone began
    Tool
    Same
    Result
    Load completed VIDEO 10:18–11:09LOG
  20. The MIDI retrofit
  21. 18SuspectedMIDI board power disconnectedConclusionPower source unknown at this stage
    Test
    Inspected the wiring
    Tool
    Visual
    Result
    Power wires taped off; 10 V-rated cap across the 5 V regulator input; no witness marks; no matching connection on the replacement PSU VIDEO 17:40–19:43LOG
  22. 19SuspectedMIDI board faultyConclusionBoard alive
    Test
    Bench-powered the board with the ribbon disconnected
    Tool
    Bench PSU; Rigol; FLIR
    Result
    8.00 V in, 5 V out, 0.193 A; clock on pin 37; data activity; MC6802 63 °C LOGVIDEO 18:39–20:05
  23. 20SuspectedMIDI input path faultyConclusionInput path OK
    Test
    Scoped the opto-isolator (TIL111) output while sending notes from Logic
    Tool
    Rigol DS1054Z
    Result
    MIDI data present at the opto output LOGVIDEO 20:12–20:24
  24. 21SuspectedCorrect supply for the boardConclusionNeeds about 10 V
    Test
    Identified the board as Groove Electronics; read its instructions
    Tool
    GROOVE pamphlet; owner and previous tech
    Result
    Originally fed from the bridge rectifier of the original PSU LOGGROOVEVIDEO 20:24
  25. 22Suspected(connection)ConclusionMIDI IN working
    Test
    Connected to the OCP board’s +10 V (at a diode) and GND; heatsink fitted
    Tool
    Meter; soldering
    Result
    10 V present; MIDI notes play the Juno VIDEO 20:40–22:30LOG
  26. 23SuspectedSupply capacityConclusionNot enough headroom: by the restorer’s rule of thumb a supply should have at least double the current required Restorer. (Position in the sequence: inferred)
    Test
    Observed the replacement PSU, then read the specs printed on the OCP board
    Tool
    Observation; OCP board silk-screen
    Result
    The PSU shut down a couple of times with the MIDI board connected to its 10 V. Printed limit 590 mA per rail, with no indication of which rail feeds the 10 V. Juno draws roughly 300 mA, plus 200 mA for the MIDI board, about 500 mA in total, close to the 590 mA limit Restorer
  27. 24SuspectedSupply overloadConclusionThe replacement PSU’s +10 V regulator isn’t designed for the extra 200 mA VIDEO 25:52LOG
    Test
    Thermal check after about 1 hour
    Tool
    FLIR
    Result
    77.0 °C hotspot VIDEO 22:48; ">70 °C" LOG
  28. 25Suspected(verification after the fix)ConclusionOverload resolved
    Test
    Measured 5 V on the MIDI board; soak test
    Tool
    Meter; FLIR
    Result
    5 V present; about 60 °C after 2 hours with the lid shut LOG; hotspots 58–64 °C; converter about 34 °C VIDEO 26:26–27:42
  29. Mains safety
  30. 26SuspectedMains cable entryConclusionRepaired
    Test
    PAT test
    Tool
    PAT tester inferred
    Result
    Fault at the cable entry; passed after the fix VIDEO 27:51LOGRestorer
  31. MIDI out
  32. 27SuspectedMIDI OUT not workingConclusionNormal behaviour of the retrofit
    Test
    Function button + B
    Tool
    Logic Pro
    Result
    Notes sent in that mode; it doesn’t receive in that mode VIDEO 28:19–28:34LOG

Faults and causes

Eight faults, F1 to F8. F1a and F1b are consequences of F1. The tag on each card is the component class.

F1

Panel Board A: pot multiplexers and sample/holds (control voltages)

other (PCB copper earth traces)
Reference / part
Ground path to pin 8 of both 4051 multiplexers, IC8 and IC3 (HD14051B)
How it failed
Earth traces ripped off on both sides of the board; open circuit
Evidence
Continuity OL from pin 8 to ground; identical buffered outputs; stepped CV at chorus board pin 14; visible under the microscope LOGVIDEO
Likely cause
Unknown. Not recorded (possibly mechanical damage or earlier rework, inferred)
F1a

Voice level (one voice)

— (consequence of F1)
Reference / part
Not recorded which voice
How it failed
Quieter than the others
Evidence
Cured by the F1 repair LOG
Likely cause
Consequence of F1
F1b

Envelope (S/D control lines)

— (consequence of F1)
Reference / part
Not recorded
How it failed
Interference at minimum decay
Evidence
Listed as cured with the earth fault LOG
Likely cause
Consequence of F1
F2

MIDI retrofit power

other (wiring disconnected)
Reference / part
MIDI board red/black power leads
How it failed
Disconnected and taped off
Evidence
Taped wires LOGVIDEO 17:44
Likely cause
Previous repair (deliberate isolation by the previous technician, believed, not confirmed) VIDEO 17:53
F3

MIDI retrofit power / replacement PSU +10 V rail

voltage regulator
Reference / part
MIDI board 7805 (LM340T-5); OCP board +10 V regulator (reference not recorded)
How it failed
MIDI board drew about 200 mA from the replacement PSU’s +10 V regulator, which ran hot (77 °C)
Evidence
FLIR readings; current measurement LOGVIDEO; PSU shut down a couple of times with the MIDI board on its 10 V Restorer
Likely cause
Design weakness: a 1985 retrofit designed for the original unregulated rail, combined with a modern PSU not sized for it (inferred from VIDEO 25:52 and LOG)
F4

MIDI retrofit power

electrolytic capacitor
Reference / part
Input cap at the MIDI board regulator, 10 V-rated
How it failed
Under-rated for a 10 V rail; no failure recorded
Evidence
Rating noted LOGVIDEO 18:25
Likely cause
Design weakness inferred
F5

MIDI retrofit power

other (missing part)
Reference / part
Regulator output decoupling cap
How it failed
Not fitted originally
Evidence
Datasheet calls for one VIDEO 23:27
Likely cause
Design weakness
F6

Patch memory

Not recorded
Reference / part
Backup RAM / battery (CR-1/3N)
How it failed
Memory almost empty
Evidence
Checked before battery removal VIDEO 09:23
Likely cause
Unknown. Previous technician disconnecting the RAM’s power is suspected, not confirmed VIDEO 09:32. Battery voltage not recorded.
F7

Mains input

mechanical
Reference / part
Mains cable at the rear entry
How it failed
Cable not pulled through or clamped tightly
Evidence
Found in the PAT test LOGVIDEO 27:51
Likely cause
Unknown
F8

Mains plug

other (fuse rating)
Reference / part
Plug fuse 13 A
How it failed
Over-rated fuse
Evidence
LOG
Likely cause
Unknown. Not recorded who fitted it.

The decision record

Twelve interventions, I1 to I12. Each card shows what was done, whether it can be undone, and whether the original part was kept, followed by the alternatives that were considered and the reasons.

  • Fully reversible
  • Partly reversible
  • n/a or not recorded
I1

Panel Board A earth

  • Actionrepair
  • ReversiblePartly inferred
  • Original keptn/a
Original part removed
None (traces damaged)
Replacement
Two wire links LOGVIDEO 06:41
Why
"A good solid connection"; didn’t want to scrape and bridge the traces VIDEO
Alternatives considered
Trace repair (scrape and bridge): rejected VIDEO
Historical evidence lost
Not recorded
I2

4051 multiplexers IC8 and IC3

  • Actionkeep
  • Reversiblen/a
  • Original keptn/a
Original part removed
—
Replacement
—
Why
Chips not faulty once grounded VIDEO "points to double-check" 7
Alternatives considered
Replacing IC8, which the previous technician suspected: not pursued inferred
Historical evidence lost
None
I3

Backup battery

  • Actionsubstitute
  • ReversiblePartly inferred
  • Original keptYes, kept by RNA in labelled bags Restorer
Original part removed
Original 3 V lithium CR-1/3N, soldered (maker and date code not recorded)
Replacement
Coin-cell holder with CR2032 LOGVIDEO 08:09
Why
"Save a lot of grief later on" VIDEO 08:24
Alternatives considered
Not recorded
Historical evidence lost
Original battery and its solder joints inferred
I4

Patch memory

  • Actionother (reload)
  • ReversibleNot recorded
  • Original keptNot recorded (no dump of the previous contents recorded)
Original part removed
Previous memory contents (almost empty)
Replacement
Factory A/B patch WAVs from presetpatch.com, loaded through tape LOAD LOG
Why
Memory empty
Alternatives considered
Not recorded
Historical evidence lost
Any remaining previous patches inferred
I5

MIDI board power connection

  • Actionrepair (reconnect)
  • ReversibleFully inferred
  • Original keptn/a
Original part removed
—
Replacement
Leads to the OCP board +10 V (at a diode) and GND LOGVIDEO 20:40
Why
Board needs about 10 V GROOVEVIDEO
Alternatives considered
Hooking to a nearby 5 V point was first considered VIDEO 18:00; rejected because the 5 V rail lacked headroom for the extra 200 mA Restorer
Historical evidence lost
Original connection point to the original PSU’s bridge rectifier: no witness marks found VIDEO 19:32
I6

OCP board +10 V regulator

  • Actionother (add heatsink)
  • ReversibleFully inferred
  • Original keptn/a
Original part removed
—
Replacement
Heatsink cut down from a larger one VIDEO 22:06
Why
Retrofit instructions suggest heatsinking VIDEO 21:02
Alternatives considered
Not recorded
Historical evidence lost
None inferred
I7

MIDI board regulator

  • Actionsubstitute
  • ReversibleFully (inferred: pin-compatible)
  • Original keptYes, kept by RNA in labelled bags Restorer
Original part removed
7805 / LM340T-5 (maker and date code not recorded in the log)
Replacement
Recom R-78E5.0-0.5 switching regulator, 7–28 V in, 5 V 500 mA, 7805 pinout; RS 757-7239 LOG
Why
Regulator and supply running hot; board is all digital VIDEO 22:44–23:03
Alternatives considered
Not recorded in the log
Historical evidence lost
Not recorded
I8

MIDI board input cap

  • Actionreplace
  • ReversibleFully inferred
  • Original keptYes, kept by RNA in labelled bags Restorer
Original part removed
Original 10 V-rated cap (value, maker and date code not recorded)
Replacement
10 µF 35 V LOG
Why
Under-rated for a 10 V rail; datasheet calls for 10 µF LOGVIDEO 23:27
Alternatives considered
Not recorded
Historical evidence lost
Not recorded
I9

MIDI board output cap

  • Actionother (add)
  • ReversibleFully inferred
  • Original keptn/a
Original part removed
—
Replacement
10 µF 35 V Panasonic between the existing regulator output and earth holes LOGVIDEO 24:56
Why
Required by the Recom datasheet; none fitted LOG
Alternatives considered
Not recorded
Historical evidence lost
None
I10

Mains cable entry

  • Actionrepair
  • ReversibleFully
  • Original keptn/a
Original part removed
—
Replacement
Cable pulled through and clamp retightened LOG
Why
PAT test finding
Alternatives considered
Not recorded
Historical evidence lost
None
I11

Mains plug fuse

  • Actionsubstitute
  • ReversibleFully
  • Original keptYes, kept by RNA in labelled bags Restorer
Original part removed
13 A fuse
Replacement
3 A fuse LOG
Why
Rating appropriate to the instrument inferred
Alternatives considered
Not recorded
Historical evidence lost
None
I12

VCA gain trim (VR4)

  • Actionkeep (no adjustment)
  • Reversiblen/a
  • Original keptn/a
Original part removed
—
Replacement
—
Why
Quieter voice cured by the earth repair LOG
Alternatives considered
VR4 trim (service notes adjustment 5-1): not needed
Historical evidence lost
None

Testing: before and after

Test results before and after the repair
TestBeforeAfterSource
Continuity, 4051 pin 8 to groundOL (open)Continuity on both 4051sVIDEO 04:51, 07:04LOG
Chorus board pin 14 control voltageStepped and noisyNot recorded (no after measurement recorded)VIDEOLOG
Listening test (wobble)Wobble on every note"Sounds good"; everything workingVIDEO 07:34LOG
Voice levelsOne voice quieterCuredLOG
Patch save/recall with the new battery holder—Patches saved and recalledVIDEO 08:43–08:52
Factory patch loadLoad error (LOAD pressed too early)Load completedVIDEO 10:05–11:09
MIDI board bench test—8.00 V in, 5 V out, 0.193 A; clock pin 37; data activity; opto output OKLOGVIDEO
+10 V regulator temperature>70 °C LOG; 77.0 °C after about 1 hour VIDEO 22:48About 60 °C after 2 hours, lid shut LOGLOGVIDEO
Soak test—Several hours with MIDI streaming from Logic; hotspots 58.5–64.1 °C; DC-DC converter about 34 °C (spoken); MC6802 about 63–64 °CVIDEO 26:50–27:42LOG
MIDI board 5 V supply—5 V confirmedVIDEO 26:26
MIDI INNot workingWorkingLOGVIDEO 22:17
MIDI OUT—Working in MASTER mode (function button + B)LOGVIDEO 28:19
PAT testFault at the mains cable entryPassed after the cable fix RestorerLOGVIDEO
CalibrationNone performed. VR4 / service notes adjustment 5-1 judged unnecessary—LOG
Final sign-off"STATUS: COMPLETE, everything working, no open items" (30 Oct 2026)—LOG

Outcome

Final status

Complete. Everything working, no open items LOG.

Remaining issues
None recorded LOG.
Advice given to the owner
Not recorded as given to the owner.

Advice in the video, for viewers

  • Newer replacement power supplies may struggle to power older MIDI retrofits VIDEO 28:34.
  • Be careful changing the backup battery VIDEO 09:18.
  • Press LOAD after the leader tone VIDEO 10:18.

Likely future failures

  • The CR2032 backup cell will need replacing in time inferred.
  • The MC6802 on the MIDI board runs at about 63–64 °C, which may age it and nearby parts inferred.
  • The OCP board’s +10 V regulator still runs at about 60 °C (inferred risk).
  • The wire-linked earth repair on Panel Board A is the known weak area if the board is flexed inferred.

Time and cost

Hands-on time compared with documentation time (about 12 hours in total; unattended soak testing not counted)
Hands-on: diagnosis, repair and testing4 h
Documentation: filming, editing and writingabout 8 h

Documentation took about twice as long as the hands-on work.

Total time (all stages)
About 12 hours: 4 hours hands-on (diagnosis, repair and testing) plus about 8 hours of filming, editing and documenting Restorer. Unattended soak testing is not counted Restorer.
Diagnosis time
Not recorded separately; part of the 4 hours hands-on Restorer
Repair time
Not recorded separately; part of the 4 hours hands-on Restorer
Testing time
Not recorded separately; part of the 4 hours hands-on Restorer. The soak test (a couple of hours, then "hours" VIDEO 26:59–27:22) was unattended and is not counted Restorer.
Documentation: writing the log
Not recorded separately; within the 8 hours of filming, editing and documenting. Typed as the work went Restorer.
Documentation: filming
Not recorded separately; within the 8 hours Restorer
Documentation: editing
Not recorded separately; within the 8 hours Restorer. Finished video length is 29:35 VIDEO.
Parts cost
£10 Restorer. Parts: Recom R-78E5.0-0.5 (RS 757-7239), 2 × 10 µF 35 V capacitors, coin-cell holder and CR2032, heatsink, 3 A fuse, hook-up wire.
Did documenting slow the repair?
Typing the log as the work went felt comfortable and did not noticeably slow the repair. Most of the documentation time went on filming and editing Restorer.

Knowledge that is hard to write down

Much of a restorer’s skill lives in judgement, rules of thumb and the senses rather than in measurements. This part of the record tries to capture it, and is explicit about what it could not.

Where experience or instinct outweighed measurement

  1. Two buffered outputs that "shouldn’t" be identical led straight to "some kind of grounding issue", before any ground measurement was taken VIDEO 04:13–04:22.
  2. Choosing to remove Panel Board A and work "top down" as quicker than reverse-engineering from the other side VIDEO 02:51.
  3. Choosing wire links over trace repair for "a good solid connection" VIDEO 06:37.
  4. Choosing a DC-DC converter "because it’s only running digital anyway" VIDEO 22:50.
  5. Rule of thumb that a supply should have at least double the current required: about 500 mA drawn against a 590 mA limit, after the PSU shut down a couple of times, was judged too close Restorer.

Sensory cues

  • SoundThe wobble heard on a held note VIDEO 00:19; "that sounds good" at power-on VIDEO 07:34; the tape data heard during loading VIDEO 10:45.
  • Feel and sightThe damaged trace area "actually moving" when prodded VIDEO 06:20.
  • HeatMeasured with the FLIR, not by touch VIDEO.
  • SmellNot recorded.
Things found hard to record, or not recorded
Not recorded.
How documenting changed the way of working
Not recorded.

What to tell another restorer facing the same fault

  • If separately held sample-and-hold outputs look identical, check the multiplexer’s ground (4051 pin 8) for continuity before replacing chips (inferred from the case).
  • Press LOAD just after the leader tone starts LOG.
  • A newer replacement PSU may not supply an older MIDI retrofit VIDEO 28:43.
  • Be careful with the battery holder fit VIDEO 09:18.

Log, video, and neither

LogVideoNeither

The repair was documented two ways at once: a written log typed as the work went, and a filmed video. Comparing them shows what each method captures, and what slips through both.

Only the log captured

  • The serial number (305451)
  • The dead end: DC offset at C5/R14 that turned out to be a measurement error
  • The replacement CPU (D8049C-028) on Panel Board B
  • The OCP board’s silk-screen version (JU-6/60_PSU_3e) and trip ratings in writing (the label appears on screen)
  • The MIDI board details: EPROM "ju-6/v3.65", 74HC logic, SN74LS04, TIL111 part number, DCB mini-con wiring, full mode and operation summary
  • The Recom exact part number (R-78E5.0-0.5) and RS stock number
  • The input cap now 10 µF 35 V (the video calls it "the original cap")
  • The quieter voice cured by the earth repair
  • The envelope interference at minimum decay
  • The mains plug fuse change from 13 A to 3 A
  • The backup battery circuit details (D26/D27/C15, test points, below 2.5 V means memory loss)
  • The original PSU architecture (service notes p12)
  • The source URLs for the factory patches

Only the video captured

  • The previous technician’s suspicion of a multiplexer
  • Test-point pin headers fitted
  • The full scope sequence: VCA outputs, chorus board in/out, IC3 versus IC8 comparison, INH check, A/B versus outputs capture
  • Rail measurement at a ground point
  • The printed layout with highlighted earth traces
  • Microscope view of the damage
  • Power-on test of Panel Board A on the bench
  • Patch save/recall test
  • First tape load error
  • The demo section
  • An initial idea to hook the MIDI board to a nearby 5 V point
  • No witness marks found
  • FLIR readings at each stage (including 77.0 °C)
  • The heatsink cut down from a larger one
  • The soak test with MIDI streaming from Logic
  • The warning about newer PSUs and older MIDI retrofits

Neither captured

  • The replacement PSU shutting down a couple of times with the MIDI board on its 10 V
  • Reading the OCP board’s printed 590 mA limit
  • The "double the current" rule of thumb and the roughly 300 mA + 200 mA estimate

Recorded here only because the restorer supplied it directly Restorer.

Which captures the diagnostic reasoning better? Assessment, not a recorded fact

Each captures a different part.

The video is better at in-the-moment reasoning. It shows the identical outputs prompting the ground suspicion (04:13), the decision to trace the earth on a printed layout (05:04), and the wrong guess about tape-load timing being corrected (10:05–10:18).

The log is better at explaining causes and decisions. It explains why a floating multiplexer ground produced stepped control voltages, the warble, the envelope noise and the quiet voice. It records part numbers and current figures behind the regulator swap, and keeps the C5/R14 dead end, which the video leaves out.

Neither records timings, photos, or the alternatives considered in detail.

Tools, sources and the role of AI

Equipment VIDEOLOG

  • Rigol DS1054Z 4-channel oscilloscope, plus a second Rigol scope
  • Fluke multimeter
  • FLIR thermal camera
  • Bench power supply with V/A/W display
  • Hot-air rework station
  • Microscope and magnifier lamp
  • Logic Pro on a Mac with an audio interface
  • Genelec monitors
  • PAT tester inferred

Documents consulted

  • Roland Juno-60 Service Notes, First Edition, 10 April 1983 SN: chorus board, panel board, CPU board and power supply schematics; adjustment procedures
  • Printed Panel Board A copper layout, earth traces highlighted VIDEO 05:04
  • Groove Electronics Juno 6/60 MIDI Interface pamphlet GROOVE
  • Recom R-78E-0.5 datasheet VIDEO 23:08
  • RS Components listing, stock no. 757-7239 LOG
  • Factory patch WAVs from presetpatch.com LOG

Pages, diagrams and images from the Roland service notes and the Groove Electronics pamphlet are not reproduced here. They are cited as sources only.

Forums and earlier videos
Not recorded.
Advice received from other people
The owner and the previous technician identified the MIDI board as Groove Electronics VIDEO 20:24. The previous technician had suspected a multiplexer VIDEO 02:21.

The role of AI

Mainly routine reference lookups, such as which pin carries the clock, not diagnostic answers Restorer. Some AI-suggested hypotheses were tested and ruled out:

  1. Leakage through C5 or across the board at the VCF input (the offset was a measurement error)
  2. A polarity-inversion tip for loading patches from WAV (couldn’t be sourced; pressing LOAD after the leader tone was the actual fix)
  3. An "IC3 INH fault", read from a capture taken on the wrong probe pin
  4. Suspected scope-ground artefacts

About this record

How the record was made

This record was prepared on 30 October 2026 from the sources below and no others. The repair log was typed as the work went; the video analysis was prepared from YouTube metadata, automatic captions and about 80 sampled frames. The order follows the video timeline. Where the order isn’t recorded, it’s marked inferred.

Source badges

LOG
Juno-60 repair log, written as the work went (final version).
VIDEO
Analysis of the repair video https://youtu.be/sDFHMipudyw (prepared 30 Oct 2026 from YouTube metadata, automatic captions and about 80 sampled frames). Times are mm:ss into the video.
SN
Roland Juno-60 Service Notes, First Edition, 10 April 1983.
GROOVE
Groove Electronics "Juno 6/60 MIDI Interface" installation and operation pamphlet.
Restorer
Details supplied directly by the restorer on 30 Oct 2026.

Honesty conventions

Not recorded
The sources don’t say. Gaps are shown rather than filled.
inferred
A conclusion drawn from the sources rather than read directly.

Consent and anonymity

Owner consent to publication
Yes, the owner has consented Restorer
Named or anonymous
Anonymous: the case corrects a previous technician’s work Restorer. Neither the owner nor the previous technician is identifiable. The serial number (305451) is published with the owner’s permission, as proof of provenance Restorer.

Record details

Record
Case record 001
Date prepared
30 October 2026
Version
1.0
Permanent identifier (DOI)
To be assigned
Machine-readable copy
Download the record as JSON
Fields marked Not recorded (22)

Numbers refer to the parts of the original record.

  • 1 – Year or estimated year
  • 1 – Original mains voltage
  • 2 – Cosmetic condition
  • 2 – Photos taken (list)
  • 3 – Tool used for the C5/R14 measurement (step 1)
  • 4 – Cause of the ripped earth traces (F1)
  • 4 – Which voice was quieter (F1a); envelope line references (F1b)
  • 4 – Component class and cause for the empty memory (F6); backup battery voltage on arrival
  • 4 – Reference of the OCP board +10 V regulator (F3)
  • 4 – Cause of the loose mains cable (F7) and who fitted the 13 A fuse (F8)
  • 5 – Maker, value and date codes of the removed parts: original battery, 7805, 10 V input cap
  • 5 – Historical evidence lost (earth repair, regulator swap, caps)
  • 5 – Alternatives considered for the battery, patch reload, heatsink, regulator, caps and fuse
  • 5 – Whether the previous memory contents were dumped before reloading
  • 6 – Chorus board pin 14 control voltage after the repair
  • 7 – Advice actually given to the owner
  • 8 – Split of the 4 hands-on hours (diagnosis, repair, testing) and of the 8 documentation hours (log, filming, editing)
  • 9 – Forums and earlier videos consulted
  • Part 2 – Smell
  • Part 2 – Things found hard to record, or chosen not to record
  • Part 2 – How documenting changed the way of working
  • Part 4 – Commercially sensitive material
Fields marked inferred (16)
  • 1 – UK-market unit
  • 2 – Photos were taken but not catalogued
  • 3 – Step 1 positioned early in the sequence
  • 3 – PAT tester used (step 26)
  • 4 – F1 possibly mechanical damage or earlier rework
  • 4 – F3 design-weakness explanation
  • 4 – F4 design-weakness cause
  • 5 – Reversibility of I1, I3, I5, I6, I7, I8, I9
  • 5 – Replacing IC8 not pursued (I2)
  • 5 – Historical evidence lost: original battery and its solder joints (I3); previous patches (I4)
  • 5 – Heatsink loses no historical evidence (I6)
  • 5 – Reason for the 3 A fuse (I11)
  • 7 – All four "likely future failures"
  • Part 2 – Advice on checking 4051 pin 8 before replacing chips
  • Part 3 – Which record captures the reasoning better (an assessment)
  • 3 – Position of step 23 (PSU shutdowns) in the sequence