EMS 256 Full Log

VIDEO 1

Video 1: https://youtu.be/i2raXXpRmVM

Chapters 9 Length 9:26

  1. Intro – stuck on start/stop
  2. The power supply & back panel
  3. Inside: Nixie tube & card rack
  4. The power supply board
  5. Removing the cards
  6. Testing & replacing the caps
  7. Checking the voltage rails
  8. First power-up – it runs!
  9. Speed control & what's next
VIDEO 2

Video 2: https://youtu.be/p_OIijiahJs

Chapters 10 Length 15:20

  1. Intro – no recording, no pitch
  2. Pulling the cards
  3. Triggering now works
  4. Testing the layers
  5. Memory test with the BeatStep
  6. Matching schematics to boards
  7. Plan: making extender cards
  8. Board-by-board fault finding
  9. Six faulty ICs on the A-to-D board
  10. The full chip list & plan
VIDEO 3

Video 3: https://youtu.be/jV81WAPKQW0

Chapters 7 Length 10:13

  1. Intro – every IC now socketed
  2. What's working now
  3. Faulty chips board by board
  4. Designing an extender card in KiCad
  5. Pin-outs from the schematic
  6. Ordering with the PCBWay plugin
  7. Why make extender cards?
VIDEO 4

Video 4: https://youtu.be/b7SfifstXm8

Chapters 15 Length 19:59

  1. Intro – the extender boards arrive
  2. First fit test
  3. Fitting board E on an extender
  4. Power-on & probing the clock board
  5. Checking board F timing signals
  6. Comparing working & faulty layers
  7. Layers one & three working
  8. Layer two: a 5V rail fault
  9. Oops – capacitor on the wrong rail
  10. Test rig setup
  11. Recirculation board signals
  12. Probing the memory boards
  13. Missing shift register input
  14. Removing the time extender – it records!
  15. Wrap-up
VIDEO 5

Video 5: https://youtu.be/XHgoqLrZ_kg

Chapters 8 Length 12:41

  1. Recap of the series
  2. The faulty 7404
  3. Moment of truth
  4. Setting up three oscillators
  5. Recording via external clock
  6. Playback on internal clock
  7. Demo
  8. Thanks & wrap-up

Really Nice Audio · Repair case records

Case record 004: EMS 256 Sequencer: restoration

A retrospective record of one repair, reconstructed after the work.

Retrospective record

Retrospective: reconstructed after the work was finished from the five videos' YouTube titles, descriptions and chapters, and the restorer's answers. The video captions have not been added, so some details are Not recorded.

This page is a structured record of one repair: the fault, how it was traced, every decision taken, and what was kept, repaired or replaced, so that the work can be checked, repeated and learned from.

Bench time
7 hours
Parts
£200
Videos
5
Outcome
Records and plays back

Record prepared 7 November 2026 · Version 1.0 · About this record · Download as JSON

The videos

Video series "EMS 256 Sequencer Repair" by Really Nice Audio, 5 videos: https://youtube.com/playlist?list=PLKcEnsx2qcDw

Video inventory
#TitlePublishedLengthSummary
1EMS 256 Sequencer Repair Part 19 July 2026 (YouTube publish date)9:26The power supply is checked and its capacitors replaced; at first power-up it runs VIDEO 1
2EMS 256 Sequencer Repair Part 2 – Re-Capping the Circuit Cards20 July 2026 (YouTube publish date)15:20The cards are pulled and re-capped; triggering works and the memory fills with a key input; six faulty ICs are found on the A-to-D board and a repair plan is made VIDEO 2
3EMS 256 Sequencer Repair Part 310 August 2026 (YouTube publish date)10:13Every IC is socketed and almost 20 faulty ICs are found; an extender card is designed in KiCad and ordered from PCBWay VIDEO 3
4EMS 256 Sequencer Repair Part 416 August 2026 (YouTube publish date)19:59With the extender boards the clock, timing, recirculation and memory boards are probed; removing the Time Extender Board makes it play back recordings VIDEO 4
5EMS 256 Sequencer Repair Part 5 – Finale1 September 2026 (YouTube publish date)12:41A faulty 7404 is found; recording on an external clock and playback on the internal clock, then a demo VIDEO 5

Titles, lengths, publish dates and chapters as shown on YouTube on 7 November 2026.

The instrument

Identity and provenance

Instrument
EMS 256 Sequencer
Serial number
6014 Restorer
Collection
Part of the Pete Townshend Synth Collection VIDEO 1
Owner
Pete Townshend (inferred from the collection name VIDEO 1)
Location
University of West London, the Townshend Studio VIDEO 1VIDEO 3VIDEO 5
Restorer
Really Nice Audio (RNA)

What was wrong

Condition on arrival

Stuck on start/stop VIDEO 1. After the power supply work it ran, but would not record and gave no pitch VIDEO 2. Cosmetic condition and other symptoms on arrival: Not recorded.

The diagnostic path

Diagnostic sequence

  1. 1
    The power supply and back panel were looked at, then the inside of the unit: the Nixie tube and the card rack VIDEO 1.
  2. 2
    The power supply board was examined, the cards were removed, and the capacitors were tested and replaced VIDEO 1.
  3. 3
    The voltage rails were checked VIDEO 1.
  4. 4
    At first power-up it ran. The speed control was looked at and the next steps outlined VIDEO 1.
  5. 5
    It still would not record and gave no pitch. The cards were pulled and re-capped, after which triggering worked VIDEO 2.
  6. 6
    The layers were tested, and a memory test with a BeatStep showed the memory filling up with a key input VIDEO 2.
  7. 7
    The schematics were matched to the boards, and the plan became making extender cards and fault-finding board by board. Six faulty ICs were found on the A-to-D board, and a full chip list was drawn up VIDEO 2.
  8. 8
    Every IC was socketed and everything that could be tested was tested. Almost 20 faulty ICs were found VIDEO 3.
  9. 9
    An extender card was designed in KiCad, using pin-outs from the schematic, and ordered from PCBWay VIDEO 3.
  10. 10
    With the extender boards, board E was fitted on an extender, the clock board was probed at power-on and board F's timing signals were checked VIDEO 4.
  11. 11
    Working and faulty layers were compared. Layers one and three worked; layer two had a 5 V rail fault, and a capacitor was found on the wrong rail VIDEO 4.
  12. 12
    On a test rig, the recirculation board signals and the memory boards were probed, and a shift register input was found missing VIDEO 4.
  13. 13
    After the recirculation circuits and shift registers had been checked, the Time Extender Board was removed, and the sequencer then recorded and played back VIDEO 4.
  14. 14
    A faulty 7404 was found, and the I/O scaling was worked out until it was correct VIDEO 5.

The Time Extender Board: Part 4 ends with more research on this board planned VIDEO 4. The board had a faulty logic IC, which had measured fine when it was first examined Restorer. Whether the board was refitted is Not recorded.

Faults and causes

  • Stuck on start/stop on arrival VIDEO 1; cause Not recorded.
  • No recording and no pitch VIDEO 2.
  • Faulty logic ICs: six on the A-to-D board VIDEO 2, and almost 20 in total once every IC was socketed and tested VIDEO 3. Which ICs: Not recorded in this record (the videos go through them board by board).
  • Layer two: a 5 V rail fault VIDEO 4.
  • A capacitor on the wrong rail VIDEO 4; whether it was fitted that way during this repair is Not recorded.
  • A missing shift register input VIDEO 4.
  • With the Time Extender Board fitted, recordings did not play back VIDEO 4. Cause: a faulty logic IC on the board, which had measured fine when first examined Restorer.
  • A faulty 7404 VIDEO 5.

The decision record

Decision record
ActionOriginal partReplacementReasonAlternativesReversible?Original kept and where
Replace the power supply capacitors VIDEO 1Not recordedNot recordedThey were tested first VIDEO 1; result Not recordedNot recordedNot recordedYes: labelled bags Restorer
Re-cap the circuit cards VIDEO 2Not recordedNot recordedNot recordedNot recordedNot recordedYes: labelled bags Restorer
Socket every IC VIDEO 3ICs soldered in (inferred)IC socketsSo the ICs could be tested VIDEO 3Not recordedNot recorded—
Replace faulty ICs (almost 20) VIDEO 3Not recordedNot recordedFound faulty VIDEO 3Not recordedNot recordedYes: labelled bags Restorer
Make extender cards VIDEO 3VIDEO 4—Extender cards designed in KiCad, made by PCBWay VIDEO 3So the circuits could be probed while working VIDEO 4Not recordedYes: a test aid, not fitted permanently (inferred)—
Share the extender card design VIDEO 3——If the design proved correct, so other owners could order their own VIDEO 3———
Correct the capacitor on the wrong rail VIDEO 4Capacitor on the wrong railNot recordedWrong rail VIDEO 4—Not recorded—
Remove the Time Extender Board VIDEO 4Time Extender BoardNoneAfter the recirculation and shift register checks; with it removed, it recorded and played back VIDEO 4Not recordedYes (inferred)Not recorded
Replace the faulty 7404 VIDEO 5 (inferred)7404Not recordedFaulty VIDEO 5—Not recordedYes: labelled bags Restorer
Set the I/O scaling VIDEO 5——Not recorded—Not recorded—

Testing

  • Voltage rails checked after the power supply work; values Not recorded VIDEO 1.
  • Memory test with a BeatStep: the memory was seen filling up with a key input VIDEO 2.
  • Layers tested VIDEO 2; working and faulty layers compared on the extender boards VIDEO 4.
  • Final test: three oscillators set up, a recording made on an external clock and played back on the internal clock, then a demo VIDEO 5.

Outcome

Outcome

Working: it records on an external clock and plays back on the internal clock, shown in the Part 5 demo VIDEO 5. Original parts kept in labelled bags Restorer. Whether the Time Extender Board was refitted is Not recorded.

Time and cost

Time
7 hours Restorer
Parts
£200 Restorer; itemised breakdown Not recorded
Labour cost
Not recorded
Dates
arrival Not recorded; Part 1 published 9 July 2026 and Part 5 on 1 September 2026, so the work ran over about eight weeks (inferred); completion on or before 1 September 2026 (inferred)

Tools, sources and the role of AI

  • Seen in the chapter titles: a BeatStep (memory test), KiCad (extender card design), PCBWay (extender cards made), a test rig, the schematics, an external clock and three oscillators for the final test VIDEO 2VIDEO 3VIDEO 4VIDEO 5.
  • Oscilloscope: Rigol 1054Z Restorer. Other test equipment: Not recorded.
  • Schematics: used to match boards and take pin-outs VIDEO 2VIDEO 3; which edition or source is Not recorded.
  • AI in the repair: none Restorer.
  • AI in this record: the record was compiled with the help of Claude (Anthropic) from the videos' YouTube titles, descriptions and chapters. and the restorer's answers. Every fact comes from those sources.

Sources

  • Video series "EMS 256 Sequencer Repair" by Really Nice Audio, 5 videos: https://youtube.com/playlist?list=PLKcEnsx2qcDw
  • The videos' YouTube titles, descriptions and chapters, as shown on 7 November 2026
  • The restorer's answers, 7 November 2026 Restorer

Knowledge that is hard to write down

  1. Work out a repair strategy before diving in: the restorer found this the hardest part VIDEO 2.
  2. Making PCBs was essential to moving the repair forward Restorer: the extender cards let the circuits be probed while the cards were working VIDEO 4.
  3. A part that measures fine can still be faulty: the Time Extender Board's logic IC passed its first check Restorer.
  4. Expect worn-out logic in a unit this old: almost 20 faulty ICs turned up once every chip was socketed and tested VIDEO 2VIDEO 3.

What was captured

The videos captured

the diagnosis, each stage of the repair, the extender cards and the final recording and playback test.

The restorer's answers add

the serial number, the owner's consent, time and cost, that the originals are kept in labelled bags, the faulty logic IC on the Time Extender Board, the oscilloscope used, and that no AI was used in the repair.

Neither captured (in this record)

the arrival date, the part numbers and the list of ICs replaced, the voltages measured, the cause of the start/stop fault and whether the Time Extender Board was refitted.

About this record

How the record was made

Retrospective: reconstructed after the work was finished from the five videos' YouTube titles, descriptions and chapters, and the restorer's answers. The video captions have not been added, so some details are Not recorded.

Sources

  • Video series "EMS 256 Sequencer Repair" by Really Nice Audio, 5 videos: https://youtube.com/playlist?list=PLKcEnsx2qcDw
  • The videos' YouTube titles, descriptions and chapters, as shown on 7 November 2026
  • The restorer's answers, 7 November 2026 Restorer

Source badges

VIDEO n
Video n of the series "EMS 256 Sequencer Repair" by Really Nice Audio: its YouTube title, description or chapters.
Restorer
The restorer's answers, 7 November 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.

Publication and consent

Owner
Yes, the owner has consented to publication Restorer.
Custodian
the University of West London, the Townshend Studio VIDEO 1.
Third parties
PCBWay is named as the maker of the extender cards VIDEO 3VIDEO 4VIDEO 5.
Documents
No schematics, manuals or other copyrighted documents are reproduced; they are cited as sources only.

Record details

Record
Case record 004
Date prepared
7 November 2026
Version
1.0
Permanent identifier (DOI)
To be assigned
Machine-readable copy
Download the record as JSON

Gaps and unverified items

Not recorded (11)
  • Arrival date
  • condition apart from the symptoms
  • labour cost
  • itemised parts cost
  • part numbers of the capacitors and ICs replaced
  • which ICs were faulty
  • voltages measured
  • the alternatives considered
  • the cause of the start/stop fault
  • whether the Time Extender Board was refitted
  • other test equipment
Inferred (7)
  • The owner's name, from the collection name
  • that the ICs were soldered in before socketing
  • that the extender cards are a test aid, not fitted permanently
  • that removing the Time Extender Board is reversible
  • that the faulty 7404 was replaced
  • the length of the work
  • the completion date
Other open items (2)
  • The video captions are still to be added.
  • Publish dates are as YouTube gives them (US Pacific time).