ZX Spectrum +2 Repair (No. 4). Plus a look at methods of improving picture quality. JoulesperCoulomb 2014-03-07 | Following the repair of a simple fault, this video describes the display output options offered by the (grey cased) ZX Spectrum +2 and the modifications that might be necessary to use some of them. Finally, a couple of modifications that may improve the quality of the composite video signal produced by this computer are examined.
TEAC A-R600 Amplifier Repair. Part 1. JoulesperCoulomb 2016-12-21 | TEAC A-R600 Amplifier Repair. Part 1.
Experiments in Powering a Diesel Engines Glow-Plug JoulesperCoulomb 2015-10-16 | Experiments in Powering a Diesel Engine's Glow-Plug. Another example of calculations using the relationships between current, voltage, resistance and power.Similar: youtube.com/watch?v=beG78EXlXkw
ZX81 Video Conditioning JoulesperCoulomb 2015-07-15 | ZX81 Video Conditioning. Two circuits are presented that can improve the video output of ZX81 computers, particularly of those that contain a ULA that does not generate a back porch following each line synchronisation pulse.A document containing the circuit diagrams and stripboard layout can be downloaded at http://zx.zigg.net .
Hitachi HA-4800 Amplifier Repair. Part 2. JoulesperCoulomb 2015-05-16 | Hitachi HA-4800 Amplifier Repair. Part 2.Replacing indicator lamps. Adjusting output stage quiescent current. Testing ASO (monitoring) circuit. Final testing.Part 1: youtube.com/watch?v=GPrIdu1SYpA
Hitachi HA-4800 Amplifier Repair. Part 1. JoulesperCoulomb 2015-05-15 | Hitachi HA-4800 Amplifier Repair. Part 1.Overview of the HA-4800's circuit and how it compares to the HA-4700. Diagnosing a power supply fault.Part 2: youtube.com/watch?v=qCVrsUTuo4U
ZX Spectrum Initialisation and Investigating Initialisation & Memory Faults using a Logic Analyser JoulesperCoulomb 2015-04-16 | 16/48K ZX Spectrum Initialisation...plus an example of using a logic analyser to investigate initialisation and memory faults.A look at the first few steps taken by the ZX Spectrum's firmware when the computer is switched on, followed by an example of how using a logic analyser to study this process can help uncover the source of faults.
ZX Spectrum +2 Repair. (No. 7). Part 6. JoulesperCoulomb 2015-03-19 | ZX Spectrum +2 Repair. (No. 7). Part 6. Resolution of the memory access fault, checking the joystick interface and putting it all back together.PART 1: youtube.com/watch?v=gNEdJMUA-2gPART 2: youtube.com/watch?v=nLCi4da3f1gPART 3: youtube.com/watch?v=qUIv-A_DOc0PART 4: youtube.com/watch?v=yY-TBLP9vWcPART 5: youtube.com/watch?v=ySaAENniLKU
ZX Spectrum +2 Repair. (No. 7). Part 5. JoulesperCoulomb 2015-03-10 | ZX Spectrum +2 Repair. (No. 7). Part 5. Continued investigation of the intermittent RAM access fault and of the organisation of the +2's RAM. This part probably won't make much sense if you haven't already watched part 4.PART 1: youtube.com/watch?v=gNEdJMUA-2gPART 2: youtube.com/watch?v=nLCi4da3f1gPART 3: youtube.com/watch?v=qUIv-A_DOc0PART 4: youtube.com/watch?v=yY-TBLP9vWcPART 6: youtube.com/watch?v=FY6UdjkBdLc
ZX Spectrum +2 Repair. (No. 7). Part 4. JoulesperCoulomb 2015-03-09 | ZX Spectrum +2 Repair. (No. 7). Part 4. The start of a somewhat prolonged investigation of what seems to be an intermittent RAM access fault, miscellaneous repairs and a look at the hardware that implements the +2's memory paging.PART 1: youtube.com/watch?v=gNEdJMUA-2gPART 2: youtube.com/watch?v=nLCi4da3f1gPART 3: youtube.com/watch?v=qUIv-A_DOc0PART 5: youtube.com/watch?v=ySaAENniLKUPART 6: youtube.com/watch?v=FY6UdjkBdLc
ZX Spectrum +2 Repair. (No. 7). Part 3. JoulesperCoulomb 2015-01-30 | ZX Spectrum +2 Repair. (No. 7). Part 3. Changing the ROM. Overhauling the cassette player and repairing its broken keys. Re-balancing the volume levels of audio outputs. Adding an external audio input for loading software from phones, laptop computers, etc.PART 1: youtube.com/watch?v=gNEdJMUA-2gPART 2: youtube.com/watch?v=nLCi4da3f1gPART 4: youtube.com/watch?v=yY-TBLP9vWcPART 5: youtube.com/watch?v=ySaAENniLKUPART 6: youtube.com/watch?v=FY6UdjkBdLc
The Importance of Matching Series Wired Light Bulbs (...and why Xmas lights stay on when one fails.) JoulesperCoulomb 2015-01-06 | The Importance of Matching Series Wired Light Bulbs (...and why Xmas lights stay on when one fails.)P.S. Please tell me if you know where 12 V, 1 W miniature screw based bulbs as seen in this video can be obtained from.
ZX Spectrum +2 Repair. (No. 7). Part 2. JoulesperCoulomb 2014-12-08 | Repair of a (grey cased) ZX Spectrum +2. Part 2. Testing the serial I/O ports and adjustments & modifications to improve the RF and composite video outputs.I apologise for the slightly croaky voice at times during this video.PART 1: youtube.com/watch?v=gNEdJMUA-2gPART 3: youtube.com/watch?v=qUIv-A_DOc0PART 4: youtube.com/watch?v=yY-TBLP9vWcPART 5: youtube.com/watch?v=ySaAENniLKUPART 6: youtube.com/watch?v=FY6UdjkBdLc
ZX Spectrum +2 Repair. (No. 7). Part 1. JoulesperCoulomb 2014-12-07 | Repair of a (grey cased) ZX Spectrum +2. Part 1. Initial investigation, PCB repair and problems with the switching voltage converter circuit.PART 2: youtube.com/watch?v=nLCi4da3f1gPART 3: youtube.com/watch?v=qUIv-A_DOc0PART 4: youtube.com/watch?v=yY-TBLP9vWcPART 5: youtube.com/watch?v=ySaAENniLKUPART 6: youtube.com/watch?v=FY6UdjkBdLc
48K ZX Spectrum Repair. (No. 6) JoulesperCoulomb 2014-10-07 | Troubleshooting and correction of several faults, including a failed transistor and some circuit board problems.
Philips PM 3214 Oscilloscope Repair. Part 4. JoulesperCoulomb 2014-09-22 | Part 1: youtube.com/watch?v=iPYzzsRXaMYPart 2: youtube.com/watch?v=AcoqsxT7xCQPart 3: youtube.com/watch?v=zPLBcDFB5gAThe final part. Fitting optional features and making it look nicer.
16/48K ZX Spectrum with Lower RAM Removed JoulesperCoulomb 2014-09-02 | This is the display a 16/48K ZX Spectrum should produce when it has had all its lower RAM ICs removed.
48K ZX Spectrum Repair (No. 5) JoulesperCoulomb 2014-09-02 | This one had an unusual and frustrating to track down fault.The memory test program used can be found at http://zx.zigg.net
Philips PM 3214 Oscilloscope Repair. Part 3. JoulesperCoulomb 2014-06-21 | Part 1: youtube.com/watch?v=iPYzzsRXaMYPart 2: youtube.com/watch?v=AcoqsxT7xCQPart 4: youtube.com/watch?v=cqFtjEkYTNoThis time: adjustment and verification, getting the mains supply working and improving the method of graticule illumination.
Philips PM 3214 Oscilloscope Repair. Part 2. JoulesperCoulomb 2014-04-11 | Part 1: youtube.com/watch?v=iPYzzsRXaMYPart 3: youtube.com/watch?v=zPLBcDFB5gAPart 4: youtube.com/watch?v=cqFtjEkYTNo
Philips PM 3214 Oscilloscope Repair. Part 1. JoulesperCoulomb 2014-04-10 | Part 2: youtube.com/watch?v=AcoqsxT7xCQPart 3: youtube.com/watch?v=zPLBcDFB5gAPart 4: youtube.com/watch?v=cqFtjEkYTNo
ZX Spectrum Hardware Description JoulesperCoulomb 2014-03-18 | A technical introduction to the ZX Spectrum hardware.A lot of research went into verifying the information presented here. Please add a note below in the unlikely (I hope) event of noticing a mistake.
Dismantling the Hitachi D-85S Cassette Deck JoulesperCoulomb 2014-02-26 | You'll likely only find this of interest if you need to repair or service one of these. This video is here as a note on how to dismantle some parts of this unit.
48K ZX Spectrum Repair (No. 3) JoulesperCoulomb 2014-02-17 | A brief look at another very common type of fault.
ZX Spectrum Power Supplies JoulesperCoulomb 2014-01-19 | A description of the main types and where they should and shouldn't be used. Includes suggestions for reducing the heat generated inside the ZX Spectrum and for repairing a broken cable strain relief. Finishes with a series of tests to measure how several ZX Spectrum power supplies perform.IMPORTANT NOTE: UK700 power supplies: There is reason to think these were sometimes supplied with early ZX Spectrum computers, but the vast majority were shipped with the UK1400 model. In most cases a 16/48K ZX Spectrum can be powered by a UK700 supply, provided the Spectrum has NO device connected to its expansion connector, though a very basic joystick interface probably won't cause a problem. However, a UK700 supply will be highly stressed, operating close to its maximum capacity when powering a ZX Spectrum and so may be more prone to failure. There is quite a bit of variation in power consumption between different examples of 16/48K ZX Spectrums and in keeping with the Sinclair cost-cutting philosophy, the power supplies aren't of the highest quality, meaning some particular combinations of ZX Spectrum and UK700 supply may not work. If at all possible, a UK1400 or later supply should be used.
48K ZX Spectrum Repair (No. 2) JoulesperCoulomb 2013-12-23 | Investigation and repair of one of the most common types of fault to affect 48K (and 16K) ZX Spectrums.The ZX Spectrum lower RAM (4116) replacement module is available here: http://zx.zigg.net/LRR
Replacing Electrolytic Capacitors in a ZX Spectrum JoulesperCoulomb 2013-10-17 | Links:Basic tests to carry out on a 16/48K ZX Spectrum: http://www.youtube.com/watch?v=IzgCmldm2H4World of Spectrum forums: http://www.worldofspectrum.org/forums
Hitachi HA-4700 Amplifier Repair - Part Two JoulesperCoulomb 2013-10-06 | Part one: http://www.youtube.com/watch?v=d4z1uQrMRpsRelated: Hitachi HA-4800 repair: youtube.com/watch?v=GPrIdu1SYpA
Hitachi HA-4700 Amplifier Repair - Part One JoulesperCoulomb 2013-09-17 | The first part of the investigation of a faulty Hitachi HA-4700 integrated stereo amplifier.Part two: http://www.youtube.com/watch?v=GuyJjAbi7tYRelated: Hitachi HA-4800 repair: youtube.com/watch?v=GPrIdu1SYpA
48K ZX Spectrum Repair (No. 1) JoulesperCoulomb 2013-09-01 | Some of the steps in the repair of a 48K ZX Spectrum that did not produce any video output. It was sent to me by a member of the worldofspectrum.org forums who had been unsuccessful in his attempts to repair it.
Assembling the ZX Spectrum Upper RAM Module JoulesperCoulomb 2013-07-26 | See here for more information on this device: http://www.worldofspectrum.org/forums/showthread.php?p=713732#1Installation instructions: http://zx.zigg.net/URR/ZXURR-Installation_Instructions.pdf
Removing Components from a Double-Sided Through-Hole Plated (ZX Spectrum) Circuit Board JoulesperCoulomb 2013-07-25 | This video is mainly aimed at those wanting to remove RAM ICs from a ZX Spectrum, but may be of help to anyone wanting to remove components from a circuit board.If you're removing 4116s from a ZX Spectrum, then this device may be of interest to you: http://zx.zigg.net/LRRThe ZX Spectrum upper RAM module is also now available. Pending a proper web page, see here for details: http://www.worldofspectrum.org/forums/showthread.php?p=713732#1
Repairing a ZX Spectrum+ Reset Switch. JoulesperCoulomb 2013-07-19 | I've since found that now and then the new rubbery insert would turn itself and become squashed down beside the new switch, preventing it from working. This problem seems to be cured by making sure that what was its outward facing protuberance (oo-er!) is cut off perfectly flush and the newly created flat surface placed face down against the new switch.
ZX Spectrum (48K & 16K) Initial Tests JoulesperCoulomb 2013-03-20 | If you've got a 48K or 16K ZX Spectrum computer and you aren't certain it is in proper working order, carry out the tests demonstrated here BEFORE you switch it on.If one or more of the 4116 ICs in your ZX Spectrum is faulty, then this modern replacement module may be of use to you: http://zx.zigg.net/LRR
