Why? I would agree that this problem sounds like a capacitor problem (I would want to make sure the relateively low-frequency vertical sync pulses were getting to the appropraite point, and I'd also want to be sure thete was no mains ripple on the supply lines that could be confusiogn the sync circuitry), but I realyl don't find the all 10 eyar ole (or all 40 year old for that matter) electrolytics are defective. No, torubleshoot first. It may be a capacitor, but you can't be sure unless youtrace the signals and find out what is actually wrong. The CM8833 (al lversions) has a swtich-mode PSU (on a separate PCB to the rest of the monitor). -tony

On 30/01/12 13:43, Jules Richardson wrote: Two for two, Jules... Damaged connector on the monitor side of the cable, *AND* a broken wire inside the cable (monitor side again). This thing's been slammed against a wall at some point in its life. Hardly surprising seeing as it's an ex-school machine. The broken wire killed one of the colour channels, turning the picture magenta. The broken pin killed the sync, but only some of the time. Reseating the cable got the sync to work (ish), but wiggling it buggered up the colour. Said cable has now been replaced with a homebrew cable made from a couple of DE9 connectors and shells and some 6-core screened cable. Little hint for anyone thinking of using the pinouts in the A3000 Service Manual and Acorn Application Note 249 to make a cable. The diagram on AN249 page 4 has the pins mirrored. Assuming you're using the pin numbers on the back of the DE9 socket, the pinout for the AKF17 is: 1. Blue 2. Green 3. Red 4. n/c 5. GND 6. n/c 7. n/c 8. Composite sync 9. n/c Connector on the monitor is a DE9 plug (male), so you want a socket (female connector) to make a cable. The A3000 also uses a DE9 but of the opposite gender. Pinout is: 1. Red 2. Green 3. Blue 4. HSync or CSync If LK24 is set 2-3, you get CSYNC. If it's set 1-2, you get HSYNC. 5. VSync or Mode If LK25 is fitted, you get VSync. If not, you get MODE (required for SCART cables) 6, 7, 8, 9: All GND To get the machine to talk to the AKF17 -- Hold numpad 0. Power on. F12 *Configure Sync Auto *Configure MonitorType 0 Enter Hit the RESET button. Enjoy! Jobs for later: new power switch on the monitor, find or buy an Acorn mouse, seeing as the PS2MouseMini adapter won't fit in the socket on an A3000... :-( -- Phil. philpem at philpem.me.uk http://www.philpem.me.uk/

On Jan 31, 2012, at 3:24 PM, Tony Duell wrote: The same applies to power cords: the electronics store near my parents' house in Baltimore (similar idea to what Radio Shack used to be, back when it was really Radio Shack) will sell me a power cord with a wall plug on one end and exposed wires on the other for $5. It will sell me an otherwise identical extension cord for $2. A pair of cutting pliers is the great equalizer. :-) - Dave

On Feb 1, 2012, at 4:00 PM, Tony Duell wrote: Yeah, the MegaDrive (called the Genesis over here) had DE9 connectors. It seemed like an odd choice in an era when Nintendo used much more durable and convenient (but much less standard) proprietary connector for theirs. Either one was better than Nintendo's Famicom (the original Japanese version of the NES), which had hard-wired controllers. - Dave

Not suprising... IIRC, they won't fit the mouse socket on the back of an A300/A400 leybaord either, at least not without cutting them. My A310 came (second-hand) without a mouse. At the time, Maplin sold quadrature mice as spares for the ST and Amiga (one was 2 button, the otehr was 3 button, and they had different connectiosn to the DE9 IIRC). So I bought the 3 button one of those, cut the DE9 off and soldered the wires to a 9 pin mini-DIN ARGH!. What made it even more ARGH! was that of coruse Ididn't know which way round the quadrature signals had to be (wich is X1 and which is X2, for example), so I had to swap over a couple of pairs of wires. Moving wires in the mdidle of an already-soldered mini-DIN is a lot worse than DMD rework :-) Ouch!... I did find a CPC-branded 'replacement' mouse for the Archmedes in a chraity shop many years a go, No, I am not sellign it :-) This will annoy you, but my WHitechapel MG1 came not only with the original Depraz mouse (misisng some of the buttons -- Digitast rocker button swithces on the front), but also with an Acorn mouse that had had the 9 pin mini-DIN cut off and been rewired to a DE9 plug to fit the MG1. I repired the original mouse (I had some suitable switches in the junk box, and the buttons just clop on) but of course I also kept the Acorn one. But it's no use on an Acorn machine any more. Are those pads at a suitalbe spacing to fit some kind of plug to the PCB (e.g. a Molex KK)? If so, fit it and make whatever plug-in adapter you need... I agree. I hade mini-DINs, They are painful to wire, and don't make good contact even when new. Are they really a DIN standard, or are they named miniDIN simply becuase they look like a smaller version of the well-known audio conenctor? -tony

ARGH! That's not pleasant... I asume the next workpiece that drill was used on was your (ex?-) friend ;-) Is this the clipped-togheter membranee keyboard that Acorn used at one point? If o, I thin it comes apart from the bottom (unclip the metal backing plate, then take off the memberane layers). The LEds have their leadouts bent over the keyboard moulding and come into contact with pads on one of the membrane sheets. It's worth making sure it;s not contact trouble between the LED and the seeht before you replace them. True :-) It's just a pity the origianl ownder didn't just replace the switch caps on the Depraz mouse. At least he kept said mouse and gave it to me with the machine. Do RS no longer do them? I';ve not looked for years... It's possibel I have 1 or 2 in the junk box, but it'd take me some time to dfidn them. And they'll be the massive solder-on type. Watch out.. As you must know by now, there are 2.5mm pitch and 0.1" pitch connecotrs, and it matters on something with 9 or 10 pins... Right... Yes, but you know how to clear those (heat from one side, suck from the other). The connector isn;t too bad, athough I wish the isulator round the pins was made of a plastic with a higher melting point. Often at least one pin moves out of the right position when you solder them. But the standrd audio wirign has the same problems as RS232 only worse. The original 3 pin DIN was used to link a tape recorder to an amplifier (mono) using a straight-through cable. This menas that pin 1 is an output on the amplifier and an input on the recorder (signal to record), pin 3 is an output o nthe recordfer and an input on the amplifier (palyback signal) and pin 2 is ground, Ok so far... The problem comes when it's used fro things that aren't ampliifers or recorders. At least one respected manufacturer says a singal source should output on pin 3 if it's intended ot conenct to an amplidier, and ouput on pin 1 if it's intended to connect to a tape recorder. How the heck should I (as the designer of said signal sourve) know what it's likely to be conencted to. Of course if the pinout is wrong you can wire a corssover cable. Stereo doens't make matters any worse. There were 2 more pins added, pin 4 betwee npins 1 nad 2 and pin 5 between pins 3 and 2. The orignal pins 1 and 3 carry the left cahnnel signals, the new pins carry the right channel signal in the same direction as the adjacent pin. So no extra problems So it's like the null-modem problem with RS232, but worse i nthat all chassis connectors are sockets. So you can't tell by looking which way it's wored (withRS232 , a DTE shoudl be male, a DCE should be female fo course). I think I'd have used a 240 degree one there. It's less likely to get mis-connected to an audio device. :-). Indeed... There are some phone plubs with a sliding sleeve on the outside so tha the froudn makes first, but they are not common... Indeed. The _original_ use of the jack plug, on telephone switchboards, was quite sensible, in that it made use of the fact you could touch the tip of a plug to the sleeve (mouting bush) of a socket. An operator would do that wit hte plug of the interconneing cable to the socket of the lien to be connected to, and if there was a click in the operator's headset, it meant the line was in use (voltage on the sleeve connection). The oriignal wiring of the 4 pole Plug 420 was sensible too. It was used for the operator's headset (mouthpiece and headphones), the headphoens were connected between tip and sleeve (ring nearest to the body), so they were not conencted until the plug was fully home -- so no clicks as the plug contacts touched other contacts in the socket But dont;' get be started on the wiring of Plug 420 and Plug 505 for British telephones (this is sort-of on-topic becuse the latter was used for Viewdata sets). I have found 15 wiring schemes so far... A telephone is wired differnetly to am answering amchine which is wired differnetly to a fax machine. Heck a telephone for 1 phone-at-a-time plugged in is wired differnetly to a telephone wired for several-phones-plugged-in-at-ocne...ARGH. I have this little multi-way switchbox to sort it all out... But not for audio... My biggest moan ins that there is no compatibiltiy between mono and stereo. If you plug a 2 conecutor plug into a 3 conductor socket, you end up shortign the ring on the socket to the sleeve. This normally means groudn ign the right channel. Not good if it's the output of an amplifier. -tony

Is that _all_ you hurled at him? I would have thought a medium-sized mains transformer would be a suitable missile here :-). Even more so if it has exposed connections and is plugged in at the time... Soudns like the Acorn membrane one. I may be confusing it with something else (I've had hundreds of keybaords o nthe bench over the yers...) but there's one where there's a plastic key greap with little plastic hooks that fit through slots in the metal bakcing plate. You can carefully free each hook with a small screwdriver (start in one corner) and lift the metal plate off. Yes. It just all clips back together again if it's the one I am thinking of. Of course you have to be careful not to break the plastic hooks, but breaking one or two won't make too much difference Many are heat-staked, which makes life difficult. I've never managed to reassemble an LK201, for example. The IBM Type M can be done (yes, that's a membrane keybaord), but you have to drill out the old stake posts on the plastic chassis, tap them, and fit machine screws with nuts on the underside. It's only worth doing because it's a Type M. On the other hand, the membrane keyboard in the Tandy CoCo 2 and 3 is assembled with lots of small self-tapping screws. It comes apart and goines back together with few problems. And I've eseen severa; cheap PC-clone keybaords where the membrane layers are held together by the case (these keyboards have many screws on the bottom), again, you can take them apart and put them together again (but it's questionable if it's worth it :-)). Take the keyboard apart, clean the membeane pads and the LED leads with a Q-tip and propan-2-ol. For obvisou reasons don't try to solder to the membrane sheet... And surely you know how to test LEDs... (analogue ohmmeter, some DMM diode test ranges, battery and resistor, etc) I often use an offcut of stripboard or a DIL socket/IC for this.... Sure. I do much the same thing (although I probably have a suitable socket in the junk box, remember that a 6 pi nsocket will take a 5 pin 'B' plug, and an 8 pin circular socket will take 3, 5A and 7 pin plugs too. I have a small metalwork vice on my electronics bench for criming IDC sockets, holdign things when soldering, etc. I've never needed the helping hands, I cna normally hold the cable by hand when soldering to a DIN plug. Even if I do end up with burnt fingers... I can't rememebr where I saw them, but it was one of the well-known connector manufacturers who made them. Sure... But if the slding sleeve foe fail, the thing still works as a normal phono plug, so you are no worse off. You don't live in my workshop... ;-0 -tony

Right :-) I would love to see you melt PTFE with a noraml soldering iron :-) In other words, it depends on the plastic. But the melting point of keyboarf membrane sheets, at least all the ones I've seen, is much lower than that of normal soft solder. I've seen it, I don't have one. The doucmentauton is IMHO inadequate for such a complex device. If I need to know more aobut a transistor/diode than a simple multimeter test will tell me, then I fire up the Tekky 575... Right... I use an analogue meter for this. On the Ohms*1 range it'll light every LED I've tried. However, even if the DMM doesn't pass enpugh current to get a decent glwoe from the ELD, it will display its forware votlage drop (I assume you have a 3+3/4 digit meter). And that will pick up open-circuit LEDs. Ah, OK... I've never needed one (or the 'helping hands' which I think I haev somewhere, but haven't use since the day I was given them). I have got quite good at holding a PCB between middle and 3rd fingers of my left hand, using the little finge to suppor the component, thumb and index finger to feed i nthe soder while my right hand holds the soldering iron... Oh, I know where mine are, in the same toolbox as the modualr plug crimp tool. The latter gets quite a bit of use, but I prefer to crimp ICD connectors in the vice. That's who I was going to say, but I didn't have any way of checking... I think an ECL86 would be preferable for that application. -tony

On Jan 30, 2012, at 7:32 PM, Philip Pemberton wrote: Defender? :-) I'd sell one of my two board sets, but I haven't verified the sound board properly yet. Otherwise, they're working and output both composite and regular sync (selectively invertible). Of course, someone makes a JAMMA harness for it, so I suppose you could consider it a subset of the above. - Dave

IIRC the true CM8833 has an internal PAL decoder. The Acorn version doesn't, but it's the same PCB, just with lots of components not fitted and maybe a few links. If you get the full service manual (yes, I know you're looking for it), you cna probalby add the decoder. Findign soem of the bits might be interesting, it'll involve raiding old TV sets for the delay line a(and maybe even the ICs now). Juast about anything given a scan converter :-) -tony