Gary C
Veteran Member
Got given two of these machines in a poor state. Cases open, keyboard hanging out and no PSU or video cable.
PSU nocked up from an AT PSU as this machine needs a -5V as well as a +5V and +12V
First machine powered up on UHF and my really old LCD won't take it. RGB nocked up and I get a very faint ghostlike display but at least its working. More investigation and its because I haven't put any power to pin 16 of the scart plug and the TV thinks its composite video being sent to it. Had a spare lead at the museum that has a +5v from the adjacent port to pin 16 and now a nice clear display, yay
Second unit, no such luck. Missing a bank of memory. The working unit has some 4564 and I just happened to have 8 4164's on stock which are equivalent, replaced and away we go. Two beeps and the Lynx logo on the screen.
Also a burning smell ? nothing appears to be hot and its still running ? Humm... However the cursor is happily moving across the screen by itself. Plug a keyboard in and it responds to presses but still with almost but not quite random spaces. Looking at the drawing, the keyboard bus comes through a 74LS244 buffer and touching it, the blanks have gone. Close inspection and the topside of the board, the float solder hasn't sucked up the legs and the top pads on three pins are dry. I have seen this a number of times recently (the ACT Sirius disk interface) and is something to look out for. Seems like poor wetting of the via not allowing good capillary action.
Liberal application of some good rosin flux and reflowed.
Oh, and I found the source of the burning. The machine 'de-modified' itself. It looks as if this unit had a jumper wire from +5V to the RGB socket, probably to make a scart plug work but with a more elegant single plug solution. Must have shorted out with the retrocomputing dual plug
So thats two working units.
The disk interface is interesting. It used an interface that just contained a ROM with the disk operating system and an actual interface with a FD1793 on board. Never seen a set for sale but someone has produced Gerbers and the IC's used aren't rare so have ordered the parts
PSU nocked up from an AT PSU as this machine needs a -5V as well as a +5V and +12V
First machine powered up on UHF and my really old LCD won't take it. RGB nocked up and I get a very faint ghostlike display but at least its working. More investigation and its because I haven't put any power to pin 16 of the scart plug and the TV thinks its composite video being sent to it. Had a spare lead at the museum that has a +5v from the adjacent port to pin 16 and now a nice clear display, yay
Second unit, no such luck. Missing a bank of memory. The working unit has some 4564 and I just happened to have 8 4164's on stock which are equivalent, replaced and away we go. Two beeps and the Lynx logo on the screen.
Also a burning smell ? nothing appears to be hot and its still running ? Humm... However the cursor is happily moving across the screen by itself. Plug a keyboard in and it responds to presses but still with almost but not quite random spaces. Looking at the drawing, the keyboard bus comes through a 74LS244 buffer and touching it, the blanks have gone. Close inspection and the topside of the board, the float solder hasn't sucked up the legs and the top pads on three pins are dry. I have seen this a number of times recently (the ACT Sirius disk interface) and is something to look out for. Seems like poor wetting of the via not allowing good capillary action.
Liberal application of some good rosin flux and reflowed.
Oh, and I found the source of the burning. The machine 'de-modified' itself. It looks as if this unit had a jumper wire from +5V to the RGB socket, probably to make a scart plug work but with a more elegant single plug solution. Must have shorted out with the retrocomputing dual plug
So thats two working units.
The disk interface is interesting. It used an interface that just contained a ROM with the disk operating system and an actual interface with a FD1793 on board. Never seen a set for sale but someone has produced Gerbers and the IC's used aren't rare so have ordered the parts
