The Sinclair QL Forum

NormanDunbar wrote:

Cristian wrote: Scotty, beam me up!

Scotty was actually Irish! Well, the actor was. Mind you, in Highlander, the Scotsman was French and the Spaniard Scottish!

Cheers,
Norm.

James Doohan (Scotty) was Canadian

And just missed someone else's reply to the same - oops, sorry!

No worries. It appears he's Canadian of Irish parents. I was close!

Cheers,
Norm.

mk79 wrote:Pin 1 is near the plus-symbol. Pin 40 is the battery connection, which is why there is only a hole instead of a connection to the QL board.

Marcel, had a quick question. Looking at the QL schematic for the ZX8302, it seems that pin 40 is getting 5 volts but my little board uses a 3 voly CR2032. Since my little board replaces the pin 40 input for the ZX8302, how come it still works? Is pin 40 the only voltage input to the ZX8302 (I see that pin 11 is also getting it and the board does seem to make a connection with that as well, though it still gets connected through the socket so I guess it's getting voltage from both?!?)...couldn't find a pin out sheet for it to see what the pins are for.

Just curious what the little board is doing. Does it basically replace the QL's power with the button cell for the ZX8302 and then power the chip 24/7? If the button cell runs out of power, I'm guessing in that instance the QL stops working until I replace the battery. Also, one reason I ask is, since these chips are so rare, is it a good idea to power them indefinitely vs when you use the machine?

bwinkel67 wrote:Marcel, had a quick question. Looking at the QL schematic for the ZX8302, it seems that pin 40 is getting 5 volts but my little board uses a 3 voly CR2032. Since my little board replaces the pin 40 input for the ZX8302, how come it still works? Is pin 40 the only voltage input to the ZX8302 (I see that pin 11 is also getting it and the board does seem to make a connection with that as well, though it still gets connected through the socket so I guess it's getting voltage from both?!?)...couldn't find a pin out sheet for it to see what the pins are for.

The chip is powered through pin 11, pin 40 is a dedicated battery input that only powers the clock inside the chip.

Just curious what the little board is doing. Does it basically replace the QL's power with the button cell for the ZX8302 and then power the chip 24/7? If the button cell runs out of power, I'm guessing in that instance the QL stops working until I replace the battery. Also, one reason I ask is, since these chips are so rare, is it a good idea to power them indefinitely vs when you use the machine?

When the button cell runs out of power I guess your clock might stop ticking, but the chip should continue to work. I've never had a ZX8302 die on me, I wouldn't worry too much about it. The ZX8301 is much more problematic, I've got a graveyard of those.

By the way, there are much better re-created schematics like http://www.dilwyn.me.uk/docs/hardware/QLissue6.pdf which even fix some errors on the original.

Thanks for info and the schematic! I bet the pcb board's connection to pin 11 keeps the clock ticking when the battery is dead.

Yes, looks like the battery pin is powered through the diode when the QL is powered on.

Btw, I saw this design by Martin Head/Martyn Hill. It seems to be a bit more complex so I'm curious what it adds.

If you just supply power to the ZX8302. The clock will reset when you power the QL off and On. I guess that's why Sinclair never implemented it. There was space for the battery on the issue 5 boards.

I found that if you held down the reset button while powering down and powering up. Then with the battery backup, the clock kept the right time. Although sometimes it would still reset itself.

The extra circuitry just does a power down and power up reset, like holding the button down. As I remember (and it is 30 years ago) I lifted the power up/down circuit from somewhere else. I think it used a 3.3v rechargeable battery, That's the diode and resistor off the 5 volt rail. And I think the IC was an LM339.

I don't know where Martyn Hill found it, probably somewhere on Dilwyn's site. I think I first uploaded it to a Bulletin Board (Tony Firsham's?)

Martin_Head wrote:If you just supply power to the ZX8302. The clock will reset when you power the QL off and On. I guess that's why Sinclair never implemented it. There was space for the battery on the issue 5 boards.

The little board I have from Mechanical Affinity (a few pages back on this thread), which plugs in between the ZX8302 socket, and supplies 3 volts to the clock part, keeps time when powering off and on. It's pretty simple, with 2 caps, 2 resistors, and a diode. I think that circuitry is mostly for powering the clock via QL's power when plugged into mains.

bwinkel67 wrote:The little board I have from Mechanical Affinity (a few pages back on this thread), which plugs in between the ZX8302 socket, and supplies 3 volts to the clock part, keeps time when powering off and on. It's pretty simple, with 2 caps, 2 resistors, and a diode. I think that circuitry is mostly for powering the clock via QL's power when plugged into mains.

Right, but with only the board it will occasionally corrupt the time because on power-up/down spurious signals will be on the access lines and thus the clock will sometimes be overwritten with random data. All my QLs with battery powered clocks had additional circuitry somewhere ob the board to set RESET on those unstable conditions so the ZX8302 doesn‘t react to them.