Sinclair ZX80 / ZX81 / Z88 Forums

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Regulated 7.5v definitely makes a huge difference on my ZX80 compared to my Sinclair PSUs. Hard to say how much cooler the switching regulator in my ZX81 is. Maybe worth trying that as a first step towards a cool running system?

britain4 wrote:Regulated 7.5v definitely makes a huge difference on my ZX80 compared to my Sinclair PSUs. Hard to say how much cooler the switching regulator in my ZX81 is. Maybe worth trying that as a first step towards a cool running system?

I agree with Mark, having fitted switching regs to my ZX80 and 81's I have to say they make a world of difference in comparison to the standard regs, but that's as far as I go.

Swapping CPU's to save a few milliamps and a few degrees in temp' is pointless over-kill for what it achieves, to my mind, but that is just me so each to their own way of thinking.

But to keep it in perspective we're not talking argon arc furnace temperatures here and whatever you do please don't heat-sink the ULA unless you mount the board free to air or find a way to pass air through the case, as in such an enclosed environment with no air movement whatsoever the heat-sink/ULA junction with its piss poor thermal interface will more than likely reflect heat back into the chip as it fails to reach thermal equilibrium because of a poor thermal interface now made poorer by having a slab of metal bunged on top,nor will it convect once the small amount of surrounding air heats up, plus neither the ROM or CPU generate enough heat to warrant heat-sinking anyway.

If you'll pardon the pun a lot of folk get heated up re zeddy cooling and for something that wallops less than an amp it really isn't worth worrying about just use and enjoy.

Moggy wrote:

britain4 wrote:Regulated 7.5v definitely makes a huge difference on my ZX80 compared to my Sinclair PSUs. Hard to say how much cooler the switching regulator in my ZX81 is. Maybe worth trying that as a first step towards a cool running system?

I agree with Mark, having fitted switching regs to my ZX80 and 81's I have to say they make a world of difference in comparison to the standard regs, but that's as far as I go.

Swapping CPU's to save a few milliamps and a few degrees in temp' is pointless over-kill for what it achieves, to my mind, but that is just me so each to their own way of thinking.

But to keep it in perspective we're not talking argon arc furnace temperatures here and whatever you do please don't heat-sink the ULA unless you mount the board free to air or find a way to pass air through the case, as in such an enclosed environment with no air movement whatsoever the heat-sink/ULA junction with its piss poor thermal interface will more than likely reflect heat back into the chip as it fails to reach thermal equilibrium because of a poor thermal interface now made poorer by having a slab of metal bunged on top,nor will it convect once the small amount of surrounding air heats up, plus neither the ROM or CPU generate enough heat to warrant heat-sinking anyway.

If you'll pardon the pun a lot of folk get heated up re zeddy cooling and for something that wallops less than an amp it really isn't worth worrying about just use and enjoy.

Fair enough! I know it made a huge difference on the Sinclair PSU but never compared it directly with the 7805 on 7.5v

I did heatsink my ULA a few years back when I bought the Zed but I'm thinking of removing it after reading that.

I did fit a new Z80 due to one failing but had to go back to an NMOS due to it causing timing issues. Although the 'old' chip is warmer to touch I don't think it made a blind bit of difference to internal temps

Well. I didn't mean to spark such a heated debate!

I was just curious about whether the comment on the web site about it running cooler were valid! A lot learned about what works for reducing heat output though. I would like to keep my zeddy running for as long as possible (once I get it sorted at least) so i suspect running cool will help that.

Lardo

Lardo Boffin wrote:Well. I didn't mean to spark such a heated debate!

These kind of debates can get religious sometimes.

There is a couple of pictures showing how I mounted a Recom switching regulator on an issue 1 board in this post.

Mark

I only find wilfs wait in "this post"

Paul wrote:I only find wilfs wait in "this post"

Sehen Sie sich die Bilder an, Paul.

Lardo Boffin wrote:Well. I didn't mean to spark such a heated debate!

I was just curious about whether the comment on the web site about it running cooler were valid! A lot learned about what works for reducing heat output though. I would like to keep my zeddy running for as long as possible (once I get it sorted at least) so i suspect running cool will help that.

Lardo

Change the reg as that is the biggest culprit and don't worry about the rest, Sinclair may have boasted that the 81 could run a nuclear power station but it sure as hell doesn't run as hot as one!