Hang on whilst I just clear my throat COUGH COUGH switching reg switching reg COUGH COUGH.
Who left this here?....
http://uk.farnell.com/tracopower/tsr-1- ... dp/1696320
Not sure where you are in the world but you get the idea,9v regulated wall warts also good and am loving that thin profile fan.
With Marks blessing,I hope, I include one of his excellent posts explaining why the damn thing runs so hot.
The thread can be found here.
viewtopic.php?f=7&t=2201&p=22570&hilit=heat+sink#p22570
QUOTE.
"Postby 1024MAK » Sat Jan 21, 2017 8:27 pm
Using ZX81 2C184E and 2C210E ULAs as an example, These are most likely Ferranti ULA 2000 series very high speed CML (Current-Mode Logic cell) types, that have the following specs: max. clock speed 20MHz, gate delay 8ns, gate current 210µA, matrix size 15 x 15 x 1, total matrix cells 225, total peripheral cells 40.
The CML type has a Vcc to suit the logic it is interfacing to (3.5V to 5.5V). The peripheral cells run directly from this supply. The CML matrix cells use a 0.95V supply and are fed via on chip series voltage regulators. If required, the regulators can have their own supply pin (Vreg), in which case the input supply voltage can be between 1.3V and Vcc to minimise power dissipation without compromising speed. Otherwise (like in the Sinclair ZX81 design) both are fed via the same power pin (the ZX81 ULA only has a single positive power supply pin).
As well as the regulator circuitry, a large power consumer is the peripheral cells.
To construct a logic gate, one or more CML matrix cells are needed:
Buffer =1 cell
2 input NAND gate = 1 cell
3 input NOR gate = 1 cell
monostable = 2 cells
data latch = 3 cells
binary divider with preset and clear = 3 cells
D-type flip-flop with preset and clear = 6 cells"
It seems it doesn't help having all the ULA's connected up instead of the 3/4 internal connection recommended by Farranti.
As a final curiosity in the last thirty odd years my only ULA failures (as far as I can ascertain) have been from clumsy power on/off whilst attaching peripherals and never sudden failure through heat damage so the ULA is probably more hardy than we give it credit for and its scarcity is what gives us cause for concern not its fragility and if truth be told none of the chips inside the 81 run hot enough to warrant heat-sinking (damn I promised I wouldn't start ranting about heat-sinks again).