Hi I have a ZX 81 power supply UK700 .
Can any body tell me what the output should be but NOT plugged in to a ZX81 .
The one i have is given out 16 V DC .
I know that a ZX81 needs 9v
Dave
ZX81 power supply
Re: ZX81 power supply
I believe the voltage drops under load, what load did you test this with?
Also as much as it is nice to keep these original I would seriously replace the PSU with a modern one. Not the easiest to find so I got a 9V one cut the cable and put a mono jack on it. Works great just be careful with polarity.
Also as much as it is nice to keep these original I would seriously replace the PSU with a modern one. Not the easiest to find so I got a 9V one cut the cable and put a mono jack on it. Works great just be careful with polarity.
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Re: ZX81 power supply
Hi Dave,
That’s normal. That type of power supply is unregulated. It only produces about 9V when the load draws 700mA (it’s rated maximum current) from it.
When connected to a ZX81, the 9V nominal voltage will be between about 10.5V to 12V.
The 7805 voltage regulator in a ZX81 can manage these voltages okay.
Mark
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Re: ZX81 power supply
Thanks mark
I should have asked it does not have a 9v plug on the power supply can you recommend one.
Dave
I should have asked it does not have a 9v plug on the power supply can you recommend one.
Dave
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Re: ZX81 power supply
For use with a ZX81, it needs to be a 3.5mm mono jack plug. Like the one second from left (above the “2” on the ruler) in this picture:
The positive needs to be wired to the tip (signal) contact and the negative to the GND/screen/shield connection.
Mark
The positive needs to be wired to the tip (signal) contact and the negative to the GND/screen/shield connection.
Mark
Standby alert
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: ZX81 power supply
Thanks Mark
You have been a great help
Dave
You have been a great help
Dave