Timex Sinclair 1000 worked briefly with new PS

[TS1000 Library User]

My Timex Sinclair 1000 previously displayed a rolling screen.
I switched the power supply to an Atari 2600 power supply and got a crystal clear image with the K (shielded RF cable).
As soon as I pressed a key the screen went black with columns of white dashes.
Trying again and also with a newer Atari 2600 PS and the original PS made no difference.

Any ideas what likely made it work briefly?

The old Atari PS was slightly over voltage but powers Atari consoles fine; did I cause a leaking capacitor to work again briefly with the extra current?

It was cool to see the prompt, hoping to type in some code if it is possible can get it running

[1024MAK]

Hello and welcome

All the circuitry for an unexpanded TS1000/ZX81 runs off the +5V DC supply from the 7805 voltage regulator. This in turn is supplied by the (nominal) +9V DC input.

A unexpanded TS1000/ZX81 should work if the input supply has a voltage of between 8V to 15V (see note #1 below) at sufficient current for the ZX81.

Most original power supply units (PSU) are rated at 600mA (0.6A) or 700mA (0.7A), but most TS1000/ZX81 boards only need between 400mA and 550mA (it depends on which types/makes of chips are used).

So if another PSU is used, if it has a current rating of 550mA (0.55A) or greater, that’s fine. A higher current rating makes no difference to the TS1000/ZX81, it will only draw the current it needs.

Note #1 - the limitation here is the voltage rating of the one or two (depending on board version) electrolytic capacitor(s) and the amount of heat that the 7805 voltage regulator and its heatsink has to dissipate. The 7805 generates a nice steady fixed output by “getting rid” of excess voltage by converting the electrical energy to heat. Hence as the input voltage is increased, more heat is generated by the 7805.

The situation may be different if you want to use expansions/interfaces.

I don’t know, and hence can’t answer why your machine worked and then when wrong when you pressed the keyboard. It’s possible that there is either a poor connection (maybe a chip not making good connection in a socket) or a poor/dry solder joint. Or maybe a cracked PCB track or one of the chips has an intermittent defect.

Of the two or three electrolytic capacitors inside, only one is essential (and that has a very easy life), so your fault is unlikely to be due to an electrolytic capacitor having become faulty.

Do you have a digital multimeter?

Which chips are in sockets? Have you tried pushing them in the middle of the top of the chip to check that they are fully pushed into the socket?

Do you only have one TS1000 or do you have another?

Mark

[TS1000 Library User]

Hello and welcome

All the circuitry for an unexpanded TS1000/ZX81 runs off the +5V DC supply from the 7805 voltage regulator. This in turn is supplied by the (nominal) +9V DC input.

A unexpanded TS1000/ZX81 should work if the input supply has a voltage of between 8V to 15V (see note #1 below) at sufficient current for the ZX81.

Most original power supply units (PSU) are rated at 600mA (0.6A) or 700mA (0.7A), but most TS1000/ZX81 boards only need between 400mA and 550mA (it depends on which types/makes of chips are used).

So if another PSU is used, if it has a current rating of 550mA (0.55A) or greater, that’s fine. A higher current rating makes no difference to the TS1000/ZX81, it will only draw the current it needs.

Note #1 - the limitation here is the voltage rating of the one or two (depending on board version) electrolytic capacitor(s) and the amount of heat that the 7805 voltage regulator and its heatsink has to dissipate. The 7805 generates a nice steady fixed output by “getting rid” of excess voltage by converting the electrical energy to heat. Hence as the input voltage is increased, more heat is generated by the 7805.

The situation may be different if you want to use expansions/interfaces.

I don’t know, and hence can’t answer why your machine worked and then when wrong when you pressed the keyboard. It’s possible that there is either a poor connection (maybe a chip not making good connection in a socket) or a poor/dry solder joint. Or maybe a cracked PCB track or one of the chips has an intermittent defect.

Of the two or three electrolytic capacitors inside, only one is essential (and that has a very easy life), so your fault is unlikely to be due to an electrolytic capacitor having become faulty.

Do you have a digital multimeter?

Which chips are in sockets? Have you tried pushing them in the middle of the top of the chip to check that they are fully pushed into the socket?

Do you only have one TS1000 or do you have another?

Mark

Thank you!

Great information on the TS1000. I will try to seat the chips, I can see one socketed under the board.

It looks like I have to remove an allen bolt to access the chipset?

I have an analog multimeter.

This is my only TS1000.

It appears to be in excellent condition and the video was impressively clear as a Monitor over my shielded RF cable for the brief instant.

[mrtinb]

I belive there are two regular philips screw that connect the pcb to the top case. Be careful with the brittle keyboard connector, when you remove the pcb.