Zx Spectrum 128k +2 POWER on

[elmanoduarte]

hi all,,,

I have buyed a 2nd hand Zx Spectrum 128k +2 (grey version)

I think it supose to work with a power Suplly 9 Volts with 2 or 3 ah.
But when I connect it , the RED LED does not power UP.
I have read about the L78S05CV Chip, it makes the 9v tension to 5v.
I m not shore how to mesure it wih the multimeter!
I ´ll let here 2 Pictures, if someone could give me please some advices to get the conclusion if if is this L78S05CV it gone, or not!

best regards for all.

[1024MAK]

The original PSU (Power Supply Unit) is an unregulated type. 9V is just the nominal value when the PSU is supplying its maximum rated current.

Here are it’s specifications:

ZX Spectrum +2:
* Input: 220V to 240V AC, 50Hz
* Output: 9V (nominal) DC 2.1A
* Output polarity: outside is positive (+), inside is negative (-)(inner diameter is 2.1mm)


A ZX Spectrum +2 (grey) should work with an input voltage of 8V to 12V.

The details in this post may help.

Is the polarity correct on your PSU?

Mark

[elmanoduarte]

Hi,, many thanks for your very good answer.
In fact there was 2 problems!
The 1st its the 78S05 its was burned!
The 2nd the polarity from the Power Suplly was wrong, the + was in the center pole, and has you said,, center must be - (negative).
After a new 78S05 and new heat Thermal mass, it comes to life at all starts!

has you know this Grey Version 9V, was made more than 1 coutry, like in China, others in Taiwan, this model I think is from China,
many years ago saw a model like this one, but from TAIWAN,, and the 9v input system could not hand with inverted polarity, it damages the board,
This from China, the 78S05 when stoped work, i think it worked like a protetion.


Best regards, for all.
And thank you very much

[1024MAK]

Good to hear that you have it working now

The grey +2 was definitely made in both the U.K. and Taiwan. See this site for details (alternative link).

Mark

[elmanoduarte]

Hi,, thank you very much.
Yes, your abolutly rite....Tawian and UK.
And the one I hade was from UK. Now i have a Taiwan.
In that tine mine was gone becsuse an inverted polarity. It never turned no more. A local tecnic in that time tould me the biard was all afected, and was very hard for me with 16 y old loose 1 of the bestt things i had. And my dad could not buy me another.
This one. I have now, so far i know was an inverted polarity to, but it starts and its working,
But it could have a problem or not.
Have opened a new post because of it.

Best regards.
Duarte