Sinclair ZX80 / ZX81 / Z88 Forums

After receiving my first Sinclair Spectrum 128 +2, I was overjoyed to see it was operating normally. Unfortunately, a few weeks later it’s producing this blue-tinted output:
I’d greatly appreciate any ideas you may have as to solving this issue. My system was tested blue with multiple NTSC/US LCD monitors via this SCART cable and SCART-HDMI box:
EDIT: The motherboard indicates "Z70833, 1988, Issue 2" which I suppose means model +2B. The boot screen reads, "128 +2A." The unit is Black.

EDIT: This cable is labelled for the +2A, +2B and +3 models, version 2.3. It was working fine on my +2 the first few times I used it. This was the cable I received with the unit. I'm new to the Spectrum so I know very little.

Okay, before you get carried away...

There are officially only two models of the +2, but as it’s Amstrad, it’s a bit more complex...

So, what is the colour of the case? Black or dark grey?
Does it use a 9V power supply unit (PSU) fitted with barrel power plug or a power supply that outputs +5V, +12V and -12V fitted with a DIN plug?

A +2 in a grey case with a 9V PSU fitted with barrel power plug is known as a +2 (grey). These need a 128K / +2 SCART cable. E.g, like this one: Sinclair ZX Spectrum+ 128K & +2 (Grey Model) RGB Scart Lead.

A +2 in a black case with a PSU that outputs +5V, +12V and -12V fitted with a DIN plug is either a +2A or a +2B (see the bottom of the case). These need a +2A / +2B / +3 SCART cable. E.g, like this one: Sinclair ZX Spectrum +3, +2A, +2B High Quality RGB Scart Lead.

Other sellers of suitable video cables are available. The above are just examples.

Mark

After opening the computer up and doing a little research it appears I have a BLACK +2B model due to the motherboard reading: Z70833, 1988 Issue 2.
Source may be dubious since boot screen indicates +2A.

Now the unit is producing video which is yellow-ish and keeps switching on and off, cutting in and out. Perhaps I need to perform the RGB SCART blanking signal mod?

It appears I am using the proper RGB-to-SCART cable as I have the +2A or +2B model.

The most strange portion of this mystery is everything was working fine a few weeks ago with the same components:
Maybe the SCART-to-HDMI unit failed?

All guesses accepted and appreciated.

Airshack wrote: ↑Sat Feb 27, 2021 1:58 am After opening the computer up and doing a little research it appears I have a BLACK +2B model due to the motherboard reading: Z70833, 1988 Issue 2.
Source may be dubious since boot screen indicates +2A.
IMG_5168.jpg

Both the +2A and the +2B report “+2A” on screen because they can use the same ROM chips.

Mark

Airshack wrote: ↑Sat Feb 27, 2021 2:01 am Now the unit is producing video which is yellow-ish and keeps switching on and off, cutting in and out. Perhaps I need to perform the RGB SCART blanking signal mod?

It appears I am using the proper RGB-to-SCART cable as I have the +2A or +2B model.

The most strange portion of this mystery is everything was working fine a few weeks ago with the same components:

Maybe the SCART-to-HDMI unit failed?

All guesses accepted and appreciated.

Sounds like the function switching inputs on your HDMI box are detecting what they consider to be a marginal voltage level. Hence the erratic symptoms.

Mark

1024MAK wrote: ↑Sat Feb 27, 2021 2:26 am Sounds like the function switching inputs on your HDMI box are detecting what they consider to be a marginal voltage level. Hence the erratic symptoms.

Weird how it worked fine a few weeks ago when I first hooked it up. Looks like the parallel R44 resistor mod is in order then?

https://www.retrocomputershack.com/Tec ... ex.html


Thanks Mark

Turns out I simply had a bad (new) HD converter unit which is brilliant news! The R44 mod didn't make a difference so I ordered a second HD converter.

You'll probably find the HDMI converter failed due to overheating - it's an idea to dismantle them and put heatsinks on the 2 main chips inside, and if possible drill some holes in the outer case to allow for airflow...

JD