Blue tint video issue

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Airshack
Posts: 6
Joined: Fri Feb 26, 2021 1:34 am

Blue tint video issue

Post by Airshack »

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:
342798CE-E8B8-4FB1-A22D-0DB0697EBC70.jpeg
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:
ADF36EE9-E6A5-4AF8-AE20-8469EE4B4615.jpeg
EDIT: The motherboard indicates "Z70833, 1988, Issue 2" which I suppose means model +2B. The boot screen reads, "128 +2A." The unit is Black.
Last edited by Airshack on Sat Feb 27, 2021 2:13 am, edited 1 time in total.
Airshack
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Joined: Fri Feb 26, 2021 1:34 am

Re: Blue tint video issue

Post by Airshack »

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.
Last edited by Airshack on Sat Feb 27, 2021 2:16 am, edited 2 times in total.
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1024MAK
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Re: Blue tint video issue

Post by 1024MAK »

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... :roll:

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
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ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

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Airshack
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Joined: Fri Feb 26, 2021 1:34 am

Re: Blue tint video issue

Post by Airshack »

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
Last edited by Airshack on Sat Feb 27, 2021 2:17 am, edited 1 time in total.
Airshack
Posts: 6
Joined: Fri Feb 26, 2021 1:34 am

Re: Blue tint video issue

Post by Airshack »

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:
IMG_4480.jpg
IMG_4482.jpg
Maybe the SCART-to-HDMI unit failed?

All guesses accepted and appreciated.
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1024MAK
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Re: Blue tint video issue

Post by 1024MAK »

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
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: 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.
User avatar
1024MAK
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Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: Blue tint video issue

Post by 1024MAK »

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
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: 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.
Airshack
Posts: 6
Joined: Fri Feb 26, 2021 1:34 am

Re: Blue tint video issue

Post by Airshack »

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
Last edited by 1024MAK on Sat Feb 27, 2021 11:11 am, edited 1 time in total.
Reason: Edited to tidy up quote tags
Airshack
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Joined: Fri Feb 26, 2021 1:34 am

Re: Blue tint video issue

Post by Airshack »

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.
hellraiseruk
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Joined: Tue Oct 12, 2021 5:58 pm

Re: Blue tint video issue

Post by hellraiseruk »

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
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