Recapped +2 - RF Colour bleed appears worse

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WDeranged
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Recapped +2 - RF Colour bleed appears worse

Post by WDeranged »

So I took the time to fully recap my grey +2 and it appears that the colour bleed on the RF output is worse, RGB is as clear as ever. I was very methodical and I've triple checked everything, looks fine.

Am I being paranoid or is it possible one of the new caps I fitted was a dud? Do the electrolytic caps even affect image quality? They're Nichicon branded and I got them from what seems to be a reputable ebay merchant.

I did notice that some of the caps were a different voltage to the ones coming out of the machine but as far as I'm aware this isn't a big deal. I also had one extra 100uf cap left over. I'm thinking maybe some units came with an electrolytic cap in place of a ceramic somewhere?

I'm kinda bummed that I've not seen any noticeable improvement in image or sound quality from the recap, shows what excellent condition this speccy was in.

Here is a list of the replacement caps.

4 x 1uf 50v
1 x 4.7uf 25v
1 x 10uf 25v
5 x 22uf 16v
2 x 47uf 16v
3 x 100uf 25v
2 x 220uf 16v

1 x 1uf 50v
1 x 10uf 25v
1 x 22uf 25v
1 x 100uf 25v
1 x 470uf 10v

Suitable for 128K Grey +2 Issue 3 models ONLY.
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RMartins
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Re: Recapped +2 - RF Colour bleed appears worse

Post by RMartins »

Nichicon, are some of the best caps out there, if they are not fake (most probably are not).

Without a picture is difficult to evaluate what you are seeing, but in a general if the output is still RF, it's going to have noise, no matter what.

You might want to mod the RF into a composite video out, since it's very simple to do, and you can find the instructions easily online.
But since this is a +2 and you already have RGB and a cable to use it, you may also want to leave the RF output as original.
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WDeranged
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Re: Recapped +2 - RF Colour bleed appears worse

Post by WDeranged »

RMartins wrote:
Thu May 14, 2020 9:45 pm
Nichicon, are some of the best caps out there, if they are not fake (most probably are not).

Without a picture is difficult to evaluate what you are seeing, but in a general if the output is still RF, it's going to have noise, no matter what.

You might want to mod the RF into a composite video out, since it's very simple to do, and you can find the instructions easily online.
But since this is a +2 and you already have RGB and a cable to use it, you may also want to leave the RF output as original.
Here is a quick snap of the RF output. What jumps out at me is how much worse the blue smearing is, the yellow is also slightly worse than before the recapping. I'm adverse to removing the RF as I actually find the sound output far more pleasing (more bass) than the jack output.

Image
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RMartins
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Re: Recapped +2 - RF Colour bleed appears worse

Post by RMartins »

Are you using any modern power brick ?
A switched-mode power supply .
i.e one of those that are small and have an high frequency oscillator inside ?

I have experienced a lot of interference, with some of the cheap ones.
Usually some kind of wave going down or up the screen.

But usually they don't affect much the color.

Are you sure you didn't force any of the legs of those new capacitors you replaced, that it might be broken, or even have a bad solder joint, because you might no have cleaned the old solder properly ?

Have you tried to re-seat the ULA after cleaning its contact pins ?

Do you have the RGB cable also connected at the same time ?

Have you tried another TV ?

You can always try, and check if the power is stable at the PAL video encoder chip.
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Ast A. Moore
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Re: Recapped +2 - RF Colour bleed appears worse

Post by Ast A. Moore »

WDeranged wrote:
Thu May 14, 2020 5:51 pm
I'm kinda bummed that I've not seen any noticeable improvement in image or sound quality from the recap, shows what excellent condition this speccy was in.
It rather shows that 128K Spectrums rarely benefit from recapping. That is, if we’re talking blindly replacing the electrolytics, which are just crude power filtering devices. They only filter out low-frequency ripple, and unlike in the 48K Speccy, replacing them will hardly produce any noticeable effect.

If you truly want to improve the picture quality—particularly the color banding, you’ll need to improve the characteristics of the color delay line of the TEA2000 or filter out the higher frequencies that find their way into the luma signal and can be misinterpreted by the TV as color information.

Here’s a great and very detailed guide on how to achieve this:



(If the video doesn’t start there automatically, the relevant segment begins at 18:26.)
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Guesser
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Re: Recapped +2 - RF Colour bleed appears worse

Post by Guesser »

On the plus side you can play Chromatrons Attack :D
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Ast A. Moore
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Re: Recapped +2 - RF Colour bleed appears worse

Post by Ast A. Moore »

Guesser wrote:
Wed May 20, 2020 2:17 pm
On the plus side you can play Chromatrons Attack :D
Indubitably! :lol:
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Every man should plant a tree, build a house, and write a ZX Spectrum game.

Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.

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