SNES THS7374 Mod on a 1CHIP-02 Question

jcaston83 · Post by **jcaston83** » Sat Mar 17, 2018 1:27 pm

I'm familiar with the benefits provided by the THS7374 mod to the SNES 1CHIP-03 and the SNES Mini. However, I'm curious about the benefits received from installing it into a 1CHIP-02. Most of the videos and discussions I find only discuss how it works with the aforementioned two but not much is said about the 1CHIP-01 or the 1CHIP-02.

I have the 1CHIP-02. Should I get the mod?

Thanks!

maxtherabbit · Post by **maxtherabbit** » Sat Mar 17, 2018 6:08 pm

if you want to get your hands dirty on a 1chip, you might be better served by spending your time on this

Syntax · Post by **Syntax** » Sat Mar 17, 2018 11:08 pm

I have a 1chip 01 stock amp c11 r3 replaced and a mini ths7374 c11 r3 replaced,

I personally wouldn't amp a 1chip, they already produce an awesome picture.

FBX · Post by **FBX** » Sun Mar 18, 2018 1:37 am

If you use a Framemeister, don't amp the 1CHIP. Just add 750 Ohm pull-down resistors to the RGB lines and you're good to go. If you go with a bypass amp, you're likely to see aliasing black jail bar lines in the picture. These don't show up on the OSSC (when video LPF is set to 9Mhz or "Auto"), but they do show up on the FM.

Syntax · Post by **Syntax** » Sun Mar 18, 2018 1:40 am

FBX wrote:If you use a Framemeister, don't amp the 1CHIP. Just add 750 Ohm pull-down resistors to the RGB lines and you're good to go. If you go with a bypass amp, you're likely to see aliasing black jail bar lines in the picture. These don't show up on the OSSC (when video LPF is set to 9Mhz or "Auto"), but they do show up on the FM.

Even if the LPF on the bypass is turned off??

leonk · Post by **leonk** » Sun Mar 18, 2018 5:15 am

many rgb bypass sellers have the lpf off by default. hence the noise on xrgb. The mini has a lpf but not strong enough. I keep lpf on mine but in essence it converts 7374 to 7314.

snes stock amp is more like the 7314 where it has a sufficient lpf for the xrgb mini.

Xaranar · Post by **Xaranar** » Mon Mar 19, 2018 11:23 am

Syntax wrote:I have a 1chip 01 stock amp c11 r3 replaced and a mini ths7374 c11 r3 replaced,

I personally wouldn't amp a 1chip, they already produce an awesome picture.

I can see why you would replace C11, as I have done so in my Mini, but why replace R3? And what with?

Syntax · Post by **Syntax** » Mon Mar 19, 2018 12:04 pm

You replace R3 instead of adding 3 resistors to RGB output to attenuate brightness. I think its around 1.7k ill check when home and edit.

Link83 · Post by **Link83** » Mon Mar 19, 2018 12:55 pm

Xaranar wrote:
Syntax wrote:I have a 1chip 01 stock amp c11 r3 replaced and a mini ths7374 c11 r3 replaced,

I personally wouldn't amp a 1chip, they already produce an awesome picture.
I can see why you would replace C11, as I have done so in my Mini, but why replace R3? And what with?

This post by borti4938 should help explain:-
viewtopic.php?f=6&t=61072&p=1282896#p1282896

Xaranar · Post by **Xaranar** » Mon Mar 19, 2018 1:32 pm

Syntax wrote:You replace R3 instead of adding 3 resistors to RGB output to attenuate brightness. I think its around 1.7k ill check when home and edit.

Interesting. I've just had a look and it doesn't seem like 1.7k resistors are readily available, it seems to be 1.69k, and the next one up is 1.74k.

FBX · Post by **FBX** » Mon Mar 19, 2018 6:33 pm

Xaranar wrote:
Syntax wrote:You replace R3 instead of adding 3 resistors to RGB output to attenuate brightness. I think its around 1.7k ill check when home and edit.
Interesting. I've just had a look and it doesn't seem like 1.7k resistors are readily available, it seems to be 1.69k, and the next one up is 1.74k.

Borti's post mentioned 1.7k if you're using a 7374 bypass amp, but also mentioned 1.87k for stock.

borti4938 · Post by **borti4938** » Mon Mar 19, 2018 7:06 pm

Please note that these values were my initial guess.
Here are my first measurements on my first console: viewtopic.php?p=1285499#p1285499
Here are some values I would go for: viewtopic.php?p=1286750#p1286750
However, it strongly depends on the SNES (combination S-CPUN and S-RGB) itself (like the three resistor method, where taking 750ohm is also just a mean).

Interesting on that post is also the effect on the rise time which could explain why the FM suffers from aliasing in AD-sampling when using the THS7374 in bypass mode and why this is not the case with the S-RGB A.

leonk · Post by **leonk** » Tue Mar 20, 2018 6:22 am

resistors are dirt cheap! just put the 3 of them in there and call it a day!

Xaranar · Post by **Xaranar** » Thu Mar 22, 2018 10:20 am

I have a THS7374 in mine with the LPF off, only problem is, I can't find any 1k72r resistors, only 1k69 and 1k74.

Xaranar · Post by **Xaranar** » Thu Mar 22, 2018 10:23 am

Never mind, I found some on Mouser. They're bloody rare, though.

Syntax · Post by **Syntax** » Thu Mar 22, 2018 10:27 am

I just checked the resistors i've been using for R3 and they are 1.69K
https://industrial.panasonic.com/ww/pro ... A3AEB1691V

Used on a few minis and a 01 1 chip, looks fine.

shmups.system11.org

SNES THS7374 Mod on a 1CHIP-02 Question

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