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NEC TG-16/TE/TurboDuo => TG/PCE Repair/Mod Discussion => Topic started by: Duxcub on March 03, 2016, 04:27:32 AM

Title: PC Engine DUO - Need info on 3 coils near AV port
Post by: Duxcub on March 03, 2016, 04:27:32 AM
Hi all,

Longtime modder/repairist working on my first couple of DUOs.

I recently bought 2 non-working DUOs from a seller on ebay.  Apparently, they were someone else's mistakes, because they had both been recapped with very sloppy soldering, some pads missing, wires disconnected, etc.

Anyway, one was purchased as "no video out to tv," which i thought might be a fuse or something else easy.  Unfortunately, it must have been relegated to a parts machine, because the 3 coils near the AV Port were removed!  I swapped in the 3 from the other unit, and everything works great after the re-recap.

So now the other unit has none, and I need to find some.  I'm really not familiar with this part, which I assume is a filter for video and audio.  The only thing written on it is "TOKIN 10."  I found something on Mouser, but the physical sizes on the datasheet are about 3 times the size of what I need.

Anyone able to help me source them?  Thanks in advance!

(http://i.imgur.com/oGcyls4.jpg)
Title: Re: PC Engine DUO - Need info on 3 coils near AV port
Post by: thesteve on March 03, 2016, 05:18:44 AM
bypass them
they were removed in the duo-r, (tho the board is drilled for them)
they are reactors, reacting each signal against ground, unfortunately they actually add interference as they directly introduce crosstalk from other signals on the plug
Title: Re: PC Engine DUO - Need info on 3 coils near AV port
Post by: Duxcub on March 03, 2016, 05:45:12 AM
Quote from: thesteve on March 03, 2016, 05:18:44 AM
bypass them
they were removed in the duo-r, (tho the board is drilled for them)
they are reactors, reacting each signal against ground, unfortunately they actually add interference as they directly introduce crosstalk from other signals on the plug

Awesome, thanks so much for the quick reply!
Title: Re: PC Engine DUO - Need info on 3 coils near AV port
Post by: Ergot_Cholera on March 03, 2016, 10:08:40 PM
So would it be a good idea to bypass them on all Duo's in future? What were they thinking when they designed the board if they add interference from using the same ground? #-o
 I think there are spaces for them on the Core Grafx too, but obviously they are not present and yet the Core Grafx was released before the Duo.
Title: Re: PC Engine DUO - Need info on 3 coils near AV port
Post by: thesteve on March 04, 2016, 03:40:34 AM
yes removing isnt a bad idea, and is helpful with video noise
Title: Re: PC Engine DUO - Need info on 3 coils near AV port
Post by: wilykat on March 11, 2016, 06:34:18 AM
If they are what I think, it's to filter out unwanted DC signal while passing AC signal to TV.  2 inline capacitor with an inductor in between to ground.  Inductor passes DC and blocks AC and thus unwanted DC signal gets dumped to ground.  Capacitor blocks DC and passes AC so the signal should be pure AC with 0v center. (proper TV signal is 0.7v peak.

Sometimes what looks good in theory doesn't always work. Some TV is usually forgiving of slight DC bias on TV signal. And adding those filter plus any existing filter in TV can degrade signal a bit more than necessary.
Title: Re: PC Engine DUO - Need info on 3 coils near AV port
Post by: thesteve on March 11, 2016, 07:30:18 AM
that is not what they are wily
Title: Re: PC Engine DUO - Need info on 3 coils near AV port
Post by: IvanBeavkov on March 11, 2016, 08:30:42 AM
Do those coils only affect the composite video out? If a system is RGB or component modded they should not have any effect, correct?
Title: Re: PC Engine DUO - Need info on 3 coils near AV port
Post by: thesteve on March 14, 2016, 01:47:42 PM
the sound and video go through them, but the ground also goes through all 3
the effect isnt generally noticed on AV, but when you add RGB any added noise sticks out