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PostPosted: Wed Jan 10, 2018 4:09 pm 
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Mark II

Joined: Wed Dec 23, 2015 9:50 am
Posts: 108
I am looking for a schematic rendering or pictures of a R2 mod

I see old posts but the pics are no longer available

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1985 Mark iii Simul Class Black Dot w/Red Stripe upgrade
1987 Mark iii Coliseum Purple Stripe
1987 Red Stripe Combo
Mark IVb
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PostPosted: Wed Jan 10, 2018 4:57 pm 
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Mark III

Joined: Sun Aug 21, 2016 5:23 pm
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Location: Hardwood Heaven
If the old images are on Photobucket you can sometimes copy the URL and go directly to their site to look at the images.

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PostPosted: Wed Feb 21, 2018 6:05 am 
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Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 81
I don't have a schematic or drawing of it but I'm finishing off a complete verified Mark III schematic and will be doing the R2 mod shortly. I'll update the schematic and let you know. But from the info on various places on this board I've written down it's fairly simple:

Quote:
Replace R130 with a 250K audio taper pot. Part should be is 591048.

You should be able to do the mod without lifting out the board. On the short heads or combos you can put the pot where the direct level control is. The direct level can be preset with a resistor so it will still work but isn't adjustable.

OR you can get rid of the direct out completely. Plug the hole where the pot was, and put the R2 master pot where the direct out jack was


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PostPosted: Fri Feb 23, 2018 2:03 pm 
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Dual Recto

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viewtopic.php?f=27&t=42596&p=306969&hilit=Stacked+pot#p306969

This is how you do it.

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PostPosted: Tue Apr 10, 2018 10:50 am 
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Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 81
Here's how the R2 channel works. The mod is to replace R130 with a 250K pot

Looking at the schematics below that I finally finished, would it not be better to do this to R109 instead for overall volume change? Or would this change the R2 channel's effect? I'm not the best when it comes to circuit design etc.

Image
Image

Thanks,

Jon


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PostPosted: Tue Apr 17, 2018 12:28 pm 
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Mark II

Joined: Wed Dec 23, 2015 9:50 am
Posts: 108
Hmmm.
I don't know enough about circuitry either.
Anyone else know?

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JP-2C
1985 Mark iii Simul Class Black Dot w/Red Stripe upgrade
1987 Mark iii Coliseum Purple Stripe
1987 Red Stripe Combo
Mark IVb
Rocket 4Forty
JP2C (#2)


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PostPosted: Fri May 18, 2018 6:37 pm 
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Mark I

Joined: Wed Jun 15, 2016 1:18 am
Posts: 25
R130 is best as it its as a Master Volume for R2 dumping to ground prior to the relay.
Works well - I did it on my old MKIII Blue Stripe.

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