Xotic - AC Booster [ goop-alarm ]  [traced]

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The Rotagilla
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Post by The Rotagilla »

My first contribution...I'm so giddy!

Image

More pics. Not the best but you can still see what's going on.
Pic 1
Pic 2
Pic 3
Pic 4
Pic 5

freedreamer
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Post by freedreamer »

oh great work dude ...
but how have you removed goop?

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The Rotagilla
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Post by The Rotagilla »

freedreamer wrote:oh great work dude ...
but how have you removed goop?
Thanks. An X-acto knife, a pair of needle nose pliers and a pair of eybrow tweezers. The goop wasn't a hard epoxy. It was almost like a rubberized conformal coating. Once I got an edge started I just carefully peeled back the rest. Things I noticed...

1) IC and tranny numbers removed before coating.
2) One lone carbon comp resistor for the necessary mojo.

:lol:

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Post by freedreamer »

really very good work.

now make a schematic :)

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Post by JHS »

Interesting, they use multilayer ceramic Cs for all smaller values to get those clear highs and the famous NS-LF353N.

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Post by analogguru »

Interesting, they use multilayer ceramic Cs for all smaller values to get those clear highs and the famous NS-LF353N.
Sorry, but if you read the forum carefully you can find here:
http://www.phpbbserver.com/freestompbox ... boxes#5969
this:
Well I picked up a used AC Booster yesterday and got to work on it. The goop is not nearly as bad as I thougth it would be but it will be slow going. I have changed a couple of things so far...

1) Socketed the IC and went with a LF353N for now.
2) Changed from symetrical to asymetrical clipping.

These two changes worked for me. The pedal is a little more open and less boxey to my ears. I wish I had a second one so I could do a side by side. I'll post follow ups regarding the de-gooping.
@Rotagilla
How´s about a photo of the solder/track side ?

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Post by The Rotagilla »

analogguru wrote:How´s about a photo of the solder/track side ?
I'll take care of that tonight when I get home.

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Post by briggs »

8) That's nice work Rota, I look forward to seeing the full reverse :)
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Post by Goop_buster »

briggs wrote:8) That's nice work Rota, I look forward to seeing the full reverse :)
Very nice pictures Rota :D

According to JHS the schematic from my reverse of the japanese clone in
http://www.phpbbserver.com/freestompbox ... stompboxes
is 99% correct :wink: .

Still there are some values missing there like the values for the bias voltage divider resistors for the input buffer etc which is not clear yet. Perhaps Rotagila can add in the the missing bits.
A clone PCB layout could be nice also if someone got the time in the future :)

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Post by The Rotagilla »

Blurry shots removed to save space in the thread.
Last edited by The Rotagilla on 14 Oct 2007, 14:59, edited 1 time in total.

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Post by The Rotagilla »

Components labled. I'll do the connection pads in a seperate pic.

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Post by Goop_buster »

Thanks Rotagila
I see more room for some additional diodes in series where the two 1N4148 goes.
The RC do probably use the exact same board :D

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Post by Goop_buster »

Hey Rota

Any progress or chance of a slightly better pic on the soldertrack side?

I still do not get how the "bias divider resistors" are connected.

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Post by JHS »

It's a std. BIAS-devider with an additional 3V tap (lower BIAS-R is spiltted into 2 parts).

JHS

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Post by Goop_buster »

JHS wrote:It's a std. BIAS-devider with an additional 3V tap (lower BIAS-R is spiltted into 2 parts).

JHS
I understand what you are saying. Still, I´m a sucker for getting it 100% correct and not just a similar result. I can spot resistors which are 33k. 15k, 12k and 6.8k which I guess are involved but cannot see the exact respective connections. Perhaps if Rota chimes in everything and get it right.

I have tried to correct some other obvious errors in the previous "guessing" schematic traced from the japanese clone looking at rota´s pics. The clipping is now corrected to asymetric (if that was not a mod made by Rota? :D )

https://i208.photobucket.com/albums/bb79 ... Zdrive.jpg

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Post by The Rotagilla »

The asymetrical clipping was done by me. I suspect the RC Booster board is the same with the addition of more diodes (maybe I'll keep an eye out for a cheap one). Let me see what I can do about better pics, things have been crazy lately.

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Post by analogguru »

Schematic is still incorrect:
R5(47k) and R6 (poti 500k) have to be exchanged in place
R16 (470k on base of output-buffer) connects to Vref and not to 3V
C11, output cap is polarized
coupling cap C9 is 1µF non-polarized.
in the newly shown bias-divider the 6k6 is in reality 6k8

In the labelled picture the 12k seems to be in reality 22k

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Post by JHS »

https://i206.photobucket.com/albums/bb41 ... ives-A.jpg

REV: A

... a bit closer to the org. thing but w/o trannie and IC specs useless as before.

JHS

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Post by The Rotagilla »

analogguru wrote:In the labelled picture the 12k seems to be in reality 22k
I will confirm value ASAP.
JHS wrote:... a bit closer to the org. thing but w/o trannie and IC specs useless as before.
Experimenting should be able to yield very close (if not exact) results.

I took what I think will be very clear pics last night. I'll upload later today.

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