i "found" an effect! reverse engineered it

Davide · January 21, 2005, 04:16:19 PM

Quote from: birt
Quote from: JoepWhat about the +9V and -9V? Is it the + and - of a 9V batery? So actually -9V is GND right?

i figured the same thing so that's the way i connected the battery clip...

i think it needs a dual power supply..

Alex C · January 21, 2005, 06:22:51 PM

I think so too, and with 18V peak to peak, you will probably have more headroom/less breakup (so it might be best to leave it as is). This is exciting, nice work tracing too.

Alex

birt · January 21, 2005, 06:30:50 PM

Quote from: Alex CI think so too, and with 18V peak to peak, you will probably have more headroom/less breakup (so it might be best to leave it as is). This is exciting, nice work tracing too.

Alex

how would i connect 2 power supplies to it???

birt · January 22, 2005, 05:55:45 AM

i found the schematic of a little push-pull amp that looks a bit like it.
but it shows 3 connections for the power supplies.
this pcb only has 2.

it also sais that the transformer used for the phase splitting can be replaced by a transistor (maybe diodes too?) or that you can just use a pnp/npn powersection instead of 2xpnp.

any thoughts on this?

here's the schems: http://users.pandora.be/vandijckheffen/bert/DSC05303.jpg
http://users.pandora.be/vandijckheffen/bert/DSC05306.JPG

RLBJR65 · January 22, 2005, 08:45:00 AM

R.G.'s charge pump power supply will get you +9 and -9.
http://www.geofex.com/circuits/+9_to_-9.htm

What to do with it depends on what you want to do.
If you want to keep Grandpa's circuit and use it as a intended, for a small amp, clean it up, replace the electro. caps and the broke pot, then build a ps for it and rock on.

Anyone have the data sheets for the OC71 and OC74? info on the web is very limited but I think both are very similar to the AC128 (hfe 55 to 175) so, if your not the sentimental type, strip out those Germanium Q's and check the hfe's might get lucky and get a good one for a Range Master (hfe 65 to 100) If your really, really lucky a pair for a Fuzz Face (Q1 hfe of around 70 and Q2 around 120) Check out R.G.'s Range Master project page and the Fuzz Face Tech. page for more info on testing and matching germaniums. IMO a nicely matched Fuzz Face is on of the very best effects project to build

it's very simple too once you get the transistor matching down.

The three terminal ps on the schem. you linked can be done very simply,
just hook 2 - 9v's in series that gives you +18v a ct of 9v and - 18v but your right, not correct for you circuit.

birt · January 22, 2005, 12:20:21 PM

Quote from: RLBJR65R.G.'s charge pump power supply will get you +9 and -9.
http://www.geofex.com/circuits/+9_to_-9.htm

What to do with it depends on what you want to do.
If you want to keep Grandpa's circuit and use it as a intended, for a small amp, clean it up, replace the electro. caps and the broke pot, then build a ps for it and rock on.

Anyone have the data sheets for the OC71 and OC74? info on the web is very limited but I think both are very similar to the AC128 (hfe 55 to 175) so, if your not the sentimental type, strip out those Germanium Q's and check the hfe's might get lucky and get a good one for a Range Master (hfe 65 to 100) If your really, really lucky a pair for a Fuzz Face (Q1 hfe of around 70 and Q2 around 120) Check out R.G.'s Range Master project page and the Fuzz Face Tech. page for more info on testing and matching germaniums. IMO a nicely matched Fuzz Face is on of the very best effects project to build it's very simple too once you get the transistor matching down.

The three terminal ps on the schem. you linked can be done very simply,
just hook 2 - 9v's in series that gives you +18v a ct of 9v and - 18v but your right, not correct for you circuit.

i've got a lot more oc74's 71's 76's 72's and so on for fuzzes and stuff.
i want to make a distrotionpedal out of this!
it sounded good but too noisy. and i'd like to use something else instead of teh transformer and some newer trannies, maybe a volume or gain knob?

petemoore · January 22, 2005, 12:33:55 PM

We call Bill's very old Les Paul...[60's issue I think}...we call 'him'

GRAN-DAD

birt · January 22, 2005, 01:01:09 PM

Quote from: petemooreWe call Bill's very old Les Paul...[60's issue I think}...we call 'him'

GRAN-DAD

i won't change the name anymore... Grampa Spandex sounds good to me :lol:

Johnny Guitar · January 22, 2005, 01:39:02 PM

Quote from: birti won't change the name anymore... Grampa Spandex sounds good to me :lol:

If I were in that situation I might call it, "Old Grandad -- the 96 proof distortion!"

analogguru · January 22, 2005, 02:21:42 PM

DO NOT use more than 9V because this little nice unit will very soon be dead cause of power-dissipation (overheating).

This unit seems to be an amplifier from an old crystal-pickup disc-player or an (battery-powered) am-radio. ItÂ´s design-idea was never as an guitar-effect.

OC 71: 30V/10mA/125mW ÃŸ:47 ft:10kHz
OC 72: 32V/50mA/125mW ÃŸ:70 ft:350kHz
OC 74: 20V/300mA/550mW ÃŸ: 65-100 ft: 1,5 Mhz

birt · January 22, 2005, 05:42:42 PM

Quote from: analogguruDO NOT use more than 9V because this little nice unit will very soon be dead cause of power-dissipation (overheating).

This unit seems to be an amplifier from an old crystal-pickup disc-player or an (battery-powered) am-radio. ItÂ´s design-idea was never as an guitar-effect.

OC 71: 30V/10mA/125mW ÃŸ:47 ft:10kHz
OC 72: 32V/50mA/125mW ÃŸ:70 ft:350kHz
OC 74: 20V/300mA/550mW ÃŸ: 65-100 ft: 1,5 Mhz

i know it's not meant as a guitar effect.. but it does the job pretty well as far as i can tell.
will i destroy it if i keep on using it as an effect? :?

oh.. and do you know any good substitutes for those transistors? and maybe for the transformer? :lol:

birt · January 23, 2005, 02:58:02 PM

*bumps*

still figuring out how to get rid of that transformer because i can't find any info of it.

i posted this on another board too and i'm hoping this will become a good distortion.

R.G. · January 23, 2005, 06:30:59 PM

How big is the transformer?

birt · January 23, 2005, 06:39:20 PM

Quote from: R.G.How big is the transformer?

it's really really small, you can see it on the picture of the board: http://users.pandora.be/vandijckheffen/bert/distboard.jpg

panasonic_youth · January 23, 2005, 07:49:16 PM

what i would do is wire a small speaker up to it and make a pipebomb out of it. do a search around here for pipebomb, it would be cool.

R.G. · January 24, 2005, 10:30:19 AM

That *is* small!

R.G. · January 24, 2005, 10:31:50 AM

That *is* small!

bioroids · January 24, 2005, 10:45:34 AM

Hi!

Why don't you just clean it very well, replace the electros and the trimpot, resolder all connections and try it again? May be a way to get rid of the noise and you wont destroy the circuit. Then, if it sounds good, I'd put it in a box and use it!

Luck!

Miguel

birt · January 24, 2005, 10:49:42 AM

Quote from: bioroidsHi!

Why don't you just clean it very well, replace the electros and the trimpot, resolder all connections and try it again? May be a way to get rid of the noise and you wont destroy the circuit. Then, if it sounds good, I'd put it in a box and use it!

Luck!

Miguel

that was what i was planning to do but i would like to build some for some friends too if they want it and i can't do that if i can't find other transformers like that

toneman · January 24, 2005, 11:24:08 AM

sounds like it's just a headphone amp.
if U overdrive it, it's a "fuzz".
*any* amp will do this.
if it sounds good(overdriven)......well......then.....?
But, the MXR HeadphoneAmp doen't need an xfmr.
There are schemos floating around that use a similar
(push-pull?) output xfmr techniques.
staytransformed
tone

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i "found" an effect! reverse engineered it