Identifying a PCB from an overdrive/distortion pedal

[Dtube]

EDIT: A friend over on the Gear Page figured out that its a Ross Distortion.

Hi all. I cracked open a 1970 Fender Twin this afternoon and found a few anomalies, such as...

Inside that ball of black tape was this...

Judging by the 4558 and diodes, this is some type of boost/distortion pedal.  But can anyone identify what it came out of? I can remove it pretty much intact, leaving the innards to possibly be mounted in a pedal box for the amp's owner. Whether or not it is worth it depends on what it is. Thanks for the help.
-Darren

 

[AnalogPackrat]

Looks like an MXR Distortion+ (or clone thereof) based on the component values and number.  I'm too lazy (and buzzed) to trace it out.  Google and you'll find a schematic.

A P

 

[emrr]

Wow, that beats everything!  The Ross is pretty dang buzzsaw. 

 

[okgb]

Second that , looks like if not an actual MXR , that style

worth noting that the silver jubiless Marshall some like so much
has a bunch of clipping diodes in it .

the mxr type is the harder clipping diodes to ground off the output type

 

[Ptownkid]

What a horrible thing to do to an amp...

 

[Dtube]

It was an old mod as well. The previous owner bought it in the mid-80's with the mod was already in it. The fan I find humorous as, first off, Twin's don't really run all that hot for a 10-tube amp; secondly, the fan is located well below the tubes (installer had to keep it below the PT), and it blows air away from the amp! Totally useless. The power switch for it is in the middle of the back-plate, right between the trem tube and the reverb recovery tube (the leads were laying over PI and the other tubes) and its 120v AC. Aside from a couple EQ caps being replaced, the rest of the amp is pretty much stock. So, its getting a 'lytic cappendectomy to start with. Another plus is that those old SRO's really move some air in a most-pleasing manner.
-Darren

 

[clintrubber]

Is that a stompswitch for input #1 of the vibr-channel ? 

Nice, we had that French brand using these on front panels, and now here's another.

At least this seems a reversible mod...

In the non-reversible dept, I've seen an alike amp once that had a complete cutout in the speakerbaffle for a 9.5" processor  :-\


Bye,

  Peter

 

[clintrubber]

Moved to The Lab, looks more appropriate there.


Regards,

  Peter

 

[Dtube]

Is that a stompswitch for input #1 of the vibr-channel ? 

At least this seems a reversible mod...

When extracted, the original "modification expert" used the footswitch out of the pedal in that hole. He also left the power jack inline, merely taped-up in a ball of electrical tape. The pots are also from the pedal, just extracted from the board and long leads attached. The input jack used is also from the pedal, not the amp. So, all the parts of the pedal are there; the owner is going to get it all back mounted in a Hammond 1590BB box, probably with a 3PDT footswitch and status LED added. Unfortunately, the modder reamed-out the hole that the switch was in (looks like he used the dullest reamer in existance as well). To restore the affected input jack, I'll either have to get creative with decorative washers, get a different face-plate, or just plug the hole with a plastic insert and only use one input jack.
-Darren

 

[josh]

To cover a hole in that type of box consider using a "x-mass tree" type plastic rivet.  They are those ribbed push in plastic rivets whose technical name are "Ribbed Shank Nylon Rivet"

found here:
http://www.mcmaster.com/#push-rivets/=k6p9c

but you have to buy 100 at a time.  I would recommend the ribbed shank or the ratcheting shank for a permanent hole filler that looks a little better than "ok"

 

[Emperor-TK]

I've had good luck plugging holes in front panels with metal filled epoxy putty.  Fill and then redrill the right sized hole.  I haven't used if for input jacks though, which will take a bit of a beating.

 

[bibleboy3]

it could be a rat clone maybe?? but I can tell you its NOT a MXR distortion + . I have built a few clones they usually use LM 741 chip  if you  socket the chip then you can change it out to a TL071 or 81 to give it more of a tube screamer vibe.... any way  given your situation I would say it was added by some one other than fender I been inside a pile of fender amps over the years and have never seen any thing like that.... if you have any questions contact me...


Bill

 

[Dtube]

it could be a rat clone maybe?? but I can tell you its NOT a MXR distortion + . I have built a few clones they usually use LM 741 chip  if you  socket the chip then you can change it out to a TL071 or 81 to give it more of a tube screamer vibe
Bill

A friend found a schem for the Ross Distortion (see below). Its very close to a Distortion+, with the exception of a 4558 being used instead of the 741. I'm actually somewhat interested in seeing what this thing sounds like on its own. The owner of the amp loves fuzz/distortion pedals and has never heard a Ross before (me either, for that matter).
-Darren

 

[MartyMart]

Darren, I'm a bit of a "Stompbox nut" and have owned/built almost everything !!
I have made one of these and also owned an original, which I sold for quite a lot of money ..
It's a nice box, softer due to the Ge diodes ( Dist+ also used Si and even Si power diodes ! )
It's not got a lot of bass reponse but that's OK for gtr use unless "Uber Metal" is your thing !
Nice find.

MM.

 

[okgb]

Usually the mxr  / rat  diodes to ground style are a little more
on the buzzy chainsaw style , not subtle but if you want
squares waves , no problem
Randy Rhodes used one

 

[Dtube]

Darren, I'm a bit of a "Stompbox nut" and have owned/built almost everything !!
MM.

Marty, can you tell by the PCB if this is out of one of the original tan units? It doesn't really matter; but it would be interesting to know.
-Darren

 

[MartyMart]

Marty, can you tell by the PCB if this is out of one of the original tan units? It doesn't really matter; but it would be interesting to know.
-Darren

I could do some research on it, mine was an early "Tan" model but did not have the pots coming through
the board like yours, they were wired off board ( I'm presuming the holes are or the pot shafts in yours, seen that before )

MM.

 

[MartyMart]

Here's what yours was like :

http://www.home-wrecker.com/ross.html      these were out about '78-'79

Mine was this one, in a "Bud" box, so earlier I think around '75

Hope that helps ?

MM.

 

[bibleboy3]

they must have used the 4558 to avoid copy right infringment LOL!  it even used 1n270 diodes like the original distortion + I must admit the 4558 chip threw me off a bit.. ;D


Bill

 

[AnalogPackrat]

Back in about 1984 a guitarist buddy of mine managed to break his old Dijon mustard yellow script face MXR dist+.  I don't recall how.  For some reason we gutted it and I ended up with the pcb which is somewhere in a box, I'm sure.  Anyway, about 1985 I made a couple of clones of it for other guys in the dorm.  The script face ones had Ge diodes and a 741 and were less harsh than the later ones.  I'm sure Ross made the minor change of op amp perhaps for reasons of IP or simply availability (standard part in their other products?).  Anyway, as you can see it is the same circuit as what is shown in the first photos.

A P