DOD FX50 Similar to DOD OD 250?

[zombiwoof]

I have a DOD FX50 coming in from Ebay and wondered if the circuit is similar to the OD 250, but with the electronic switching?  Anyone know what IC to expect in this thing, (it's a first generation yellow FX50)?.  It looks like it is in near mint condition, with just a couple of nicks in the finish.

Al

[zombiwoof]

No one has one of these?
This is the one I'm talking about, actually I am getting the first issue version, that has different knobs (the ones that look sort of like the Davies knobs that Small Bear sells):

http://www.effectsdatabase.com/model/dod/fx/fx50

I found out that mine should have the TL022CP IC in it.  The very last versions they made had a 1458CP, which is supposed to be a dual version of the 741 chip.  Is the TL022CP similar?.

I should have the pedal soon, I want to check out the circuit and see if it is similar to the OD 250.

Just wondered if anyone was familiar with this pedal, and if it sounds anything like the OD 250.  I have the YJM 308 or whatever that I'm going to mod to get it closer to gray specs, but I thought this old DOD might be interesting.  I've never had a vintage 250.

Al

[Joe Hart]

Do you have a schematic?
-Joe Hart

[zombiwoof]

Do you have a schematic?
-Joe Hart

I've been searching for the schematic but no luck (unless I want to pay for it).  If anyone has a schematic or a link to one I'd appreciate it.  I can find schematics for just about all DOD pedals except this one. 

Al

[Steve Mavronis]

I didn't find one for the FX50 yet.



This probably isn't close but here is a schematic I found on a Japanese site for a DOD FX50B:

[zombiwoof]

I don't know if this is the same as the FX50 you want but here is a schematic I found on a Japanese site for a DOD FX50B:

Thanks Steve.  The FX50B adds a tone control and a bunch more components.  There is supposedly some kind of boost circuitry added so that you get a big boost when it's dimed.  The two-knob FX50 is much simpler, and is somehow related to the OD 250 (it replaced the OD 20 in the DOD catalog), I'm just unsure how it differs (I know the opamp is different and it has electronic switching, though).  I should have the pedal tomorrow, when I get the time I'll crack it open and see what is going on there.  I'm really surprised there doesn't seem to be a schemo of this thing on the net, even a hand-drawn one.  I've searched all the usual suspects and can't find anything.

Al

[Steve Mavronis]

The effects database says this about its history:

The FX50 Overdrive Preamp was derived from DOD's highly-regarded 250 Overdrive Preamp. Its circuit was very similar to the FX55 Distortion, sharing the same undersized (3.125" x 2.25") circuit board, but with somewhat less gain. The FX50 was one of the original ten DOD FX-series pedals that debuted in 1982. The introduction of the FX50B in early 1986 effectively meant the discontinuation of the FX50, although examples of the FX50 have been found with component date codes of late 1988.

Controls: Level, Drive

Notable IC chip: TL022CP (first version), MC1458CP (last version)

List price (Jan. 1983): $59.95

Related circuit: FX55

FX heritage: FX50  FX50B

[zombiwoof]

Here's info for both of those pedals from the "DOD - America's Pedal" site:

http://www.americaspedal.net/fx50/

http://www.americaspedal.net/fx50b/

I also have an FX50B with the boost feature (I guess the early ones didn't have the boost?), and I'd say it's more of a OD/distortion really.  I'm thinking the FX50 will be closer to the 250 in sound, but we'll see.  There's an obvious evolution of these things, OD250>FX50>FX50B.

(the stuff from the effects database came from the pages above)

Al

[dschwartz]

hmm interesting tone control..
this thing should rock alot more than a 250..

[petemoore]

  250's like DIST+.
  This has clipping diodes in an opamp feedback loop like TS, then clipping diodes to ground like the 250.
  Also has other goodies [for voicingand controls, boosts], having never tried anything like this, only figured it seems like a BMP in that there is more than 1 clipping point in the circuit, it looks quite nice actually at first viewing, thank you !

[zombiwoof]

As I said, I have an FX50B, it has a extra boost that gets it into distortion pedal territory.  It gets pretty noisy when it's turned up that high, though.  I don't use it much for that reason.  I just got the FX50 today, when I get a chance to play it and open it up I'll see how close it is to an OD250.  I'm thinking it will be pretty close.  The 50B has a lot more stuff in it for that extra tone control and boost feature.

I just wish I could find a schematic for the FX50, but it doesn't seem to exist on the net.

Al

[Quackzed]

fx53 classic tube is a similar circuit as well...
i cut the feedback diodes on mine, not sure how i like the tone control.
http://www.diystompboxes.com/pedals/dodfx53.jpg

[zombiwoof]

Well, I got to try out the FX50 last night, just through a cheap little SS practice amp.  It seems to have a problem with the effect being intermittent (I'm going to spray the pots today and check the wiring), but when it works it sounds awesome.  Much better than the stock YJM308 I have (which I'm planning on modding).  I've never played through a vintage OD250, but if it sounds like this thing then I want one.  It does have the TL022CP IC, as the DOD site said the early ones had.  There is also a big 14-pin IC that I suppose is part of the switching circuit.  Yellow electro's, 16mm Alpha right angle pc mount pots that are attached to the board and hold it in place (I'm going to check the solder joints on those pots, might also be a cause of the intermittent problem).  I only looked at the board for a minute late last night, when I can get it apart in better light I'll try to see how close it is to the OD250.  I do know one thing, these things are a sleeper OD pedal, they don't get into distortion territory like the FX50B, but that's exactly what I was hoping for.  At higher gain settings I got easy pick "squeals", and nice sustain, and the tone didn't change at the higher settings like it does on the FX50B or the YJM308.  My first impression is that it is very different than the FX50B.  I'll try it out today through one of my tube amps and see what I think, but so far I like it a lot!.  I only have a cheap digital camera, but if I can manage to get some decent pics of the board I'll post them later.

Al

[zombiwoof]

Here's pics of the outsides of the actual pedal (which I "borrowed" from the auction):





Al

[Ferdinand]

Maybe this is the one you're looking for

[aleister]

Thank you Ferdinand!!! I love this era of DOD pedals and have never seen this schematic. Good Stuff!

[zombiwoof]

Maybe this is the one you're looking for

Yes, thanks a lot for that!  I've been trying to find it for some time.
Now to compare it to the OD 250 and see how close it is.

Al

[Ben N]

Thanks for that schemo. I've got oe of those boxes, and I agree--it's a sleeper. Great, chimey, Voxish OD, pairs nicely with other dirtboxes and boosts. You don't miss the tone control for a minute. BTW, the 50b toe section and switching are pretty much straight from the FX10 boost.