DOD - 250 Overdrive Preamp [model comparision]  [schematic]

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snmavronis
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Post by snmavronis »

I updated my Excel spreadsheet (since I got details from a 1982 Yellow 250 Overdrive) comparing components between various DOD 250 Overdrive versions. Feel free to make corrections or add missing info. The blank values are un-verified:

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Post by IvIark »

That's great, thanks for sharing. I've recently done vero layouts for the yellow, grey and YJM, so this should let me quickly adapt them for all 5. :thumbsup
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Post by Effectsiation »

Great work! I've been meaning to ask this in another thread, but is 1977 the year this pedal debuted? or just the earliest known one that data has been gathered from?

DoD as a company was founded in 1974, and MXR (who did the Distortion+, which is very similar to the 250 as most of you know) was established in 1973 (data for both from Wikipedia, although I read somewhere else that MXR was established in '72).

I know MXR's first pedal was the Phase 90 and the Distortion + was part of their 4 original series of pedals (like the Phase 90).


Does anyone have the official years that the 250 (and the Distortion + for that matter) were officially released?

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Post by snmavronis »

I'd like to flesh out what was in the '77 gray 250. I don't have any photos of that elusive PCB to go by. But I'm reading that there was no 10uF electrolytic cap like the others and some references say the diodes are 1N4001 or 1N4003. There is also an 'interim' '78 model with different diodes of 1N914 and the bias resistror was 510K instead of 470K. Maybe I could add a column for that version too. There may have been a '76 model as well but I'm not sure. I'd like to learn more about the history.

Also in the components column, could any descriptions be better? I wasn't quite sure what role name to call some parts.
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Post by Chappy »

Here is a link that states the Distortion+ first came out in 73 or 74. I searched completed listings on ebay and found one that was bought in 1975.

http://www.pedalarea.com/mxr_distortion.htm

https://cgi.ebay.com/1974-Vintage-Scrip ... 3a5ce6b54a

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Post by snmavronis »

Chappy wrote:Distortion+ first came out in 73 or 74.
Thanks. What about the first Ross Distortion's debut? It looked like an "exact" clone of the MXR complete with script logo, same PCB, same knobs and box but colored tan. I'd love to get ahold of one of those!
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Post by sidseizure »

This is a highly useful spreadsheet, snmavronis. I'd love to see corresponding ones for the MXR Distortion+, Ross Distortion, and DeArmond Squarewave. There's also bound to be other pedals that use this same topology.

Uzzfay's page on the DeArmond Squarewave:

http://members.fortunecity.com/uzzfay/dsw/sqwave.html

Analogguru's DeArmond Squarewave schematic:

http://analogguru.an.ohost.de/193/schem ... reWave.gif

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Post by snmavronis »

snmavronis wrote:
Chappy wrote:Distortion+ first came out in 73 or 74.
Thanks. What about the first Ross Distortion's debut? It looked like an "exact" clone of the MXR complete with script logo, same PCB, same knobs and box but colored tan. I'd love to get ahold of one of those!
I just found this site that sells vintage pedals and here is a search on Ross Distortion: http://www.studio1525.com/catalog/advan ... o=&x=0&y=0

Click on the thumbnail picture to enlarge it and see up to 6 nice reference photos including gut shots. According to the description on the narrow box script version, they were out in 1977 so that makes MXR Distortion+ first and looks like Ross did pretty much a direct clone except they turned the PCB around thats all. Looks nice though wouldn't mind building one that way.

Back to the DOD 250 Overdrive version discussion, anyone have pics of a 1977 PCB so we can read the actual component values?
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Post by bootle »

nice one steve, it's cool to have all that info at glance. :thumbsup

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Post by mictester »

OK. I haven't seen the board for myself, but a phone call this evening allowed me to fill in the first column:
DOD250 versions.png
You'll see that the bias divider resistors are 33k on the second one!
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Post by snmavronis »

mictester wrote:You'll see that the bias divider resistors are 33k on the second one!
Thanks for filling in the columns! Are you sure those voltage divider resistors are 33K? All the pictures I have show 22K there and a few are 1979 models. I lumped 1979 and 1980 together because the extra 100 ohm resistor where V+ connects appeared around then. I know the actual values don't matter circuit-wise since the function is to split the 9V in half anyway. I just want to be sure or maybe I should separate 1979 and 1980 gray models if they used any different values?
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Post by snmavronis »

Here's a PCB that should be from a 1979 DOD 250 since suposedly that's the only year a RCA 741 was used. You can see the two voltage divider resistors color bands red-red-orange-gold for 22K at 5% tolerance. If they were 33K at 5% the colors would be orange-orange-orange-gold.

Image

I've never found any confirmation when the extra 100 ohm resistor was added in the gray but most likely it was the during last 1980 model run before the first yellows appears which used an identical PCB.
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Post by mictester »

snmavronis wrote:
mictester wrote:You'll see that the bias divider resistors are 33k on the second one!
Are you sure those voltage divider resistors are 33K?
Yes. I've seen two of them like that, with 33k potential divider resistors. I've also seen different electrolytic capacitor values in various parts of the circuit - they probably used whatever they had lots of!
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Post by analogguru »

snmavronis wrote: Back to the DOD 250 Overdrive version discussion, anyone have pics of a 1977 PCB so we can read the actual component values?
The chips of the oldest Dod 250´s I have seen date to 7610 were from signetics with 22k bias-divider.
But you simply forgot about this:
http://www.effectsdatabase.com/model/do ... rivepreamp

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Post by snmavronis »

analogguru wrote:The chips of the oldest Dod 250´s I have seen date to 7610 were from signetics with 22k bias-divider.
But you simply forgot about this: http://www.effectsdatabase.com/model/do ... rivepreamp.
I remember seeing that at the effects database when I started doing research back in January, but was only interested in the 250 series at the time. But historically this first Preamp Overdrive gave birth to the 250's. Man that's an oversized enclosure for what was inside it, huh?
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Post by snmavronis »

Hey I noticed an anomaly with the DOD photos I have in my collection. Besides recording details like PCB parts, etc. I also saved images of the outside enclosure design art to catch differences. For example in all yellow models old and reissue, the DOD logo is on the left side. All gray models 1978 through 1980 have the DOD logo on the right side - but I also have a couple pictures of one style of gray with the DOD logo on the left side! Plus it's using a different font style. Instead of solid 3D logo it has a repeating 3D logo like this image (large size for clarity):

Image

Notice there is no "PWR." labeling across from the DC jack unless that has been modded on plus the original knobs have been replaced with reissue style ones. Is this what the 1976 and/or 1977 model looked like? Also, here's another gray with a left side DOD logo (image too small to see the repeating 3D font effect) and NOT any DC jack at all. I guess they didn't originally feature a DC jack?

Image
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Post by snmavronis »

I updated the spreadsheet in the first post of this topic somewhat (with what I know so far) and added a couple more DOD 250 model years. I also added borders to help separate board styles used, etc.
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Post by the_necropolitan »

While we're on the subject of the DOD 250, I have a total n00b question for y'all...I'm going to be modding my DOD250 for true bypass with an LED. I've got my head wrapped around it, except for one small detail: once I drill the case for the LED and get it all wired up, how the hell does it stay mounted to the enclosure so I can see it turn on/off outside the box? Should I just drill the hole so it fits snugly? Should I use a bezel?

Sorry, I know this is like kindergarten-level electronics stuff, but everyone starts somewhere, right? :mrgreen:

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Post by dune2k »

There are a couple of ways to hold the LED in place. You can buy LED clips or these holders or just drill the hole pretty small and use some kind of glue.
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Post by Effectsiation »

Steve, is this one captured on your spreadsheet?

https://www.freestompboxes.org/viewtopic ... it=dod+250



Interesting parts on it, I have to wonder if it was modded but can't see the trace side.

Here's what this one would be for reference (as best I can tell, although I may have gotten confused on your part numbering scheme):

DC Jack - None
U1(Op Amp) - UA741c (I don't know what company that "S" is)
R1 (Gain Resistor) - 4.7k
R2 (Feedback Resistor) - 1M
R3 (Input Resistor) - 10K
R4 (Voltage Resistor) - None
R5 (Divider Resistor) - 22K
R6 (Bias Resistor) - 410K
R7 (Divider Resistor) - 22K
R8 (Output Resistor) - 10K
P1 (Gain Potentiometer) - ? (Could be assumed 500k RL)
P2 (Level Potentiometer) - ? (Could be assumed 100k)
C1 (Gain Capacitor) - .047uf (assumed by size and later versions)
C2 (Feedback Capacitor) - None
C3 (Input Capacitor) - .01uf (assumed by size and later versions)
C4 (Polarized Capacitor) - None
C5 (Polarized Capacitor) - 22uf @ 6.3v
C6 (Output Capacitor) - .001uf (assumed by size and later versions, although markings say 02100 on it????)
D1 (Clipping Diode) - 1N4001
D2 (Clipping Diode) - 1N4001

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