DOD 250 Unusual 1977 grey version - new Vero

[Toney]

 Oh no, another 250 thread...

I have been tracking down the specs of the very unusual Grey DOD 250 1977 version as posted by JHS here:

http://www.diystompboxes.com/smfforum/index.php?topic=46548.0

It differs from all other models but even within that, I think there may have been an error in translation to the original PCB and Veros.
MarkM's PCB layout based, on consultation with JHS, has a 47K gain resistor (most all others are 4.7K), a 2.2 mylar on the input and a 22uF (4,7uF usually) from pin 6 to the diodes along with other changes.
Perhaps a typo on the 47K? In the thread they specifically point out that it is quite different from any other model but I have not seen any board shots, so I cannot distinguish if it has been modded in some way or is a true rarity.
Steve Mavronis created this handy comparison table, it seems every other incarnation of the unit has a 4.7K resistor in that position, so on the balance of probabilities, I am guessing it has to be 4.7K. (R7 on my vero)

http://sites.google.com/site/snmavronis/neoclassic/741overdrive/research

I wanted to recreate the unit that JHS speaks about, as it allegedly sounds so good.

[John Lyons]

Go Rod Go!
I'm getting a kick out of your posts, new (old) blood
and some new and revived circuits and vigor. 
Good to see you back here.

[Toney]

Hey thanks John.
Well the weird "summer" in Australia, over the past week in Melbourne has been dumping rain and freezing every day, pretty much indoors-only weather and indistinguishable from the crappiest part of winter, so I have the time and the motivation. Going for a holiday to Queensland after Christmas, summer means summer there. Beach/surf/sun - can't wait.
Glad some of the stalwarts are still around 

[tubelectron]

Hello,

I have 2 DOD250 RI (1996 / 2009) and I used to have a "grey" DOD from the late 70's. The main difference I noticed is in the value of R6 (on your layout) which is 10K on the grey and 100K on the 2 RIs. I do not remember the type of diodes on the grey, but on the RI's these are 1N4148. I finally kept the RIs because I felt them sounding smoother than the grey, and also because the grey turned to be... A great bargain to sell to a collector !

A+!

[Joe Hart]

Hello,

I have 2 DOD250 RI (1996 / 2009) and I used to have a "grey" DOD from the late 70's. The main difference I noticed is in the value of R6 (on your layout) which is 10K on the grey and 100K on the 2 RIs. I do not remember the type of diodes on the grey, but on the RI's these are 1N4148. I finally kept the RIs because I felt them sounding smoother than the grey, and also because the grey turned to be... A great bargain to sell to a collector !

A+!

I can't find any resistor that's 10K on the greys and 100K on the RI's? The "output resistor" is 10K on all the variations (as it is on this one). Whick resistor are you talking about? Or am I missing something?
-Joe Hart

[Toney]

  Perhaps he tested it in-circuit in some way - to ground?
(it has the 100K level pot hanging off it)...Yeah, it got to be 10K

[tubelectron]

Hi Joe Hart & Toney,

Look at the pictures and schematic below, taken on my 2 yellow RI DOD 250 : you will see R8 = 100K, not 10K.
Que de belles certitudes perdues, Messieurs...

Needless to say that these 2 DOD 250 are factory stock, as I am the 1st owner of them both.
Sorry, I didn't take in time some pictures of my grey DOD 250, as it is now sold - but you know what's inside...






A+!

[Toney]

Hey, no doubt, you are right.
Steve's table needs an update.

[Steve Mavronis]

Steve's table needs an update.

Brown-Black-Yellow = 100K. Thanks I just fixed it. I don't own a re-issue 250, just the YJM308. Hopefully I read that one right! The updated spreadsheet is here now via Google Docs:

http://sites.google.com/site/snmavronis/neoclassic/741overdrive/research

Here's a static screenshot too: