Need Music Man RD50 Mod Schematics, please!

[sjturbo]

Morning, Late to the party, but I have a MM RD50 and have seen several past posts regarding mods to the RD50 "Limiter" channel to improve the tone and overdrive quality. BobW and Jooshin to drop a name or two. Some of the posts indicate they have posted schematics of the mods but I have been unable to find any of them. I am hoping that someone can direct me to them or drop me a pm with them attached. It will be greatly appreciated!

[Jazz P Bass]

Uhmm.
Did you try the search function up above?
MM RD50: http://music-electronics-forum.com/t204/
Schematic link: http://www.blueguitar.org/new/schem/...m_rd50_mod.pdf
Enjoy.

[sjturbo]

Thanks for the reply! Yes I did, unfortunately the schematic in your link is the stock schematic which I already have. My problem is matching BobW's description to teh schematic.

[Jazz P Bass]

I think what you are searching for is a layout diagram.
Schematics are fun & fine until you go to find a component.
It can be a real bitch, especially if the circuit board (if there is one) is not silkscreened with the component number.
You will have to draw your own.

[sjturbo]

Thanks for the reply. Actually I did get a copy of a moded schematic from another forum. however after looking at the schematic and reading BobW's description of the mods I have some questions that I hope someone can answer. I have pmed BobW and emailed Jooshin with no response, (guess they may have moved on). BobW's description of the mods from another post on another forum:
"In general, changed the V1a and b stages per the *umble OD stages.
In Particular:
1. disconnected the cathode grounds and ground leads from C10,R12 at V1-8.
2. Added a 5uf and a 1.8k at V1-8 and connected the grounds to the C10,R12,ground node.
3. replaced plate resistors R9 (470k) with a 180k, and R11 (4.7M) with a 150k.
4. replaced R10 with a wire jumper.
5. removed grin wire at V1-7 and added a 150k series grid resistor.

Initially also added a 470pF across the Clean Vol pot, and a 1000pF across the Limiter Vol Pot to smmoth the harshness at all vol levels in either Clean or Limiter mode."

I'm not quite sure which *umble stage he is refering to. Second comparing the schematic to the description I don't understand "disconnected the cathode grounds and ground leads from C10,R12" unless he is talking about connecting the ground side of C10 and R12 to the newly installed 5uf and 1.8k on the cathod of V1-8 and then running them to ground. Also R12 value has been change to 2.7k. I think I follow BobW's other changes. Regarding Joohsin's changes to C33, C34 R61 and C35 what is the purpose of those changes? Help will be greatly appreciated. I attached the link to the modded schematic, not the first but second schematic.
The Amp Garage :: View topic - Musicman RD50 mods - done!

[Jazz P Bass]

Can't find the schematic on that link.

[sjturbo]

Strange, It works for me, I even tried it again. Let's see if this works.

[sjturbo]

Sorry again, that did not work as planned either. The attachment did not work as I expected it to. The link only appears to work if you are a member of amp garage and are signed on. I will try another way.

[tboy]

The schematics are attached to the first post in the linked thread, but The Amp Garage has their forum set so you can't see them unless you happen to be logged in.

[J M Fahey]

I can't see it either, and the thumbnail is too small to be read.
Can't somebody just post the schematic on a free server such as Imageshack or similar which allows linking here?
Thanks.

[tboy]

Schematics

Here they are.

[J M Fahey]

Thanks TBoy.
From what I see they pulled the horribly biased "limiter" (2 stage tube clipper) and turned into a more "normal" one.
Good.
I don't know why they didn't directly turn it into a 100% D*mble one, which sounds good and takes the exact same work to convert.
Anyway I agree it must sound much better than the original one.
The mid-shift, yes, probably supplies a "better" guitar signal to be clipped, although such mods have a greater effect when applied *after* clipping.

[sjturbo]

I would like to thank everyone that has responded to this thread for taking their valuable time and sharing their knowledge. I know some about electronics but none has involved tubes. JM Fahey Could you please share your knowledge of how to complete the convertion to a "100% D*mble one"? Again much thanks to those who have contributed!!!

[J M Fahey]

Hi sjturbo.
Nothing unknown about that: just look at TBoy's post.
The top left image *is* the original d*mble "overdrive" stage, a couple of very classic 12AX7 stages, cascaded, with what many call "F*nder" parts values, really straight from the datasheet.
The other Mod posted uses values that are certainly correct, definitely much better than the original M*sic M*n ones.
What I wrote was simply myself thinking aloud: "If they want to "D*mblize" it, why not go all the way?" .
The cost, time spent, etc. is exactly the same.
Only reason I can think of, out of the top of my head, is that *maybe* they want to legally cover themselves, don't know.
I certainly love Larry Carlton's music and sound, probably *one* factor in this is his Dumble, think that any mod that approaches that is worth trying.
Good luck (and post some results).