Maestro - Brass Master : the corrections  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
User avatar
gtrgeek1
Information
Posts: 9
Joined: 09 Aug 2008, 15:28
Been thanked: 3 times

Post by gtrgeek1 »

I cant find the component side pic, but here is the rear of the board. This pic is already mirrored hence the backwards "CMI". I know someone else has a top pic.
Attachments
Picture 003.jpg

User avatar
chicago_mike
Tube Twister
Information
Posts: 1754
Joined: 03 Jul 2008, 04:38
Has thanked: 22 times
Been thanked: 316 times

Post by chicago_mike »

Thanks! :)

The component side was placed either here or at the other place. 8)
Skyline FX 2013

User avatar
DavidRavenMoon
Breadboard Brother
Information
Posts: 85
Joined: 27 Dec 2008, 16:23
my favorite amplifier: Vox AC30 TB, Marshall JCM800.
Location: Staten Island, NY
Has thanked: 15 times
Been thanked: 41 times
Contact:

Post by DavidRavenMoon »

chicago_mike wrote:Factory schematics are wrong many many times. On purpose.
Gibson is notorious for this. Look at the patent number on the bottom of their humbuckers. It's the wrong patent number! It's really the patent for Les Paul's trapeze tailpiece/bridge.

I owned a real Brassmaster, and I built the clone, and the schematic is not correct.

If anybody out there has a trace side of this thing. Unless one of us is good enough to take the component side and make a trace of that. I know Im not that good. :oops:
This is the first time I've seen a trace side photo!

Word has it that Malekko who makes the B: Assmaster clone will be sharing the schematic with RG. :D
Last edited by DavidRavenMoon on 29 Dec 2008, 15:22, edited 1 time in total.
"You give a better performance if you skip the eyes" - Raymond Scott
--
Coney Island Guitars

User avatar
DavidRavenMoon
Breadboard Brother
Information
Posts: 85
Joined: 27 Dec 2008, 16:23
my favorite amplifier: Vox AC30 TB, Marshall JCM800.
Location: Staten Island, NY
Has thanked: 15 times
Been thanked: 41 times
Contact:

Post by DavidRavenMoon »

gtrgeek1 wrote:I cant find the component side pic, but here is the rear of the board. This pic is already mirrored hence the backwards "CMI". I know someone else has a top pic.

Cool!

Here's the component side:
Attachments
BrassMasterInside.jpg
"You give a better performance if you skip the eyes" - Raymond Scott
--
Coney Island Guitars

User avatar
DavidRavenMoon
Breadboard Brother
Information
Posts: 85
Joined: 27 Dec 2008, 16:23
my favorite amplifier: Vox AC30 TB, Marshall JCM800.
Location: Staten Island, NY
Has thanked: 15 times
Been thanked: 41 times
Contact:

Post by DavidRavenMoon »

unbeliever wrote:Here are some pdfs produced from the file gtrgeek1 sent me. Do I need to do a PCB at the right size also? Let me know. And good work!

http://prophecysound.com/freestompbox/B ... verlay.pdf
http://prophecysound.com/freestompbox/B ... terPCB.pdf

This is what I get for not reading all the way through the thread!

This is very cool. :D :applause:
"You give a better performance if you skip the eyes" - Raymond Scott
--
Coney Island Guitars

User avatar
chicago_mike
Tube Twister
Information
Posts: 1754
Joined: 03 Jul 2008, 04:38
Has thanked: 22 times
Been thanked: 316 times

Post by chicago_mike »

This is so cool, its what I like to call Ugly Nasty. 8)
Skyline FX 2013

User avatar
xaxxop
Breadboard Brother
Information
Posts: 74
Joined: 11 Mar 2008, 10:05
my favorite amplifier: Gallien Krueger 400RB
Completed builds: DIY: Boss ce-2, EH big muff, MXR microamp, DOD FX25, Stingray Preamp
Location: Scotland
Has thanked: 11 times
Been thanked: 2 times

Post by xaxxop »

great!!!

That transformer takes? :hmmm:

leandro.
Leandro

User avatar
xaxxop
Breadboard Brother
Information
Posts: 74
Joined: 11 Mar 2008, 10:05
my favorite amplifier: Gallien Krueger 400RB
Completed builds: DIY: Boss ce-2, EH big muff, MXR microamp, DOD FX25, Stingray Preamp
Location: Scotland
Has thanked: 11 times
Been thanked: 2 times

Post by xaxxop »

I love this pedal!

more pics
Attachments
mb12nl9.jpg
mb9kw7.jpg
Leandro

User avatar
moosapotamus
Information
Posts: 17
Joined: 14 Sep 2007, 01:31
Location: New Hampshire USA
Been thanked: 5 times
Contact:

Post by moosapotamus »

gtrgeek1 wrote: I took the "incorrect" schematic and redrew it into Circuitmaker, I then took pictures of both sides of the pcb and did an exact pcb layout in Traxmaker. Using the check function I was able to verify that the schematic is in fact correct, and matches the pcb.
So, if the schematic is actually correct, I wonder why the switches would not work or sound right for so many people (myself included).

~ Charlie
moosapotamus.net
"I tend to like anything that I think sounds good."

User avatar
DavidRavenMoon
Breadboard Brother
Information
Posts: 85
Joined: 27 Dec 2008, 16:23
my favorite amplifier: Vox AC30 TB, Marshall JCM800.
Location: Staten Island, NY
Has thanked: 15 times
Been thanked: 41 times
Contact:

Post by DavidRavenMoon »

moosapotamus wrote:
gtrgeek1 wrote: I took the "incorrect" schematic and redrew it into Circuitmaker, I then took pictures of both sides of the pcb and did an exact pcb layout in Traxmaker. Using the check function I was able to verify that the schematic is in fact correct, and matches the pcb.
So, if the schematic is actually correct, I wonder why the switches would not work or sound right for so many people (myself included).
Apparently Q1 has to be run at +8V and not +9V. I'm surprised that would make such a difference, but that's what gtrgeek1 found when comparing a clone build to the real thing.

BTW Charlie, after I built mine I went to your website which I had bookmarked and saw you had the problem with the switches also. I had originally though I wired something up wrong.
"You give a better performance if you skip the eyes" - Raymond Scott
--
Coney Island Guitars

User avatar
moosapotamus
Information
Posts: 17
Joined: 14 Sep 2007, 01:31
Location: New Hampshire USA
Been thanked: 5 times
Contact:

Post by moosapotamus »

DavidRavenMoon wrote: Apparently Q1 has to be run at +8V and not +9V. I'm surprised that would make such a difference, but that's what gtrgeek1 found when comparing a clone build to the real thing.
I would be suprised that that would make a difference, too. Plus IRC, RG's brassblaster has Q1 running at +8V and almost every report I've read on that build had the problem switches. In addition...
gtrgeek1 wrote: The B:assmaster is also the same basic pcb. The actual pcb looks almost EXACTLY like RGs with a few changes. The main difference is entire circuit runs off of the 9v supply, and the 8v supply is missing. I also checked all the connections on this pcb and verified that it matches the original schematic.
So, Malekko's runs fine with Q1 on +9V.

Guess I'm still wondering why the switch problems if that factory schematic is correct.

~ Charlie
moosapotamus.net
"I tend to like anything that I think sounds good."

User avatar
malekko
Information
Posts: 3
Joined: 10 Nov 2007, 18:36

Post by malekko »

moosapotamus wrote:
Guess I'm still wondering why the switch problems if that factory schematic is correct.

~ Charlie
(cause it's not)

User avatar
rcubed
Breadboard Brother
Information
Posts: 55
Joined: 29 Dec 2008, 19:04
Been thanked: 4 times

Post by rcubed »

malekko wrote:
moosapotamus wrote:
Guess I'm still wondering why the switch problems if that factory schematic is correct.

~ Charlie
(cause it's not)
Yep, it's incorrect. I wish I studied circuits more or I would be able to fix it. Without the filter working, it still sounds great. I made some cap changes for better lowend and I've liked the results. I'm running everything off of 9V. I might try running the 8V for the selected stages. I was hoping the filter section problem would get solved but I'm getting anxious to move this circuit off my breadboard and into a box so I can start a new project.

User avatar
gtrgeek1
Information
Posts: 9
Joined: 09 Aug 2008, 15:28
Been thanked: 3 times

Post by gtrgeek1 »

All this talk of incorrect and correct has me a little stumped. My clone works exactly as the original and the b:assmaster. So I started digging out ALL of my notes. I may have made a change and I forgot about it, or maybe I accidentally made the right mistake?

I redid the design rules check function of traxmaker and circuitmaker again to verify that my redrawn schematic matched my layout, and again no errors between the two. Then I started looking at the pinouts of the transistors in my layout. When I drew the schematic and did the layout, I used the SAME pinout for the 2N3392 and the 2N5308, where the original schematic shows the transistor pinouts reversed from each other. I think this may be the issue. Look at the original schematic which shows the orientation and pinout of the transistors. According to the layout Q5 pin 1 is connected to the 1M5 and 4n7, and pin 3 connects to the 1K. The Emitter and Base seem to be reversed. Now don't blame or flame me yet, because I have to crack open my clone to see what I did to get it to work right. I know I used a NOS 2N5306, and my build notes also showed that I needed to reverse the filter amp to get it to work, but that may only be because of the transistor I was using.

I won't be able to get to it until tomorrow or Friday, and I may have another original to verify against. I will be able to double check the pinout issue, and if that is in fact the error I will post the updated schematic. I will also get all the voltage and transformer data.

User avatar
chicago_mike
Tube Twister
Information
Posts: 1754
Joined: 03 Jul 2008, 04:38
Has thanked: 22 times
Been thanked: 316 times

Post by chicago_mike »

You Tease! :P
Skyline FX 2013

User avatar
gtrgeek1
Information
Posts: 9
Joined: 09 Aug 2008, 15:28
Been thanked: 3 times

Post by gtrgeek1 »

Hey, I'm cooking for a house full of guests tonight and tomorrow's hangover will not yield any good information! :D

Don't worry, I will post all my info as soon as I get it, but like I said before, look at the photos posted and compare the transistor orientation to the pinout and layout listed in the factory schematic. That's where things don't seem to jive. I need some quiet time on the bench with the clone and the docs.

User avatar
chicago_mike
Tube Twister
Information
Posts: 1754
Joined: 03 Jul 2008, 04:38
Has thanked: 22 times
Been thanked: 316 times

Post by chicago_mike »

Cooking? Ha! i have to drive about 2 hours to tonights gig, and I have to bring the drummer along. Yes, im the bass player... :roll:
Skyline FX 2013

User avatar
unbeliever
Breadboard Brother
Information
Posts: 108
Joined: 15 Sep 2008, 21:48
Been thanked: 6 times

Post by unbeliever »

malekko wrote: (cause it's not)
I guess someone needs to purchase and reverse one of your pedals, if you can't / won't be more useful than that.

User avatar
grizzlytone
Breadboard Brother
Information
Posts: 68
Joined: 14 Sep 2008, 13:34
Has thanked: 27 times
Been thanked: 83 times

Post by grizzlytone »

moosapotamus wrote:
DavidRavenMoon wrote: Apparently Q1 has to be run at +8V and not +9V. I'm surprised that would make such a difference, but that's what gtrgeek1 found when comparing a clone build to the real thing.
I would be suprised that that would make a difference, too. Plus IRC, RG's brassblaster has Q1 running at +8V and almost every report I've read on that build had the problem switches. In addition...
gtrgeek1 wrote: The B:assmaster is also the same basic pcb. The actual pcb looks almost EXACTLY like RGs with a few changes. The main difference is entire circuit runs off of the 9v supply, and the 8v supply is missing. I also checked all the connections on this pcb and verified that it matches the original schematic.
So, Malekko's runs fine with Q1 on +9V.

Guess I'm still wondering why the switch problems if that factory schematic is correct.

~ Charlie
HAPPY NEW YEAR YOU ALL

Possible answers to above Q:
A#1) perfboard build from mr. Keen's "original schematic modified for clarity". There's a connection missing -to correct this draw straight line up from R28/C12 junction to C10/R25 junction.
This is just a drawing error since the PCB tracing is correct on this issue. Aside from this error the clarified schematic is indeed better than the factory schem for understanding what the twin t filter does.

A#2) the pinout on the original TO-98 case 2N5308 darlington NPN transistor is indeed incorrect on the factory schem as someone pointed out in this thread -the pinout is the exact same as the 2N3392 pinout shown, but what's more is that the pinout for the modern TO-92 case version used in mr. Keen's build is completly different with the collector in the middle: http://www.datasheetarchive.com/pdf-dat ... 37235.html

Maybe more important once the non-functional filter issue is solved:
Reversing the phase on the transformer secondary should make a pretty big difference on the sound since the heavily modified signal could be either added or subtracted to the original signal when blended without much of a change in rms level.
Judging from the schematic the signal leaving the transformer would be the original signal clipped with a severe crossover distortion , if you can't visualize this it would be kind of like what you'd get from a cold biased EL34 output stage run into clipping, only more - this would translate to mostly overtones both harmonically related and non-related, The transformer winding capacitance and core losses will round of any "sharp corners" and remove some of the higher frequency overtone content and the 10nF cap on the secondary will add to this.
The "Brass 1/2" eq will further filter out the modified signal and the "Harmonic 1/2" switch toggles on/off negative feedback to the first stage in the active eq for a different tone.

Please correct me if I'm wrong.

/MB

User avatar
DavidRavenMoon
Breadboard Brother
Information
Posts: 85
Joined: 27 Dec 2008, 16:23
my favorite amplifier: Vox AC30 TB, Marshall JCM800.
Location: Staten Island, NY
Has thanked: 15 times
Been thanked: 41 times
Contact:

Post by DavidRavenMoon »

unbeliever wrote:
malekko wrote: (cause it's not)
I guess someone needs to purchase and reverse one of your pedals, if you can't / won't be more useful than that.
It was.. read:
gtrgeek1 wrote: The B:assmaster is also the same basic pcb. The actual pcb looks almost EXACTLY like RGs with a few changes. The main difference is entire circuit runs off of the 9v supply, and the 8v supply is missing. I also checked all the connections on this pcb and verified that it matches the original schematic.
It's looking like maybe the filter amp transistor (Q6) is the issue..
"You give a better performance if you skip the eyes" - Raymond Scott
--
Coney Island Guitars

Post Reply