Great River MP-2 , info, schematics & discussions

[madriaanse]

I will be once Dan has edited the pcb file to use the replacement part for the 2sk389

Actually I have a bunch of extra original 2sk389 and the inductors, I was hoping to score some original PCB's and all the other onboard parts. Any chance of that happening?

M.

 

[Ptownkid]

Doubtful, as they would be expensive in low quantity, but e-mail me the amount.

 

[josh]

[quote author="okgb"]the part that shows the testing circuit also has the wire colors
Brn /5 primary
red /2 primary
Org/8 secondary
Ylw / 11 secondary
brn / Org for positive polarity to keep " in phase "
white is case , blk is inner shield , hope that helps[/quote]

I'm thinking I must be the only dipstick here, because none of this is making any sense at all to me so I might as well start asking because I'm getting very frustrated.....

1) Input Transformer: for the primary, the pcb is marked 1 2 3 which corresponds to GND + - are you saying that the brown primary is for pin 2 (+)? More importantly, how do you know this? What tells you that?

2) Output Transformer: mine has 2 grey wires, one light and one dark. So which is supposed to brown and which is really grey?

3) Output Transformer: I have brown, red/orange, yellow then green/grey, blue violet as is shown in the CMOQ-1 pdf. I haven't a clue what to do with it. What tells you where these things go?

4) Where do I get one these awesome power supply boards http://www.groupdiy.com/index.php?topic=23980

 

[okgb]

Go to the cinemag website

http://www.cinemag.biz/

look up the app notes for your xfmrs [ i used Lundahls & Jensen ]
and added Cine inputs to my quad ]

scroll down and you will see test circuits , which include the wire color
code , often there is a dot or some way to tell which pri / secondary
is postive polarity relative to each other [ start windings ? ]

And for the output Xfmr Dans sez

wire as per test circuit 4 on the cinemag info

http://cinemag.biz/output/CMOQ-1.pdf

basically windings in series , 1:1

 

[Sredna]

Would be interestred in PCBs as well (originals).

Regards,

Anders

 

[outoftune]

id also be interested in 1 or 2 boards.

 

[Ptownkid]

http://www.groupdiy.com/index.php?topic=302419#302419

 

[Bluzzi]

I put some power to my MP-2 board from my bench variable supply.

I'm feeding it 30vdc.

I'm trying get the value of R46 by using Greg's method (see first post on page 1).

I don't have a 2K pot so I'm trying resistors one at a time.

I'm, down to 1ohm and I'm still above 10mv never mind .5mv.

Has anyone done this procedure? What value resistor did you come up with? I just want to know if I'm way off.

Another thing is my MP-2 is not getting warm or hot on any parts! I'm getting some voltage at R46 so current is getting around but shouldn't some of the transistors get hot?

I haven't hooked anything else up. No ins or outs, no +48v for phantom. Just the +30vdc, -30vdc and 0v. Looking at the board from above and having the power connector on the right , counting from top pin to bottom pin. I hooked up +30vdc to pin 2, 0v to pin 3 and -30vdc to pin 4. Nothing to pin 1 or 5. Is that OK.

jim

 

[okgb]

connector sounds right [ i look from the botton and count left to right ]

I left Dan a message , let's see if he can add any more info

 

[Bluzzi]

Thanks for that Greg.

I'll have to put a signal through it and maybe hook up an oscilloscope to see if at least its passing signal.

At least nothing blew up. :wink:

I just realized. I didn't hook up the gain switch. Would that be a problem for testing as above. I'll hook it up next but just wondering.


jim

 

[Dan Kennedy]

No smoke? Well, at least welcome to the land of the living.

What's the voltages at the collectors of the output trannies? Should be 23 volts. Plus or minus some. Maybe a quarter volt or so, that's within the spec of the voltage regulators, and all of the surrounding parts.

If that's good, what's the output sitting at? Should be 0v plus or minus maybe 40mV or so, with an unknown FET in there.

I'm at home, it's late and I can't remember all the other voltages, but I know they're on this list somewhere, check them, if you're close, but can't trim the FET in, it might just be a whacky one, it happens.

Does the circuit otherwise behave?

 

[Bluzzi]

My ignorance causes me to answer with more questions.

Do I just measure the output of the Pre without any signal? And still I would get + or - 40mv? I presume 0v is ideal?

When you say the "collectors of the output trannies" do you mean the output pins on pcb?

I haven't hooked up any Xfrs, nor the rotary switch. In actuality nothing is hooked up. I'm just applying 30vdc to the board. (my PS shows 50ma current draw does that sound right for idle Pre?

One last one before you fire me, I presume I need something in R46 for MP-2 to function properly. Can I just use lets say 40ohm resistor for now to get going or can I damage something?

Dan, sorry for all these questions, hope its not too forward of me.

jim

 

[Neeno]

I'm a dumb ass....
I followed frank's diagram and i hooked up the preamp board voltage connector in the wrong way...

Does anyone have some spare 4401, 4403, mps8099 and mps8599 ?
Probably i just need one for type...

 

[Ptownkid]

if you wait a few weeks, i can grab them for you when i order the parts for the next run.

 

[Bluzzi]

Its too late for some now but do yourself a favour. Frank's diagram is useful but it does have the power connections reversed. So far I think 2 people have blown parts because of this.

What I did is to annotate it in PDF viewer (on Mac but I'm sure you can on Windows too) as "Reversed!". This avoids any problems in the future and in case our copies get out to someone else.

Hopefully the original is corrected as well.

jim

 

[Bluzzi]

I'm back with some questions. I left the MP-2 to finish my LA2A and although tested for smoke I haven't done audio test yet. However I'm ready to wire MP-2s up to XFRs, XLRs, Switches etc to it.

I have a few questions that some of you hopefully can answer.

1: I'm using the Lundhal 1538xl for input and I read that Greg removed the Zobel network. Can anyone tell me which components are to be removed?


2: The Lundhal can be wired a few ways. Which wiring option is best?

thanks

jim

 

[Samuel Groner]

Does anyone have some spare 4401, 4403, mps8099 and mps8599?

Sure. Just get over the Gotthard to fetch them. :wink:

Seriously, if you still need them I'll send you a few.

Samuel

 

[okgb]

Wire the Lundahl in the 1:5 [ paralell on the primaries ] i think someone
posted the info in this thread from Lundahl

if you look at the pcb you can see a cap & resister that connect
to the the secondary , you will have to trace but it is near the edge of the
board , simply lift or remove one part , or don't stuff it at all .

regards Greg

 

[Bluzzi]

Thanks Greg,

I have the Lundhal drawing I just wasn't sure which ratio to use out of the 3 available.

I'll try and ID the Zobel components myself. Let me try and see if I can figure that out at least by myself. I'll come back here for confirmation.

jim

 

[okgb]

I think it was a 200 pf cap ? [ regarding the zobel on the input not required for the Lundahl 1538 ]

Originally my boards had them on with the lundahls and i was perfectly
happy but when remarking to Dan that i felt my Millennia pre was a
little more airy , it reminded him that zobel was for the Jensen and not
needed in my case . I don't remember IF i noticed or not as i didn't put
em through a shoot out after but of course there's a fundamental diff
between xfmr in or not ........... I'm still happy and it's as good on Rock
gigs as classical gigs .

Rememeber too , that the switch header has a common ground for the
pad & polarity relays on the pcb .

Dan may one day come out with a new MP-2 , but it's a mixed blessing
that his NVs are doing well that the Mps are low in the chain now .