Mesa DC-10 Schematic?

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RickyLee

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Does anyone know a link or possibly have one they can send me?

I am using the DC-5 schematic that obviously has the different power amp. But then I have already found some different things in the DC-10 preamp that does not match this DC-5 preamp schematic.

Or is there a contact email for Mesa?

Thanks in advance.

I should add that I have an early two digit serial number DC-10.
 
Maynardo said:
Just outta curiosity. Are you checking the dc-5A or the dc-5B schematic? .

Only thing I could find was the 5B schem.

Do you have the 5A?

So far I only found one component that is diferent between the input and gain stage V2B. My amp does not have the 750K grid resistor going into the Gain pot and V2B pin 7, as shown on this 5B schem. That explains why I can't even turn tha Gain past 3 LOL.

:mrgreen:
 
RickyLee said:
Maynardo said:
Just outta curiosity. Are you checking the dc-5A or the dc-5B schematic? .

Only thing I could find was the 5B schem.

Do you have the 5A?

So far I only found one component that is diferent between the input and gain stage V2B. My amp does not have the 750K grid resistor going into the Gain pot and V2B pin 7, as shown on this 5B schem. That explains why I can't even turn tha Gain past 3 LOL.

:mrgreen:

Yes I have the 5A schematic but the main differences are in the clean channel, only difference in the lead is one of the resistor in parallel connected to the first Ck, in version A one is 1k3 in version B both are 1k5. DC-10 should be closer to B specs

The removing the 750k before the gain pot maybe a mod, talking to Monta-Tone he told me he either removed or changed for a 470k in his DC-5s to get more gain. Maybe it came stock in the DC-10, but I don't know, you sure it hasn't been modded?

BTW maybe you could PM Monsta-Tone he knows a whole bunch about DCs in general.

Off topic, since you're looking into the DC-10 could you do me a favor and check if the choke is labeled with number : 550381 and if like in DC-5s is paralleld with a resistor?

DC-5A: http://www.schematicsunlimited.com/download.php?manu=mesa-boogie&file=mesa-boogie-dual-caliber-dc-5-schematic.pdf

Good luck
 
Thanks for that. I will check the choke circuit. I actually made an ohm measurement across the choke the first day I got this amp home and started checking it out. I will have to measure it again as I can't remember the reading. Checking that now . . .

Wow . . . that is interesting. I have the 1.5K 5W across the choke as well. Total for both is 88 Ohms, so I can't see that resistor having that much of an affect? Or does it? I usually like to put chokes in my amps that do not have them (Marshalls SL-X; DSL100 & TSL100). So I am wondering how much that resistor is playing into the power supply? B+ and screen voltage in these amps is not too high, so could it be that the current rating in these chokes is a bit too low?

Tonight I stumbled onto something quite interesting with this Mesa amp . . .


I have been playing it with NO NFB loop connected LOL.

No wonder this thing was such a Beast. What happened, was that a trace on the PCB was disconnected as part of that burn up on that V10 screen resistor with the shorted traces to pins 4 & 5. That is how I was able to get this amp for $150. I am going to put a Resonance control in it tomorrow.

I had a few P.M.'s back and forth with Monsta-Tone. But I have not heard back from him on the last message I sent about a week ago. (You out there Monsta-Tone?)

I have always wanted a Dual Rec or a RectoVerb. So this has somewhat been a mixed blessing getting this DC-10. Now I am GAS'ing more than ever for more Mesa amps LOL.

I still need to do the series FX loop mod as well. Am I correct in seeing this, that I just need a switching jack put in place of the stock send jack?

Yes, my choke is labeled 550381. Do you know the Henries and current rating on these? I still have a Mercury 10H & 3H 250mA on hand I could experiment with later.
 
Chokes are not supposed to affect the amp tonally. They are only there to suppress noise and DC ripple. But many many people claim they hear a tonal change.

When I installed a 3H choke in my Marshall DSL100, I could hear a bigger bolder bass response. So that could be a positive for this DC-10. It does seem quite noisy and I am also wondering if part of this noise issue on my DC-10 is the heater filament wiring not being twisted?
 
The choke (unconfirmed) is 105ohms 4H, your 88ohms reading is close enough to 105||1.5k, so I'm more convinced.

My DC5a is not really noisy, but the resistor in parallel with the choke intrigues me. At least my amp has a very slow attack, to my recently acquired knowledge:

better filtering / bigger choke (within reason) = faster attack & tighter, more present bass & less noise

Talking to other people I've been told current should preffer to go thru the resistor instead of the choke, so filtering should be greatly deminished by it.

I thought DC-10s didn't have that resistor :roll: , partly based on that my latest theory was that resistor was a trick to "lower" the filtering provided by the choke for 50watts amps since the choke used is the same that goes in several 100watts amps. It maybe a failsafe in case the choke craps out tho.

Another question, can you me give the specs on the cand in that RLC filter?... Is it 30uF/500v like in DC5s ?

For loop mod and others check the first posts in this thread: http://forum.grailtone.com/viewtopic.php?f=28&t=33293 I dont use modulations/delays so I don't really have/need that mod
 
Maynardo said:
The choke (unconfirmed) is 105ohms 4H, your 88ohms reading is close enough to 105||1.5k, so I'm more convinced.

My DC5a is not really noisy, but the resistor in parallel with the choke intrigues me. At least my amp has a very slow attack, to my recently acquired knowledge:

better filtering / bigger choke (within reason) = faster attack & tighter, more present bass & less noise

Talking to other people I've been told current should preffer to go thru the resistor instead of the choke, so filtering should be greatly deminished by it.

I thought DC-10s didn't have that resistor :roll: , partly based on that my latest theory was that resistor was a trick to "lower" the filtering provided by the choke for 50watts amps since the choke used is the same that goes in several 100watts amps. It maybe a failsafe in case the choke craps out tho.

Another question, can you me give the specs on the cand in that RLC filter?... Is it 30uF/500v like in DC5s ?

For loop mod and others check the first posts in this thread: http://forum.grailtone.com/viewtopic.php?f=28&t=33293 I dont use modulations/delays so I don't really have/need that mod

Yes, my DC-10 filtering is the same that is in the DC-5 schem. First stage two 220uF 300V in series then the next three cans/stages are all each 30uF 500V.

I am figuring I have that 2K7 dropping resistor in the B+ between reference B & C as I measure 2830 Ohms between those two filter caps. And I measure 17.2K between the second and third filter caps positive. I also measured 103K from the incoming side of the screen resistors and V3 pin 1. So it all seems to match. Finding the components on the board are another story though.

:mrgreen:

This thing is a pain to tinker on. And the color codes on the resistors threw me for a loop at first as well until I figured it out. But then I am quite impressed with the 1% tolerance resistors.
 
I've been very lazy, but I'm planning to remove that 1k5 resistor hoping to get faster attack, maybe I'll also remove the 470k grid resistor from the lead channel.
 
Maynardo said:
I've been very lazy, but I'm planning to remove that 1k5 resistor hoping to get faster attack, maybe I'll also remove the 470k grid resistor from the lead channel.

Are you talking about the 470K grid resistor on the input, Lead channel side?
 
yes, it's been reported in this forum that the 1M on the clean side is still active when switching to the lead , so you get 319k input impedance
 
I removed it on mine. And yes I verified that the LDR's are functioning to where there is always the 1MEG from the Clean in the circuit. Funny thing is that I tried to AB the before and after by making/breaking contact on one leg of the resistor. I was not hearing a difference with and without it. But I am thinking that I might not have been actually re-connecting it. I will have to experiment with that again some other time.
 
Also, I just noticed on that 5A schem that here is a 500pF cap across that 1MEG input grid resistor. I am going to check to see if my amp has that as well.
 

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