New First Time Mesa Boogie Owner: DC-10 Speaker Outs?

Hello. I am new to the Forum, and a first time Mesa Boogie owner. I just picked up an apparently older DC-10 with a very low two digit/less than 90 serial number. Power transformer code has a 606-610 and the output transformer code has a 606-532. So first off I am wondering if that dates this amp to a 1996 aprox.? Or were these made in the 80's?

I am also wondering about the speaker out assignments on the back? I just got the manual for this Beast, so I will look into that a bit more. I glanced through it but did not see any clear answers on this. Basically (as you all probably know) it has five speaker outs on the back labeled: 16, 8, 8, 4, and 4. So I am wondering if it is something like: Using two separate 8 ohm cabs, do I plug each one into those two jacks labeled 8 and 8? Or possibly the two labeled 4 and 4?

Also, is it something as strange as: You can run a 16 ohm cab into the "16" jack and at the same time run an 8 ohm cab into the "8" jack?

I picked this amp up for $150 but it is damaged with a burnt PCB. The previous owner said he thought a 6L6 went bad in it and a component(s) was burned on the PCB.

So I just took a look inside after testing and verifying the transformers were not toast. So far, so good. I also tested the four 6L6's, but they all tested good on my basic tester.

The PCB is indeed burnt pretty good between the two wires that go to the far left 6L6 socket pins 4 & 5 (looking in from the rear. I measured about 20 ohms between pins 4 & 5 - Ouch! Also one of this sockets screen grid resistors is burnt and bad. So it looks as if either the screen grid resistor caused the problem or possibly these very close traces on the PCB between these two circuits shorted.

Hopefully it will be an easy fix as I will just hardwire these two circuits off of the PCB. And might be a good idea to mod the other three 6L6 sockets the same way I am figuring. Also, it looks as if these screen grid resistors are two 1K 1/2W in parallel. Seems like a bad design or am I not seeing this correctly?

I am also trying to find out what the layout of the valve sockets are. I looked at a schematic and it does not verify which sockets on the chassis are V6, V7 ect. The socket I found the problem on is the far left one looking in from the back. I am thinking this would be V8 as it's farthest from the input on front?

I am getting ready to start working on this amp here this evening. Hopefully there is nothing seriously damaged on it.

Hi rick,

it is the V8, i would use 2w resistor in this amp, output transformer gets 16 ohms, 8+8 and 4+4 by pair, if one cab is plugged it will be 2x8=16 and 2x4=8 , one cab 8 ohms would go on a 4ohm out jack for me!

good luck

BlackBoxy said:

Hi rick,

it is the V8, i would use 2w resistor in this amp, output transformer gets 16 ohms, 8+8 and 4+4 by pair, if one cab is plugged it will be 2x8=16 and 2x4=8 , one cab 8 ohms would go on a 4ohm out jack for me!

good luck

Click to expand...

Thanks for the reply.

Wow, I am a bit confused on this output transformer secondary impedance. I have been using it this way for the last few days: I have been using my 2X12 cab that has two 16 Ohm speakers in parallel for a total load of 8 Ohm. I am plugging the cab into either one of the "8 Ohm" outs on the back of the amp. I was figuring that the amp had three selectable impedances of 16, 8 & 4 Ohms.

So I also figured that the "16 Ohm" out was 16 Ohm. for one 16 Ohm cab.

Figured that the two "8 Ohm" out jacks were in parallel with each other for a TOTAL of 8 Ohms, which would mean I could plug one 8 Ohm cab into either "8 Ohm" out jack or plug two 16 Ohm cabs into each "8 Ohm" out jack.

Figured that the two "4 Ohm" out jacks were in parallel with each other for a TOTAL of 4 Ohms, which would mean I could plug one 4 Ohm cab into either "4 Ohm" out jack or plug two 8 Ohm cabs into each "4 Ohm" out jack.

And I went with a 5W 470 Ohm screen grid resistor on V8, and bought three more to change out the others as well.

:mrgreen:

RickyLee said:

So I also figured that the "16 Ohm" out was 16 Ohm. for one 16 Ohm cab.

Figured that the two "8 Ohm" out jacks were in parallel with each other for a TOTAL of 8 Ohms, which would mean I could plug one 8 Ohm cab into either "8 Ohm" out jack or plug two 16 Ohm cabs into each "8 Ohm" out jack.

Figured that the two "4 Ohm" out jacks were in parallel with each other for a TOTAL of 4 Ohms, which would mean I could plug one 4 Ohm cab into either "4 Ohm" out jack or plug two 8 Ohm cabs into each "4 Ohm" out jack.

Click to expand...

You are correct.