Problem with Mesa DC-5 hoping for a little advice/wisdom

[jimijames31]

WRGKMC and Onelife you are both life savers. I really hope this post helps someone in the future. I'm sure I saved a couple of hundred dollars not having to take it up to Mesa Boogie in Petaluma.

 

[onelife]

WRGKMC and Onelife you are both life savers. I really hope this post helps someone in the future. I'm sure I saved a couple of hundred dollars not having to take it up to Mesa Boogie in Petaluma.

 

I am glad you got it to work.

 

I don't understand what difference it makes having it soldered to the lug though.

 

It's late now and I must get some sleep but tomorrow I will write up an explanation of how the circuit works using the schematic as a reference.

 

It helped when you posted the photos - I was able to compare them to the schematic and see where the problem was. As I mentioned in a previous post, the first place to look when you have these problems is at what has changed. In this case, it was the mod.

 

[WRGKMC]

[onelife]

[ATTACH=CONFIG]n31967044[/ATTACH]

Notice the arrowhead just above the word MIX. It represents the centre lug on the pot and had two orange wires attached to it. One of the wires went to the send jack as you can see on the diagram, The other orange wire goes to the main circuit board and, through the 470 Ohm resistor, connects to V3b.

 

The white wire from the send jack goes to the circuit board and comes back to connect to one end of the pot. This is represented on the diagram with the line from the word SEND, over the word FX LOOP and connects to one end of the pot near the 0% label.

 

The red wire that comes up from under the small circuit board connects the other end of the pot to the RTRN jack as you can see on the schematic.

 

On the diagram, notice the difference between the SEND jack and the RTRN jack. The difference is the third lug on the SEND jack and when there is nothing plugged in to it, the white wire and orange wire are connected together. This allows the signal from the 1uf coupling capacitor to pass through the circuit to the next stage (V3b). When a cable is plugged into the SEND jack, the connection is interrupted so the signal has to pass through whatever is plugged into the effects loop before it can get to the next stage.

 

Before the mod, turning the MIX POT to 0% connected the input to the send jack, through the 470 Ohm resistor to V3b.

 

 

When you did the mod, which is essentially removing the MIX POT and the wire on the diagram that goes from the SEND jack to the 0% end of the pot, you still needed to have the third lug of the SEND jack connected via the orange wire to the 470 Ohm resistor to V3b in order for the amp to work without anything plugged into the loop. The RTRN jack also needs to connect to the 470 Ohm resistor which is why the red wire and orange wire need to be connected together. Connecting both the orange and red wires to the third lug of the SEND jack is what allows the signal to pass through whether or not there is anything plugged into the loop.

 

 

 

btw, were you able to solve your initial problem with your effects rack not working with the DC-5?

 

 

 

[jimijames31]

Yeah the effects rack problem was because the Fx loop wasn't working. I have now got it all working together. I actual built a box and transferred the dc-5 into it and have my FX unit in it as well. Now I'm dialing the effects for each song my cover band does.

[jimijames31]

It's all working like a charm. My drummer was worried that the head wouldn't be powerful enough to run my 4x12. Right up until I hit the first chord.

[onelife]