Schematic help

[Rod]

Hi everyone!

Well i have been locking to this marshall jvm 410 h schematic (attached file), but i dont understand some things.

Can someone explain to me what is the con7 - to CN 202, con 8 - to CN 201?

This is the switching system ,right? but how this switching system works with the footswitch?, how the relays rl3B, rl4b are activated?


Thanks.

[Jazz P Bass]

Full schematic link:MetroAmp.com Forum • View topic - JVM schematics
Con 7 & 8 are on the preamp board. Con 202 & 201 are on the front panel.
Both cables are for control potentiometer routing purposes, depending on which mode is selected.
The input for the footswitch circuit is in the lower left corner of this schematic. (410-60-02).
The actual switching circuits are on a different schematic page.

[Rod]

Thanks Jazz!

But i still have one question, how the relays rl3B, rl4b are activated?

Full schematic link:MetroAmp.com Forum • View topic - JVM schematics
Con 7 & 8 are on the preamp board. Con 202 & 201 are on the front panel.
Both cables are for control potentiometer routing purposes, depending on which mode is selected.
The input for the footswitch circuit is in the lower left corner of this schematic. (410-60-02).
The actual switching circuits are on a different schematic page.

[Enzo]

If you have not yet reailzed it, CN means connector, and each drawing represents a portion of the system. CNxxx on one board connects to CNyyy on another. You have to follow that between pages.

Rl3 and Rl4? Look on the Preamp page lower left. Rl3 and 4 are driven by transistors TR7, TR5. Those are in turn controlled by signals A2 and A3. Whence those? From the ribbon upper right "to CN303." That leads to the front panel board. FInd A2,A3 and they come from IC306, outputs Q4,5. What tells that IC to turn those off and on? Data lines D0-D8. To find their source go back through CN303 ribbon to the preamp board. IC3 there lower left produces those data lines. And ultimately, the IC3 is told what to do by the footswitch jack and whatever is conected there. And looking at the schematic, presumably the MIDI input could as well.

[Jazz P Bass]

Thankyou, Enzo.
I could not find A1-A4 for love or money.

[Enzo]

Oh, I love money, feel free to send me any you have that you don't love...


Come to think of it, in parts of town where my shop has been located, as well as the diner I frequent, um, well love and money are more closely related than perhaps oh in the suburbs.


When looking for things like "A3", in general a thing like that is on the same page, or if it leaves the page, there should be a place for it to do it - usually a connector or a bus indication.