Calling 6100 owners : no sound when FX loop set2 Serie

[Thames]

Hi guys,

Im not sure if I had this problem at first as I tried many settings (new owner here).

If I dont plug anything in the loop and set the switch on Serie mode, I get no sound at all, even if I turn the Effect Level in front. Is it normal ?

 

[Micky]

What have you got plugged into the loop?

 

[Thames]

What have you got plugged into the loop?

Im using a Rocktron Xpression.
But right now, I have nothing plugged in.
No sound in Serie, ok in Parallel.

Original message updated.

 

[Keeb]

Have you tried patching the loop (chord between send and return) in series mode?

If the jacks are worn out maybe they're always "open" and therefore the signal doesn't get from the pre amp to the power amp... I don't know if this is likely but it seems possible (to me at least!).

 

[Mat_P]

Uhm, maybe a dump suggestion but have you turned up the mix pot at the front panel?

 

[Micky]

Don't you have to jump the loop in order to use it in series? (with nothing in between?)

 

[Keeb]

Don't you have to jump the loop in order to use it in series? (with nothing in between?)

I was thinking that the jacks are switchable. Although I was too lazy to look at the schematic. (according to this schematic they are switched jacks).

 

[anitoli]

Operational Note F: Effects Loop
The main effects loop on this amplifier can be configured either as a series or a parallel loop by using the
series/parallel selection switch (item 43). The parallel loop (switch out) splits the pre-amp signal into two, retaining the
direct signal within the amplifier itself, whilst sending a parallel signal out to the effects processor. By turning the direct
signal within the processor to zero only an effects signal is returned to the amplifier where it will be mixed back in with
the direct signal. This leaves the original direct signal uncoloured by any circuitry within the processor. By using the
effects level control (item 28) your ideal mix of dry and effects signal can be easily set up.
The series loop (switch in) diverts the whole pre-amp signal through the effects loop and switches off the internal direct
signal. The effects level control (28) now acts as an overall master level control.
In terms of application, units that are time based (eg Chorus, Delay, Reverb etc) are best suited to the parallel loop.
Real time effects (eg. Graphic or Parametric EQ, Compressors etc.) suit series loop operation.
It is worth noting that the line in (40) and line out (38) circuit could be used as a series effects loop at 0 dBm, giving​

you the ability to use both types of loop simultaneously.

 

[anitoli]

I was thinking that the jacks are switchable. Although I was too lazy to look at the schematic. (according to this schematic they are switched jacks).

No. If set to series CCW of the effects knob bypasses the loop completely. As you turn it CW it sends more of the signal to the loop. You shouldnt need to jumper the loop.

 

[Thames]

Great. Thanks all. Will do some testing this weekend !

 

[Keeb]

No. If set to series CCW of the effects knob bypasses the loop completely. As you turn it CW it sends more of the signal to the loop. You shouldnt need to jumper the loop.

I know you shouldn't have to but I was thinking if the jacks are dirty/broken and therefore their switching function fails; THEN you would need to jumper the loop. Right? (not sarcastic, just trying to understand this thing).

 

[anitoli]

I know you shouldn't have to but I was thinking if the jacks are dirty/broken and therefore their switching function fails; THEN you would need to jumper the loop. Right? (not sarcastic, just trying to understand this thing).

If the loop is in series you wont get any signal through it when turning the knob clockwise as the jacks are grounded. With a jumper you should get a signal. When set to fully counterclockwise the loop jacks are bypassed internally so theres no need to jumper the loop if you are not using it.

You said you arent getting any signal at any knob position in sereis, right?

 

[Keeb]

If the loop is in series you wont get any signal through it when turning the knob clockwise as the jacks are grounded. With a jumper you should get a signal. When set to fully counterclockwise the loop jacks are bypassed internally so theres no need to jumper the loop if you are not using it.

Even if the jacks are faulty?

(I'm sorry if I'm beating a dead horse right now and even derailing the thread but I'm not sure if I'm understanding you correctly. This is a beast of a schematic so I might be wrong.)

My question was simply if the jacks switching was faulty, so that in series mode there is no connection between send and return when the loop is not used, would that not result in silence unless the loop was patched?

I know the loop is supposed to work without being patched and I would imagine that comes down to the jacks being switched, meaning no plug in jack means rerouted signal. However I can't figure out the switching by looking at the schematic. So maybe I'm not understanding the switching part of the jacks wrong.

You said you arent getting any signal at any knob position in sereis, right?

Thames said it was silent regardless.

 

[HOT TUBES 70]

Have you bumped the POWER AMP MUTE button !
I did this once , and it took my stupid ass 20 mins. to figure it out ..... boy was my face red !

 

[anitoli]

To the OP: I have to eat crow. I made a visual error when looking at the schematic and told you the wrong thing. When the loop is in series, if there is nothing in the jacks you will get no signal at all regardless of the knobs position. If you insert an effect or a jumper then the signal will increase as you turn the knob CW.

In parallel, you get full loop bypass at the CCW position, full loop in the CW position, and a blend of the two anywhere in between.

I just verified this with my 6100.

I apologise for any confusion i may have caused.

 

[Micky]

To the OP: I have to eat crow. I made a visual error when looking at the schematic and told you the wrong thing. When the loop is in series, if there is nothing in the jacks you will get no signal at all regardless of the knobs position. If you insert an effect or a jumper then the signal will increase as you turn the knob CW.

In parallel, you get full loop bypass at the CCW position, full loop in the CW position, and a blend of the two anywhere in between.

I just verified this with my 6100.

I apologise for any confusion i may have caused.

That is what I thought... Glad you could verify it.

 

[Thames]

Hi everyone! Back from vacations with family. Thank you all for your replies.

That is interesting, 'cause when my FX loop is set to SERIE, even if I turn down (CCW) the FX "blend" knob, I still get no sound.

Im about to replace the pot, I bought a full new set of replacement pots anyway. Would this help ?

 

[Marshall Mann]

Pots tend not to fail catastrophically (all at once), but it's impossible to say with out testing.

Have you tried installing a jumper cable as Micky suggested?

 

[Micky]

Really. It is working as intended.
Serial with nothing plugged in, no path to the power.
Parallel is a mix, the pot controls the bypass.

 

[Thames]

Pots tend not to fail catastrophically (all at once), but it's impossible to say with out testing.

Have you tried installing a jumper cable as Micky suggested?

Pots : about 40% of them are scratchy, I cleaned them with D5, but as I plan to replace the Master Volume pot, I'll replace all of them on that board too.

Jumper : yes, it works if I plug a jumper cable (SERIE). So as Micky said, it works as intended ?