Trouble with level/gain Loop ACTIVE or NOT - 3ch Dual Recto

[Guiguibobo]

Hi guys,

I've got a problem with my Dual Rectifier :
I've got an extra gain and volume (+10-15%) that appears when my FX Loop is activate, even when nothing is plugged in the loop. The most scary for me is that the SEND LEVEL pot modify my MASTER VOLUME both when LOOP is ON or OFF ... So I can't set any volume difference with the loop SEND LEVEL and my MASTER ... I don't use the BOOST. I try playing with the SOLO level pot, but nothing changed ...

Is this a Relay/LDR problem .. Or a PREAMP Tube problem ? I'm a power-electronic engineer and I must say that sound-electronic is a bit confused for me ...

Thanks for you help,

Guillaume.

 

[afu]

Hey buddy,

The Send is always working when the rear panel loop selection is set to any of the "ON" selections, whether or not the loop is active at the moment. The Send adjustment is used to balance any differences between the dry path and the loop path. Put the Send control to straight up Noon and see how that works. Too large a Send level will overdrive the Return stage. Then the Output will shoot that over to the power amp and it will probably overdrive again.

 

[Guiguibobo]

Hey buddy,

The Send is always working when the rear panel loop selection is set to any of the "ON" selections, whether or not the loop is active at the moment. The Send adjustment is used to balance any differences between the dry path and the loop path. Put the Send control to straight up Noon and see how that works. Too large a Send level will overdrive the Return stage. Then the Output will shoot that over to the power amp and it will probably overdrive again.

Hi afu,

Thanks for your answer,

The problem is that this "volume step" is shifting with the SEND LEVEL. If I put the SEND Control to straight Noon, I've got the step between Loop Active and Not, if I put it to 10 o'clock, I will get this step again when I'll active the loop, and if I put it to 2 o'clock, I got the same ...

 

[afu]

My apologies, I don't think I understood the original post the first time I read it. A couple questions:

1) is it the reborn or 2001-style?
2) If it is the older one, have you varied the Return?
3) Have you cracked it open?
4) Has it been modified?
5) Is the tube in V4 rated to withstand the voltage on the cathode for V4a (217 Volts)? This can cause some issues.

Depending on the results of the above, if you are comfortable with checking it, check voltages and ground around V4's pins, check the Send pot for wear or grounding, and look at the track and Return wiring. I'm wondering if someone tried to mod it, but wired it incorrectly. I'm also wondering if the feedback/impedance voltage divider on the grid or Send Pot around around V4a is dirty, damaged, or loose.

The only time I have experienced something similar, the effects in the loop were either dropping the output, or the gain on an effects unit was too high. The Send level would balance the offset and that doesn't seem to be happening. In my case, I had to drop the Send to find unity.

I don't feel well, so I hope this makes sense.

 

[Guiguibobo]

My apologies, I don't think I understood the original post the first time I read it. A couple questions:

1) is it the reborn or 2001-style?
2) If it is the older one, have you varied the Return?
3) Have you cracked it open?
4) Has it been modified?
5) Is the tube in V4 rated to withstand the voltage on the cathode for V4a (217 Volts)? This can cause some issues.

Depending on the results of the above, if you are comfortable with checking it, check voltages and ground around V4's pins, check the Send pot for wear or grounding, and look at the track and Return wiring. I'm wondering if someone tried to mod it, but wired it incorrectly. I'm also wondering if the feedback/impedance voltage divider on the grid or Send Pot around around V4a is dirty, damaged, or loose.

The only time I have experienced something similar, the effects in the loop were either dropping the output, or the gain on an effects unit was too high. The Send level would balance the offset and that doesn't seem to be happening. In my case, I had to drop the Send to find unity.

I don't feel well, so I hope this makes sense.

Hi afu,

Thanks a lot for your time and your great answer, I will take a look carefully to my amp, and get an answer for all your 5 questions. I'll open it and measure the point you mentioned.

I keep you in touch,

Thanks again, Have a nice day,

Guillaume.

 

[3124+]

Just to clarify... you are hearing the level change when pressing the FX button on the Recto's footcontroller?

 

[Guiguibobo]

Just to clarify... you are hearing the level change when pressing the FX button on the Recto's footcontroller?

Hi 3124+,

Yes, I'm hearing a master level up when turning ON my FX Loop, by the 1/4" jacks controller, and via my Voodoo Lab controller. (And a MASTER volume/gain down, when turning it down ...).

Thank you !

G.

 

[Guiguibobo]

Hi Everyone,

I've opened my amp, and I've spotted a broken diode (a 1N4007) between V4A and V3B (physically), pictures below (front of the amp is on the right) :

Can this the cause of my trouble ...?

Thank's guys,

G.

 

[afu]

That looks like the 'low v supply' bridge rectifier circuit. That would affect the switching, the photoresistor for activating the loop, and the heater for V1. You can get a 4007 from Radioshack or any other electronic parts store.

 

[vick1000]

Holy crap. I have never seen anything like that. It looks like some one took some cutters to it intentionally. I don't know if that's the cause of your problem, but it certainly needs to be replaced. It looks more like a power filtering section off hand.

 

[Guiguibobo]

That looks like the 'low v supply' bridge rectifier circuit. That would affect the switching, the photoresistor for activating the loop, and the heater for V1. You can get a 4007 from Radioshack or any other electronic parts store.

Okay !

Thank's afu, I can get 4007 everywhere at my work ;-), I think I've got some at home, from my personal components...

The more difficult so far will be to flip the board to get it un-soldered, and solder the new one ... Do you have a tip for this step ?

 

[vick1000]

That looks like the 'low v supply' bridge rectifier circuit. That would affect the switching, the photoresistor for activating the loop, and the heater for V1. You can get a 4007 from Radioshack or any other electronic parts store.

Okay !

Thank's afu, I can get 4007 everywhere at my work ;-), I think I've got some at home, from my personal components...

The more difficult so far will be to flip the board to get it un-soldered, and solder the new one ... Do you have a tip for this step ?

There is no esy way if you want to solder on the back side, just get to work and make sure you have a few hours. But you can cut the remaining body of the diode out, and solder the new one to the leads that are left. It would work, but it would drive me nuts knowing it was in there and not properly done

Just be glad you don't have an old 2ch revG like me, with no boards or ribbons, imagine that job.

 

[afu]

Thinking about it more had me concerned about it blowing from reverse avalanching. I've never seen one blow, but they can get quite hot when the reverse power potential is trying to go through it. The black on the solder joints looks funny, as if it may have overheated and the positive end has lost its solder joint.

I can't think of what the issue might be right now. Perhaps Vick has some thoughts about that.

 

[Guiguibobo]

Hi guys,

Today I replace the broken diode, and I think it was clearly the problem source.

I've identify the broken one on the schematic below. The missing diode causes a partial supply of the V1 heater and doesn't drive the RY2 Relay (Loop Bypass), this can explain why my FX Send Level was always active. And my gain loss.

Schematic :

Cause of the failure : Bad soldering on one lead of the diode, run to an overheating of it, and destruction.

Pictures :

Once repaired :

I'll test this tonight, and tell you if everything's right....

Thank you guys !

Guillaume.

 

[Guiguibobo]

Aaaaaahhhhh => No change !!

Except a little 'hum' that disappeared (that can be explain ...)

My FX SEND Level is still acting as a MASTER, even when the Loop's not active ... And still have this step between On and Off ...

I will check tonight the different points that afu mentioned.

 

[afu]

I did the parallel to series mod, so I can't test my loop for level differences.

The most scary for me is that the SEND LEVEL pot modify my MASTER VOLUME both when LOOP is ON or OFF ... So I can't set any volume difference with the loop SEND LEVEL and my MASTER ... I don't use the BOOST. I try playing with the SOLO level pot, but nothing changed ...

When you say "on or off" do you mean when the loop is active or not active, or do you mean when the loop is bypassed or not bypassed? If the Send still works during bypass (back panel), the bypass relay has an issue.

The thing I thought about is whether the dry path from the Send to the Return has a problem with the solder joint. If the signal is being reduced on the dry path, the wet path would definitely sound louder. The Return pot's lug 3 would be the most obvious culprit in this case. Check the short bit of dry signal track on the PCB, too.

Also, the correct schematic for a 3 Channel is here.

 

[Guiguibobo]

Hi afu,

When I said "On or OFF", I meant "ACTIVE or NOT ACTIVE" and not "Bypass or not. Last night I ByPassed it, and everything was right, the FX Send Level pot was not acting anymore, as the SOLO and OUTPUT pots ...

Oh, afu, I don't have a RETURN POT, only a SEND one. And a MIX one (10 to 100% Wet)...

 

[afu]

Mix is Return. Sorry for using the wrong word.

 

[3124+]

The schematic posted is for a 2ch dual rectifier. The 3ch circuit is totally different.

When footswitching loop, the send level remains active at all times. This is normal. Send level is only defeated by hard bypassing the loop using the rear panel selector knob.

The level difference you hear is typical of these amps. It is the result of changing load on the MIX pot. When loop is footswitched on, J175R closes and the mix pot references to ground through the low output impedance of your fx processor. When loop is footswitched off, J175R opens and the mix pot loses its reference to ground. Poor circuit design, but knowing Randall I'm not surprised.

 

[Guiguibobo]

The schematic posted is for a 2ch dual rectifier. The 3ch circuit is totally different.

When footswitching loop, the send level remains active at all times. This is normal. Send level is only defeated by hard bypassing the loop using the rear panel selector knob.

The level difference you hear is typical of these amps. It is the result of changing load on the MIX pot. When loop is footswitched on, J175R closes and the mix pot references to ground through the low output impedance of your fx processor. When loop is footswitched off, J175R opens and the mix pot loses its reference to ground. Poor circuit design, but knowing Randall I'm not surprised.

Thank you 3124+,

So .. If I've well understood, there's nothing to do ...?

I think I'll go for the series Mod ... I've found a schematic weeks ago, is this correct ? :

Just to not go wrong, I won't have this issue anymore with the series mod right ?

Thank's yall,