Center stage reverb can't take it?

[thom]

Hi all,

I posted my CSR project here http://www.diystompboxes.com/smfforum/index.php?topic=103447.0

All has been well, until today when I decide to push my amp a little (It's just a 15W practice amp, Ibanez TSA15H).

When I go past 2 o'clock in clean (or past 1 o'clock with the TS on), the reverb cuts off completely  (no sound from the amp either).

I turn the CSR off, the sound from the amp comes back (minus reverb, of course).

I turn  the reverb on again, fiddle a bit with the CSR input cable, reverb and amp sound is back, but cuts off again unless I turn it down at the amp.

I doesn't seem to be a bad solder, as the issue is only when the amp is played loud. Does that make any sense 

[GibsonGM]

Quick guess - you might be driving the thing into extreme cutoff (?)   I would expect SOME signal to pass, tho, just very distorted.   Something else is going on.   

You need to post the actual schematic of the unit, and how you have it attached in your amp, thom.  Once we can see all the variables in there, we can give you ideas of how to troubleshoot.   I bet it's something fairly simple but overlooked.   If it works well at lower volume, then we have a place to start from to get you into some reliability at higher levels!

Post up the data you have (schema, how it's connected, voltages at quiescence AND driven, things like that).

[thom]

Here's the schematic http://www.generalguitargadgets.com/diagrams/stage_center_reverb_sc.gif?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

and the layout http://www.generalguitargadgets.com/pdf/ggg_sc_reverb_lo3.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

The only mod I did was replacing C4 with a 4700 pF capacitor.

CSR's Input goes into Amp's Send
CSR's Output goes into Amp's Return

Where exactly should I measure the voltage on the Vero (I'm still new at that)?

One more thing (probably unrelated, but you never know): when Mix on the CSR is pushed beyond 12 o'clock, an increasingly loud hiss can be heard (not a buzzing sound, more like a "shhhh", like the background noise of an old audio tape recorded over too many times - sorry if you're too young to know what I'm talking about  )

Otherwise, when not pushed in any shape or form, it sounds great!

Thanks for your help.

[thom]

The cutting off problem does not seem to happen when the reverb is taken out of the loop and the guitar is plugged straight into it.

I'll investigate further. Any suggestions, feel free 

[Paul Marossy]

Maybe it's cutting out due to ultrasonic oscillation?

[GibsonGM]

The cutting off problem does not seem to happen when the reverb is taken out of the loop and the guitar is plugged straight into it.

I'll investigate further. Any suggestions, feel free 

That's a piece of info, right there.  You have it in the effects loop, correct?   I am thinking you may be overdriving the input too much.  Some kind of clamping could be going on (?).     If it's designed to take a guitar as its input, and you're throwing 10X the signal at it, this could be the issue.   You sure the amp has no problem with its effects loop?   It could also just be crappy, in terms of output impedance...something is definitely going on between the two, if it works in FRONT of the amp!   

Paul has a good thought in that it could be going into oscillation, and you wouldn't necessarily hear it.  That would "keep it busy" and create a cutting out sort of problem. 

I'd measure the supply voltage to the opamps as you turn it up loud...see what that looks like under load/when problem is occurring...does it do anything weird, y'know....I am leaning more towards your effects loop being the real problem, tho....