1 Topic by Tony62 (edited by Tony62 2012-06-19 02:06:45)

  • Registered: 2012-06-19
  • Posts: 3

Topic: FF800 instrument input failure

Today I have connected a stomp box to the instrument input of my FF800 and after some hum it failed. The green (signal) LED is now permanently lit and there is no sound, just some noise. I'm guessing the input JFET died. The bad news is, both front and back inputs Ch1 are dead. How can this happen, by simply connecting a stomp box? Are there no input protection diodes?
Does anyone have a schematic, so I can fix this? Anybody with a similar issue?

Thanks,
Tony

2 Reply by MC

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Re: FF800 instrument input failure

> I'm guessing the input JFET died.

There is no such thing. There is a standard op amp for the front input. Aftert that comes the curcuit which switches between front and rear, and that one never fails.

> The bad news is, both front and back inputs Ch1 are dead.

I don't think so. Please check that you changed the input in the Settings dialog.

Regards
Matthias Carstens
RME

MC's Website

  • Registered: 2012-06-19
  • Posts: 3

Re: FF800 instrument input failure

Thanks Matthias.
I'm getting -14VDC on the +In, -In and Output of the OpAmp. Are there any protection diodes between the input and supply rails that could be blown or is it the OpAmp? Schematic please?

Oh, and In Ch1 rear works fine, I did not switch to rear.

Cheers,

Tony

4 Reply by MC

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Re: FF800 instrument input failure

Simply replace the opamp then, no schematics needed.

Regards
Matthias Carstens
RME

MC's Website

  • Registered: 2012-06-19
  • Posts: 3

Re: FF800 instrument input failure

Means there are no input protection diodes, right?
Just let me know, do none of the inputs of the FF800 have protection? Are they all prone to fail due to ESD? I need to know, so I can take safety measures. I have read about several users of FF800s where several inputs are dead.
Please let me know.

Thanks & regards,

Tony

6 Reply by MC

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Re: FF800 instrument input failure

No such diodes except for the mic inputs.

Regards
Matthias Carstens
RME

MC's Website