Digitech RP200 noise problem - no input signal

buck1107 · Joined: 14 Mar 2005 Posts: 7

Hi, I have a Digitech RP200 that only makes a hum when a cable is plugged into the input jack. There is no hum when nothing is plugged into the input. Could this be a bad input jack? It seems secure to the circuit board. Thanks, Louis

lee_UK · Posted: Tue Mar 15, 2005 12:43 am Post subject:

check your guitar cables, do they play ok from your guitar direct to the amp? try both cables, if the guitar plays ok with those 2 cables checked then i would go down the 'factory reset' route. Get the manual out and press the appropriate buttons to restore its defaults, you will lose all your user presets though, so make a note of what they are, it could be a faulty 1/4" input jack on the RP200 but i think its unlikey, try the other options first then get back to the forum.

buck1107 · Joined: 14 Mar 2005 Posts: 7

I've checked several cables with this effects unit, but the result is always the same, unfortunately. As I got this used, I don't have the owner's manual. Could you suggest somewhere online to get a free download of one?
How likely do you think it is that it could be a burned out chip, or other component? I know that capacitors usually only go out after about 20 yrs, so that excludes them hopefully. The jacks feel solid on the circuit board. I would really like to find a site, etc that has detailed information on how to use a voltmeter to test components on a circuit board (or would one need a oscilloscope to do that?)

Thanks again

lee_UK wrote:

check your guitar cables, do they play ok from your guitar direct to the amp? try both cables, if the guitar plays ok with those 2 cables checked then i would go down the 'factory reset' route. Get the manual out and press the appropriate buttons to restore its defaults, you will lose all your user presets though, so make a note of what they are, it could be a faulty 1/4" input jack on the RP200 but i think its unlikey, try the other options first then get back to the forum.

Farino · Groupie Joined: 15 Feb 2005 Posts: 11

http://www.digitech.com/ftp_mirror/PDFs/Manuals/RP200/RP200Manual.pdf

buck1107 · Joined: 14 Mar 2005 Posts: 7

Farino wrote:

http://www.digitech.com/ftp_mirror/PDFs/Manuals/RP200/RP200Manual.pdf

Thanks for the link!
I went and reset the pedal last night, but it still makes the humming noise. In the "bypass"mode, it's very loud, and in certain presets it's noticeable, although not as loud as in bypass mode. No input signal can be heard.

Are there any histories of faulty parts or things that go wrong the most with these 200s?

Thanks,
Louis

1bassleft · Posted: Wed Mar 16, 2005 1:05 am Post subject:

Louis, please don't mistake me for a sparky. I am not an electrics expert at all. That said, if the hum is atrocious in bypass mode (no decent output) and no output through the FX (but with reduced hum), doesn't that suggest that you have lost earth, or ground, to the input jack?

Solder-sniffers, please chime in; I'm only speculating here. Rather than spout bad theory (I do have a reason why I think this may be the cause), have a look at the ground wire to the sleeve connect of your RP's input jack. Does it look flakey?

Keep posting...

buck1107 · Joined: 14 Mar 2005 Posts: 7

Thanks 1bassleft!
I went back and inspected all of the jacks. As it's a fairly recent construction, they're mounted directly onto the circuit board. The jacks have the "spring type" contacts that snap tight against the plug once it's inserted. They must be "normally closed" jacks.
The solder connect points look clean and solid. I gave them all a firm tug, but nothing would wiggle. Perhaps I could resolder all of them just to test.
I worked on a Peavey amp a few months ago that had the same kind of jacks, and a very similar problem - there was no signal, and the bad solder joint wasn't apparent at first, although after resoldering, the signal was there.
So, everything *looks* good

1bassleft wrote:

Louis, please don't mistake me for a sparky. I am not an electrics expert at all. That said, if the hum is atrocious in bypass mode (no decent output) and no output through the FX (but with reduced hum), doesn't that suggest that you have lost earth, or ground, to the input jack?

Solder-sniffers, please chime in; I'm only speculating here. Rather than spout bad theory (I do have a reason why I think this may be the cause), have a look at the ground wire to the sleeve connect of your RP's input jack. Does it look flakey?

Keep posting...

lee_UK · Posted: Thu Mar 17, 2005 8:19 am Post subject:

have you tried a different guitar in this unit too? Bass is pointing toward the guitar, im assuming you would have tried a different instrument or even a microphone just to rule out the hum? hum is usualy caused by a instrument lead shorting out, or as bass says an earth problem or short on the guitar itself.

buck1107 · Joined: 14 Mar 2005 Posts: 7

Thanks Lee.
Yeah, I"ve checked it with a few different sources - guitar, bass, mic...different cables, etc.
I'm beginning to wonder if even though the input jack tested ok (that it was going to the board ok), that it might have been a false reading. It sounds like the signal isn't shoring to ground like it should...any thoughts?
Thanks,
Louis

lee_UK wrote:

have you tried a different guitar in this unit too? Bass is pointing toward the guitar, im assuming you would have tried a different instrument or even a microphone just to rule out the hum? hum is usualy caused by a instrument lead shorting out, or as bass says an earth problem or short on the guitar itself.

lee_UK · Posted: Thu Mar 17, 2005 10:16 pm Post subject:

first of all, plug some headphones in the headphone socket, does the hum still happen? if the hum has gone then this suggests a problem on the output socket and not the input socket.
2.do you get any hum when you plug a CD player in the 'jam in' socket?
3.what about when you press both pedals together to get the bypass mode on? what happens? still humming?
4. has the volume or level of the digitech at a sufficient level? you might have it set to 1 amd the amp up to 8, that would produce hum.

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