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Post subject: Roc Pro 1000 Problems
Posted: Sun Jul 01, 2012 8:13 pm
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Hello to all,
I just bought this amp head from a pawn shop. Clean sounds amazing . . . . but I can't get the gain select or drive select switches to do anything. Through some checking I've found that this head originally came with a three button stomp box but I don't have that. Is this why I can't change the settings or am I looking at an internal failure?


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Post subject: Re: Roc Pro 1000 Problems
Posted: Sun Jul 01, 2012 9:16 pm
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Joined: Tue Jun 29, 2010 1:20 pm
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Location: Indiana
Hi honez,

The foot switch, when plugged into its jack, will disable the front panel switches via a contact in the jack, so with the foot switch unplugged, the front panel switches should work. It could be a bad jack, dirty/bad contact in the jack, or broken solder joint on or near the jack, making it appear to the amp that the foot switch is plugged in. Next thought would be a possible problem with the power supply for the channel switching. :idea:

http://support.fender.com/schematics/guitar_amplifiers/Roc_Pro_1000_schematic.pdf

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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Post subject: Re: Roc Pro 1000 Problems
Posted: Sun Jul 01, 2012 9:30 pm
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Shimmilou,
Thanks for the reply. I'll definately check it out. Also, with the board out of the cabinet, I see that the two diodes marked CR56 and CR57 have obviously gotten hot. The board around the solder and under the diodes is dark / brown almost looks scorched. I removed the diodes and tested them, but they check fine. Normal? Common?


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Post subject: Re: Roc Pro 1000 Problems
Posted: Sun Jul 01, 2012 9:41 pm
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Those are the "zener diodes", used in the channel switching power supply that I mentioned. It is normal for the board to have scorch marks near the zeners, and sometimes even also near the 5 and 10 watt resistors near the zeners. All of these components get very hot. The heat, and the char marks caused by the heat aren't a problem themselves, but a common resulting problem from the heat is usually broken solder joints, and/or broken circuit traces in that circuit. Check the joints and traces on the back of the board around that circuit very closely.

Forgot to add a link to the manual, in case you don't have it.
http://support.fender.com/manuals/guitar_amplifiers/Roc_Pro_1000_manual.pdf

_________________
---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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Post subject: Re: Roc Pro 1000 Problems
Posted: Sun Jul 01, 2012 9:46 pm
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Thanks again Shimmilou. I'll let you know what I find!


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Post subject: Re: Roc Pro 1000 Problems
Posted: Thu Jul 12, 2012 8:39 pm
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Shimmilou. Update for ya!
Found a questionable solder joint on one of the zener diodes, two damaged spots on the circuit traces next to the same diodes, bad connection in the foot-switch jack that made the circuit think the foot-switch was plugged in, bad solder joints on the connections for the foot-switch to the circuit board. Fixed all of this and it works like a champ . . . . but I noticed how hot this circuit board gets while it powered up and that there is no way for the heat to vent. I added heat sinks to those zener diodes and even the sinks get very hot. Added air passages to the aluminum plate under the circuit board as air intakes and vent holes to the sides of the cabinet near the top. Now all that heat has somewhere to go. Now, after its been on a while, I can pull out the electronics and the only thing that is hot are the components themselves and not the whole board.

Thanks again for the advice. Another one back from the dead!


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Post subject: Re: Roc Pro 1000 Problems
Posted: Thu Jul 12, 2012 9:15 pm
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Awesome! Probably better than new with your improvements. Yes, those components get very hot, which is normal, not necessarily a good thing but normal for some of these circuits in Fender amps.

Great idea using heat-sinks. Just as an experiment awhile back, I fashioned some heat-sinks from some binder clips for a similar circuit in a HRDlx. The bigger chrome ones are on the 5 watt resistors, and the smaller red ones are on the zeners.

Image

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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