I HAVE A FENDER PASSPORT P.A. WHICH HAS RECENTLY DECIDED TO DROP A SPEAKER CHANNEL, ALSO TWO OF THE MIKE INPUTS. I SUSPECT THE SPEAKER PROBLEM MAY BE A FAULTY JACK SOCKET, BUT I NEED TO KNOW IF IT`S COOL TO OPEN THE FRONT TO GAIN ACCESS. ANY SUGGESTIONS WOULD BE APPRECIATED STEVE WHALLEY
These are a real pain to open. You have to remove the front panel to remove a shield to remove the back amplifier power supply area. The power supply is a switching type and has lethal voltages present. Working on this should be done using an isolation transformer. With your symptoms, it is likely one side of the power amp MAY be blown, but do check that the wiring hasn't fallen off and the jack itself. Two pairs of wires come from the power amp to the front panel jacks. document location of ALL the cables you disconnect as they CAN be confusing to restore.
I forgot to mention that Fender has downloadable manuals and schematics under support. Channel one has a VIP feature with a threshold control for doing voice over music with a mike for announcements. Depending on the setting of the control channel one will take priority over the other channels. That may be the source of your channel problem.
I was hoping it was something simple. I don't have a Passport to take apart so I will have to guess. From the outside it looks like all the controls and jacks on the front are soldered to one board and protrude through the surface to be secured by nuts and washers. If you feel comfortable doing it then go for it. I'm looking at a picture of it and if the bottom panel is separate from the top panel all the better. Start by trying to determine how the panel comes off. Remove it slowly and carefully making sure that nothing comes unplugged inside. If you can get a good look at the back of the panel take note of any connectors that allow you to take the whole panel out and make a diagram or take pictures of everything so you don't get stuck later. Once you've got the panel out look to see how you can get at the jacks you want to work on. You may have to remove knobs, nuts,washers etc to get there. Again make careful note of everything as you go.You may discover that the jack is soldered to the board and you only have to resolder any broken solder joints. Bonus. If the jack is bent internally you will have to replace it by taking it to an electronics store. One that carries a huge selection of bare parts. The pin out on the rear of the jack and the depth of the jack are important so try to obtain as close a match as possible. If you want to you could also try removing the contacts in the jack and rebuilding it. Its easier to just replace it. You might also find the source of your channel problem with careful scrutiny. Cracks on this kind of circuit board if there is one can be bridged. They aren't like computer circuit boards with internal layers. Once you have the jack replaced use a bare phone plug and insert it and with a volt ohm meter test the solder side to make sure your connection is good.Keep me informed of your progress. It can be done. I didn't see a schematic on their website and its too bad as its easier to trace the problem with a schematic.
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It is possible that the amplifier had encountered a fault with a higher current drain which had triggered it to a protection fault condition. The fault can be your output drivers- the MOSFETS/IC's fitted for both the channels, Use a meter after disconnecting to check for short in the drivers. Disconnect the positive and negative voltages to the output and see if the protect changes. Even a fault in the preamp stages that drives in high current into the output can shut the Amplifier. Sometimes this can be a noise like a HUM or HISS before the protect works. Faulty capacitors in these circuits also can cause similar issues and needs close observation.
You need to confirm and replace the specific stages or outputs. If not there can be issues in the mother board, maybe the protect circuit by itself is shutting off due to a faulty bias , maybe a leak in any voltage/current sensing circuit. Also disconnect the speakers and test, if the protect is off then check for short on the speakers.
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Thank you, I am aware of the over-riding properties of channel one,
but here only channels 1 and four are down. My system has been
seen by a technician who thinks there may be a crack in one of the boards, which is ( A ) difficult to access and ( B ) uncertain as to avaliability. The speaker jack problem I understand but need to know if it`s cool and easy to take off the front control panel by removing the screws down each side to access the internal jack clip and bringing it back into alignment...would appreciate your savvy on this before I go ahead..Thanks again Steve.
If its still under warranty, you would be better off taking it ti a good musical equipment repair shop.
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