The main amp will not work, when i plug speakers into it, it just hums. the monitor amp will work but when using it the back gets really hot (too hot). my friend seems to think its a transistor, is this a correct assumption? and if so how would i go about replacing it? anyone have any schematics on this model?
stevem Messages: 4733 Registered: June 2004 Location: NY
Senior Member
Hi. I have never seen this model, but from the way you describe it, I am guessing it has a seperate speaker jack for powering the monitors and the mains.If this is so, then the main output section has a problem. I do not know what tech/ circuit repair work you can handle, but this would not be something for a first timer. Even more so if it has to be repaired with out a schematic.
pleat Messages: 1452 Registered: June 2004 Location: Belding, Mi
Senior Member
The PX200 was vintage 1985. The amp has two 100 watt rms amps in it. One for the house with graphic eq and the second amp with a graphic eq for monitor speakers. The amp has a nice patch panel and could use both amps for the house or monitors, with signal outs for larger outboard amps. You do have a major problem with the one amp, and I would suggest that a qualified repairman fix it. With one amp still working, he should be able to compare the bad amp with the working amp. The PX 200 was a great sounding mixer, as close to a tapco as one could get for that era.
Good luck on the repair.
Don
I have that mixing board also and there is no issues with it. I would first suggest the heat problem may have to do with too low impedence. Mine gets hot also when I get the ohms around 4 ohms so I try to keep a 8 ohm cab or 2 16 ohm monitors on it and it does fine. It does a good job for small clubs. I haven't had it opened so I dont know what driver boards are in it for sure but I would guess it to be like the PC-5021 100 watt board like they used in the speaker power modules. I didn't find it to be difficult to overhaul. The one I worked on was doing the same thing as your main board, loud humm. If you have a little knowledge in electronics it could be possible to walk you through it. You'll need to have a multi meter (preferably Digital)and be able to understand how to use it. You'll also need a desoldering tool and soldering iron with a good tip and be able to use it without burning up the board or bridging the solder lines (Traces) together. The rest is information , replacement parts and a whole lot of time. This isnt something you can rush thru. As old as it is, caps would also be questioned. Steve C
PS: If this is something you plan on putting to work full time for a band, it would be best to have a good tech go through it.
I gave $100 for mine a year or two ago. There not a real collectable piece, but are very user friendly. I pulled the power module out of the back of my PX200 board and its not at all like the earlier modules I was talking about. Still using the same basic idea just newer components. I would guess a driver transistor (The small square ones mounted in the alluminum heat sinks on each end of the board) is going to be bad if theres nothing burnt looking on the board. If you have a volt meter, check to see if there is DC voltage in the speaker output jack. The main output transistors are not soldered in and can be replaced easily with the removal of the 2 mounting screws, but keep in mind these are insulated from the chassis with a plastic insulator and plastic shoulder washers. They will just pull out of the sockets by hand and can somewhat be tested by using a continuity tester (Multimeter). If you find any bad they can be replaced with the common 2N3055 NPN power transistor