I burned out some resistors on the circuit board of my Roland

Some resistors on the circuit board of a Roland KC-300 amplifier have burned out and are so charred that their specifications cannot be determined. The resistors in question are R82, R83, R85, R92, and R93. Resistors R92 and R93 are getting excessively hot, which may indicate an issue with excessive current draw. Possible components causing this problem could be IC10 or transistors Q6 and Q7 in the headphone circuit. R82, R83, and R85 have been replaced, but R92 and R93 had to be ordered due to local unavailability. After replacing the resistors, the headphone jack still does not function, and R92 and R93 continue to heat up. There is a concern about whether the headphone jack should also be replaced or if the malfunction of R92 and R93 is the root cause of the issue. It has been noted that the headphone circuit is likely the problem, as these resistors provide the positive and negative 15.4-volt supplies to the operational amplifiers and mute circuit. If these voltages are not present, there will be no output. It is typical for 2-watt resistors to become hot, but excessive heat that melts solder indicates too much current is passing through them. The headphone circuit includes IC10, Q7, Q6, D9, D10, as well as various supporting capacitors and resistors. It is essential to verify the signal flow into and out of IC10 and through capacitor C81 to resistors R83 and R82. While the headphone circuit is a likely source of the issues, it is advisable to confirm or narrow down the problem through measurements and signal tracing. A schematic diagram would be beneficial in this regard.

In the event of further problems after replacing the components, the individual seeks advice on how to establish contact for additional assistance.

To address the issues with the Roland KC-300 amplifier's headphone circuit, one must first ensure that the solder joints and connections are intact, as poor connections can lead to excessive resistance and heat. The resistors R92 and R93 are crucial as they provide the necessary voltage levels to the op-amps. If these resistors are overheating, it may indicate that either the op-amps themselves are drawing too much current or there is a fault in the headphone circuit that requires investigation.

The circuit includes a variety of components that work together to function correctly. IC10, being the operational amplifier, must be checked for proper function. If it is faulty, it may draw excessive current, leading to overheating of R92 and R93. Similarly, transistors Q6 and Q7 should be examined for any signs of failure, as they are integral to the headphone circuit's operation.

If the headphone jack is suspected to be faulty, it should be tested for continuity and proper operation. A malfunctioning headphone jack can lead to an incomplete circuit, preventing signal flow and causing other components to work harder than necessary.

Signal tracing through the circuit is essential. This involves measuring the voltages at various points in the circuit to ensure that the expected voltages are present. If the voltage levels are not as expected, it may indicate a failure in one of the components or an issue with the circuit design itself.

Using the schematic as a reference will aid in identifying the correct points for measurement and help in understanding the interconnections between components. This approach will facilitate a more accurate diagnosis of the problem and guide the repair process effectively.

Utilizing online resources for further questions can provide additional insights and troubleshooting advice, ensuring that the repair is thorough and effective.Burned out some resistors on the circuit board of my Roland KC-300 amp and they are so black that I can`t tell what they are. What kind of resistor is R82, R83, R85, R92, and R93 If R92 and 93 continue to get really hot. you may have something pulling too much current. I would suspect IC10, or transistor Q6 and Q7 in the headphone circuit. Thanks for the help so far. I replaced R82, 83, and 85, but I had to order R92 and 93 because no one in town had those resistors. I tried it again with just those in place, but the headphone jack still wouldn`t work and R92 and 93 were still heating up. Should I replace the headphone jack too, or is it possible that R92 and 93 are causing it not to work I think you have a problem with the headphone circuit.

Those resistors supply the positive and negative 15. 4 volt supplies to the op-amps and mute circuit. If they those voltages were not getting through you would have no output at all. It is normal for 2 watt resistors to get hot, but not hot enough to melt the solder. That indicates too much current is going through them. Since the headphones are not working, that is where I would look. The HP circuit consists of IC10, Q7, Q6, D9, D10, and all the supporting caps and resistors. You have to see if your getting signal into IC10, out of IC10, and through C81 to R83 and R82. While the headphone circuit is the most likely source of your issues, it is still a good idea to try to confirm it or narrow it down through measurements and signal tracing. The schematic should help in that respect. Thank you so much. That ought to do the trick. Is there some way that I can contact you again if I have any problems after I get these parts and attach them Ask-a-doc Web sites: If you`ve got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers.

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