Sanyo JCX 2400KR

[GraterFang]

Alright, so I have a Sanyo JCX 2400KR and a Sansui AU-5900 that I absolutely love. I know that by today's standards they aren't the greatest amps in world but I nonetheless absolutely love the sound that they put out. Now, recently the 2400KR has developed a problem where the right side audio doesn't work, on both A and B side speakers. At most it will hiss or pop a little. The left side audio still plays beautifully. Now, I know my way around a multimeter and a soldering iron but I'll be the first to admit I'm no electronics expert. I can troubleshoot and fix simple devices but a stereo amplifier is a bit beyond my ability (other than checking for obvious things like fuses, bad switches, and blown capacitors, etc). And yes, the fuses are fine.

I also can't seem to find a good (= free) wiring diagram for this beasty. So, where do I begin?

[HayZee518]

have you tried HOWARD SAMS electronic schematics? you'll get other diagrams in the packet besides yours.
For amplifier troubleshooting you'll need a frequency generator capable of audible frequencies and an oscilloscope single or dual trace. a multimeter is good for resistances and voltage test points.

[GraterFang]

Thanks for the reference. I have access to a frequency generator but what I really need is troubleshooting hints. I don't have any experience fixing stereo amplifiers and would like to know what I should begin focusing my efforts on first, preferably starting with the most common problems. For example, could a faulty balance dial cause my issue? What should I be looking at?

[HayZee518]

ok, since we're dealing with sound, we can eliminate power supply problems. there's a method called "half-split" method of troubleshooting. basically its taking the amplifier as a whole and mentally splitting it in half and trouble shooting one half at a time. the most common type of amplifier is called a push-pull circuit. the output of one stage is the input to the second stage. the input is applied to the base of the transistor, the output comes off the collector to the base of the next stage. ITS output goes on to the next amplification stage. Other components aid in processing the signal. Disc type capacitors can be used to couple the signal to other parts of the circuit or to block certain frequencies to ground. Resistances are used almost all the time for current regulation.

[GraterFang]

Thank you for the info so far. Although basic, your help is well appreciated as I don't have much experience with how amps operate. The individual components I understand for the most part but I become easily overwhelmed when dealing with the whole unit. Hence my cry for troubleshooting help.

Anyhow, once I have obtained a wiring schematic, what would be an intelligent starting point for troubleshooting. I would think that attempting to follow the signal from "input" to "output" seems most logical. Would I be wrong/foolish to attempt such a thing? Your notes on troubleshooting seem to suggest to me that it would be a good idea but I'm still not sure.

[HayZee518]

I can't offer you a "repair an amp in ten easy lessons." You need to know electronic basics, how transistors operate, what happens when they go bad etc. You get this knowledge from going to an electronics school and personal hands on experience. At this point and theway you are speaking, take the unit to a repair place.

[GraterFang]

I know electronic basics and I know how transistors operate. I know how to read a wiring schematic and I wasn't asking anybody to solve my problem for me or break the troubleshooting procedure down into "ten steps". My "language" that you are referring to is probably my repeated attempts to try and get this point across: "I'm not asking how it works or how do I fix it. What I really wanted to know is if there any specific COMMON failure point on these units?". I never asked you to explain the very basics of how an amplifier works but since you bothered to take the time to do it I figured I would thank you anyways for it. My apologies if that makes me look dumb to you.

Now, perhaps my question is a naive one (my apologies if it is as it very well might be) because no I didn't go to electronics school to fix amps and no I haven't spent years doing it as a profession. I spent my time at school studying a difference science. Now, on the other side of that, I'm attempting to get "hands on" experience with this and learn what I can from the sources I DO have available. Forgive me for looking for guidance from those that know more than I do. I do sincerely thank you for your "help" but apparently my time is better spent figuring these things out for myself rather than asking you.

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While I'm really trying not to be rude (I apologize if I seem that way) let's see how you've helped so far. You've suggested a source for electrical schematics. You probably mentioned a good source but I can and did find such a thing on my own and I don't need schematics for other devices. I'm more than willing to pay for one but it's nice to have free electronic copies of such things (since they are around) and I was hoping somebody would know of a source. This is the first time you didn't answer my direct question. Not a big deal but worth pointing out.

You explained what a multimeter and frequency generator is good for, which I find fairly obvious. The same goes with your suggestion on how I don't likely have a power supply problem. To me, these are fairly obvious things that didn't require explanation but I appreciate that you took the time to spell them out. Really, I sincerely do...because sometimes you don't know.

You explained the very bottom line basics of some amplifiers. I won't pretend to have known everything you said beforehand (although I did understand it as the majority of it wasn't that complicated even for somebody that didn't go to electronics school) but I'm pretty sure I could find the same information online and they would actually explain it in depth. I guess I just like talking to people (or at least most people) better. My apologies again.

You suggested I take the amp to a repair shop. Yes, well I've known I could do this all along but it's not really an option I'm interested in for reasons I stated above. That is why I posted here....

However, despite all of this, don't misunderstand that I appreciate your help. I do appreciate the time and effort you've taken into responding to my thread and trying to help. I'd be happy to read anything else you have to say but I really don't need any more witty comments on how I should have somebody else do this. If I just wanted a working amplifier I'd go and get something better than an old broken Sanyo. That much should be obvious.

[HayZee518]

OK. I can take a sams schematic, find Q1 on a printed circuit or a hard wired unit with tie points, find the base of the transistor. Couple a signal from a signal generator through a capacitor to the transistor and observe the output in the form of a waveform as shown on the schematic. if the signal is there then I go on to the next stage - same procedure and so on. When I find the signal going into a stage and nothing coming out or an output with less than optimal amplitude, then I go looking for a shorted capacitor, a capacitor that has changed value, burnt resistors or a burnt out transistor ir IC. I'm a master electrician by trade. I run a hydro-electric plant on a river here in new york state. I troubleshoot houses, industry and the power plant. I'm 63 years old and all this knowledge I've accumilated through my years.

[GraterFang]

It's honestly funny that I have to wonder what the point of your response is. It almost seems as if you're trying to prove that you're qualified (or that you know more than somebody who has already admitted not to be an electrician). Yet, I'm confused because I haven't brought that into question. I'm sure your qualified, so don't worry about that. The only thing that I have questioned is how helpful you have been with the knowledge you have accumulated (knowing versus teaching).

However, I suppose in a funny way you are beginning to elaborate on the troubleshooting techniques you would follow. That part of your post I appreciate and I do have to give credit where it is due. If this was the point of your post and not the above than I sincerely thank you for your continued help.