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Old 6th March 2013, 03:42 PM   #1
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Default JVC rx309 no output

Hello everyone,
I'm new to this forum and new to the idea of building or modifying audio equipment, so please bear with me and my ignorance for now. I do learn quick and promise not to waste anyone's time. My background in electronics is not too great, I only know what I learned in the electronics merit badge book as a kid, and what I've learned by attempting to repair broken electronic items people would give me. I was the garbage picking kid in the neighborhood growing up who would fix everyone's VCR's for ten bucks. At one point I wanted to be an electronic engineer but after 3 yrs of college and no electronics classes I decided to drop out and become an auto mechanic, and I now own my own auto repair shop. I have this JVC receiver as mentioned above with no audio output. I originally got this with the fuse on the power supply board blown. Replaced it, blew again. I read that a lot of times one of the transistors will short their collector to emitter and cause this due to shorted speaker wires, so I ohmed some transistors and found one shorted. Replaced that and installed a new fuse and it powers up but no sounds, so I bought a svc. manual for it. The speaker relay isn't coming on, and there's a "protector" chip in there that controls that. I manually grounded the contol side of the relay and it turned on, but still no sound. The weird thing is there are wrong voltages everywhere on this thing. With it powered up I got about 60 VDC on one of the speaker output wires! I'm pretty sure that's not normal.

Yes, I'm aware that to most people reading here this unit is garbage and not worth it, etc. What I hope to gain from this is a little knowledge. I'm trying to step out of my comfort zone and learn. Ultimately I'd like to someday be able to build guitar amps since I'm a bass player and I'm not happy with the sound quality of most that I've played.

If this is even the right forum for this post, and if anyone has the time to help me, I'd really appreciate that, or if this isn't the place, please direct me to where I can learn. Please just don't tell me to go back to college, nothing against any professors or college degree holders, but I wasted enough money and time on that the first time and I doubt I'd learn any more there this time than I did before.

Thanks!
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Old 7th March 2013, 03:27 AM   #2
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Should have posted this in Digital Source forum.

First of all, do not connect speakers to it and do not unsimulate the fault.

60 Volts on the speaker terminal is a sure sign of shorted power transistors mostly.

You have to first repair the power supply and presently do not bother about the speaker terminal voltage. Start from the transformer secondary and proceed further, step by step. Write down these values against their location on a paper pad.

If u need help with the power supply, post a jpeg. Someone will definitely help.

Gajanan Phadte

Last edited by gmphadte; 7th March 2013 at 03:29 AM.
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Old 8th March 2013, 04:12 AM   #3
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OK, thanks. I will get more info starting at the Power supply transformer and I'll post any testing results I get. May be later this weekend before I post back, thanks for the reply. I will repost this in the digital forum. Thanks again.
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Old 8th March 2013, 11:36 AM   #4
Mooly is online now Mooly  United Kingdom
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Moved to solid state forum.
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