SMPS AMPS TROUBLESHOOTING & REPAIR

[Bigdrums]

I have several JBL Eon 615 powered speakers here all having the same problem. Apparently a common issue with these units. Each will turn on, cycling through the startup sequence, then the white power LED comes on. However there is no output whatsoever. There is minimal current draw, .1 amps or so. So I presume there is nothing really shorted. I run into problems whenever I try to fix a powered speaker, amp, or anything else with SMPS. Can anyone give me an effective process by which to repair these units? I know it is commonly suggested to just replace the SMPS/power amp board but this is usually as costly as replacing the entire speaker. And based on the availability of the boards it is apparent the failure rate is very common. I would love to be able to repair even one of them. So far I have been able to visually inspect the boards, often finding swollen caps, and replacing them to no improvement as far as making the speakers work. I have a ESR meter for caps that works great, and in most cases can check the various transistors, diodes, and resistors. No schematics available for this unit that I can find. Thanks for anything helpful!

[The Dude]

Schematic is here:

https://music-electronics-forum.com/...etch?id=921614

I'd first check power supply voltages.

[Bigdrums]

Schematic is here:

https://music-electronics-forum.com/...etch?id=921614

I'd first check power supply voltages.

Please try opening the pdf as I cannot

[nosaj]

Same here. see if this works.
nosaj

[g1]

Can anyone give me an effective process by which to repair these units?

Here's a link you might find useful
http://www.repairfaq.org/sam/smpsfaq.htm

[SoulFetish]

Here's a link you might find useful
http://www.repairfaq.org/sam/smpsfaq.htm

Great link. Thanks for sharing.

[Bigdrums]

I found useful information in this datasheet that perhaps some of you may be able to comment on. I believe the controller is not changing from "mute" to "operate" Starting Pg 6 of the attached TDA8954.pdf

[The Dude]

Muting is controlled by pin 6 (MODE) of the output IC's, which is fed by the collector of Q7 and emitter of Q3. If the voltage there is 0 or near 0 volts, the IC's will remain muted. If you suspect the IC's are muted, check the voltage at that point. It should briefly start at 0 on initial power up to eliminate power up popping or noise. Then, that line should go high to allow the output IC's to work.

[Quentin]

I'm trying to fix an EON610 amplifier. Sometimes on powerup it works and other times it seems to imediately drop into mute. The voltages look ok. I notice that when it is working, I see a healthy high freq signal on the OSC pin of the TDA chips. When it is not working, the oscillator frequency and voltage level drops. So I go looking for the oscillator. The odd thing is that the oscillator chip U2 does not appear on the PCB? I have the schematic mentioned above which shows the oscillator but there is no chip on the U2 pads on the PCB. any ideas? What about a schematic which matches my PCB: SMPS & AMP 2014.07.303V1.0

[x-pro]

You have an amplifier module without a reference oscillator. The TDA8954TH ICs can do that all by themselves.
Good thing they are intact!
Probably the power supply is unstable at startup.
What is its PWM frequency now? It can be measured on the secondary winding. What secondary voltages is it outputting?
First check C13 and, if MUTE does not work, also- C89, R78.