I picked up a couple of Jamo MPA-101 amps the other day. The Blue power light comes on with both of them but no output. I have removed the covers and checked the only fuse I can find. The fuses on both amps are good. What should I do next? Thanks. Lee Jacobsen 804-462-3246
I can almost guarantee that you'll find bad electrolytic caps on the power supply board to be the cause of the problem. I've seen several of these with the same problem. The protect circuit stays latched due to excessive ripple.
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You need to determine if the power is getting to the audio amp section. For instance with the volume full up is it humming etc? As a 'rule' it's unlikely that both left and right channels will fail at the same time (unless you have done something silly with the amp) you are looking for something that is common to both channels. Which is why the power section is first suspect. The exception to the rule (above) is where amps use say an IC power amp for both channels. You will find this IC on the big heat sink. Check whatever is on that anyway for damage or burning. The only other area could be the pre-amp part. Again this could be a single IC controling both channels, so it's failure could cause a loss of sound. By the way if you can hear music/sound coming through when you put it up to full volume the pre-amp will be generaly good.
Hello, is this a Radio Shack PA amp or Jamo amp? The unit is probably in "Protect" mode. Is this a PA system or a receiver...receivers have a protection circuit that will not let the speaker relay activate if the amplifier output section is shorted and sending voltage towards the speakers...so they won't fry!!The speaker relay should activate within 3 to 5 seconds if your output section is ok.
Might be a failing semiconductor component (usually an old transistor) in the amplifier's front end. This caused by the oxidation through the component legs or pin. I usually touch and move each transistor's body to exaggerate the noise. You can research also what kind of noise is it producing- intermittent, static, etc.
hope this helps..
I think we're on about the same model here. I found that holding down the "Source" button whilst switching on the power at the mains would temperorly solve this issue. However, it would be nice to switch it on normally.