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I have an ARC SP-10 that seems to have a problem. After about 45-50min of playing, the signal suddenly cuts off. All sources. I am left with a faint hum, that disappears when I flip the mute/operate switch on the front panel. Only solution seems to be to turn it off, let it cool down, the power it up again. Then everything is fine....for 45-50min.
The circuit includes a turn on mute relay that delays full turn on for 2.5min. The power on LED flashes until the relay trips after 2.5min. This LED does not flash when the signal cuts off as outlined above.
Could the problem be a malfunction of the turn on relay or something else ?
Thanks.
Follow Ups:
I have contact ARC tech support regarding my problems. Waiting for an answer. Since their buyout, all contact is by VM and email. Techs will not talk to customers anymore.
They will probably tell me to send it in for an estimate, and then quote a price for a rebuild. But you never know.
Thanks
When moving the 2 pieces I noticed a loose pin in the PS umbilical cord. I used a pr of tweezers to grasp it and put it back in place. Recalling early PC peripherals, I sometimes had problems if the PCMCIA pins were not lined up correctly.
I put the SP10 back into my system and have played it for about 7hrs without difficulty. Now onto tweaking and tube rolling.
Thanks
I experienced a similar problem with my SP-9MKIII. The factory had to replace a chip in the muting circuitry.
Just a guess, if you are into doing your own repairs, there are two 6,000uF 25VDC capacitors in the power supply. Look at them, one might be bulging, and/or getting warm. If so, replace it. I had a different ARC preamp with the same symptom, that part of the power supply was the same, and it was the 6,000uF cap that caused it.
You need that serviced. Anything that ends with a "hum" and a relay kicking in is not good. There is a lot going on inside that preamp.
The automatic mute circuit uses photo conductive devices (I believe photodiodes in reverse bias) and it is my understanding that these are pretty much fault resistant. However, there are no relays in the circuit. The mute circuit is triggered by problems in the power supply either high voltage (surges) or low voltage (brown outs, etc). The muting does not protect the preamp but rather downstream components. No damage would occur to the preamp if the mute circuit was removed and damage to the downstream components really depends on the design of the amplifier. Most amps will not be damaged by transient blips from the pre but this may cause thumps and other undesireable effects on the speaker. This is why the recommendation is to turn preamp first and then the amp and reverse this when shutting down. FWIW all my preamps have had delayed muting on turn-on and the amps have been turned on/off via a 12v trigger from the pre.
In any case, I suspect the problem lies in the power suppliy but regardles the preamp will need to be serviced by ARC. Have a Merry Christmas.
I married the perfect woman. The downside is everything that goes wrong is my fault.
Edits: 12/19/16
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