Question about Yamaha DSP-A1 Receiver
This is an intermittent problem that has gradually got worse! After powering on the amp after about 2 seconds the full amp is powered (a noticeable click) then it shuts itself off! It did this sometimes during a movie and I put it down to current fluctuation. Then the phase of powering down after switching on started. It's now connected to a UPS, all the speaker and other cables have been checked and double checked for possible shorts (in fact the same fault occurs with nothing connected). Then some days (after 30 mins switching on and off) it will work without fail until switched back off. Any ideas?
The last click you hear before the amp turns on is the power relays for the amp circuit,these have 2 very small copper contacts inside them which after much time get corroded and cause high resistance when they try to power up the amplifier circuit.awkward to get to and desolder but can be opened up and serviced,done mine and a few friends with yamaha amps which use similar system,had no problem since,also worth checking for dry joints around amp chip i.c legs onto main board.
Posted on May 02, 2008
The DSP-A1 has an internal self diagnostic program which you can access from the front panel. The service manual shows how to do it and what the readout codes mean as far as the fault that caused the trip. Service manuals are cheap and readily available on the web.
Posted on Jan 20, 2008
My DSP-A1 is doing the same thing. The unit's internal circuit breaker is tripping. That's the click you hear. Mine was intermittent and I sent if over to the local Yamaha authorized service in Portland, OR for repair. If anything they made it worse. Now the unit is basically unusable. They kept the unit for 4 months and finally came back with a long list of items they think it needed (at $650+). I don't have any confidence that they knew what they were doing. I have heard some good things about Yamaha's west coast service (TAP Electronics) in Buena park, CA and may send it there. Otherwise it becomes a boat anchor or Goodwill donation I guess. Please let me know if you solved your problem and what it was. Thanks.
Posted on Jan 16, 2008
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I have had problems with this stereo mixer amplifier which had the symptoms of no sound output from either channel .
I opened up the unit and discovered that the amplifier was correctly amplifying my input signal up to a relay which switches the output through to the speakers .
This relay did not activate at all.
When the power switch is turned ON you should hear a click approximately 2 seconds later , if no click then there is a problem with the circuitry associated with this relay .
I traced out all the connections associated with this relay and made a circuit diagram .
The relay is a 24v relay and I will explain the way that I can see that this section of the amplifier works.
It has been designed to ;
This it needed because otherwise there is a current surge and sparks from the relay turning on immediately.
Q804 turns On Q805 which turns On Q806 to activate the relay .
Voltages on transistors
Q802 and Q803 2sc1815
Base 0V Collector 12.9V Emitter 0V
Base 12.9V Collector 0V Emitter 15.1V
Q805 2sc1815 (driver for Q806)
Base 0V Collector 7.2V Emitter 0V
Base 0V at Turn ON then after 2 secs increases to 0.7V
Collector 2.8V ( transistor is activated as a switch Turned Fully ON ( saturated) to turn on the Load which is the relay .
I have replaced the following transistors to fix my amplifier q805 2sc1815 and q806 2sc1815 .If you are going to use a different type of transistor it may not work and also the lead connections of a 2sc1815 for the collector and emitter are different to those such as on a 2n2222( transposed).
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