Hi all !
I plug the plug into the socket. The blue standby LED lights up. I press the standby button. But the amplifier does not turn on, the LCD display does not light up. When you press the standby button again from the 15th to the 20th time, sometimes it is possible to turn on the amplifier. Previously, a similar thing happened after a long period of inactivity of the amplifier unplugged from the outlet. But after turning it on to the outlet and warming up in standby mode, everything seemed to return to normal, and the amplifier was turned on with the standby button the first time.
And now, after standing for 3-4 weeks (unplugged from the outlet), only from the 15th or 20th time.
Thanks.
The renovation is complete. The amplifier turns on normally. 3 capacitors were replaced, as the Hifista said.
Thanks to everyone.
Special thanks to Hifista.
Buy.
0
Hi!
The years and the routine.
Such a valuable device is worth saving from being thrown away.
Happy New Year !
Hifista.
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Hi all !
If it is interesting, please read.
Renovations have begun.
I disassembled the case. Getting the right board for resoldering capacitors is not so easy, until it doesn’t work out.
I measured some voltages on the CN1 connector of the SMPS Mains PCB Schematic board page 59 Service Manual 851A:
1. Pin 3 of CN1 connector
If the amplifier is in Standby mode, then the pin is 5.2 V.
If the amplifier is TURNED ON, then the voltage at the contact drops to 0.5 V in 2-3 minutes.
And then after another 1-2 minutes up to 200-100 mV. Approximately 0 Volts
Now, the amplifier is TURNED ON. We press the Standby/ON button. The voltage instantly jumps from 0 Volts to 4 Volts, and after 10-15 seconds to 5-5.2 Volts, and amplifier became into Standby mode
Now, the amplifier is in Standby mode .
It was not very possible to measure the pulsations. I believe the reason is in the oscilloscope. I need to get a better oscilloscope. The one that is available showed: the pin is 5.2 V (oscilloscope is in DC) and ripples (oscilloscope is in AC) of + - 100 milliVolts.
If you cannot turn on the amplifier by pressing the Standby/ON button, you can see that the voltage for a very short time drops from 5.2 Volts to 4 Volts at this contact.
2. Pin 4 of CN1 connector
If the amplifier is TURNED ON, there is 4.8 Volt on this contact.
In Standby mode, this pin is 0 Volt, the oscilloscope shows noise of + - 100 milliVolt.
3. Pin 2 of CN1 connector
The Standby signal comes to this contact.
If the amplifier is TURNED ON, then there is 3.2 Volts at this contact.
If the amplifier is in Standby mode, then this pin has 0 Volts.
If you cannot TURNED ON the amplifier when you press the Standby/ON button, you can see how a short pulse about of 2 Volts jumps at this contact.
That’s all about CN1 connector.
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It’s very pity but It is not possible quickly to get to the 851A Front Panel PCB Schematic board yet.
I want to see the power and signals on the controller directly.
So far this is how things are.
I will resolder the capacitors, but this requires a lot of disassembly of the amplifier and a lot of time.
By.
Happy NEW YEAR :O))))
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Hi!
The standby power supply of this device is switched mode and the supply voltage is not sufficiently filtered.
MICOM cannot detect the power-on command, there is so much noise. Capacitors C2 and C10 ( C7 too) should be replaced, preferably with the best quality.
Since it is the power supply unit, it should only be repaired with appropriate expertise, because work must be carried out near life-threatening voltage.
Hifista.
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hifista thanks a lot !
I,m already thought about this.
The standby power supply scheme is already in the 851A manual !
0
Hi!
Now I read that the click of the relay can be heard and yet the device does not turn on.
However, the source of the error may be the relay.
There is poor contact between the contacts.
Relay RL2 switches the main transformer.
There is also a soft start, the triac does that, and then at the end of the process the relay pulls.
The RL2 relay should be replaced.
Hifista.
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Hi, hifista !
No !
Sorry for my english, but i want to say that: IF the amplifier after all (after 15...20...25... attemps to push Standby/On button) TURN ON, we CAN hear the click of the relay.
But the amplifier DON,t TURN ON, and we DON,t hear the relay click.
Only one silent after Standby/On pushing.
Please tell me:
if amplifier is in standby mode, all power supply espeshially for logic and controller we get from standby power supply ?
But after, when the amplifier turned on, the standby power supply turned OFF, and we get ALL power supply for logic, power part and etc ...from main power supply ?
Is it correct ?
0
Hi!
Don't worry about knowing English, it's not my native language either.
Let's start over.
The standby power supply only supplies necessary things with power when they are turned off - IR detector, MICOM IC, etc.
When switched on, the main transformer starts and takes over the load from there, but the standby power supply does not switch off.
The main transformer is switched on by relay RL2.
The MICOM IC needs a well-filtered 3.3V power supply.
Other than that, there are several other things needed to turn it on, but a clean power supply is the most important.
If you have an oscilloscope, check how clean the standby supply voltage is.
Hifista.
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Hi !
Hm...
I thought that the standby source was still turned off.
If the standby power supply has a problem with voltage filtering and the controller perceives it as noise and does not turn on the amplifier. Then it is not clear why the amplifier, if it does turn ON, turns off with the FIRST press of the button.
So I thought that the standby power supply was turning off.
Moreover, to turn it (the standby power supply) on, relay RL1 with normally closed contacts 3 and 4 is used. And relay RL1 operates together with relay RL2, if I understand correctly.
And then, after the amplifier is turned ON, the relay RL1 open contacts 3 and 4.
Well, these are only my arguments, they may not be correct.
Fine.
I have already found an oscilloscope and found replacement capacitors. I'll start repairs in a few days.
I'll let you know about the results.
If I haven't already bored everyone with my questions and reasoning. :O))
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hello:
https://elektrotanya.com/cambridge_audio_azur_851a_service_manual.pdf/do...
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Thanks for the link. But I think that the manual is too short.
When the amplifier does turn on, you can hear the relay operating. According to the manual, so far I have only been able to track the ON/STBY button and its connection with the controller. Further, it is not clear where the controller sends the turn-on signal, apparently this is the ON/OFF signal and the signals output relay a and output relay b.
It is not clear which relay is activated and how it supplies power to the main transformer.
I didn’t find a diagram with the main transformer in this manual at all.
What about the circuit for 840a ver.2, are they similar?
0
Hello
It looks like capacitor problem, to find it use hair dryer to heat up capacitor (because in heat the capacity increase)
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Hi!
Can you turn it on with the remote first? Or is it only possible to turn it on with the remote control after several attempts?
G
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It,s possible to turn it on with the remote control after several (10-20...) attempts !
The situation is similar to the button STANDBY/ON,
But sometimes i can see that LCD attempted to turn on, and became lightly brighter but don,t turn on.
Lets...
I will change the capacitors, as advised here.
1