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Old 13th September 2019, 04:01 PM   #21
Ian Finch is offline Ian Finch  Australia
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Most audio amplifiers now have 2 separate power supplies. A very small one powers the microcontroller and control circuits, the main power transformer is for the audio amplifier. So there is always power to the control circuits while ever the amp. is plugged into the mains. This is necessary so that power amplifier can be operated completely via remote control or the front panel logic level switches.

So standby is the normal state of the amp. but the microcontroller should always be capable of responding by switching on the mains power to the power amplifier via a relay. After perhaps 15 years of constantly being switched on, I think you can understand why the control circuits may fail before the amplifier, which may only see 10 hours intermittent use per week or even less.
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Old 13th September 2019, 04:17 PM   #22
KatieandDad is offline KatieandDad  United Kingdom
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I'd be looking at the caps in the micro's PSU supplies.
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Old 13th September 2019, 05:03 PM   #23
Behsen is offline Behsen  Denmark
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Quote:
Originally Posted by Ian Finch View Post
Most audio amplifiers now have 2 separate power supplies. A very small one powers the microcontroller and control circuits, the main power transformer is for the audio amplifier. So there is always power to the control circuits while ever the amp. is plugged into the mains. This is necessary so that power amplifier can be operated completely via remote control or the front panel logic level switches.

So standby is the normal state of the amp. but the microcontroller should always be capable of responding by switching on the mains power to the power amplifier via a relay. After perhaps 15 years of constantly being switched on, I think you can understand why the control circuits may fail before the amplifier, which may only see 10 hours intermittent use per week or even less.
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Old 13th September 2019, 05:07 PM   #24
Behsen is offline Behsen  Denmark
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Yes I understand - and I'm also having tv set etc. connected to 230V all the time.
But regarding the arcam I'm not sure if it is OK to have it connected all the time - because of the issue it has.
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Old 14th September 2019, 12:08 AM   #25
Ian Finch is offline Ian Finch  Australia
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As long as you plan to do something about it soon, I don't think being powered up is going to cause further damage in the short term, if that's what your concern is. The present problem has likely been there for some time but CMOS logic circuits operate at very low current and only when commands are entered and the clock is running. This gives the control circuits some immunity to damage even when operated as it likely has been, with intermittent power, no clock etc.

However, we can't be certain this is the case without your performing the supply voltage measurements. These would give us confirmation of what is currently happening and whether the controller is then likely to function correctly if the power to it is improved.
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Last edited by Ian Finch; 14th September 2019 at 12:10 AM.
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Old 14th September 2019, 05:32 PM   #26
Behsen is offline Behsen  Denmark
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Today I have made some measurements - and it looks like D45 (rectifier) might be faulty.
I measured the same values in both stand by and power on mode: 0V on one side and 0,1V on the other. I compared it with D25 (2V/2V in stB mode and 26V/50V in pw mode.
Also compared with D18 and D19 - both 0V/14V in stB mode and also 0V/14V in pw mode.

According to service manual (page 14) I tried to follow the line from D45 to Q42 and to Q55 - but I can not find Q42 and Q55.

Now I wonder if it is D45 that is faulty - or if instead could be Q42 or Q55. (I wish I could find those - two. I have found several others like Q41 etc - but not 42 and 55).

D45 is placed close to Z6 - but in the service manual it is shown close to Z7.
I wonder if there might be some errors in the service manual. In the area with Z6 or Z7 - I can't find the Q42/Q55 - and neither in other areas on the print board.
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Old 14th September 2019, 08:33 PM   #27
jaycee is offline jaycee  United Kingdom
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Q42 is a surface mount transistor, so probably on the solderside. Q_55 is a not a part, it's a test point.
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Old 14th September 2019, 09:05 PM   #28
Behsen is offline Behsen  Denmark
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OK - thanks.
Do you see something from the measurements.
It's not easy to trace the power to/from D45. D45's pins are not soldered to a print lane as the D25 pins are.
I assume that it is ok - that D18 and D19 has 0V on one side and 14V on the other.
But I'm not sure about neither D45 or D25.
Should D25 not be 0V on one side. And should D45 not have voltage on one of the sides?

The amp was functioning perfectly when I made the measurements.
Maybe I should wait - and make a comparison later - when I have had a chance to measure the components - when the amp will not power on.
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Old Yesterday, 01:18 PM   #29
Behsen is offline Behsen  Denmark
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Here is some measured values for comparison:
A/Amp not working (power switch pushed on - but nothing happens)
B/Amp powered (on and works fine)
C/Amp - on stand by mode

D10,D11,D12,D13 (rectifiers - “Z7 - area"):
A/ 0,3V/0V B/ 50V/0V C/ 1V/0V

D18,D19 (rectifiers - “Z7 - area”):
A/ 0V/14V B/ 0V/14V C/ 0V/14V

D45 (rectifiers - “Z6 - area”):
A/0V B/0,1V C/0,1V

D25 (rectifier - “Z6 - area”):
A/0,3V B/50V/26V C/ 2V/2V
R200 (resistor): A/ 0,3V/0,3V B/ 0,1V/26V C/ 0,5V/0,5V

Is it possible to see from the measured values - if some of the above mentioned components should be replaced.
Or could the measurements be telling something else?
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