CA Azur 650R volume problem at start

[hare011]

Hi,
I've got an approx. 13 year old Cambridge Audio Azur 650R AV-receiver. Everything works fine, but when I turn it on, it'll make a very loud sound (f.ex if it is on FM/AM), seems on max. volume for about 1 sec. then It'll turn down to the normal (where the volume control were set).Here is a video of the unit powering up - https://mega.nz/file/ZIAnQKga#esQkO9...qL18-IHmltm0bw
Any ideas for how to resolve this is much appreciated!
Best regards,
Davor

[madan1]

Re: CA Azur 650R volume problem at start

Hi, I believe it was you who few days ago posted me a PM on the other forum (where previously have discussed the same problem with other ppl).
So no - I haven't found a fix for it, but to be honest, I haven't troubleshoot the issue any further. Might give it a try in the following days. I'll update if there is any progress.
By the way, what are your impressions of the receiver?

[hare011]

Re: CA Azur 650R volume problem at start

It sounded very good in stereo mode considering it is an avr. I read somewhere that it has an audiophile dac, whatever that means. It has a large torus transformer and very bad capacitors (chang). I changed some but it didn't help. I think they cause a problem, but there are so many of them that it is not worth replacing them.
Let me know if you find out anything.


Yes, that was me

[madan1]

Re: CA Azur 650R volume problem at start

Alright, I did not have time to get under the hood, but checked the service manual to try to find probable causes.

So I can think about two possible root causes - the speaker relays are activated prematurely or the CPU is is giving wrong instructions to the volume control IC.

In the past I've had a case with other model CA receiver, which had reached the end of life of the eeprom IC, thus (if I remember correctly) there was a problem with the volume control.. something like only vol MAX and vol MIN.. and this was a common issue with that model. So I'm guessing that CA might be using kind of similar code in the firmware of 650R, but this time the dying eeprom is affecting the volume with vol MAX on startup. Anyway, the eeprom is one of things that I'm changing for sure once I start working on the receiver.

I guess corrupted firmware could also be causing the vol max and the premature speaker relay ON instructions.

Here is the path of the relay signals - IC15 MCU (1) -> data -> HEF4094B IC101(?), 100(?), 192(?) -> ST MODE and RLAY CON (pg 37) +5V -> (pg 27) -> Q15 and Q16 -> K1 K2 K3 K4

On the +5V signal there are resistors r40 r16 and caps c171 c1, so I'm thinking that if those caps have reduced capacity, q15 and q16 might be activating the relays too early..

[hare011]

Re: CA Azur 650R volume problem at start

Today, with some free time on my hands, I decided to investigate an issue with my AVR Azur 650R. Upon inspection, I discovered a suspicious swollen appearance on the decoder board.
After replacing capacitors C60 (3300uF/10V) and C105 (2200uF/16V) on the decoder board of my AVR Azur 650R, all the problems I experienced have been completely resolved. The unit is now functioning perfectly, indicating that the capacitor replacement effectively addressed the underlying issue.

Feel free to ask if you need further details or have any questions!

Best regards,
Hare

[hare011]

Re: CA Azur 650R volume problem at start

However, today, unfortunately, the problem resurfaced. Despite replacing the capacitors, problem with volume have returned.I'll be attempting to replace additional capacitors as advised. I'll keep the community updated with the results.
Best regards,

Hare

[madan1]

Re: CA Azur 650R volume problem at start

I also had some time to play around with the avr. So replaced the eeprom IC16, but that did not fix the max volume on startup issue.

p.s. found a couple of bulging caps and a faulty bridge rectifier, but that had also no affect on the issue.

[hare011]

Re: CA Azur 650R volume problem at start

An interesting observation I've made is that this issue seems to occur predominantly when the AVR is cold. When it's running hot, this problem doesn't seem to manifest.

However, I've discovered a temporary workaround that might help. Before turning off the AVR, try switching the input to a source with no sound, such as CD or another inactive input. Doing this seems to bypass the issue, preventing the sudden half-second max volume at the start when turning the AVR back on.
This workaround might not solve the underlying problem, but it could prevent potential discomfort caused by sudden volume spikes.

Additionally, switching two bad capacitors surprisingly resolved the problem that I was experiencing with the AVR earlier. Specifically, after this change, the digital inputs (HDMI and optical) started working from the start without any delay, which was an issue previously.

[madan1]

Re: CA Azur 650R volume problem at start

Is it possible that the board and components surrounding the replaced caps were still warm when you tested the AVR?

[hare011]

Yeah, I noticed that the board and components were still warm when I initially tested the AVR after the repair.
The problem occurring in the morning when the AVR is switched on and cold suggests there might be an issue related to the initial startup, and you might be right about the bad capacitor causing this.
I'm considering replacing the capacitors as you suggested; it's a logical step given the circumstances.

[Biggerruss]

My CA Azur 650R is on the healing bench this morning with the same symptoms. Powering up on radio goes to full volume regardless of where volume rotary dial is left at shutdown. Have cracked open the case and initial examination has revealed these dodgy caps on the video pcb?

Not a technician, but more used to firing salvos with the parts cannon. (However, hope grows eternal that I still have the capacity for learning).

[madan1]

3 unites experiencing the same issue.. alright, now this looks like a common issue. The good thing is that corrupted firmware now seems to be less plausible. If someone has the unit still on the bench (mine is back in service as a 7channel power amp) I would suggest doing some tests while applying heat to c1 and c171 (both are on the main board, c171 is easily accessible, but c1 is next to the decode board and can not be accessed without removing the hdmi board).
In theory, increasing the capacitance of that two caps and/or increasing the resistance of r40 and r16 should delay the activation of the speaker relays.

Back to the schematics - there seem to be 3 control circuits for the speaker relays:
1 STEREO MODE+RLAY CON - controlled by the CPU
2 RELAY-STOP - seems like it is intended to disconnect the speakers as soon as the power is turned off, thus stopping any signal still generated by the amp using the power left in the caps(?)
3 OVER LOAD - haven't checked the circuit in details, but I guess it is intended to disconnect the speakers as soon as a current limit is exceeded
I guess 2 and 3 do not affect the startup sequence unless there is a major issue with the unit, so I bet circuit 1 is to blame.

On the signal side - the signal volume is controlled by BD3812F and BD3817KS. According to their datasheets, they should be started with MUTE ON either on the dedicated mute pin or instructed on the data bus. Both ICs seem to have the mute pins connected to one of the HEF4094BT and thus controlled by the CPU. I do not know if this MUTE pin is used when the vol ICs are powered up, only when the unit is muted or at all, so if someone has the time and means, might want to check what is the case with that MUTE signal.
There are no passives on the mute control path, thus I guess nothing to age or deteriorate here apart from the ICs (CPU, HEF4094BT, BD3812F and BD3817KS which I find highly unlikely to happen on 3 units).

[hare011]

What prevents me from replacing those capacitors is that they are located on the mainboard, and everything needs to be disassembled to reach them. My AVR works all day, and I haven't noticed any other issues."
Should I cut the old capacitors with pliers without removing them from the motherboard and solder the new ones over the old? If the repair succeeds, I will solder them properly."

[Biggerruss]

Checked ESR on C171 and reading 1.4ohm and 568uf, so assume that it is bad.
Could not get a read on C1 unfortunately, but I will get back in there eventually.
Also noted that C4 is bulged, C109 and C105 are bad also, so I will not be placing back into service until it is sorted.

[hare011]

Unfortunately, replacing the capacitors C1 and C171 on the amplifier's board didn't resolve the issue. It seems like the problem might be more complex or located elsewhere within the circuitry.Any ideas what could be wrong?

[Biggerruss]

Having a look at the photo of your board it looks like c109 is bad too? It looks like a lot of the caps on these boards are failing.

[madan1]

Oh, well... I'm out of ideas.
I just probed MCU+5V hoping that a ripple would make the ICs behave bad, but "unfortunately" there was no ripple.

[hare011]

After experiencing ongoing issues with my AVR Cambridge Audio 650R and attempting various troubleshooting steps without success,
I've decided to use its parts and housing for my ongoing "Bato MM" amplifier project.
It's worth noting that the transformer voltage level fits perfectly for the requirements of the "Bato MM" project, and the cooler from the Cambridge Audio unit will be ideal for heat dissipation.
I only need to make a simple circuit for temperature regulation of the fans.