Audio amplifier Cambridge Audio Topaz AM10 no output

Zjho

Zjho

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Anyone familiar with testing and repairing this kind of thing ?
Have been using a mp3 player as input and worked well for a year into stereo 8 ohm speakers.
Noticed the voltage rails are about 50% higher than stated on their labels e.g. 5v rail shows 7.5v and 8v rail 12v.
 
Hi,

I am not familiar with this model, and may not be able to help at all! :)
I just wanted to check what troubleshooting shooting steps have you taken so far?
Were you connecting your MP3 player to the 3.5mm jack socket on the front?
Have you connected a source to any of the other inputs?
 
RandomGrinch said:
Hi,

I am not familiar with this model, and may not be able to help at all! :)
I just wanted to check what troubleshooting shooting steps have you taken so far?
Were you connecting your MP3 player to the 3.5mm jack socket on the front?
Have you connected a source to any of the other inputs?
Click to expand...

Hi RandomGrinch, Used the mp3 input on rear panel up to time of fault but now neither rear or front imputs generate speaker output.
Rear connection BD/DVD and CD inputs also dead for mp3 player. Not tested tuner or phono imputs, i only have an mp3 player to hand for input testing.
Have given both circuit boards a light tappy tap tap throughout with toothbrush handle looking for dry joints to no avail.
 
Was there a relay click when you turn the amp on? And if there was, is it still clicking?
A gentle tap of any inernal relays may free any that are sticky?

If you've tried other inputs, it does sound like an amp issue.

But if the MP3 player is the only source you have tried, It is definitely worth finding another (and trying a different cable)! Has your phone got a headphone jack?

...and do you have headphones you can plug into the headphone socket?

If all that fails, then we start looking at the boards!
 
Last edited:
RandomGrinch said:
Was there a relay click when you turn the amp on? And if there was, is it still clicking?
A gentle tap of any inernal relays may free any that are sticky?

If you've tried other inputs, it does sound like an amp issue.

But if the MP3 player is the only source you have tried, It is definitely worth finding another (and trying a different cable)! Has your phone got a headphone jack?

...and do you have headphones you can plug into the headphone socket?

If all that fails, then we start looking at the boards!
Click to expand...

Great suggestions, particularly regards relays. Have changed the cable for the inputs and changed mp3 players and makes not difference. Earphones work from mp3 players. Yes my phone has a earphone jack but different mp3 players should cover that. I don't have 6mm headphones, if this is an important test maybe could temporarily wire earphone cables into headphone board connectors. Failing that i'll get an adapter to plug earphones in properly. I forgot to mention a couple of things. Firstly, all four internal fuses were checked and are okay. Secondly i had a hunch that there were two relay clicks before output ceased and that would correspond to the two relays visible, one on each board. The louder click for the bigger relay is now absent on startup so have been trying to tap it up many times but no joy. Perhaps may not be getting the signal to fire. Suppose large relay's pins should be probed at start up as a first step ? Smaller relay's queiter click is still present. To probe underside of main board will take a bit of time as a longer earth lead need to be made amongst other things.
 
The headphones test is not essential, but it could rule out any source connection issues and source switching issues. It may also help to eliminate power supply problems.

The relay would be a useful thing to check if it switches correctly.

As winston1 says, this could be a serious fault. Given the cost of a new amp, this may be beyond economic repair.
And even if you try and get further, there isn't a guarantee that the issue can be resolved.

However, it seems as if you are interested in the problem, not just the fix.
If this is the case, then there's no harm in having a go!

Yes, the rail voltages do appear to be high, and could have damaged multiple components, if that is the case.
But, that is an assumption on our part; we don't know exactly where you probed the circuit. If this was before a voltage regulator, for example - that may be the correct voltage.

If you can post some good quality pictures of the PCB, we can have a quick nose around! :)
 
SFK said:
Was looking to see if Capacitor falure was causing voltage regaultion increase and found this horrible video showing a similar issue to yours.
For them it needed U4 a replacemnt LM3886T Audio output IC.
https://uk.farnell.com/texas-instruments/lm3886t/amp-audio-mute-68w-3886-to-220/dp/9493603

Many others here that i did not look at:
https://www.google.com/search?q=Cambridge+Audio+Topaz+AM10+repair
Click to expand...
I saw that too - was very tempted to leave a dislike!
But it did give me a bit of a look at the PCB! :)

Here's the video description:
Screenshot_20211222-224706_YouTube.jpg
...and checking the DC offset on the output could be interesting! :)
 
Last edited:
RandomGrinch said:
The headphones test is not essential, but it could rule out any source connection issues and source switching issues. It may also help to eliminate power supply problems.

The relay would be a useful thing to check if it switches correctly.

As winston1 says, this could be a serious fault. Given the cost of a new amp, this may be beyond economic repair.
And even if you try and get further, there isn't a guarantee that the issue can be resolved.

However, it seems as if you are interested in the problem, not just the fix.
If this is the case, then there's no harm in having a go!

Yes, the rail voltages do appear to be high, and could have damaged multiple components, if that is the case.
But, that is an assumption on our part; we don't know exactly where you probed the circuit. If this was before a voltage regulator, for example - that may be the correct voltage.

If you can post some good quality pictures of the PCB, we can have a quick nose around! :)
Click to expand...

Will test headphone jack as soon as get jack adapter for earphones.
I will need to learn how main pcb relay should operate. Searching web revealed this thread on the AM10 by Treeman who briefly identifies the AFE relay pins. His blurry image of rear of pcb may enable probing without removing from case which would help.

https://forum.allaboutcircuits.com/threads/relay-afe-bpm2-ss-224lm-audio-amp.98343/

Thanks for forewarning this may be uneconomic to repair. As a contingency have already a replacement amp on way, not another AM10 with its impractically designed volume control knob functionality, so this stands to be passed on as a 'parts only' flea bay item as last resort, but not without a bit of effort chasing around first. Besides, problem solving can be fun, i enjoy watching Diode Gone Wild and others on Youtube but rarely have need to get test meter out.

The voltage readings were taken from connection jacks at edge of both main and input pcbs.
Incidently the front display panel appears to work fine, it correctly shows which of the two mp3 sockets is being used so perhaps hope of not much collateral damage.
Hope to take some pictures fairly soon, though there is nothing obvious to my untrained eye, caps not looking blown as one might imagine for a relatively newish model from a reputable manufacturer. Power amplifiers haven't vapourized their thermal paste.
This was a flea bay second hand purchase and showed evidence of being dropped due to a small ding on casing around speaker terminals but due to the design this does not impact at all directly onto main pcb though suppose it might have damaged input pcb. Testing after aquisition showed working fine without intermittent fault.
 
SFK said:
Was looking to see if Capacitor falure was causing voltage regaultion increase and found this horrible video showing a similar issue to yours.
For them it needed U4 a replacemnt LM3886T Audio output IC.
https://uk.farnell.com/texas-instruments/lm3886t/amp-audio-mute-68w-3886-to-220/dp/9493603

Many others here that i did not look at:
https://www.google.com/search?q=Cambridge+Audio+Topaz+AM10+repair
Click to expand...

Thanks for those links, wish i could find a YT channel on repairing amps. Audio Amplifier Servicing Youtube Channel have offered free advice for temporary fixes but think this issue is beyond that.
Nice to see that Audio output IC is still available and affordable.
 
Here are some photos of main and input PCBs front and back, let me know should these be inadequate or if more are needed before box is reassembled for further testing.

[GALLERY=media, 107391]MainPCBTrace by Zjho posted 23 Dec 2021 at 12:29 PM[/GALLERY]

[GALLERY=media, 107390]MainPCBTop by Zjho posted 23 Dec 2021 at 12:25 PM[/GALLERY]

[GALLERY=media, 107387]InputPCBTrace by Zjho posted 23 Dec 2021 at 12:23 PM[/GALLERY]

[GALLERY=media, 107386]InputPCBTop by Zjho posted 23 Dec 2021 at 12:21 PM[/GALLERY]
 
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