Hi... I have a Arcam Alpha 10 integrated amp...
The problem is, when I turn it on it just displays on the front panel "Fault overheat" you can clear the fault message but no sound, the speaker relay does not engage so, I bought a multi meter and checked the Transistors, 2 were bad and the thermal pads (non silicon) have NO thermal paste on them, so, was wondering to, replacing the bad Transistors and buy new thermal pads, but use a tiny bit of thermal paste behind the Transistor, all would be ok?
The problem is, when I turn it on it just displays on the front panel "Fault overheat" you can clear the fault message but no sound, the speaker relay does not engage so, I bought a multi meter and checked the Transistors, 2 were bad and the thermal pads (non silicon) have NO thermal paste on them, so, was wondering to, replacing the bad Transistors and buy new thermal pads, but use a tiny bit of thermal paste behind the Transistor, all would be ok?
In the previous thread, you posted:
The wrinkling of excess silicone rubber sheet has little to do with the job of insulating between the transistor and heatsink. As long as the clip is firm and sandwiches the transistor and silicone rubber where it matters, it will be fine, as designed. Your problem of overheat sensing is not caused here, because the sensors are mounted under each heatsink. Logically, if the thermal pad (silicone rubber) is not doing its job, the overheat sensing would operate later rather than sooner, if at all.
Don't even think about it. Such metal containing pastes are more thermally conductive alright but also electrically conductive. They are intended for computer CPU coolers which fit to the chip's insulating plastic body - not the metal collector face of a power transistor. Whilst you can, with care, avoid shorts by careful application, its a bad idea to introduce that stuff into your amplifier.
The wrinkling of excess silicone rubber sheet has little to do with the job of insulating between the transistor and heatsink. As long as the clip is firm and sandwiches the transistor and silicone rubber where it matters, it will be fine, as designed. Your problem of overheat sensing is not caused here, because the sensors are mounted under each heatsink. Logically, if the thermal pad (silicone rubber) is not doing its job, the overheat sensing would operate later rather than sooner, if at all.
That's the thing, the pads feel like plastic, not silicone (with that squashy feeling) there is 4 Thermistors, 2 by the power supply socket and 2 by the PSU.... When I read the Transistors values with a multi meter, when there should have been a open line, it was reading current, 3 of them were doing this, but the 4th was ok, all the caps are ok, no swelling etc etc and only 1 resistor is reading slightly bad...
On the service manuel, I can't see any heat sensors under the heat sinks.... Btw, the Transistors are held in to place with clips and the power caps are fine also... Just baffled here
On the service manuel, I can't see any heat sensors under the heat sinks.... Btw, the Transistors are held in to place with clips and the power caps are fine also... Just baffled here
In the previous thread, you posted
The wrinkling of excess silicone rubber sheet has little to do with the job of insulating between the transistor and heatsink. As long as the clip is firm and sandwiches the transistor and silicone rubber where it matters, it will be fine, as designed. Your problem of overheat sensing is not caused here, because the sensors are mounted under each heatsink. Logically, if the thermal pad (silicone rubber) is not doing its job, the overheat sensing would operate later rather than sooner, if at all.
That is a point, but when it's switched on from a "cold start" the message is displayed straight away, no time for anything to heat up...
Exactly, and that's why poor hear transfer wouldn't cause your problem. Yes, siicone rubber is like that.
The schematic titled "Alpha 10 power control" in the service manual, specifies two 8-pin heatsense ICs, LM56C1M, as mounted under the heatsinks. I can't prove their existence or not in your amplifier but I assume these are just tiny SMD devices flat on the PCB like any other.
BTW, being power Mosfets, I should have referred to the metal face as also the Drain, not Collector.
The schematic titled "Alpha 10 power control" in the service manual, specifies two 8-pin heatsense ICs, LM56C1M, as mounted under the heatsinks. I can't prove their existence or not in your amplifier but I assume these are just tiny SMD devices flat on the PCB like any other.
BTW, being power Mosfets, I should have referred to the metal face as also the Drain, not Collector.
There's no problem with being an amateur, newb or expert even. You're very welcome here as a DIY audio guy. Don't be discouraged by replies that come across as weird, dismissive or over-technical. There are people of a wide range of qualification here and it pays to find out whether a guy is a high ranking professional, a scientist, or just a playful kid before taking offence or running for a dictionary to decipher the reply. We all use different forms of dialogue depending on our experience and who we think we are replying to. We (or at least I) get it wrong too.
There's no reason to remove the heatsinks unless they prevent removing the Mosfets which, if your tests are correct, could be all that needs replacing. I haven't serviced this model (lucky for me) so I won't attempt to advise any further. You won't, however, gain anything by seeing the sensor devices underneath.
Note that if you replace the Mosfets, you then also do need to replace their thermal pads. They aren't difficult to buy as service items but distributors like Farnell and RS components, for some reason, only stock expensive US types. This UK Ebay supplier seems reasonable (Ebay ref.) 121109545678.
Replacing the Mosfets may not be the whole solution anyway and troubleshooting an amplifier this complicated is not going to be easy for a technician, let alone an inexperienced DIY. I wouldn't touch it - I'd take it to a qualified repairer with Arcam experience, if I expected a working amplifier at the end of the exercise.
There's no reason to remove the heatsinks unless they prevent removing the Mosfets which, if your tests are correct, could be all that needs replacing. I haven't serviced this model (lucky for me) so I won't attempt to advise any further. You won't, however, gain anything by seeing the sensor devices underneath.
Note that if you replace the Mosfets, you then also do need to replace their thermal pads. They aren't difficult to buy as service items but distributors like Farnell and RS components, for some reason, only stock expensive US types. This UK Ebay supplier seems reasonable (Ebay ref.) 121109545678.
Replacing the Mosfets may not be the whole solution anyway and troubleshooting an amplifier this complicated is not going to be easy for a technician, let alone an inexperienced DIY. I wouldn't touch it - I'd take it to a qualified repairer with Arcam experience, if I expected a working amplifier at the end of the exercise.
With an Arcam the easiest way to start is with the schematic. It's available from HiFi Engine | Download Free User/ Service Manuals, Amplifier, Receiver, CD, Tape, Tuner, Video.
With a multimeter, check the inputs to the protection micro to ascertain which parameter has been exceeded.
With a multimeter, check the inputs to the protection micro to ascertain which parameter has been exceeded.
Been away for a while, just got back and time to finally sort this amp out! I did phone Arcam but they want £185 for a repair, upgrading it etc etc, just not worth it.... So, seeing as I'm such a amateur, where would one find the inputs to the protection micro?
The service manual all looks like jargon to me
The service manual all looks like jargon to me
I'd rethink that decision
It may seem like a genuine Bargain... once you have spent some time experimenting 'on your own'.
Besides they will give a warrantee with their work as well.
.....so unless you can make sense of that schematic, particularly sheet 4 which is the amplifier power control section containing the microprocessor and test points, you have little chance of being guided through trouble shooting. By your replies, I get the impression that you have a lot to learn about the basics of electronics, microprocessor control systems and amplifiers generally before tackling any repairs, particularly not on models as complex as the Alpha 10.
At an approximate resale value of only 150 UKP in good condition, there isn't much room for mistakes there either. Certainly 185 UKP to refurbish it is out of the question if you wanted to sell it but I would not count on results unless you get professional help. Seek a local technician out who may well be able to repair it for considerably less.
At an approximate resale value of only 150 UKP in good condition, there isn't much room for mistakes there either. Certainly 185 UKP to refurbish it is out of the question if you wanted to sell it but I would not count on results unless you get professional help. Seek a local technician out who may well be able to repair it for considerably less.
True. Also, they sell for around £258 - £328 (working) on EBAY (had mine since new) I have 3 sets of Nordost leads with mine (£249.99 each) and 4 runs of QED 15ft speaker wire leads with banana plugs that was £115 odd... I don't want to sell it for pennies
So, going to take it to a local place tomorrow and see what they say...
That's great news. Perhaps now you'll get your money's worth before reselling it.
As Arcam have fitted fans, it seems that overheating was known to be chronic with those tiny
heatsinks, regardless of how efficient they were claimed to be. One look at the pics would have
anyone shaking their heads, considering the dissipation of those over-worked power mosfets.
It's hard to understand why Arcam and other UK manufacturers consistently underestimate the problems
of high operating temperature to the reliability of their up-market consumer electronics. It might save
pennies at the costing stage but it must cost pounds in bad raps, warranty claims and consumer confidence.
As Arcam have fitted fans, it seems that overheating was known to be chronic with those tiny
heatsinks, regardless of how efficient they were claimed to be. One look at the pics would have
anyone shaking their heads, considering the dissipation of those over-worked power mosfets.
It's hard to understand why Arcam and other UK manufacturers consistently underestimate the problems
of high operating temperature to the reliability of their up-market consumer electronics. It might save
pennies at the costing stage but it must cost pounds in bad raps, warranty claims and consumer confidence.