Hi
I'm not sure if this is the right section but i'd really appreciate some help.
I own a 12 year old Arcam Alpha 10 and am extremely interested in servicing it. One of the channels seems a bit quieter and its just not quite as good as it was. Upon first inspection one of the main capacitors has a bit bulge on the top. Its a 63v 10,000uf alc10a103df063 bhc.
I'm fine with soldering new parts on boards just need advice as to what to change ie resisters, other caps etc.
I downloaded a service manual which goes into loads of detail from hifi engine.
Please help
I'm not sure if this is the right section but i'd really appreciate some help.
I own a 12 year old Arcam Alpha 10 and am extremely interested in servicing it. One of the channels seems a bit quieter and its just not quite as good as it was. Upon first inspection one of the main capacitors has a bit bulge on the top. Its a 63v 10,000uf alc10a103df063 bhc.
I'm fine with soldering new parts on boards just need advice as to what to change ie resisters, other caps etc.
I downloaded a service manual which goes into loads of detail from hifi engine.
Please help
I had a quick look at the manual. Seems there are two versions, a power amp and an integrated. Which is yours ?
Caps with a bulge. If the actual aluminium can is bulging then it needs replacing. If it's a plastic sleeve or plastic disc on top of the cap it could well be OK. Photo maybe 🙂
What is the voltage across the cap ? Anything approacing 60 volts at correct mains input voltage and it's marginal and a higher voltage cap should be fitted.
Quieter on one channel... you need to be sure! That would take seconds to check with an oscilloscope and signal generator but I'm guessing you don't have one.
I see there is a gain switch on each channel on the power amp. Is that OK... not intermitant contacts etc.
If you have a test CD with a lowish test tone on it (say between 100 to 1 khz) you could measure the AC voltage across each speaker and compare left and right. All the signal switching and processing is "electronic" in the preamp so unlikely there is a real problem here.
Caps with a bulge. If the actual aluminium can is bulging then it needs replacing. If it's a plastic sleeve or plastic disc on top of the cap it could well be OK. Photo maybe 🙂
What is the voltage across the cap ? Anything approacing 60 volts at correct mains input voltage and it's marginal and a higher voltage cap should be fitted.
Quieter on one channel... you need to be sure! That would take seconds to check with an oscilloscope and signal generator but I'm guessing you don't have one.
I see there is a gain switch on each channel on the power amp. Is that OK... not intermitant contacts etc.
If you have a test CD with a lowish test tone on it (say between 100 to 1 khz) you could measure the AC voltage across each speaker and compare left and right. All the signal switching and processing is "electronic" in the preamp so unlikely there is a real problem here.
Thanks for the reply, its the integrated amp.
I've not actually tested the cap but the one next to it looks fine. It does however have a sleave. I will take a picture tonight and post for an update.
Is it ok to just measure the voltage on the cap with a multimetre?
The gain switch is for the amp rather than per channel to turn it into a power amp.
I will also test the AC voltage on each speaker, I will find a test CD.
I've not actually tested the cap but the one next to it looks fine. It does however have a sleave. I will take a picture tonight and post for an update.
Is it ok to just measure the voltage on the cap with a multimetre?
The gain switch is for the amp rather than per channel to turn it into a power amp.
I will also test the AC voltage on each speaker, I will find a test CD.
Just measure on DC volts anywhere convenient that the cap connects to. On the bridge rectifier might be easiest if you can't get to the underside of PCB easily.
Ok here's some pictures of my amp insides...
Sorry for the bad quality its the lower cap on this picture
Its hard to take a pic of the bulge but you can see the sleave is different than the identical cap next to it.
Sorry for the bad quality its the lower cap on this picture
Its hard to take a pic of the bulge but you can see the sleave is different than the identical cap next to it.
What advice would you give as to the cap replacement, like for like or an upgrade?
Also the main resistors are gold band but would you recommend any upgrades for these?
Also the main resistors are gold band but would you recommend any upgrades for these?
Hard to say looking at it... I have seen caps like that many times before and it's not always a problem. The real check would be to compare the ripple on each with an oscilloscope.
If you want to replace them there are a few things to consider,
The size and spacing of the leads
Is the working voltage of the originals sufficient ? Did you measure the DC voltage to see if they are running to close to there limits ?
Try and get 105 degree C rated caps but it's not the end of the world if you can only get 85 C.
I wouldn't touch any of the resistors. You won't gain anything.
If you want to replace them there are a few things to consider,
The size and spacing of the leads
Is the working voltage of the originals sufficient ? Did you measure the DC voltage to see if they are running to close to there limits ?
Try and get 105 degree C rated caps but it's not the end of the world if you can only get 85 C.
I wouldn't touch any of the resistors. You won't gain anything.
Many of these caps have a plastic jacket. If the bulge can be popped back without too much effort you are probably barking up the wrong tree..
Arcams are well built, using reasonable components in a well designed circuit.
Every manufacturer though works to a consumer budget. You could build a Lada to Rolls Royce Specs but no-one would buy it, because it is a Lada.
Arcam can only command a certain area of the market, allbeit be very good, their reputation cannot command the £100K prices of the big boys.
To this end, they have to make compromises. How much you want to pay to correct these compromises, is up to you.
I spent £500 upgrading an Arcam AVR280 and the difference was stunning. This was predominantly down to capacitors being replaced along with a few signal level Op-Amps.
My Mark Levinson Clone, the DIY700 however, knocks socks off the modified Arcam.
How often have you heard, you cant build a palace in Tooting, but you could build a brothel in Knightsbridge.
Every manufacturer though works to a consumer budget. You could build a Lada to Rolls Royce Specs but no-one would buy it, because it is a Lada.
Arcam can only command a certain area of the market, allbeit be very good, their reputation cannot command the £100K prices of the big boys.
To this end, they have to make compromises. How much you want to pay to correct these compromises, is up to you.
I spent £500 upgrading an Arcam AVR280 and the difference was stunning. This was predominantly down to capacitors being replaced along with a few signal level Op-Amps.
My Mark Levinson Clone, the DIY700 however, knocks socks off the modified Arcam.
How often have you heard, you cant build a palace in Tooting, but you could build a brothel in Knightsbridge.
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Couldn't really see a point in which to measure the voltage, seems like it might be a board out job.
What make of cap would you get that'll be an upgrade? Would I just match the 63 volt cap providing its not too close to the limit 10,000uf with the legs the same spacing?
Its 12-13 years old and the caps only have a 18,000 hours life I think plus its been well used loudly...... The buldge can't be pushed back down its solid under there. 🙁
I would love to know how to do a few mods on this though, i'm into my hifi but don't have the money for a new amp.
Just measure (carefully as a short would be a disaster) from ground to any parts that connect to the main - and + rails or -SUP and +SUP as Arcam call them. Look at the circuit, the main caps are C18 and C19. That said replacing like for like should be fine.
As the bulge is solid it's probably wise to replace both caps. And measure the physical size and lead spacing. Can't really advise on specific types as it depends where you are and what's available.
Lifetime of caps is quoted under specific conditions, usually at near max voltage and max ripple current which these won't be passing.
As the bulge is solid it's probably wise to replace both caps. And measure the physical size and lead spacing. Can't really advise on specific types as it depends where you are and what's available.
Lifetime of caps is quoted under specific conditions, usually at near max voltage and max ripple current which these won't be passing.
Have you tried contacting Arcam? They might service the thing for a reasonable price. It sounds like you're fairly inexperienced with these things and it would be a shame for you to damage something by accident.
Don't get me wrong I am all for poking around, but sometimes it's better to make use of what the company can offer. That way you can also easily sell the unit later if you wish to.
Don't get me wrong I am all for poking around, but sometimes it's better to make use of what the company can offer. That way you can also easily sell the unit later if you wish to.
iirc Arcam should be perfectly happy to service it, even though its old. They do seem to pride themselves on their older products too - they even service old A&R Cambridge A60's when asked!!
Sure they probably would service it at a price!! I think its min £150 but I enquired about my CD player and they came back with they can't get parts for it. Besides I can change parts at board level and i'm slowly learning the rest as im really interested in it.
I do have a problem though, I can't source the 2 main caps for it.... Tried everywhere but its an old cap. KEMET has the part number but none of their suppliers have the part.
Now what I do?
I do have a problem though, I can't source the 2 main caps for it.... Tried everywhere but its an old cap. KEMET has the part number but none of their suppliers have the part.
Now what I do?
Just measure the caps dimensions (including the lead spacing) and make sure that the caps you order will fit. The voltage and temperature specifications have already been mentioned, but make sure the caps you order have a ripple current rating at least equal to the ones you're replacing, higher is better.
Changing caps won't sort out a difference in gain/loudness between the two channels, as the PSU is shared by both.
I'd first confirm that one channel is in fact louder then the other. As has been mentioned, sending a sine wave through the amplifier and measuring the AC voltage on the output with a multimeter would be a quick and accurate way.
An easy way to get a sine wave generator would be to download ARTA and use the sine generator function in that. Simply connect the sound card output to the input of the amp.
With regards to CD player replacement parts, digital audio is a completely different ball park when it comes to product availability. Old generation silicon products, that are now obsolete are sometimes impossible to get replacements for. However a power amp doesn't contain anything like this. The only thing that they might not be able to get an equivalent part for would be a micro-controller.
Changing caps won't sort out a difference in gain/loudness between the two channels, as the PSU is shared by both.
I'd first confirm that one channel is in fact louder then the other. As has been mentioned, sending a sine wave through the amplifier and measuring the AC voltage on the output with a multimeter would be a quick and accurate way.
An easy way to get a sine wave generator would be to download ARTA and use the sine generator function in that. Simply connect the sound card output to the input of the amp.
With regards to CD player replacement parts, digital audio is a completely different ball park when it comes to product availability. Old generation silicon products, that are now obsolete are sometimes impossible to get replacements for. However a power amp doesn't contain anything like this. The only thing that they might not be able to get an equivalent part for would be a micro-controller.
I'd have been very surprised if there were a channel imbalance tbh, but now you have proved it OK as well.
Room acoustics and speaker location play an important part. Try a mono recording to see if the image is located centrally. Even shifting your position by a few cms can make a big difference.
Room acoustics and speaker location play an important part. Try a mono recording to see if the image is located centrally. Even shifting your position by a few cms can make a big difference.
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