Hey guys, just thought I'd share this as I been meaning to post up a few things but haven't found the time and with CNY approaching, got some downtime so here goes:

Got this amp from a customer, its an Arcam Alpha II. The customer bought it 22 years ago and used it in the beginning but for the past 10 over years its been sitting in his spare apartment doing absolutely nothing. Actually he gave me his entire system to revive which includes a pair of Tannoy Mercury M2's and a Harman Kardon CD player. I'm tackling the amplifier first.

First signs showed a lot of dirt and corrosion. Initial test showed a very weak left channel and a cracking right channel.



Stripped the amp down and first part was cleaning it with a small brush and vacuum cleaner.


The good thing about the Arcam is it has both a top cover and bottom cover so access to the PCB is very good and only four screws opens up both covers. Flipped the amp over and checked the solder joints. These can go bad after a number of years and will need touching up with new solder. Sometimes these joints aren't so easy to find and you'll need a magnifying glass to spot bad ones. Found a few bad ones so retouched them.


Initially I wanted to swap the old volume potentiometer for an Alps unit but the budget didn't allow it and sourcing a new one is not easy as you'll have to obtain the correct size and length to fit the original knobs. So instead I cleaned out the volume, tone and balance pots. Contact cleaner does the job. Do not ever use WD40 on pots as WD40 leaves a residue which can act as a conductor.

Next on the list was to check the components. The output stage transistors were healthy but looked like they've been replaced sometime in the amp's life as the original ones are marked AAR and only one transistor out of the four still has the original markings. I also checked the bias and these had to be reset to factory specs (need a service manual for this) as one channel was slightly off.

To set the bias the amp needs to be on for at least half an hour with no speakers or anything attached. The volume has to be all the way down and then the bias is checked and set to factory specs. Most amps have a small variable resistor to adjust the bias and changing components in the amplifier stage usually requires the bias to be set and a lot of techs fail to do this. In extreme cases this can lead to premature failure. Also failing to set the bias can lead amps to sound 'slow' or too 'fast'. Some amps don't have a bias adjustment and these kind of amps need to have their components matched.


Anyway, hooked the amp back up and it actually works quite well and has been on test for awhile. For a 22 year old amp, it actually sounds very good

However for a 22 year old amp, its gonna get a complete re-cap and I've already ordered new Panasonic capacitors for it and will get to that soon. Also if budget permits will be changing the RCA jacks as they're in quite bad shape. The Deltron banana connectors however will be retained as they aren't cheap and can clean them out.

Cheers!

This post has been edited by Black Octagon: Feb 9 2013, 02:29 AM

Like always,good job!

looks sweet.....

Still remember last year doing restoration for a Leak Stereo 70,quite a lot of work but worth it.What surprise me the most is that the unit doesn't sound like an old amplifier after all.

Yup, these old amplifiers actually sound very good once brought back to factory spec and with modern day components, they can sound even better than original.

Amps like the Leak and Quad amplifiers still remain highly sought after not to mention "newer" 70s and 80s model from Arcam, NAD etc.

Will have more pics up soon. Putting in some Panasonic caps into the Arcam at the moment.

Alright, done changing the electrolytic capacitors on the board. The PCB is a bit fragile and this could be down to age.

Changed the caps to mostly Panasonic caps which have a temp rating of 105 degrees, the old caps all had a temp rating of 85 degrees. Some of the Panasonic caps have a 5000 hour lifespan. Unfortunately I couldn't get Panasonic smoothing caps as they would have exceeded the budget. The Nichicons were chosen as they are rated at 105 degrees and 1000 hour lifespan. With that being said, considering that the original caps were rated at 85 degrees, these new caps should outlast the old ones by quite a bit.



Smoothing Caps or filter caps




Did a quick test just now from the bench, the hi's are more pronounced. There's more air and soundstaging has improved considerably. Bass is still the same but the Arcam's were notoriously weak in the low's department from new. I could have increased the filter caps but besides better ratings, all values were maintained to original spec.

The amp is now warming up so I can reset the bias again. Initial test after the cap change saw the bias voltage drop by almost half. Would explain why straight off the bench the amp sounded slightly lazy. Will give it about an hour without load and retest.

Old capacitors


Will check with the owner after this to see if the budget can be stretched a bit. Still got to factor in his Tannoy's and HK CD player. If there is a bit more, will look into replacing the RCA connectors and throw in some WIMA caps.

Interesting to know that modern day components can improve the performance of such an old equipment.
Setting up a tent here waiting for your updates

The equipment from the 70s and 80s are actually very well built and component failure is actually uncommon. Problems usually surface because of corrosion, gunky pots...basically moisture and age. Sometimes wrong component matching (speakers) to a particular amp can short it out or cause it to fail prematurely and then its blamed cause its old. Also old equipment sometimes could have been sent for repair but not calibrated back to factory specs and then fail faster than it should and once again, the blame is put on old age.

Replacing components usually brings a piece of equipment back to original specifications and thus it can sound good again. Also with tolerance levels in today's electronic components, things can be improved even more at times.

Back to the Arcam. Well, I tested it straight off the bench after changing the caps. First impressions revealed:

1. Improved soundstaging, more air and improved hi-mids and hi's.
2. Tone controls (bass, treble) controls seem to be more 'effective'. Previously the bass control pot seemed like it needed another notch to have a reasonable effect on the sound. Now it sounded more like a modern amp in that it had range. Same with the treble control.
3. Bass was weak but the Arcam Alpha's weren't bass monsters from new so that's fine. I could have bumped up the filter caps to improve the bass but the point of this whole thing was to replace parts with same rating parts.
4. Overall sound was a bit sloppy. As if the amp was slow and lazy conveying drums or fast numbers.

Anyway, disconnected the CD player and speakers, turned down the volume and left it on for an hour. The Arcam service manual says to leave it on for half an hour at least before resetting the quiescent current. After an hour I checked the current and it had dropped 3mV since I adjusted it before the cap change. Brought both channels up to factory spec. Factory spec is 8mV for each channel. So the cap change did make a difference.

Connected the CD player and speakers back and put on the Best of Fourplay. It sounded like a completely different amplifier. Most noticeable was the tighter bass. Drums sounded tight instead of sloppy. Physically the output transistors were running cooler than before, even when I first got the amp. Oh yeah, didn't need to push the volume as high as it used to go. So lower volume setting for same volume level and running cooler.

Faceplate back on, knobs were brown instead of black before this


Need to repair that power button...

Where are you located? I have a NAD amp that needs restoration. It have this buzzing noise even when there's no source fed to it.

Balakong, near Mines shopping centre. I'll send you a PM bro.

Want more adventure in restoring you amp.....???? Look at those 4 little rectifier diode after the traffo....change it to fancy one like the mur860 or the ixy. Some swear it makes different but it good to try. The murs are cheap too.

BTW those RCAs and speaker terminals is aging.....change it to something clean new and shining. A good contact at the signal section is good.....

This post has been edited by gabanyayaya: Feb 11 2013, 01:16 PM

Its for a customer and the budget matters but you're right, those 4 diodes are on the list as well. The speaker terminals are banana plug Deltron's and think gonna leave them in as replacement ones are hard to come buy and pricey.

The RCA's I think I'm gonna change soon too. A bit busy at the moment with a NAD 3020A which has its internal components all done by probably some local repair shop that messed it up.

Deltron plugs is available in Farnell / Element14.........

Yup but only the Nickel plated ones are still available. The gold plated ones which the Arcam uses is no longer kept in stock though its still on their website. Already checked last week actually. And besides, the current ones cleaned up quite well.