Can anyone recommend a repairer for Musical Fidelity amp?

Can anyone recommend a repairer for Musical Fidelity amp?

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sunbeam alpine

Original Poster:

6,936 posts

187 months

Monday 22nd June 2015
quotequote all
I have a Musical Fidelity A1 amplifier dating from the late '80's. It's paired with a Linn Sondek and a reasonably decent CD player, driving Mission speakers.

It does eveything I want perfectly, but recently the volume knob has become very crackly (when I rotate it to increase/decrease volume) and one channel is noticeably quieter than the other. The quieter channel does occasionally come up to the same level as the stronger channel, but this doesn't last very long.

I've already swapped speaker outputs and audio inputs, so can confirm it's the amp which is at fault.

Does anyone have any suggestions either that I can try myself, or recommend an address (preferably in southern England) who can repair it?

I'm in Belgium but in the UK at least once a month.

Thanks in advance!

legzr1

3,843 posts

138 months

Monday 22nd June 2015
quotequote all
Have you thought about MF themselves?

A quick email will confirm if it's still serviceable.

Had mine done recently (308 power amp so quite a bit younger than the A1) - not cheap but got a decent warranty.

Or maybe try a well-regarded ex-MF engineer (best to ring as he never answered any of my emails hence going direct to MF):

http://jsaudiorepairs.co.uk

peterperkins

3,148 posts

241 months

Monday 22nd June 2015
quotequote all
A crackly knob is a pretty common fault on any amp with analogue physical adjustment of levels.

It's just a variable resistor probably with a worn track.

Anyone half decent with electronics could probably replace it if you can source a suitable part that will physically fit the chassis/case etc.

As stated the OEM may have spares and you can get a mate to fit it.

sparkyhx

4,143 posts

203 months

Monday 22nd June 2015
quotequote all
MF can do full on refurb. If you like the amp and sound it might be worth 'investing' go onto their website. There is also an independent guy who does them as well with full recap, I can't remember the name but i'm pretty sure the A1 came under his list of amps.

Edit - quick search reveals
http://www.amprepairservices.co.uk/musical-fidelit...

FlossyThePig

4,083 posts

242 months

Monday 22nd June 2015
quotequote all
In the past I have used a spray contact cleaner as crud can build up over the years.

Something like this:
http://www.maplin.co.uk/p/maplin-contact-cleaner-2...

sparkyhx

4,143 posts

203 months

Monday 22nd June 2015
quotequote all
i'd go for the full refurb, the capacitors will probably need a recap after so long.

jamesh764

184 posts

141 months

Monday 22nd June 2015
quotequote all
FlossyThePig said:
In the past I have used a spray contact cleaner as crud can build up over the years.

Something like this:
http://www.maplin.co.uk/p/maplin-contact-cleaner-2...
I had the same problem with a Leak Stereo 30 amp - fixed by unplugging from the mains, removing the top, squirting contact cleaner into the volume pot, turning the volume up and down a few times, waiting a few minutes for the stuff to dry, putting top back on and plugging back in.

The_Burg

4,845 posts

213 months

Monday 22nd June 2015
quotequote all
A very easy fix, do not use contact cleaner.
There are specific sprays and grease for this.
Quite often it's just dust and just rotating the knob, (ooh err), repeatedly will clear it.
Why not upgrade at the same time?

http://www.markhennessy.co.uk/mf_a1/technical.ht

A way down, buy the Alps pot and if you can't do it I sure someone is local on here could do it. If your anywhere near me happy to help.

ian996

837 posts

110 months

Tuesday 23rd June 2015
quotequote all
legzr1 said:
Or maybe try a well-regarded ex-MF engineer (best to ring as he never answered any of my emails hence going direct to MF):

http://jsaudiorepairs.co.uk
I think John might have a hyper-active spam filter as, once you get to speak to him, he is an incredibly helpful bloke, but his email response can be a bit sketchy.

He does a lot of straight-forward repairs, but his upgrades are worth at least considering, he is a bona-fide genius at getting the best out of electronics. He's done a load of mods to my MF kit, and I can't recommend him too highly. His testimonials don't lie.

sparkyhx

4,143 posts

203 months

Tuesday 23rd June 2015
quotequote all
from one of the sites. Recap deffo recommended based on this.

Faulty electrolytic capacitors
This is the second big problem with these amplifiers. Heat is a major enemy of electrolytic capacitors, so it will be no surprise to hear that they are a particular problem with this amplifier! The original components were of fairly average quality to begin with, which clearly doesn't help.

Look in an electronics component catalogue, and you'll see that electrolytic capacitors have a finite life expectancy, typically around 2000 hours for an average-quality device. This is quoted at an operating temperature of 85°C, and as a rule of thumb, reducing the operating temperature by 10 degrees will double the life expectancy. As the surface of the heat sink is around 60-65°C, the internal temperature will be even higher. Remember, 2000 hours might sound like a lot, but that's only 2 years if you use the amplifier for 3 hours a day!

The symptoms of faulty capacitors are hard to predict. Basically, it only takes one degraded capacitor to affect the performance of the circuit, and as it's hard to detect a gradual change in sound quality, you can be forgiven for not noticing faults developing. When they get particularly bad, it's possible that other components can fail as a result of the changes operating conditions within the amplifier. The message is simple - if you have a fault with the amplifier, don't start trying to apply logic until you've replaced all the capacitors. In 95% of the cases I've come across, this will clear the fault.

Better quality capacitors will be rated at 105°C, and will have a longer life span as well. Follow the logic of doubling the life span with every 10°C fall in temperature, and you'll soon see why fitting anything less is a false economy.

Remember to look for long-life, low-ESR, 105°C rated capacitors - Rubycon YXF, Elna RJH or Panasonic FC are all good starting points. I'd steer clear of "exotic" or "boutique" components like Black Gates as they're only rated at 85°C - it seems perverse to spend a fortune on capacitors that will be no more reliable than the originals.

It took me a little while to locate the main reservoir capacitors because of the limited space - they can only be 25mm high. From the Panasonic HA series, the 10,000uF, 25V 105°C fits the bill and is readily available from the usual suppliers.

You can replace C6 and C7 with 1µ non-electrolytics, but they have to be physically small.

Needless to say, you need to be very careful about the polarity of all the electrolytic capacitors. There are markings on the PCB, and you can check against the schematic...