Musical Fidelity A220 (23 y/o) - recap? Solve Relay scorching?

NickKUK

Member
2019-12-28 9:16 pm
I’ve owned this since new. The MF A220 is 50W I to 8ohms. The amp like all MF gets hot enough to cook eggs which does change the sound as the amp gets hot.

I’ve seen the other threads on cap failure and running overspeced caps. So I was thinking of replacing the caps which is easy enough but I notice the soft start relay area has scorch marks.

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NickKUK

Member
2019-12-28 9:16 pm
That zener diode has been overheating and will need replacing. Check the transistor next to it too.

Electrolytic caps naturally go bad and can cause problems elsewhere. I do recommend a recap with one higher voltage values. Good Japanese 105° capacitors like Rubycon.

Also resetting the bias to factory settings

Interesting point about the bias - I’ve never changed it however is there somewhere I can get the original bias value if it’s wandered?
 
It's a very heavily biased class AB. Is it any higher than 55mVs through the emitter resistors?

The MF gear don't have many schematics about, as with other British units, to try prevent the Chinese from cloning them.

I would keep a note on its current bias setting before doing a recap. At least to reset back to it and balance them out after the recap.

These units all run hot. Yet a higher bias does make amplifiers run warmer. Under biased run cooler.

Worth replacing low value caps to something like Wima's polyester/polypropylene.
 
Back the bias down some, a couple of mv lower isn't going to hurt things or sound different.


As for the relay drive circuit, replace the zener if reading out of spec, and mount it up higher off the board for better ventilation.
Check all the soldering for overheating and reflow if needed.


Doubtful that any caps are bad, but a good cap checker can eliminate questions.
Avoid the internet gods that always insist on ripping out caps - those goons seem to think they know it all.
I know better.
 
Yes I agree with wiseoldtech and presumably has the user name for a good reason 👍... a lot of people on the Internet just rip out caps because they can. Replacing with "audiophile caps".

I did however recommend the recap as I have had bad times with the Jamicon caps and don't trust them. Especially as its in a warm environment. Good Japanese 105 ° caps will give me more confidence in any cap issues for a long time. It wouldn't surprise me if most of the Jamicons still measures good.
 
StewartH83, when I see fairly newish components like this one, and discussions of "recapping", I shake my head and tell people that unless a major issue is going on, leave the caps alone.
This "re-cap craze" has worn itself out already, and in many cases is not needed.
Only perhaps of products made between 2002-2005, when there was a valid manufacturing issue with some brands of electrolytic caps.
Google the famous "bad capacitor" issue from that era.

THAT, and the internet circulation about it, started this crazy "cap change craze" by someone.
And it went wild over the internet, to this day.

I've been in the service business over 45 years, and pretty much know by now if a massive cap-change is warrented.
But not something from the late 1990's like this amp.
Even a 1971 Harman Kardon receiver still contains useable caps, among many other products.
A servicer has to do proper, intelligent troubleshooting before going into the mess of it, instead of blaring such things across the internet every time someone posts a complaint about something.


Recap-recap-recap-recap! - it's sickening to hear about it, and it's not the "fix-all" that people are led to believe it is.
 
I can't agree more. I understand about the manufacturing issue with the capacitors in that era and the key ingredient missing from stolen capacitor blueprints. I repaired most commonly the Samsung TVs made in that era. Its well known after a short research on capacitors yet the trend still carried on.

Please understand as the OP is about recapping which tells me they are not comfortable with the current capacitors. You'll know people who do recap their units can soon realise it makes no difference and possibly damage the unit even more if not careful, this is part of learning, actions can speak louder than words. I did recommend the replacement of the diode and say existing caps will probably measure well.

I just can't stand Jamicon caps, usually on the border of the 20% tolerance below rated value by that age or under and high ESR. All electrolytic degrade or fail in time, that's the nature of the beasts, yet Jamicon are the most common seen to me albeit overstressed in computers PSUs

If they wasn't Jamicon, I would advise to sort the issue in the relay drive circuit first, then if your uncomfortable with the caps, remove and measure ESR and capacitance.

I won't just say recap, recap... And I don't like to poke people with the same stick
 

NickKUK

Member
2019-12-28 9:16 pm
Thanks chaps :)

There's nothing that screams fix, although I had it in my head that caps need checking after about 20 years. Looks like the zener-issue is first on the list. I'll test the caps but my thinking is if the caps are starting to fail/short then there could be higher current for longer being sent through the soft start hence the scorching.

The amp is coupled with a Myriad MC100 CD player - that also runs AB hot giving easy listening without sounding stark like the old Audiolab 8000A or creamy like the Cyrus at the time. I did eye up the amp to replace components to higher tolerances and make the PSU better as lipstick on the pig, bring out some additional detail etc but in the end I thought I'd get more use out of a DAC/headphone setup.

Off topic - I also have a 2009 LE37 650C Samsung TV that I have on my hit list to take the back off and check. It's also has some serious issues with screen brightness (the darker the more buzzing) which was a known thing and we've simply ignored - for terrestrial TV in the UK it doesn't make much noise but for HD it makes far more noise. But that's an AV problem :)
 
I've never liked Samsung TV's, or many other of their recent products.
On any given year, in the repair shop, and I spent 25+ years there till 2016, I saw more Samsung crap come in for service.
50 to 150 Samsung flat screen sets a year (maybe more) on average.......... compared to maybe 2 or 3 Panasonic Vieras a year!
Samsung home theater stuff flooded our service benches too.
Oh, and a lot of Sony TV's were also prone to breakdowns..... they had Samsung guts!


Guess what brand of TV this old technician chose for his home?
Not a Samsung, for sure.
 

NickKUK

Member
2019-12-28 9:16 pm
I've never liked Samsung TV's, or many other of their recent products.
On any given year, in the repair shop, and I spent 25+ years there till 2016, I saw more Samsung crap come in for service.
50 to 150 Samsung flat screen sets a year (maybe more) on average.......... compared to maybe 2 or 3 Panasonic Vieras a year!
Samsung home theater stuff flooded our service benches too.

Guess what brand of TV this old technician chose for his home?
Not a Samsung, for sure.

After the TV, the PR disaster of exploding phones.. Samsung products are banned from the family too - they've already lost on sales. A replacement TV will probably go Sony.
 
I too can't stand the Samsung equipment. Terrible quality and service.

Worthy taking the back off your TV, checking the PSU electrolytic caps, particularly on its secondary outputs. Some new low ESR Panasonic/Nichicon/Rubycon caps can improve efficiency and longevity. You may find the back light setting no longer needed to be as high.

The earthering screws loosening can cause problems if loose which can be common so make sure they are all tight. Also try check for weak solder joints on the chips.
 
I too can't stand the Samsung equipment. Terrible quality and service.

Worthy taking the back off your TV, checking the PSU electrolytic caps, particularly on its secondary outputs. Some new low ESR Panasonic/Nichicon/Rubycon caps can improve efficiency and longevity. You may find the back light setting no longer needed to be as high.

The earthering screws loosening can cause problems if loose which can be common so make sure they are all tight. Also try check for weak solder joints on the chips.


All that you mentioned is a drop in the bucket of issues with these products.
Some other issues require a bench full of service equipment like scopes, tracers, etc.
And........ service information, schematics, etc.
Because "working blind" on these things is asking for trouble.
 
I agree. Test equipment and schematics can be needed and/or accelerate troubleshooting on any equipment. That goes without saying.

As I'm unsure of the test equipment available. I'm only giving advice that needs little equipment, which he has. Worthy trying with little cost.

I'm sure you've opened up a TV, tighten the earth screws and resolved issues or replaced capacitors that you tested/visibly seen bad and sorted the issue, giving your experience.

I feel we got off on the wrong foot. Something I said that you don't like? If you have an issue with me feel free to message me and save people some popcorn.

Direct your advice to the orginal poster
 
I agree. Test equipment and schematics can be needed and/or accelerate troubleshooting on any equipment. That goes without saying.

As I'm unsure of the test equipment available. I'm only giving advice that needs little equipment, which he has. Worthy trying with little cost.

I'm sure you've opened up a TV, tighten the earth screws and resolved issues or replaced capacitors that you tested/visibly seen bad and sorted the issue, giving your experience.

I feel we got off on the wrong foot. Something I said that you don't like? If you have an issue with me feel free to message me and save people some popcorn.

Direct your advice to the orginal poster


On the contrary Stewart, I have no issues with you, sorry if you took it that way.
Typing across the internet is lacking context and the personable ways which only a face to face conversation can provide.
 
After the TV, the PR disaster of exploding phones.. Samsung products are banned from the family too - they've already lost on sales. A replacement TV will probably go Sony.


I dislike Sony stuff too, from experience.


Get yourself a Panasonic set - my experience with them is excellent.


Oh, and as for Samsung (in the shop we called them samsucks) you forgot to mention the exploding washing machines they made - one, in the news, blew apart on spin cycle and tossed shrapnel and parts right through a basement wall into the garage!


You can have that junk.
 
You need to find out why some components have scorched the pcb.
They really shouldn't get that hot if designed properly.
Is the case ventilated enough ? maybe a fan would help ?
If the relay is scorched might have been arcing through bad contacts and needs replacing.
Look for bad ripple on power supply to see if main caps need replacing.
 
On the contrary Stewart, I have no issues with you, sorry if you took it that way.
Typing across the internet is lacking context and the personable ways which only a face to face conversation can provide.

I'm sorry wiseoldtech. I think you're correct again as communication on the Internet can seem totally different and I was looking at it the wrong way. I truly respect you and your sharing of advice I've seen here for a long time. Feel bad now and embarrassed haha. Wish you the best sir, no hard feelings at all
 

yodog

Member
2019-10-04 1:45 am
Very nice thread and good info.


A side question: how big of a difference in the quality of sound would one be able to audibly notice if one replaces the small value caps on a Musical Fidelity integrated amp/power amp to the metalized polypropylene capacitor type?
 
Very nice thread and good info.


A side question: how big of a difference in the quality of sound would one be able to audibly notice if one replaces the small value caps on a Musical Fidelity integrated amp/power amp to the metalized polypropylene capacitor type?


Unless the original caps are defective, you're not likely to notice a difference.
But the "internet masters" will have you believing it will make some kind of astounding difference - only in your mind.
That "recap craze" has gone on long enough already, and is tiring to read about.
It doesn't, and will never, replace proper troubleshooting, something a real technician has learned to do.