Hey guys, I've just purchased a Musical Fidelity A1 from eBay on a whim and I'd like to order some parts whilst it's in the post
I've looked around the internet and either haven't found much, or I've found contradicting statements, I was wondering if anyone could tell me what they'd recommend me replacing?
I'd like to replace the power capacitors but cannot decide what specifications to use, I do a lot of soldering but this is my first amplifier referb so I don't want to buy any incorrect parts!
So I suppose my questions are:
•What capacitors should I replace and what spec capacitors should I install in place of them
•Are there any upgrades I should make whilst I am inside the amp
I have placed an order for a 47nf 250v Polyester capacitor for the AC in and some 10A10 Rectifier Diodes to replace the stock ones, hoping they are all fine and correct!
I've looked around the internet and either haven't found much, or I've found contradicting statements, I was wondering if anyone could tell me what they'd recommend me replacing?
I'd like to replace the power capacitors but cannot decide what specifications to use, I do a lot of soldering but this is my first amplifier referb so I don't want to buy any incorrect parts!
So I suppose my questions are:
•What capacitors should I replace and what spec capacitors should I install in place of them
•Are there any upgrades I should make whilst I am inside the amp
I have placed an order for a 47nf 250v Polyester capacitor for the AC in and some 10A10 Rectifier Diodes to replace the stock ones, hoping they are all fine and correct!
The volume potentiometer will start to crackle, they suffer from the heat.
That is worth replacing, (Google for information / parts.)
That is worth replacing, (Google for information / parts.)
Couldn't help but notice the last sentence...
If that 47nF is across the mains input then you must use a Class X type rated specifically for mains use. Anything else is a safety risk and liable to fail spectacularly.
Remember 230/240 volt mains is 340 volts peak. Even 1000 volt rated caps can and do fail. Get the right ones.
If that 47nF is across the mains input then you must use a Class X type rated specifically for mains use. Anything else is a safety risk and liable to fail spectacularly.
Remember 230/240 volt mains is 340 volts peak. Even 1000 volt rated caps can and do fail. Get the right ones.
I've had a read through that and it will be handy so thank you for linking me that, unfortunately he doesn't say what caps to use for the replacement, of course when the amp comes I can just take it apart and buy exact replacements, but I'm new to this and it seems to be that people put different values in (Possibly for better results/longevity) and I'm unsure what the best specs are for the replacement caps
Exact replacements for anything inside an older piece of audio equipment likely
won't be available any longer.
won't be available any longer.
That's the joy of working with vintage audio gear, you get lucky if you can find a schematic or service manual.
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There will be many different opinions on the best brands and grades of replacement electrolytic capacitors because every DIY audiophile makes up their own list of favourites and few are the same as others because of the appeal of brand names, local availability issues and manufacturers having relentless obsolescence programs.
As rayma advises, people trying to find parts the same as original will be out of luck and NOS capacitors are often a waste of money anyway. "Audio grade" electrolytic caps are also rather expensive. e.g. A pair of only 6,800uF Nichicon LKG grade will cost about ₤30. You soon realise that this recapping exercise had better be worthwhile. Unfortunately, apart from simply replacing dying caps to restore their function, it isn't always a good idea to blanket recap. an amplifier. For the larger caps, it's better to test for ESR first than simply replace everything that looks old.
One suggestion though, is that because the A1 gets hot (too hot really) it warrants using higher rated 105°C caps. This probably limits you to standard grades but rather a safe amp that works fine for 20 years than one that needs more replacements after only a year or so.
As rayma advises, people trying to find parts the same as original will be out of luck and NOS capacitors are often a waste of money anyway. "Audio grade" electrolytic caps are also rather expensive. e.g. A pair of only 6,800uF Nichicon LKG grade will cost about ₤30. You soon realise that this recapping exercise had better be worthwhile. Unfortunately, apart from simply replacing dying caps to restore their function, it isn't always a good idea to blanket recap. an amplifier. For the larger caps, it's better to test for ESR first than simply replace everything that looks old.
One suggestion though, is that because the A1 gets hot (too hot really) it warrants using higher rated 105°C caps. This probably limits you to standard grades but rather a safe amp that works fine for 20 years than one that needs more replacements after only a year or so.
So after some digging it seems like one of my two PNP 2N2955 are dead, could have other faults but I haven't checked yet, but I bought myself an LCR meter just to check transistors and yep, one's kicked the bucket!
The issue is, the 2N2955's are discontinued and the second hand market is scarce, especially in the UK! (Shipping from America is $16-26!) even though I'd expect it to be a lot less than that as that's just eBay's autogenerated pricing
If anyone has an old dead amp that they can rip the PNP's out of/have some laying around, or you know of a guy who knows a guy or a website, please let me know!
I'd like to have the original transistors, but I'd settle for a different brand, I know there's alternatives out there but I'd like the amp sound to as close to stock as possible 🙂
The issue is, the 2N2955's are discontinued and the second hand market is scarce, especially in the UK! (Shipping from America is $16-26!) even though I'd expect it to be a lot less than that as that's just eBay's autogenerated pricing
If anyone has an old dead amp that they can rip the PNP's out of/have some laying around, or you know of a guy who knows a guy or a website, please let me know!
I'd like to have the original transistors, but I'd settle for a different brand, I know there's alternatives out there but I'd like the amp sound to as close to stock as possible 🙂
2N3055/2N2955 (metal can or plastic) can still be found from reliable sources (just google)
To Ian Finch: Nowhere in this amp is required any better capacitors than Panasonic or Nichicon above that is just wasting money (just my honest opinion) those 2 brand are a big improvement over the cheap ones fitted originally.
To Ian Finch: Nowhere in this amp is required any better capacitors than Panasonic or Nichicon above that is just wasting money (just my honest opinion) those 2 brand are a big improvement over the cheap ones fitted originally.
It's MJ2955 not 2N2955... but if youre having to replace the transistors, do yourself a favour and replace them with something more robust like MJ15024/MJ15025
The volume pot wearing out has nothing to do with the heat - it is a poor preamp design which puts DC on the track of the pot.
As for the capacitors, read the value and voltage rating, then measure the size. Find equivalents that fit the size limits, with same or slightly higher capacitance rating, with same or slightly higher voltage rating
The volume pot wearing out has nothing to do with the heat - it is a poor preamp design which puts DC on the track of the pot.
As for the capacitors, read the value and voltage rating, then measure the size. Find equivalents that fit the size limits, with same or slightly higher capacitance rating, with same or slightly higher voltage rating
I haven't found anywhere on Google in the UK, all from the US with postage 400x the cost of the item
In my previous response above, I hadn't read your initial comment!
I was not aware they were MJ's and not 2N's, a write up on the A100 somewhere online said they used Taiwanese 2N's but they must be mistaken
The SN's from Farnell were only stocked in America so the shipping and handling was through the roof
Now I know that they are MJ's that makes it a lot better, thank you so much for correcting me
With going for the MJ15024/MJ15025 for robustness, will these change the sound much? I haven't actually heard the amp yet but I've heard many fantastic things about the sound, and I don't want to alter the sound much if I do end up going with the more robust transistors you've recommended
I was not aware they were MJ's and not 2N's, a write up on the A100 somewhere online said they used Taiwanese 2N's but they must be mistaken
The SN's from Farnell were only stocked in America so the shipping and handling was through the roof
Now I know that they are MJ's that makes it a lot better, thank you so much for correcting me
With going for the MJ15024/MJ15025 for robustness, will these change the sound much? I haven't actually heard the amp yet but I've heard many fantastic things about the sound, and I don't want to alter the sound much if I do end up going with the more robust transistors you've recommended
Like i said, fit the alternate parts ive mentioned. The 2955/3055 is obsolete now, mainly because theres no good reason to use them. The transistors I have mentioned will function perfectly with no change in sound.
The capacitors on the other hand will be hard to get.. you may have to consider slightly less capacity such as 8200uF rather than 10000uF. This shouldnt make much difference. A suitable part would be Vishay's MAL225626822E3
edit: Transistor wise, MJ15015/16 are closer to the originals, and still manufactured. It doesnt matter much anyway.
The capacitors on the other hand will be hard to get.. you may have to consider slightly less capacity such as 8200uF rather than 10000uF. This shouldnt make much difference. A suitable part would be Vishay's MAL225626822E3
edit: Transistor wise, MJ15015/16 are closer to the originals, and still manufactured. It doesnt matter much anyway.
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You can even find them on the big auction site.
Just checked datasheets for the 2N2955/MJ2955 and guess what ?