Musical Fidelity A220 Schematics?

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ckng

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Joined 2006
4oh4.blogspot.com
Thanks. The page appears to have only the pre-amp section tho, the power section is not shown. I can't read russian but are they trying to bypass the op-amps for some reason?

I am also wondering (assuming the circuitry is similar, at least for the pre-amp stage) is it feasible to take the ouput from the op-amps (pin 1/7) after the 100ohm resistor and use it as a volume-controllable preamp output?

Regards
CK
 
T

t.ruppenthal

Member
Joined 2008
Musical fidelity A220 repair scematic anybody please

Hi guys,

i have a wonderful A220 which just gave up in a puff of smoke. As i love this sweet sounding amp i would love to get it fixed again but for that i need a circuit diagram. Can anybody help please.
I already had a look at previous posts but the links are dead.

Thanks guys
T.ruppenthal
 
C

cpitts

Member
Joined 2010
corptech.no-ip.org/doodads
*BACK FROM THE DEAD!!!!*

So to help people out, I'm doing a refresh/fix-up on my amp to make a really nice amp, a lot better. Won't divulge where I got this info, but here's a link to my site that's documenting my work (currently underway).

Doodads galore! We just luv em.

Have also completely rebuilt my speakers as well which is worth a read (jump to the link via the menu at the top :) ). And no, I'm not selling stuff, pushing product or anything, I'm just wanting to share as much of this as possible.
 
C

ckng

Member
Joined 2006
4oh4.blogspot.com
cpitts said:
*BACK FROM THE DEAD!!!!*

So to help people out, I'm doing a refresh/fix-up on my amp to make a really nice amp, a lot better. Won't divulge where I got this info, but here's a link to my site that's documenting my work (currently underway).

Doodads galore! We just luv em.

Have also completely rebuilt my speakers as well which is worth a read (jump to the link via the menu at the top :) ). And no, I'm not selling stuff, pushing product or anything, I'm just wanting to share as much of this as possible.
Click to expand...

Wow, can't believe this thread was revived after 5 years! Thanks for all the information that you've put up.

However, sadly, my A220 literally went up in smoke a few days ago after an hour of playing + 1 hour idling after that. White smoke came out from the vents until I powered it off and unplugged everything.

Suspecting maybe a blown electrolytic cap I wanted to open up the case but it's secured with security Torx screws. The next day I searched high and low in the nearest hardware store for a suitable driver and had to buy the whole set as they don't sell singles.

Anyway, after it's open, I found nothing that appears to be obviously burnt. One of the 1W(?) resistors in the right power stage had some chipping. I am not about to plug this in again to see what is actually burning up though.

Any idea how I can troubleshoot this safely or will it be better to get a certified pro to check it out/repair it?

Thanks!

Regards
CK
 
C

ckng

Member
Joined 2006
4oh4.blogspot.com
cpitts said:
*BACK FROM THE DEAD!!!!*

So to help people out, I'm doing a refresh/fix-up on my amp to make a really nice amp, a lot better. Won't divulge where I got this info, but here's a link to my site that's documenting my work (currently underway).

Doodads galore! We just luv em.

Have also completely rebuilt my speakers as well which is worth a read (jump to the link via the menu at the top :) ). And no, I'm not selling stuff, pushing product or anything, I'm just wanting to share as much of this as possible.
Click to expand...

And interestingly, your A220 has a pre-out, mine doesn't. Hmm...

Regards
CK
 
C

cpitts

Member
Joined 2010
corptech.no-ip.org/doodads
If yours has Video Out rather than Pre-Out I have an alternate schematic for that. :)

Either way, you've probably popped a ceramic resistor if all the caps look fine. Worst case it might be a FET that's gone (pressed against the heat sink). Either way, unless you're feeling VERY confident with a soldering iron and a few pound/$US of parts then it's probably best to send it back to MF (or authorised repairer) for a refresh/fix. Might be worth getting it 'tuned up' by MF at the same time!

I've just finished my parts order for a complete refresh of my amp from input to speaker leads. All resistors, caps, links, vol dial and poly prop film caps. Am leaving the diodes, FETs and Phono stage completely alone given I don't have a record player, nor the inclination to redo the FET's.

Either way, if you're game, you could repair it. If you're not super confident and have already modded other things and are up to the challenge, the PCB is very easy to work with (single sided, nice size holes in the PCB, all very open and clean).
 
C

ckng

Member
Joined 2006
4oh4.blogspot.com
cpitts said:
If yours has Video Out rather than Pre-Out I have an alternate schematic for that. :)

Either way, you've probably popped a ceramic resistor if all the caps look fine. Worst case it might be a FET that's gone (pressed against the heat sink). Either way, unless you're feeling VERY confident with a soldering iron and a few pound/$US of parts then it's probably best to send it back to MF (or authorised repairer) for a refresh/fix. Might be worth getting it 'tuned up' by MF at the same time!

I've just finished my parts order for a complete refresh of my amp from input to speaker leads. All resistors, caps, links, vol dial and poly prop film caps. Am leaving the diodes, FETs and Phono stage completely alone given I don't have a record player, nor the inclination to redo the FET's.

Either way, if you're game, you could repair it. If you're not super confident and have already modded other things and are up to the challenge, the PCB is very easy to work with (single sided, nice size holes in the PCB, all very open and clean).
Click to expand...

Mine actually has 2 tape outputs (Tape 1 Record and Tape 2 Record). I studied electronics engineering a long time ago, so I am comfortable with a soldering iron and have built amplifier and DAC kits. I just need to (safely) identify which part needs replacement. If it's really a cap/resistor/FET it should be easy, but seeing no obvious damage makes this difficult, so I'll probably give the MF distributor a call to see how to goes. Hopefully not too expensive!

Do you have higher resolution versions of the schematics? Would be great if you can post them.

Thanks!

Regards
CK
 
C

cpitts

Member
Joined 2010
corptech.no-ip.org/doodads
Are you talking the MOSFET's or something else?

What basic testing have you done?
Do you get both channels coming out the Pre-Out or Tape Out?

I had a channel failure in the Pre-Amp itself! Was able to diagnose with some simple RCA plug swapping. As for part replacement, I'm about to head down that path having collected a vast number of bits, ready for a rebuild/refresh.
 
rubli

rubli

Member
Joined 2008
afaudiolab.com
cpitts said:
Have you considered getting it repaired by a MF service agent? They'll be able to replace them appropriately?

I just checked on rscomponents website and they stock the MagnaTec BUZ900P for ~$US25 each, so they're still available.
Click to expand...

I own a repair shop in Mexico city, mainly tubes, but do also SS...

thanx for the tip on rscomponents, hefty price on these.. wonder if there is something less expensive...

best regards
 
C

cpitts

Member
Joined 2010
corptech.no-ip.org/doodads
I'm sure there are cheaper alternatives, but given the design of the amp and all aspects of tuning that have gone into it, why would you not replace like for like?

If you look along the 8 MOSFETS though, you'll see that there are:
- 4 x 900's
- 4 x 905's
So you only need up to 4 x BUZ900's depending on what you're going to replace. Not much considering the original value of the amp and it's ability.
 
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