Yamaha MX-55 service manual ?

AsRock

Member
Hi, i am after a service manual for this unit or at least some one to confirm the main transistors in it.

Well why i am asking about this is that the MX55 is a 4 channel Amplifier and it has 2 different pars of transistors.

Why bother with such unit's, well they are in such a awesome condition and have audio drops out's which i am still looking in to, but trying to save my self $20+

Thanks.
 
Anything wrong with the amp? can't compare?? Look up whats in there for hfe. might be good replacement. might be exact replacement just another pn for stock. or post numbers here if you have problems searching or don't understand hfe etc. Member avionic can probably recite off his memory. (no shit!... he can!) if they are good to go.

Gotta be an equivalent amp rated for outputs to compare if you want to look yourself.
https://www.hifiengine.com/manual_library/yamaha/mx-50.shtml
or anything wattage close..
 
Norman has HiDef pdf files. Have always gotten excellent manuals and is my go-to for manuals.
Just email him and tell him what you need.:thumbsup:

https://www.analogalley.com/osccart...Csid=42081e686c876ccc527b9aad5316728f&x=6&y=5

Thanks, i actually just ended up buying one from ebay.

Anything wrong with the amp? can't compare?? Look up whats in there for hfe. might be good replacement. might be exact replacement just another pn for stock. or post numbers here if you have problems searching or don't understand hfe etc. Member avionic can probably recite off his memory. (no shit!... he can!) if they are good to go.

Gotta be an equivalent amp rated for outputs to compare if you want to look yourself.
https://www.hifiengine.com/manual_library/yamaha/mx-50.shtml
or anything wattage close..

MX-50 is a different beast.

Besides when it''s been unplugged for a while there is distortion but soon clears up and works how it should. The transistors i checked in to were the SA1491\2, same with the pairs for them a digit difference but from what i have seen they are different. Maybe it's just how they work i am sure the SM will make things much clearer.

Maybe that's how it handles going from 2 to 4 channels. although from what i been told they have been put away for a very long time.

So wanted to make sure this is how they should be before pushing the unit as they are in perfect looking order inside and out.
 
Besides when it''s been unplugged for a while there is distortion but soon clears up and works how it should.
May have fouled protect relay contacts. From a cold start and when you hear distortion. Quickly crank the volume way up then back down. See it the distortion disappears.

Cold solder connections may also produce the same symptoms.
 
ill have to check the relay's later but the distortion does go once the volume has been higher, it's mainly when when it's just been plugged in which could just be the main caps charging still.

First thing i did was check the main board for dry\cold joints, i guess another look will do no harm.

Will have the take the back off too and have a closser look at those relays and speaker terminals as they are right next to the heatsink.

I will tryy to get some pics up as this thing is like near new looking, little dust but when i 1st took the lid off i was shocked how shiny the parts were lol, Although my picture taking skills are not the best hehe.
 
l have to check the relay's later but the distortion does go once the volume has been higher, it's mainly when when it's just been plugged in which could just be the main caps charging still.
Relay..Most likely.
 
I had thought that but it's a none issue after the unit has been plugged in and used, don't know how long it takes to do it again as i have only had it a week so.

But i think your on to some thing though and might be worth taking a peek and cleaning as they might be just starting to get dirty

Thanks for your input. :o).
 
Well taken them off and carefully opened and cleaned them, will have to see in a week or so if it solved it.

There was more dirt in there than i though, good ol camera got it all to show, but all nice and new looking now :banana:

Here's a few pics.

It's no 29 years of dust that's for sure, 2 maybe ?.
imgp9940.jpg


imgp9978.jpg

imgp9976.jpg

imgp0032.jpg

imgp0039.jpg
 
Thanks for the link, i soldered them and opened them up and give them a clean, re flowed a bunch of joints in high voltage and high heat area's like the speaker terminals.

Did a quick test once that was done and left them for about a week and just tested one of them with 0 problems.

Thanks for your help and advice.
 
Well, I just bought a MX-55 to replace my M-35. Such a more robust amp. Got it hooked up but can't really exercise it as the kids are on their way to bed for their first day back to school tomorrow. One thing that disappointed me was I thought that the speaker posts could accommodate banana plugs, but they can't! Sheesh. :(
 
Asmodeus, you running it in 2 or 4 channel? I'm thinking of get a MX-55 to replace the two 35s I have in the bedroom.
 
Well, I just bought a MX-55 to replace my M-35. Such a more robust amp. Got it hooked up but can't really exercise it as the kids are on their way to bed for their first day back to school tomorrow. One thing that disappointed me was I thought that the speaker posts could accommodate banana plugs, but they can't! Sheesh. :(

Sorry not been on for a little while, glad you like it though, i went back to using my MX-630 and been thinking of just selling them. How ever other than wpc they don't do to bad so might just keep at least one for a backup.

As the the terminals i could not agree more and found that annoying too haha, how ever the covers come of my banana plugs so they fir in though were the wire goes in with about 2-3mm clearance all so put a bit of electrical tape on the back were the banana plugs show just in case.
 
Asmodeus, you running it in 2 or 4 channel? I'm thinking of get a MX-55 to replace the two 35s I have in the bedroom.
I am using it in 2 channel mode right now. I seem to aquire more amps and AVRs than I can keep in service though, so it may get some time in 4 channel mode someday if I reconfigure. I lust after a bigger amp like a MX-1000, M-85 or even an M-45, but this MX-55 will hopefully tide me over...I aim to do a little comparison listening between the M-35 and MX-55 soon. I have not had multiple amps before so I am curious to see if I can hear the difference between these amps and the AVR's.
 
I am using it in 2 channel mode right now. I seem to aquire more amps and AVRs than I can keep in service though, so it may get some time in 4 channel mode someday if I reconfigure. I lust after a bigger amp like a MX-1000, M-85 or even an M-45, but this MX-55 will hopefully tide me over...I aim to do a little comparison listening between the M-35 and MX-55 soon. I have not had multiple amps before so I am curious to see if I can hear the difference between these amps and the AVR's.
How did the mx-55 compare ? There is one near me for 200. Which is a bit high. I'd only want to use it with a topping d50s DAC and my TV. Perhaps digital music.
 
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