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Marantz SM80 repair

glenn jarrett

pfm Member
Got hold of a SM80 power amp
no relay click
all semis seem ok
but every single capacitor so far except the power supply way out of spec
changed the caps in the secondary power supply board a lot of heat damage to the pcb and a few lifted tracks (shite pcb )
thats now working
and i have a relay click
but 250mv drifting dc offset on one side
and 20mv the other
hopefully changing the rest of the caps will sort this out another 16 caps to go

nn by glenn jarrett, on Flickr
nm by glenn jarrett, on Flickr
20210324_163908 by glenn jarrett, on Flickr
20210326_120821 by glenn jarrett, on Flickr

20210326_122848 by glenn jarrett, on Flickr
20210326_123108 by glenn jarrett, on Flickr
 
If the DC-offset is wandering, look at the coupling cap to signal 0v in the feedback network first; tired caps with dc leakage there would cause what you report in the worst channel.

Good luck, and keep us updated : )
 
the tiny electrolytics near the pots middle off heatsinks were completely gone too here in one I had and threw away after some soldering fun, horrible pcbs, the preamp is even worse, good luck
 
Markvdv your not joking
half way through i realized i was pissing in the wind o_O
loads of heat damage to tracks
every single time i tried to remove a cap i lost the pads
this has got to be the worst pcb i have ever come across
even tried my work soldering irons antex c15 c18 with braid
the solder on the pcb pads was that thin if you moved a cap the leads would break the solder and you could almost pull it out :eek:
that said i now have a case for my ( borrowed NCC200's modules ) to drop in to with plenty of heatsinking and a ready made +/- 50vdc power supply with 4x 12000uf 63v Elna for Audio caps which are still in spec the only ones in the entire amp !


20210328_135516 by glenn jarrett, on Flickr

20210328_124635 by glenn jarrett, on Flickr
20210328_143139 by glenn jarrett, on Flickr
 
That's a real shame, however, that transformer looks good. I am on a crusade to banish all toroids in my system. Only one left :cool:
 
its the biggest EI core i have seen in an amp gives after rectification +/- 52v to output and +/- 60 regulated for the front end in the marantz amp set up
4 nice smoothing caps also
 
I thought about drawing new pcb's and ordering those, that really would be only option for these amps, I didn't. My poweramp wasn't that bad, I mean it functioned without damaging speakers, but left me wondering when it would and so many replaced parts were messy looking on those pcb's and the preamp... well oscillating a lot and only sometimes not lol, the times you thought you had fixed ALL problems lol, same quality pcb's. Try these series and you will learn to appreciate evrything made in China these days, 10 times superior quality at least, I mean I can still feel goosebumps on my back thinking about these Marantz's, really horrible.
 


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