:'( fried me amps

[sparky68]

recapped my Musical fidelity ma65's powered them up and the tropical looking resistors at the back of the PS caps and a couple on the pcb start to smoke
there must be a short but i have no idea what to look for.

anyone have any ideas before i shoot myself please

[anthonyTD]

recapped my Musical fidelity ma65's powered them up and the tropical looking resistors at the back of the PS caps and a couple on the pcb start to smoke
there must be a short but i have no idea what to look for.

anyone have any ideas before i shoot myself please
hi sparky,
daft question,
but,,,are you sure you have wired the caps up the right way round!
ie, the power supply electrolytics ???
Anthony,TD...

[sparky68]

cheers Tony
yeh i believe so the pcb has markings for + and - and ive put the ps caps with the - sign going to the - on the board ?
im really gutted

Mark

[anthonyTD]

cheers Tony
yeh i believe so the pcb has markings for + and - and ive put the ps caps with the - sign going to the - on the board ?
im really gutted

Mark

hmmm,
well,,,do a genral check around to make sure there is no solder shorting some high current tracks etc, unfortunetly its a case of tracing your steps and looking for obvious mistakes or as sugested,,, shorts.
Anthony,TD...

[anthonyTD]

if nothing obvious is found, you may have to remove the caps to see if there is a short under one of them, do you have a circuit diagram that you can put up here for us to have a look at ?
A...

[sparky68]

its very strange as both monobloks are doing exactley the same, i couldnt have shorted both of them out surely ?

[sparky68]

this was them before
http://i121.photobucket.com/albums/o220/sparky68_photos/Amp/DSC_0020.jpg
and ive put all the caps in the right way according tp the minus stripe down the sides as far as im aware ?

[lurcher]

Make sure the underside of the board hasn't been pulled against the case.

Do you have a afterward picture?

[Reid Malenfant]

That pic looks so similar to the internals of my P150s it's unreal :eek: Having taken them apart & fitted new capacitors i should know. MF are notorious for fitting capacitors that are underated voltage wise :rolleyes:

I doubt that is the reason yours have hit the bucket though...

Capacitor replacement shouldn't involve things going pop. Reversed electrolytic caps will certainly follow that route though... They'll stink like all hell :doh:

[sparky68]

sorry for quality

http://i121.photobucket.com/albums/o220/sparky68_photos/Amp/after%20mods/DSC_0005.jpg
http://i121.photobucket.com/albums/o220/sparky68_photos/Amp/after%20mods/DSC_0004.jpg
http://i121.photobucket.com/albums/o220/sparky68_photos/Amp/after%20mods/DSC_0003.jpg
http://i121.photobucket.com/albums/o220/sparky68_photos/Amp/after%20mods/DSC_0001.jpg

i tried lifting the board out of the case and propped it and its still the same :scratch:

[sparky68]

hey Mark
its not the caps that are burning they dont get a chance its the stripey things behind the PS caps that roast instantly ?
http://i121.photobucket.com/albums/o220/sparky68_photos/Amp/after%20mods/DSC_0001.jpg

[Techno Commander]

The big power resistors? They look like 3 to 5 watt ones from the photo.

[sparky68]

hi Techno Commander
thanks for the reply, i have no idea what they are to be honest, Just that they cook in about 3sec flat :scratch: sorry

Mark

[Reid Malenfant]

Lets get this straight ;) You only changed the big capacitors on the right next to the transformer???

Did you change anything else at all?

I find it hard to believe that both output stages have gone short circuit, but if those emitter resistors next to the output transistors are "cooking" as you describe it then this appears to be the case :rolleyes: Either that or for some reason the amp has no control over the output stage biasing & it's turning the output transistors hard on :doh:

Did you change any other components at all, if so what?

[Marco]

I feel that a public announcement is necessary at this point to say that if you don't know what you're doing with your kit, leave it the f*ck alone! ;)

Marco.

[DSJR]

+1

Been there, done it too many times and with balls, bells, whistles, a library full of well-read books and a clothes store full of tee-shirts to go with it.. :mental:

[Techno Commander]

if you don't know what you're doing with your kit, leave it the f*ck alone! ;)

Marco.

Indeed.:)

[sparky68]

yeh i know i deserve all that :rolleyes:
but just trying to learn, took them apart looked an ok job and went for it im gutted ive screwed them up i really loved these amps,
now have nice new caiman and no amps to use it on.

i changed all the caps and to be honest all the soldering looked spot on, its just baffled me why both amps are doing the same thing.

update tonight is i removed all the caps i put in, tried it without any in and its still the same, replaced the old PS caps leaving others empty and still no good :scratch:

[Reid Malenfant]

update tonight is i removed all the caps i put in, tried it without any in and its still the same, replaced the old PS caps leaving others empty and still no good :scratch:
:eek: :eek:

:doh:

That's probably really stuffed it :(

[sparky68]

ah well thats it then in the bin they go :'(

[anthonyTD]

hi mark,
realy sorry to hear this, unfortunetly it does sound as though either the output devices and or the drivers have snuffed it,:( not sure what you could have done that has resulted in both amps developing the same faults though,:scratch: come on guys give him a break, can anyone near mark offer some positive help here ???
Anthony,TD...

[Reid Malenfant]

I wouldn't recommend binning them :doh:

Lets just say that you certainly haven't helped the situation testing things as you have done :eyebrows: They might be repairable at a decent price which would make them worth saving.

Unfortunately you really haven't helped with the situation, i'd suggest leaving them well alone & giving them to someone to fix who knows what they are doing :)

[anthonyTD]

hi mark,
realy sorry to hear this, unfortunetly it does sound as though either the output devices and or the drivers have snuffed it,:( not sure what you could have done that has resulted in both amps developing the same faults though,:scratch: come on guys give him a break, can anyone near mark offer some positive help here ???
Anthony,TD...

bump!!!

[Tripmaster]

bump!!!

Mark and I have corresponded :)

[anthonyTD]

Mark and I have corresponded :)
hi Richard,
thats great!:)
Anthony,TD...

[sparky68]

Thanks Anthony i know ive been a right tit trying to do this myself and its a painful lesson as i dont watch TV its very quiet in here now, In future ill leave it to the experts for sure,
Rob and Richard have been absolute diamonds offering help for which im truely greatful and maybe one day soon ill be back on track and saying goodbye to the soldering iron for good.

All the best
Mark

[Marco]

Hi Mark,

I hope your amps can be saved. It's great to see the AoS community spirit doing what it does best :)

Excellent stuff, chaps! :cool:

Marco.

[Tripmaster]

Mark's more than welcome. No promises though, just a good pair of eyes :eyebrows:

[anthonyTD]

Thanks Anthony i know ive been a right tit trying to do this myself and its a painful lesson as i dont watch TV its very quiet in here now, In future ill leave it to the experts for sure,
Rob and Richard have been absolute diamonds offering help for which im truely greatful and maybe one day soon ill be back on track and saying goodbye to the soldering iron for good.

All the best
Mark
:)

[sparky68]

btw i live a few doors up from Lawrence of Arabia's old house in hythe :)
bit of useless info for ya