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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

PrimaLuna Prologue 5 Issue and schematic

Hi All

Last night my prologue 5 decided to stop working properly i was using it in the evening for a few hours, i stopped playing music but left the amp on for another hour or so.

When i went to play some music nothing happened, no output at low volume, i had to raise the volume on my preamp to almost 90% which gave me output but it was distorted.

Now i thought thats not good a proceeded to switch it off, now this is the strange bit, when i switched it off the music played come on really loud and clear for like a second before it fully switched off?

So i thought lets open it up and see whats going on, now i was actually impressed with the build, what i wasnt happy about was the lack of thought on resistor placement! Look at those large solen capacitors just being burnt by the heat (i always thought there was a strange smell when it was on).

Even the 100uf electrolytics look bad and they are only 85 degrees, surely they need to be high temp and better brand.

Now check out the auto bias board, those mkp caps look like they need changing.

I clearly need to do a recap on this thing, do you think this will help the issue i currently have?

Anyone on here got a schematic?

Thanks
 
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IMG_20191201_195842.jpg

IMG_20191201_194422.jpg

IMG_20191201_194416.jpg

Even here these capacitors look like there in trouble

IMG_20191201_194404.jpg

resistor too close to capacitor!
 
Well primaluna won't give me a schematic, rayma they should be fitted as standard with 105c capacitors so they do last long.

I think perhaps the auto bias maybe the issue or one of the capacitors have failed.

I'm going to recap it all and see if that solves the issue. If not then I'll have to send it to get repaired.
 

rayma

Member
2011-04-29 8:37 pm
I'm going to recap it all and see if that solves the issue.

You should troubleshoot first, at least with a DVM. If the sound comes back on at power off, it's probably not a capacitor, certainly not a coupling capacitor. If both channels are bad, it's likely to be either a relay or the power supply, either of which would be common to both channels.
 
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Well primaluna won't give me a schematic, rayma they should be fitted as standard with 105c capacitors so they do last long.

I think perhaps the auto bias maybe the issue or one of the capacitors have failed.

I'm going to recap it all and see if that solves the issue. If not then I'll have to send it to get repaired.
One should let primaluna keep their amps if they refuse the customer essential
documentation ! Shame on them ! They gain nothing on hiding the design,
competitors will reconstruct the schematics the only loser is those
poor customers that hve bought the stuff and encounters problems.
 
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rayma

Member
2011-04-29 8:37 pm
@ rayma - In case it's relevant, there is a plate fuse situated on top of the Adaptive Autobias board.
The manual gives instructions on how to locate and replace it:
http://www.absolutesounds.com/pdf/main/brochures/PL5.pdf
Forgive me if this is too obvious a cause.

I don't know anything about these amps, but if there's a fuse, it shouldn't turn on and off like he says it does,
when powered off.
 
One should let primaluna keep their amps if they refuse the customer essential
documentation ! Shame on them ! They gain nothing on hiding the design,
competitors will reconstruct the schematics the only loser is those
poor customers that hve bought the stuff and encounters problems.


I completely agree peter useless service, i even explained the issue and that i would appreciate a schematic.