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PrimaLuna Prologue 5 Issue and schematic
PrimaLuna Prologue 5 Issue and schematic
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Old 2nd December 2019, 11:35 AM   #1
vishalk is offline vishalk  United Kingdom
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Default 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

Last edited by vishalk; 2nd December 2019 at 11:47 AM.
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Old 2nd December 2019, 11:44 AM   #2
vishalk is offline vishalk  United Kingdom
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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!
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Old 2nd December 2019, 04:04 PM   #3
petertub is offline petertub  Sweden
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PrimaLuna Prologue 5 Issue and schematic
You need to contact your vendor for a copy of the service manual.
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Old 2nd December 2019, 04:27 PM   #4
vishalk is offline vishalk  United Kingdom
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Trying peter, contacted primaluna in USA, Denmark and UK
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Old 2nd December 2019, 05:55 PM   #5
rayma is offline rayma  United States
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Is there a relay in the circuit? Sounds like a relay (or its supporting circuitry) is not operating properly.
An 85C capacitor is fine, they just won't last as long as a 105C part of otherwise similar ratings.

Last edited by rayma; 2nd December 2019 at 06:11 PM.
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Old 2nd December 2019, 06:06 PM   #6
vishalk is offline vishalk  United Kingdom
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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.
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Old 2nd December 2019, 06:10 PM   #7
rayma is offline rayma  United States
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Quote:
Originally Posted by vishalk View Post
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.

Last edited by rayma; 2nd December 2019 at 06:28 PM.
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Old 2nd December 2019, 06:24 PM   #8
OldHector is online now OldHector
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It feels a little dangerous to perform an improvement involving multiple changes before identifying the root cause of this issue. Once you have recorded all the voltages on all pins of all the valves, then chances are you will have a better clue.
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Old 2nd December 2019, 06:32 PM   #9
vishalk is offline vishalk  United Kingdom
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Of course I'll start trouble shooting, only thing is i wouldnt know what to look for in terms of voltages.

My thoughts were a psu issue aswell, If I had a schematic I could work my way through it all.
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Old 2nd December 2019, 06:42 PM   #10
mravinsky is offline mravinsky  Europe
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It's the same as Cayin TA-30/TA-35 except adaptative bias.
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