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PrimaLuna Prologue 5 Issue and schematic
PrimaLuna Prologue 5 Issue and schematic
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Old 2nd December 2019, 08:41 PM   #21
petertub is offline petertub  Sweden
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PrimaLuna Prologue 5 Issue and schematic
Quote:
Originally Posted by vishalk View Post
Thanks to mravinsky for the schematic which the cayin ta-35 which is similar if not the same as the prologue 5


Attachment 799298
This seems to be a beginners amp, at a quick look i identified C5 and C6

who will have overvoltage at power-on. ( 407V at one side, -30V at the other
while spec at 400V)

Maybe this is a reason not to supply schematics
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Old 2nd December 2019, 09:22 PM   #22
aboos is offline aboos  Germany
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Do not change the capacitors - all these MKPs are ok. Nothing is burned or looks like damaged by heat.
The first thing I would check are the bias voltages of the output tubes and the bias voltage supply. As far as I understood, both channels are affected.Bias voltages can be checked as well as plate and G2 screen voltages of the output tubes. Depending on the installed output tubes you can look up in the valve datasheet if the measured voltages will make any sense.
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Old 2nd December 2019, 09:30 PM   #23
aboos is offline aboos  Germany
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Next step would be the supply voltage for the input tube(s). Left and right channel have one common supply of 200V regulated by a zener diode. A failure of the zener could bias the input tube and/or phase splitter completely on or off. When switching of the amp, voltages will go down and you get a somehow reasonable biasing of the input section even if the zener is open.
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Old 2nd December 2019, 09:52 PM   #24
vishalk is offline vishalk  United Kingdom
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Quote:
Originally Posted by aboos View Post
Next step would be the supply voltage for the input tube(s). Left and right channel have one common supply of 200V regulated by a zener diode. A failure of the zener could bias the input tube and/or phase splitter completely on or off. When switching of the amp, voltages will go down and you get a somehow reasonable biasing of the input section even if the zener is open.

Aboos this is great information and makes sense thank you for your input this gives me more confidence to source the problem and solve it.
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Old 2nd December 2019, 11:05 PM   #25
Galu is offline Galu  Scotland
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Quote:
Originally Posted by vishalk View Post
Aboos this is great information and makes sense.
Sure beats my mention of a plate fuse, but thanks to you and rayma for taking the trouble to recognise my contribution!
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Old 2nd December 2019, 11:10 PM   #26
rayma is offline rayma  United States
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Quote:
Originally Posted by Galu View Post
Sure beats my mention of a plate fuse, but thanks to you and rayma for taking the trouble to recognise my contribution!
There are often hidden fuses around, even inside transformers, and in speaker enclosures (thermal tweeter fuse/switch).

Last edited by rayma; 2nd December 2019 at 11:17 PM.
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