This amp is fairly new to me and owning it is a bit of a mixed bag. Something is wrong and I need some advice as to what may be the issue. Or at least some ideas as to what may be at play. The amp, while working, sounds marvelous. Best I have ever owned. Then I'll hear a brief crackling sound and them the amp produces no output from both channels. Turn the amp off then back on again....nothing. Replace the front 2 12AU7's, fire the amp up and off she goes sounding wonderful. Might go a week, lately a couple days then poof, off again. All tubes light up just no sound from either channel. Replace the front 12AU7's and away we go playing fine music. Till I hear that brief crackle.
Arrrgh. I have run 4 sets of 12AU7's through the amp and none stop this from happening.
Other observations.....
After swapping the 12AU7's the longer the amp is off the longer it seems to go between shut offs. Looking for things to try or look for before sending the amp in for a check up. Any ideas?
f1jim
Arrrgh. I have run 4 sets of 12AU7's through the amp and none stop this from happening.
Other observations.....
After swapping the 12AU7's the longer the amp is off the longer it seems to go between shut offs. Looking for things to try or look for before sending the amp in for a check up. Any ideas?
f1jim
Did you buy the amp new, and does it have a warranty?
I would call Upscale on Tuesday and describe the symptoms. The amp obviously has an issue, which needs to be addressed.
jeff
I would call Upscale on Tuesday and describe the symptoms. The amp obviously has an issue, which needs to be addressed.
jeff
I never managed to get a diagram for this series from Primaluna (with the auto bias) the others being simple cayin, mingda, rebadged yaqin.
This series is more complex and requires some skills to find the fault.
Here is the only document that I found and with which I have been working for years, with a little concentration and zooming (page 3, at 300%, we can read the values and follow the diagram.
Find a brand specialist and entrust them with it.
https://storage.ning.com/topology/rest/1.0/file/get/9881276466?profile=original
This series is more complex and requires some skills to find the fault.
Here is the only document that I found and with which I have been working for years, with a little concentration and zooming (page 3, at 300%, we can read the values and follow the diagram.
Find a brand specialist and entrust them with it.
https://storage.ning.com/topology/rest/1.0/file/get/9881276466?profile=original
Have you tried to put back the previously replaced tubes in the amplifier, to check if they are truly faulty? Crackling noises followed by no signal may be caused by faulty/dirty tube sockets or dirty tube pins.
This reminds me to never buy an amp where the vendor refuses to supply proper documentation.
A schematics is the very minimum documentation.
A schematics is the very minimum documentation.
I might have the answer to this issue. I swapped out the KT150's for KT77's and they have been playing for 3 days with no shutting off. So it's either the draw for the KT150's or perhaps one of the tubes is problematic without triggering the "bad tube" light on the amp. I will keep playing the KT77's until I am confident the amp is not shutting down. I do have a TV-7 tester but have never tried to test anything larger than a KT88 in it. I will try the KT150's using the settings for KT88 and see if anything odd pops up.