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Tube Novice Encounters First Hiccup

Bought a PrimaLuna Prologue Classic integrated in Feb., 2019 which I ran with the supplied EL34s for a little over a year before switching to Gold Lion KT77s in Spring 2020. Have LOVED this amp thus far...
Several days ago, and approx. 2 weeks after putting a Bluesound Node 2i on input #1, the PrimaLuna made a very faint ‘bump’ noise about 30 seconds after turning the unit on and the bad tube indicator on the front panel lit up red (This is the smaller PL integrated without bad tube indicators adjacent to each tube.). I shut the amp down, unplugged everything, and removed power tubes and the smaller (signal?) tubes, and re-seated them one by one. Problem solved for about 36 hours. This morning, turned PL on and the BTI on the front panel red lighted again, accompanied by the faint ‘bump’ noise about 30 seconds in again. So far, problem solved by reseating KT 77s only.
Unsure if this has any bearing on anything, but the electrical utility co. has been doing a total replacement of power lines in our area which has directly coincided with everything on our wifi grid basically going ape-s**t for the last couple of weeks along with numerous provider-related internet outages of short duration. Immediately prior to the PL indicating a bad tube this morning, I had installed cat 6 Ethernet cable from router to Node 2i...

I haven’t been able to discern any changes in sound quality during any of this, nor have I seen anything out of the ordinary with the PL’s tubes from a visual-appearance standpoint...no smell of smoke, etc, etc...

Do any of you with more tube amp experience than I have any thoughts as to what may be going on here? Thanks in advance.
lg1
skypunk's avatar
skypunk
499 posts
 
@facten 

Kevin is only the US Distributor.

If he owned it he would have PL in his system, he has all Pathos Acoustics Inpol in his system.
facten
2,767 posts
 
@skypunk - get yourself a copy of the Absolute Sound's Illustrated History of High-End Audio - Electronics - go directly to page 293 PrimaLuna and take a read. Yes he is the US Distributor but he and Herman van den Dungen started PrimaLuna in 2000


rshak
416 posts
 
I suspect you've got an iffy power tube.  I own a PrimaLuna DiaLogue Premium integrated (with a BTI light in front of each of the four power tube sockets).  Over the six or seven years I've owned this amp, the BTI has proven its worth on two occasions.  

The first time, I heard a slight "pop" a couple of times, and then the amp shut down.  I wasn't sure what was going on and turned the amp back on after about 10 minutes.  Everything was fine for several minutes, and then another "pop" and the amp shut down.  This time I noticed the red LED (BTI) light in front of one of he power tubes - consulted the manual, changed out the offending tube, and all was well.

A year or so later the same thing happened:  "pop" and the amp shuts off.  This time the BTI light identified a different tube, which I replaced.  All has been well since, although a couple of months later I decided to retube all four of the Gold Lion KT88's. No problems since.

Since your amp doesn't have a BTI for each power tube, you'll need to get all of them tested to determine the culprit.  As another  member has suggested, I would first call Kevin at Upscale - he may offer some additional guidance. 
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