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fire spark in 5AR4 rectifier tube for PrimaLuna Pr

All of a sudden, I see fire spark in one of the 5AR4 tube in my PrimaLuna Prologue 3 preamp so I turn it off immediately. I tried it again, and the same thing happen. What is going on?

Does it mean my tube is bad that I need to replace it? Or there is something wrong with my preamp? I did some research, it seems people said it may be the capacitance is too high, but I didn't change anything, could it be something goes wrong in the unit that results in capacitance being too high? Did I already damage my unit?

Thanks.
gte357s
pehare's avatar
pehare
835 posts
 
just replace the bad one...they don't need to be a matched pair. Although I'd probably replace the pair w/a nice pair of matching NOS & then keep the good single for a backup. enjoy!
rodman99999
6,125 posts
 
Just a little FYI; The best sounding, most reliable and longest lasting rectifiers out there, are the Blackburn Plant, Mullard tubes(the earlier the production-the better). Unfortunately, do to all of the aforementioned facts; they are also the most expensive. ie:(http://www.ebay.com/itm/Mullard-Blackburn-Branded-Amperex-Bugle-Boy-GZ34-5AR4-Rectifier-Matched-Pair-/220910480753?pt=Vintage_Electronics_R2&hash=item336f4a6d71) (http://www.ebay.com/itm/vintage-Mullard-Blackburn-5AR4-GZ34-NOS-Hi-Performance-rectifier-tube-/200687014748?pt=Vintage_Electronics_R2&hash=item2eb9e0d35c) (http://www.ebay.com/itm/NOS-box-Mullard-GZ34-5AR4-double-halo-tested-1958-Blackburn-never-used-/120827434079?pt=Vintage_Electronics_R2&hash=item1c21e0545f) Personally(being your preamp is a dual-mono design), I'd replace both rectifiers, with a matched pair, to insure a balanced presentation from the two channels.
gte357s OP
281 posts
 
Yes, mullard blackburn tubes are too expensive. Any cheaper but good NOS alternatives? Also, if I don't want to spend too much, is it still worthwhile to get 1 Mullard Blackburn? Or better to get a match pair of new stock?
pehare's avatar
pehare
835 posts
 
GE, you can drive nails w/them, try Jim McShane Tubes or Andy at Vintage Tube Services.
gte357s OP
281 posts
 
OMG, the 5AR4 must be extremely popular. They are so hard to find and so darn expensive. It seems I need to buy one JJ to replace it for now so I can start listening to music, it may take me a long time to score a pair of NOS.
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