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SVT VR help

Mikaelbass

Mikaelbass

May 29, 2011
570
1,020
Sydney, Australia
#1
Hey guru's

My SVT VR's two bias lights have always worked fine etc etc until recently number 1 no longer lights up when off stand by, but flickers green when I play. When I try to reset the bias on it there is still just no green LED. Balance LED is lit when in standby, and second bias light is fine.

Any ideas? I was figuring I would probably just take it to a tech or something if it needs something done.

Cheers
 
#2
You probably just have a power tube that either drifted from matching the others or it's on the way out. You could replace the three on that side and rebias it, but if it still sounds good, you could probably wait a little while. But that's usually an indication that something is a little off with your power tubes on that side.
 
#3
JimmyM said:
You probably just have a power tube that either drifted from matching the others or it's on the way out. You could replace the three on that side and rebias it, but if it still sounds good, you could probably wait a little while. But that's usually an indication that something is a little off with your power tubes on that side.
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Cheers thanks!

What tubes would be good to go for? I love the sound of my amp as is, but I would rather get all the tubes matched up instead of leaving it till it dies. I use the amp for a pretty heavy sound, bass nearly on full, mids at about 130, treble flat and volume sits at 1130. Not sure if this info would effect power tube choices.

:bassist:
 
#4
The stock Sovteks are ok and probably the cheapest. SED Winged C are an extremely popular choice and a lot of people think they're the best new production tubes for SVTs. They can be had for about $350. I recently went to T/C tubes.com and got some NOS Svetlana 6550Bs ( made in the old St. Petersburg factory, NOT Reflektor) for $180 and I am extremely happy with them. If you type 6550 into the search bar at the top of the page there are pages and pages of threads about this topic. I guess money not being an object, my personal recommendation would probably be the Winged Cs.

Just be sure the amp biases properly after retubing. If it doesn't, there could be other issues. I definitely would not continue gigging the amp if it isn't biasing up.
 
#6
Mikaelbass said:
I emailed a local tech to see his side of it. $350 is a lot for me to fork out on the chance its a tube going out, but if it has to be done then that is okay.

Tube choice seems to be a realm of the bass world I have not ventured before
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I had a similar issue with my CL 2 months ago. My first step was to spend $180 on tubes, but I was positive I had blown a tube and I saw the arc. When the amp wouldn't bias with the new tubes, I sent it to a tech, who replaced some open resistors and bad caps and a bad OP AMP for about $250.

I wouldn't start with the tech in your situation. If you are happy with the tubes you have currently, buy 3 tubes that are matched and replace the three on the side that won't bias. If it fixes your problem, great. Or you can buy 6 matched tubes and replace them all. Again, if the amp biases, your golden and you know you have all good tubes.
 
#7
My Heritage has JJ 6550's in it, which are like $35 a pop. They've been real good so far. Honestly though, I think the Sovteks that come in the VR stock are pretty good, too, and they're only $25 a pop. Just buy 3, though. No need to replace them all.
 
#10
wighat said:
My experience: you should stop using your amp and fix it. Sounds like a bad/going bad output tube. If you wait, other damage may result.
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+1. Too many people don't get a slightly wrong amp fixed because they think fixing is expensive. Its often only expensive because of the damage caused by using it when its got a minor problem.
 
#15
B-string said:
The 6550B's were made by the people, equipment and factory that is now known as SED Winged =C=. The last revision being the 6550C.
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Before I bought these tubes, I spent a few days reading threads here about 6550s, including one that you were all over. SVT tube megathread or some such thing. Several people didn't think too fondly of the Bs. I almost went ahead and just got the Sovteks. God **** I'm glad I didn't.
 
#16
Floyd Eye said:
Before I bought these tubes, I spent a few days reading threads here about 6550s, including one that you were all over. SVT tube megathread or some such thing. Several people didn't think too fondly of the Bs. I almost went ahead and just got the Sovteks. God **** I'm glad I didn't.
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IIRC we shared some PM's about them. I'm happy they are doing the job for you. :) They are darn nice tubes.
 
#18
Any new 6550s come out? nothing I handle uses them, so not kept up, but would like to be ahead of the game. Shuguang GE KT88 and Gold lion ones seem to be current flavour for KT88s (more my area), not sure how they get on in SVTs, slightly higher current draw, so might not be safe.
 
#19
I find that newly manufactured tubes go through a lot of revisions. Something comes out, you buy it, try it for a while, decide that you like it, and they've moved on to a new revision, the quality goes down or in the case of the Winged C 6550, they go out of production. It really is hit and miss.

If someone buys a new set of tubes every 5 years, the way things are going, what are the chances that you will be able to buy the same tube?

BTW, I have a set of GE 6550A's in an SVT. My first choice for NOS tubes in that amp. I dread the day that I have to change them.
 

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