#1
One on the 6L6 tubes on my valveking 112 (the tube on the right if your looking at the back) is glowing significantly less than the other. does this mean my tubes are dying? this is my first tube amp and i bought it used. the tubes probably need to be replaced anyway but can you guys help me figure it out?

So i guess in summary what i want to know is.

Why is one glowing less?

Do i need new tubes?

What tubes should i get?(i play in an alternative rock band on my own time i prefer to play metal)
#2
Post a decent pic. You can't draw conclusions from your description. The filaments (heater) in a tube are what glows normally. They either work or don't but if you have a bias problem, the excess current flowing in your tube(s) will cause the plate(s) to glow as they overheat!
Moving on.....
#3
What do you have the texture control on? I believe if you set it all the way to A one tube get's more bias voltage than the other, which would make it glow less.
I don't give a shit if you listen to me or not
#5
yea. i thought that might have been it. so i switched it. and it got a tiny bit brighter i think. but it was still noticeably dim.
#6
also. my amp gives out a faint buzz/hum when its on. i dont know if thats relevant or not
#8
The power tubes might not be matched, or their bias has drifted over time. If the amp sounds fine then you're probably alright. If it doesn't then replace them.
I don't give a shit if you listen to me or not
#9
FWIW, I have the exact same amp. I fired mine up and had a look. Looking at the amp from the back, the right tube has very little, if any, blue glow. The left tube has more blue glow to it. Both filaments appear to be equally lit. The Valveking 112 uses fixed bias, so there's nothing to twiddle with on this amp. Adjusting my Texture knob had no apparent effect on either tube.

You only need to replace tubes when your tone starts to suffer. Normally, you'll notice a loss of highs - a muddier sound. I've had my VK112 for almost 3 years with the same tubes and they're still going strong. Before I got my Mesa, I played it probably 3 to 4 times a week. Now I play it once or twice a week.
#10
Quote by Doc-Pepper
also. my amp gives out a faint buzz/hum when its on. i dont know if thats relevant or not


This is normal with the VK112. If you have a look at Peavey's forum, you'll see some comments about it. I believe a tube job would fix the problem. In fact, I recently pulled a pair of 6L6 tubes from my Mesa and tried them in my Peavey and it was a bit quieter. In another year or two, I may retube my 112, but for now I can live with the hum.
#12
Quote by Doc-Pepper
im talking about the yellow/orange glow



To fully assess this problem, you'd have to measure the filament voltage with a voltmeter. I haven't looked at the schematic, but my guess is the filament voltage is in parallel. You could try swapping the 6L6 tubes - which isn't too tough on this amp. Remove the 4 screws from the protective cage and gently rock the tubes as you pull on them. Swap their positions and try again. Just make sure you do this with the amp off - not in standby. Also allow them to cool down for a couple of minutes before handling them.
#13
yea. i dont know how long the guy before me had this amp(i bought it on ebay) but he didnt use it often and it just sat in his studio all day. and it looks like it did, its in perfect condition.
#14
Quote by Kevin Saale
The power tubes might not be matched, or their bias has drifted over time. If the amp sounds fine then you're probably alright. If it doesn't then replace them.


It's highly possible they're no longer matched. Especially if he's been running the texture in Class A. I recently pulled my tubes out and noticed that one showed some evidence of being run hotter - the printing on the tube had darkened in one area. I run mine in Class A, so that one tube is working a lot harder. When I finally reinstalled my tubes, I swapped them. The bias on this amp is fixed.
#16
I know, it's fixed an non adjustable (seriously, why do they make amps like this? Even Mesa does it!). The tubes are cheapies, no? I wouldn't be surprised if they cheaped out and didn't get the tubes as closely matched as they should.
I don't give a shit if you listen to me or not
#19
i have no idea what the tubes are. but i dont think the guy was a cheapy if he replaced them before me. cause he put a celestion vintage 30 in it so im sure that wasnt cheap. but they might still be the stock tubes. so if they are they would definitely be cheap
#21
Stop double posting, there's an edit button for a reason

No, if the amp sounds fine then don't worry about the tubes.
I don't give a shit if you listen to me or not
#22
The amp calls for 6L6GC tubes. Mine has Sovtek 6L6WXT+ tubes installed from the factory. They actually have better specs than the 6L6GC. Tube Depot has them on sale for $22.95 for a matched pair.

http://www.tubedepot.com/so-6l6wxt.html

If you decide to replace them, you have quite a few choices. It all depends on what you want to pay.

http://search.store.yahoo.net/cgi-bin/nsearch?catalog=yhst-8476489043850&query=6l6gc&.autodone=http%3A%2F%2Fwww.tubedepot.com%2Fnsearch.html

If you check out that link, you'll see that you can really pay a small fortune for a replacement tube. I'd be tempted to go with the Black Sable 6L6GC. However, I'd want to read some reviews first.
#23
Quote by Kevin Saale
I know, it's fixed an non adjustable (seriously, why do they make amps like this? Even Mesa does it!). The tubes are cheapies, no? I wouldn't be surprised if they cheaped out and didn't get the tubes as closely matched as they should.



I don't know. I'm not all that big on matched tubes. I used to be at one time, but after doing a lot of reading and thinking about it, I just don't think it's all that necessary. If anything, I really think it's a marketing scam to suck extra $$$ out of your pocket. Here's the Reader's Digest down-and-dirty of why I don't believe it's so important - All of the components in the circuit must be absolutely matched, otherwise you'll have a slight load imbalance. Naturally, all components have a specified tolerance and you're never going to have 2 resistors, or 2 caps, or 2 of anything that match 100%. Even if you install perfectly matched tubes today, the imbalance caused by the other slightly mismatched components is going to cause an imbalance in the load - thereby causing one tube to wear at a faster rate that the other. Lastly, even if you buy a pair of supposedly matched tubes, they don't match them exactly to each other. They classify or match tubes within a range. There's another mismatch right there. I know I said "lastly," but let's toss one more variable into the variable pie - If your amp is capable of running Class A and has more than one tube, like the Peavey or my Mesa Lonestar and you run it in Class A, you're putting all that wear on one tube, while the other(s) idle(s). So much for paying extra money for that matched pair or quad.
#24
Matched tubes don't cost extra at most places. I agree, you can't get the load perfectly balanced, nor would I want to (I set one tube hotter in my BJr because it sounds better to me). If amp companies didn't have their thumbs up their asses they'd make the bias adjustable on every tube in the amp for anything with 4 or less tubes (ala the bill m mod I did on my BJr) and anything with more would make the bias adjustable pair wise (ala diezel herbert).

But I digress, if there were no matched tubes then you could end up in a situation where you had two tubes with large enough differences to cause an impedance imbalance in the OT that could destroy it. I agree, the components won't match properly (hell, just check the impedance of your OT onboth sides, it'll be slightly different), but they won't be as different as unmatched tubes could be.
I don't give a shit if you listen to me or not
#25
Mismatched tubes would affect gain more than anything else! If their gains were significantly different you could theoretically end up with unwanted distortion in a push pull configuration. This could simply be crossover distortion where the tubes turn on/off (Class AB or Class B bias) or even the negative or positive halves of the output waveform not being as close in amlitude as they should.
Years ago tube testers were common and anyone could mtach tubes simply by testing them and selecting pairs based on similar test results. Now it's nearly impossible to check tube performance yourself so I would advocate buying matched pairs to eliminate a potential problem.
Moving on.....
#26
Quote by KG6_Steven
I don't know. I'm not all that big on matched tubes. I used to be at one time, but after doing a lot of reading and thinking about it, I just don't think it's all that necessary. If anything, I really think it's a marketing scam to suck extra $$$ out of your pocket. Here's the Reader's Digest down-and-dirty of why I don't believe it's so important - All of the components in the circuit must be absolutely matched, otherwise you'll have a slight load imbalance. Naturally, all components have a specified tolerance and you're never going to have 2 resistors, or 2 caps, or 2 of anything that match 100%. Even if you install perfectly matched tubes today, the imbalance caused by the other slightly mismatched components is going to cause an imbalance in the load - thereby causing one tube to wear at a faster rate that the other. Lastly, even if you buy a pair of supposedly matched tubes, they don't match them exactly to each other. They classify or match tubes within a range. There's another mismatch right there. I know I said "lastly," but let's toss one more variable into the variable pie - If your amp is capable of running Class A and has more than one tube, like the Peavey or my Mesa Lonestar and you run it in Class A, you're putting all that wear on one tube, while the other(s) idle(s). So much for paying extra money for that matched pair or quad.

if you were talking about a phase inverter, I would agree. I disagree about the matched powertubes however, depending on application. Most adjustable fixed bias amps have only one bias pot. Have you ever tried biasing a poorly matched set with one bias pot? It's not fun. I've had instances with poorly matched sets where in order to get a good balance, one tube was well into crossover distortion, while another was running very hot at close to 75% of max current. That was the best average I could get without burning up one of the tubes, or running some way too cold. A well matched set of tubes will all ideally draw current within a few mA of eachother, depending what plate voltage they were tested at, and what the amp is running. I've had tubes matched at 400V plate voltage that tested fine, but were widely mismatched when run at 520 plate volts. Matching power tubes for the application is very important IMO.
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
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