ValveKing II 50w Combo Problem

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kilrcuda
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ValveKing II 50w Combo Problem

Post by kilrcuda » Wed Apr 12, 2017 8:55 am

Guys/Gals,
Having an issue with my Valveking II 50w combo. The amp is about 2 years old and hasn’t had any mods and had original tubes (Rubys) – I’ve owned it since new. It first started about an hour and a half into a gig. Wasn’t pushing it hard, was running it through a PA using the XLR output on the back. Was jamming along all well and good when I noticed the volume started to gradually decrease to nothing. I looked at the amp and both of the TPI lights were red (should not have been since the amp was not in standby). I then flipped it into standby for a few seconds and then back out of standby. Both lights turned green and I started playing. After about 20 seconds, the volume started decreasing and the TPI lights turned red. Powered the amp off and then back on and the same thing happened again.

When I got it home and powered it on and turned off the standby, only one light turned green. Thought this might be a power tube thing so I powered it down and took out the tubes and swapped their positions in the chassis. Turned it back on and off of standby and the other TPI light didn’t turn green. Thinking that one of the power tubes may have gone bad, I got a set of JJ 6L6 tubes. That seemed to fix the issue. Played through the amp for a couple hours and it was good.

Take it to another gig and the same thing happens as what happened at the first gig when it tanked. Volume gradually dropped and the TPI lights went red. Again, cycled the standby switch and power switch and still came up with no volume and red TPI lights after an hour or so of playing. I take it home and it plays fine for about an hour and then the volume drops slightly and one of the TPI lights come on.

I took it to a local, reputable repair shop and they couldn’t get the amp to act irregularly. They cleaned all the pots, connectors, and jacks. Bring it home and after an hour or so pf playing, same volume drop and one TPI light out issue.

I’m baffled by how the symptoms of the problem are not consistent. Thinking it may be a power issue, I’ve plugged it into different electrical circuits in my house and it happened ate two different venues.

Any help from the vast pool of knowledge that is here would be greatly appreciated!!!

Thanks!
Sean

dalrymple
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Re: ValveKing II 50w Combo Problem

Post by dalrymple » Wed Apr 12, 2017 10:06 am

Sounds to me like it is consistent. Get it good and hot for over an hour and it does what it does. Seems like it might be heat related somehow.
Maybe aim a fan at it next time you try it out for over an hour and see if that has any effect.

That crap can drive you nuts.
Dalrymple

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Enzo
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Re: ValveKing II 50w Combo Problem

Post by Enzo » Wed Apr 12, 2017 10:55 am

Fading out to me usually means the tube heaters are going dark. You have been watching the LEDs, but next time it goes out like this, look at the tube and see if the little glowing heaters intide than have faded to dark.

In my mind, most likely thing to cause that is an iffy ribbon cable connection.

Now, you bought it new, two years old. Unless warranties have changed in the last year or two, is it not still under warranty? In which case take it to an authorized Peavey repair shop.

You described the symptom well enough, but if you had the extra clue that the tube heaters were going dark as it happened, that is a MAJOR clue to any good tech.

kilrcuda
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Re: ValveKing II 50w Combo Problem

Post by kilrcuda » Fri Apr 14, 2017 2:33 pm

Thank you for your ideas of things to look for! I'll check them out over the weekend and let you know how it goes! I'll pull out the chassis and make sure all the connectors are well seated. They should have done that when I took it to get looked at but you never know.

Thanks again nd will update you all shortly!!!

Sean

rogue777
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Re: ValveKing II 50w Combo Problem

Post by rogue777 » Fri Apr 14, 2017 11:21 pm

Yes, a ValveKing II 50W combo.
I own one. Good all-around sounding amp.

Those TSI leds (tube monitoring indicators) are your friends. Those are built in trouble signals. TSI, a neat little circuitry with some sophisticated components. They monitor the 6L6 tubes. You knew that. Their telling you something, the tubes are shutting down, or else. You knew that. I forget the color indicators, green, yellow, red. So now you now when there is a problem. You know this.

Enzo's right on it, focusing on the critical signals to make your output tubes work. He mentioned the heaters. Perhaps you can get a hand held V-meter (with clips) in there to monitor the voltage, let it bake, or visual as Enzo suggested. Check the output tubes connections and components. You'll fix it. It sounds consistent, it happens after a while when you use the amp, so heat over-time may be an issue. That ribbon cable comment too, great clues.

heavycream
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Re: ValveKing II 50w Combo Problem

Post by heavycream » Sat Apr 15, 2017 2:22 pm

I'm no amp tech by any means. This may have been implied when you said you took the amp to a service tech, was the amp properly biased? Don't forget, the new VK II series has adjustable bias. I can't remember where, but I read a thread where the op had a similar issue with the same amp and was eventually remedied with a simple bias.

I noticed you use the XLR out. Do you also use speaker defeat? Does this issue only occur when using XLR output?

kilrcuda
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Re: ValveKing II 50w Combo Problem

Post by kilrcuda » Thu Apr 27, 2017 10:24 pm

Gentlemen, thank you for your patience! I opened the chassis and made sure ant and all ribbon cables are tightly seated to their connectors. Also ran a fan innit while playing and it still happened. When the amp was in the shop, tube bias was checked and checked good. I have played with the xlr cable connected and with out as well as with and with the speaker defeat disabled, I'm a at a point where it goes to an auth peavey service shop and gets set back or whatever for repairs/replacement. Will hero everyone posted.

kilrcuda
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Re: ValveKing II 50w Combo Problem

Post by kilrcuda » Thu May 04, 2017 5:23 pm

Found out what the problem is. A resistor in the auto bias circuit was out of tolerance. The shop I took it to is going to replace the resistor and I should be good to go. The shop also advised that they are getting in a 'upgrade' kit from Peavey to replace some other things in the auto bias circuit. Apparently, my amp is in a range of serial numbers that is affected by some insufficient parts installed in the amp from the factory. This upgrade should prevent this issue from occurring again.

Cheers!

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