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ceeceevee
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xx My pre-amp V1 tube may have died?
« Thread started on: Jan 14th, 2016, 10:52pm »

Hi, guys

When I went to turn on my ROS the other day, I was surprised to not get any output whatsoever. There's a faint hum when turning up the master volume on either channel but no sound from the guitar or even playing around with the jack.

I tried plugging things in and out of the loop (in case dirt/corrosion caused the issue) to no avail until I eventually worked out that one of my pre-amp tubes didn't seem to be "on". I can clearly see the other 4's filaments glowing red but not the V1 tube.

First question: is it a reasonable assumption that the pre-amp tube has died and changing it to a new one will fix the problem? That was my first thought but then, I've just read somewhere that pre-amp tubes almost never die so that got me wondering...

Second question: is changing the pre-amp tube something I can do myself? I understand that these don't typically need re-biasing and it's as simple as changing a light bulb. Does that hold true for Soldanos?

Been playing for a while now but, somehow, I've always managed to avoid tinkering with my amps so I don't know that much about tubes. Never too late to learn, I guess.

« Last Edit: Jan 14th, 2016, 10:53pm by ceeceevee » User IP Logged

ryanmichael95
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xx Re: My pre-amp V1 tube may have died?
« Reply #1 on: Jan 15th, 2016, 2:59pm »

Pre-amp tubes are plug and play.....very easy to do and nothing else has to be done. If it is not glowing, at all, then yes it sounds like one has went out. Less common than output tubes but not at all impossible. We've all had them go out at some point.
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xx Re: My pre-amp V1 tube may have died?
« Reply #2 on: Jan 16th, 2016, 05:11am »

Thanks, this gives me a bit more confidence. JJ 12AX7 on order!
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xx Re: My pre-amp V1 tube may have died?
« Reply #3 on: Feb 8th, 2016, 5:23pm »

https://www.youtube.com/watch?v=oq8ITOSb990

This should help a little..
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xx Re: My pre-amp V1 tube may have died?
« Reply #4 on: Feb 9th, 2016, 10:06am »

First of all: there are lots of preamp tubes that have very faint glow. Sometimes checking in a dark room helps.

The easy way of checking if a problem such as yours is in the pre or poweramp is plugging straight into the fx return jack. That should at least give a clean sound and that tells you the poweramp is working.

You cab also go from the fx-send to a seperate poweramp. That can tell you if the preamp is working or not.

Giga
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xx Re: My pre-amp V1 tube may have died?
« Reply #5 on: Apr 12th, 2016, 10:08pm »

Just to close this one off:

I eventually changed my V1 to a brand new JJ 12AX7 and it fixed the problem. Interestingly enough, the original tube (as well as all the other pre-amp ones) bore no markings. I can see that the power tubes are the Sovtek but no idea what the pre-amp ones are.

Oh well, anyway, my amp is running away again and I'm very happy grin

Also, as one of the previous posters noted, the JJ glows a lot dimmer than the other ones.
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xx Re: My pre-amp V1 tube may have died?
« Reply #6 on: Apr 14th, 2016, 6:17pm »

Glad to hear you got it going!!
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