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SVT problem
- Thread starter Paddy515
- Start date
Some connection is failing as the amp warms up... loose solder joint or bad part. Take it to an amp tech. You ought not be attempting to use it in the meantime in case there's potential for making it worse.
You mean you want a second opinion on whether to take it to a tech?
Yes, take it to a tech
Yes, take it to a tech
Shrill sound makes me think there's a bad tube. You could try tapping each tube lightly with a light wooden (for obvious reasons) stick while it's turned on and plugged in to see if you can spot a bad tube. The only other problem you could check out on your own is corrosion in the preamp in/out jacks. I had a rental SVT a couple nights ago that had this problem and the volume was cutting out. I fixed it by running a plug in and out of the jacks several times fast. However, there could also be other reasons, and if these things don't work out, taking it to a tech is of course the sensible thing.
I have an 89 SVT II that was experiencing some intermittent cutout issues. Similar to Jimmy's advice, try this first before you take it to a tech.
Plug one short 1/4 inch cable into the preamp in and out jacks on the back of the head (Left side, next to XLR out). This simple thing eliminated the problem completely and now I just keep the cable plugged in all the time just to avoid any problems that may crop up during a show.
It hasn't cutout since.
Plug one short 1/4 inch cable into the preamp in and out jacks on the back of the head (Left side, next to XLR out). This simple thing eliminated the problem completely and now I just keep the cable plugged in all the time just to avoid any problems that may crop up during a show.
It hasn't cutout since.
Clean the jacks with Deoxit or by the plug method I posted and you can skip the cable. Just a matter of getting that corrosion out of there so you get good contact.
All true. The cable is good for troubleshooting as it isolates the issue and positively identifies it as corrosion in the jacks.
I have never heard of a shrill sound coming from a bad jack connection. That sounds more like something a tech should investigate.
I think it's most likely going to be a microphonic tube, and I think callofcthulhu is right about it being a bad preamp tube. I've heard plenty of shrill sounds from them. They would be the first ones I check. However, the sound fading could be dirty preamp jacks, and that's why I suggested taking a look at them while he's at it, especially since they and the tubes are pretty much the only user-serviceable parts.
What you are describing, fading and high pitched sound, is often an issue with a pramp tube. Here is a guideline as to when to change tubes, note the symproms:
Tubes | TalkBass.com
It never hurts to have all the metal-on-metal contacts, including jacks, tube pins and sockets, cleaned with Deoxit.
Tubes | TalkBass.com
It never hurts to have all the metal-on-metal contacts, including jacks, tube pins and sockets, cleaned with Deoxit.
Guys - head back from the tec. Diode was to blame. Swapped out - full check over and long run. £30 GB pounds. Thanks for all your advice. Back to its earthquaking best.
Interesting...I will have to remember that if someone else has a similar problem.
Excellent, and the repair cost was reasonable.
Often the sign of a bad diode is distortion.
