svt6 cutting out

locriansharpsec · #1 08-24-2011, 11:49 PM

about a month ago plugged into my svt6 at band practice and had the sound quickly fade away. Opened up the top and a bandmate found a bad tube and we replaced it. The rest of practice went fine. (I play my svt6 thru an 8x10 once a week at rehearsal)
The next week power cut out again but before I opened it up I thought to try a different power cord- problem went away for rest of night. Thought that was it.
Then last sat it started cutting out again so I tried a different speaker cable into the second output on my amp. I have the old svt 8x10 with only 1 input 1/4"(no speakon). Problem went away but then came back later a few times and had to wiggle cord to get sound to come back on. Cords are both fine on other rigs. I still need to try the speakon out to a cab with a speakon to see if it is the actual 1/4 " jack ouputs.
The tubes are all glowing.
Any ideas on why the sound is cutting out?
What can I try to dial in what the problem might be?
Any thoughts are appreciated.

JimmyM · #2 08-24-2011, 11:56 PM

Could be a few things. One thing you might want to check for is corrosion in the effects loop jacks. If they don't get used, they can build up corrosion after a while. A shot of contact cleaner clears it up, or if you don't have any, just run a plug in and out of the jack several times rapidly and that should bust most of it out. Could also be a bad tube you haven't found yet. Tubes can glow and still not work right. If those don't take care of it, best to have it looked at by a tech.

anderbass · #3 08-25-2011, 09:13 AM

Quote:

Originally Posted by locriansharpsec

had to wiggle cord to get sound to come back on. Cords are both fine on other rigs.

I still need to try the speakon out to a cab with a speakon to see if it is the actual 1/4 " jack ouputs.

Yeah It sounds like your amps 1/4" speaker jacks just need repair or cleaning.

You could make your own speakon to 1/4" adaptor speaker cable. Just cut 1 plug off your old speaker cable and then you'd just need a screwdriver to install a speakon plug in its place...

locriansharpsec · #4 08-25-2011, 09:45 AM

thanks guys! I will get some contact cleaner and clean the outputs and also the effects loop jacks (I havent used the effects loop)- So corrosion here Jimmy in loop would cause power to cut out even when not using this?

I will also make a speakon adapter like you said Anderbass or would it be just as simple to convert the input jack of my 8x10 to a speakon input? I havent taken it off to see whats inside but I imagine it being pretty simple to convert?? If so where would be the best place to buy this type of jack?

Also even though the tubes are all lit up there still might be a bad one in there?

Appreciate your help!!

JimmyM · #5 08-25-2011, 10:53 AM

Quote:

Originally Posted by locriansharpsec

thanks guys! I will get some contact cleaner and clean the outputs and also the effects loop jacks (I havent used the effects loop)- So corrosion here Jimmy in loop would cause power to cut out even when not using this?

I will also make a speakon adapter like you said Anderbass or would it be just as simple to convert the input jack of my 8x10 to a speakon input? I havent taken it off to see whats inside but I imagine it being pretty simple to convert?? If so where would be the best place to buy this type of jack?

Also even though the tubes are all lit up there still might be a bad one in there?

Appreciate your help!!

Not using the effects loop is exactly why it builds up corrosion. And yes, a tube can light up and still be a dud. Seen it many times.

locriansharpsec · #6 08-25-2011, 07:56 PM

Bought some contact cleaner and cleaned it all up. Played for about an hour and a half and couldnt duplicate the problem- so far so good.

Also bought the speakon adapter that I will eventually use. Just want to be certain that the contacts were dirty and caused the problem.

Rehearsal saturday will be a good test.

Thanks again for all the help!

locriansharpsec · #7 08-27-2011, 01:38 AM

Update: rehearsed tonight and after 4 hours of very loud volume Im happy to report not one time did it cut out. It looks like problem solved.

I would have never guessed that the contacts were dirty and caused this amp to shut down the way it did.

Thanks again for the suggestions on what to try first before spending a bunch of money I didnt have to take it in.

WhoDidTheElf · #8 08-27-2011, 01:40 AM

Yeah I've had it happen on other amps before, don't know the technical reason behind it, but it can be frustrating if you don't know what's going on.

SkiFor3 · #9 08-27-2011, 05:46 AM

I've got a svt 400 that I've had problems with. Im eager to give this a try and see how it works.

Jerrold Tiers · #10 08-27-2011, 08:07 AM

The contact material is attacked by sulphur-containing pollution, which eventually "opens" the contact. I made corrosion tests, and proved it.

From around 2000 until the Loud buyout, we used special jacks made in the UK by Cliff, with a special void-free tin plating which drastically reduced this problem.

Since the units are made in china and Korea, the jacks may no longer be the "good type".

The SVT-400 is old enough that it will NOT have the 'good type" jacks, so contact cleaner is a good plan.

locriansharpsec · #11 08-27-2011, 10:43 AM

Great info and at 5$ for a bottle of cleaner a small price for a simple fix.
Thanks again!