Tweet
Okay, I don't really know much about tube amps, but I can muddle my way around with a meter pretty well, and I have been using a soldering iron since I was 9 years old. My Randall RGT100 is acting very strangely, and it's about time I went through it and found out what the problem was. I guess the first thing to do is check and resolder all the connections in the amp, correct? Then what? if all the solder joints are good, what's the next thing, components? Caps, resistors? That's pretty much it isn't it?
-
-
Re: Tube Amplifier Troubleshooting
Define strangely. -
Re: Tube Amplifier Troubleshooting
You should maybe start with a book on trouble shooting tube circuits. Jack Darr had one called "Guitar Amplifier Handbook" but I am sure there are many others.
Usually testing tubes is first, followed by a volatge check. If you don't know tube amps you could be in for a big shock, literally. Tube amps can kill you if you don't follow some simple rules. Too much for me to type though. There are also many links on the net, look for safety notes first.
Good luck.
PS.
Defining strangely would be a good start too [img]/images/graemlins/wink.gif[/img]Comment
-
Re: Tube Amplifier Troubleshooting
Proper name and publisher of my fav book on the subject-
Electric Guitar Amplifier Handbook, 2nd edition - Jack Darr. Published by Howard W. Sams & Co., Inc. Indianapolis, Indiana, 1968.
A link that may help-
http://www.diyguitaramp.com/ampmanus.htmlComment
-
Re: Tube Amplifier Troubleshooting
Oh, don't worry, I've had plenty of experience working on other electrical, and electronic devices. I also know first hand how badly a capacitor can hurt you.
Perhaps I should have said I am somewhat knowledgeable about tube amps, but not an expert.
I know that the power tubes are good for a start. I just replaced them with brand new JJs. The pre-amp tubes are fine also. I tried them in another amp with no problems.
Basically, the amp just seems to randomly drop off in volume, and crackle. It seems worst when I have something in the effects loop. I'm betting it's a poor connection that is causing it. I'm not 100% on this, but I think it used to only do it when it got warmed up, but now it does it pretty much all the time. So, I think there is a bad joint somewhere that has gotten worse from expansion and contraction.Comment
-
Re: Tube Amplifier Troubleshooting
Hey, Zeegler! My friend had a very similar problem with his Fender Twin. It turned out that he needed to replace some capacitors. Not the filter caps, though. I believe they were supply capacitors.Comment
-
Re: Tube Amplifier Troubleshooting
[ QUOTE ]
Hey, Zeegler! My friend had a very similar problem with his Fender Twin. It turned out that he needed to replace some capacitors. Not the filter caps, though. I believe they were supply capacitors.
[/ QUOTE ]
Thanks man. I'll have to give that a try.Comment
-
Re: Tube Amplifier Troubleshooting
zeegler there is a small grey barrel looking part in that amp. its about an inch long & about a half in in diameter grey with a wire coming out of each end, they go bad in those randalls. i also have an RGT100 & that parts has been replaced at least 3 times in mine.Comment
-
Re: Tube Amplifier Troubleshooting
[ QUOTE ]
Oh, don't worry, I've had plenty of experience working on other electrical, and electronic devices. I also know first hand how badly a capacitor can hurt you.
Perhaps I should have said I am somewhat knowledgeable about tube amps, but not an expert.
I know that the power tubes are good for a start. I just replaced them with brand new JJs. The pre-amp tubes are fine also. I tried them in another amp with no problems.
Basically, the amp just seems to randomly drop off in volume, and crackle. It seems worst when I have something in the effects loop. I'm betting it's a poor connection that is causing it. I'm not 100% on this, but I think it used to only do it when it got warmed up, but now it does it pretty much all the time. So, I think there is a bad joint somewhere that has gotten worse from expansion and contraction.
[/ QUOTE ]
It sounds like you could have bad caps, either power supply or coupling, maybe both. If you have a schematic you can check the B+ for normal functioning voltage. That's a start. The coupling caps are a bit trickier to check. You need to disconect the grid end and check the volatge on a meter, preferably analog. If there is any leakage you need to replace them. Sorry my typing is slow/bad or I would go into more detail. That grey barrel like small can, that the other poster mentions, start by testing that cap. Not into Randells too much, but a bad cap is a bad cap, after tubes they are the #1 cause of failure. Also check, after draining the B+, the tension on the socket pin contacts. Look closely for signs of arking, that can mean other stuff. Hope there ain't no grammor and spelling police on this BB. If not, report back on the B+, socket tension etc, and I will throw out some more bad typing with maybe useful IDs.Comment
-
Re: Tube Amplifier Troubleshooting
[ QUOTE ]
So, I think there is a bad joint somewhere that has gotten worse from expansion and contraction.
[/ QUOTE ]
PS
That could be it, but intermitant problems are the worst to track down. Just keep an eye on your power tubes after the problem shows up, if the coupling caps are shot then it will effect the bias in a very bad way. If they show any red glow on the plate(not from the heaters) then I would replace the coupling caps in front them, but after you check the bias supply. Any red glow on the plates will kill your new power tubes in a very short time. I have the schematic, maybe we could do play by play [img]/images/graemlins/band.gif[/img]Comment
Comment