The sunn Forum
Sunn Musical Equipment => Q & A => Topic started by: FatsoForgotso on June 26, 2008, 11:17:05 pm
-
I just bought a coliseum slave and its not working which has cause me to be some what frustated. It powers up and the fans works. No matter how I plug anything into it, all it does is loudly hum like I'm touching the end of a jack. What I'm trying to do is take an Acoustic 124 http://acoustic.homeunix.net/twiki/bin/view/Acoustic/GuitarCombo124 (http://acoustic.homeunix.net/twiki/bin/view/Acoustic/GuitarCombo124) and run multiple cabs and get more volume a la the slave amp. I'm using two 8 ohm cabs (a 2x12 and the 124's combo speakers) and I was told that the slave is 4 ohms. I tried plugging my V4 in using the slave amp output and I'm still getting the hum. I think it might be a jack because I used all the same cords in my rig without the slave and they sound perfect but I have no idea. I opened it and everything looked fine, just a little dirty. Please help me as I'm extremely frustrated. Thanks.
-
Hi there,the first thing to check is for DC volts at the output.Does this loud hum happen with only the spkrs. hooked up and no input connection,and do your spkrs. seem to jump forward and stay there ? If so you've got a/some bad outputs. If the hum only appears when you hook up an input to it,it could be a ground loop.Make sure you're coming from a line or preamp output when you plug into the slave,you can't use a spkr. out to drive the input of the slave amp.If you can post some pics. of the insides,maybe I can be of more help.Good luck,Mel.
-
Like you said it "jumps" forward when turned on and stay there, even when nothing is in the input jack. How would I go about changing the outputs?
I'll take some inside pics tonight when I get home from work. I had it open last night to see if there was anything obviously wrong but I couldn't see anything other than dust balls heh.
-
Hi there,sounds like DC volts at the output to me.Don't hook it up to any more spkrs., it'll destroy them !! If you're unfamiliar with transistor power amps,I'd recommend taking it to a tech,good luck,Mel.
-
What does DC volts at the output mean exactly?
-
Hi there,spkrs. operate on AC volts.When you have DC volts at the output it usually means a component,typically an output,has shorted and is connecting one side of your power supply directly to the output,very,very bad for spkrs.The DC volts will have either a plus or minus polarity depending on which side of the supply is being "passed" to the output.Hard to say what's bad,could be an expensive fix if you replace all the outputs,emitter res.,etc.Hope this is of some help,Mel.
-
How much would you suspect it to be? Can I find these parts online? Would it be smart to attempt this on my own as I don't have too much money right now?
-
Hi there,no I wouldn't recommend doing it on your own if you've never done it before and have no electronics exp.It could cost $200 or more depending on labour costs,etc.If you have a tech buddy,you could order the parts from Digi-Key or any parts place and he could guide you through the process.Good luck,Mel.
-
I don't have too much electronics experience aside from modding pedals. Would it just be replacing one of the bad coupling capacitors. I'm only pushing this because I'm interested in learning how to work on amps. I hate taking them to techs.
-
A friend on another forum is saying that maybe one or more coupling capacitors is bad maybe??
here the gut pics you asked for
(http://i4.photobucket.com/albums/y133/hardcore454502/IMG_1399.jpg)
(http://i4.photobucket.com/albums/y133/hardcore454502/IMG_1400.jpg)
(http://i4.photobucket.com/albums/y133/hardcore454502/IMG_1401.jpg)
(http://i4.photobucket.com/albums/y133/hardcore454502/IMG_1402.jpg)
(http://i4.photobucket.com/albums/y133/hardcore454502/IMG_1403.jpg)
(http://i4.photobucket.com/albums/y133/hardcore454502/IMG_1404.jpg)
(http://i4.photobucket.com/albums/y133/hardcore454502/IMG_1409.jpg)
-
Hi there,the coupling cap.issue is really more of a tube amp prob.,it won't give you DC at the output in a solid state amp.If you can use a meter,analogue/digital,doesn't matter,shut the amp off,plug a spkr.cable into the amp and measure the res.on the other end of the cable,if it's close to 0 ohms,you have a bad output.You can also use the diode check on newer meters,it'll still show close to 0 ohms.Or you can power up the amp and measure the volts on the spkr.cable,typically DC volts should be under 100mV.Hope this is of some help,good luck with this task,Mel.
-
What kind of meter should I get, can I grab one at radio shack?
-
Yeah prob.,they'll call them a DMM-digital multi meter or a DVM-digital volt meter.It should be able to measure DC volts,AC volts,resistance,diode/transistor check.READ the manual or get someone to show you how to use it safely before you try measuring voltages,Good luck,Mel.
-
cool thanks. Also this might help with the diagnosis, everytime I plug it in, the head has a charge running through it that spreads to all my rig in a bit so everything I touch electrocutes me.
edit: I found out my initial efforts to ground the bastard hadn't worked. I'll fix it tomorrow and update.
-
Hi there,go through your rig and look for any piece of gear that is 2-prong unpolarized ( 2-prongs the same width in dia.) or any piece with a "polarity" sw. or has the Gnd.pin removed.Disconnect the signal path from all the pieces,power them up and measure the AC volts between the chassis'.Flip the "polarity"sw.till you get close to 0 volts AC.Connect the signal path and you should be ok.Good luck,Mel.