Opening up my amp

[Nightburst]

Just great! :yell: I have to go into the studio the upcoming monday and my stuff starts to crap on me! My guitar is all of a sudden buzzing like hell (I think there is something wrong with on of the frets) and now when moving my combo I hear something's loose inside! When I lift up one side I can hear something rolling to the lower side. I've never opened up an amp before but saw a friend do it once, he just loosened all the screws and pulled out the cicuit board.
The amp is still working fine but I don't want to take any chances, what if the loose part shorts something? I want the loose part out!
So what do I have to pay atention to when opening up an amp? I'm fairly handy so I don't think it should be a problem but I just want to check before I go at it. Any things I should NOT touch in perticular?
By the way the amp is a Randall RG100SC 2x12 100W combo.

 

[mrid]

Re: Opening up my amp

I go at it. Any things I should NOT touch in perticular?

Don't touch anything! :laugh2:

 

[PUCKBOY99]

Re: Opening up my amp

With this in mind, how do you "discharge" an amp? I heard you just turn the power switch & stand by switch on while the unit is unplugged & this will realease whatever current is left in the caps & transformer.........anything more to it???

 

[mrid]

Re: Opening up my amp

With this in mind, how do you "discharge" an amp? I heard you just turn the power switch & stand by switch on while the unit is unplugged & this will realease whatever current is left in the caps & transformer.........anything more to it???

Turn the amp off WITHOUT engaging the standby switch and play til you don't hear sound anymore. THEN, check the caps with a multimeter.

 

[PUCKBOY99]

Re: Opening up my amp

YOU DA' MAN MRID !!! :beerchug:

 

[Lewguitar]

Re: Opening up my amp

Turn the amp off WITHOUT engaging the standby switch and play til you don't hear sound anymore.

Following that, it'll probably be safe. Unplug the amp from the wall before opening it up.

Lew

 

[rspst14]

Re: Opening up my amp

First of all, I would be less concerned about your amp and more concerned with electrocuting yourself silly if you open it up and start poking around inside. The filter capacitors hold large charges for long periods of time, and if you're not careful, you could end up discharging them through your body. There are several ways of discharging the capacitors. I usually do all of them just to make sure everything's safe. Here's how I do it:

1. Let the amp warm up in standby for a few minutes, then turn it on and start playing. As you're playing, unplug the amp from the wall, and keep strumming as the sound fades out. This will drop the voltages below a lethal level.

2. Next, construct a probe with an alligator clip on one end and a multimeter probe on the other. Cut the cable in half, and solder in a 150 ohm 10 watt resistor. Clip the alligator clip to either the chasis or the central ground point, and touch both sides of all the filter capacitors using the probe end.

3. Once you're sure you've got all the filter caps, touch all the tube pin sockets on one preamp tube and one power tube. I recommend touching all the pin sockets, because I can't remember which one is the correct one to touch, and it varies depending on the type of tube.

After all this, you can safely open up the amp.

Ryan

 

[PUCKBOY99]

Re: Opening up my amp

AND YOU TOO LEW!!! :beerchug:

TWO FOR YOU, RYAN !!! :beerchug: :beerchug:

And Nightburst, sorry if I jumped in with my question.......didn't want ya' to get zapped. I've never delved into the depths of the nether regions of my amps, but I knew there were BIGGER concerns other than probably a lose screw!

Good luck Brother!!!

 

[mrid]

Re: Opening up my amp

2. Next, construct a probe with an alligator clip on one end and a multimeter probe on the other. Cut the cable in half, and solder in a 150 ohm 10 watt resistor. Clip the alligator clip to either the chasis or the central ground point, and touch both sides of all the filter capacitors using the probe end.

I see my tech do this all the time, but I've always been afraid to try it. What's the likelyhood of a resistor "popping?"

 

[rspst14]

Re: Opening up my amp

I don't think you'll have a problem if you drop the voltages by doing step #1 first. I just picked up a multimeter probe at Radio Shack, cut one end off, soldered in an alligator clip, and then cut it in half and soldered in the resistor. I wrapped the soldered resistor leads in electrical tape, and then discharged the filter caps. I didn't think to check the voltages with a multimeter before I started, but I did check when I was done just to make sure I'd drained all the voltage.

Ryan

 

[Nightburst]

Re: Opening up my amp

Thanks guys but errr..ehhhmm.... It's not a tube amp, like I said it's a Randall 2x12 combo...
But now I'm too affraid to open up the damn thing...

 

[Lewguitar]

Re: Opening up my amp

Thanks guys but errr..ehhhmm.... It's not a tube amp, like I said it's a Randall 2x12 combo...
But now I'm too affraid to open up the damn thing...

Assuming it was a tube amp, I spoke with my brother Bruce (http://www.missionamps.com) last night about this. He said to just do this:

1. After the amp has warmed up for a few minutes, turn it off but leave the standby on.

2. Play your guitar through it until there's not more sound to discharge the filter caps.

3. Unplug your amp from the wall.

He said the filter caps would not need any further discharging to be safe, altho there might be a tiny, tiny amount of voltage left in them.

Good luck!

Lew

 

[rspst14]

Re: Opening up my amp

Assuming it was a tube amp, I spoke with my brother Bruce (http://www.missionamps.com) last night about this. He said to just do this:

1. After the amp has warmed up for a few minutes, turn it off but leave the standby on.

2. Play your guitar through it until there's not more sound to discharge the filter caps.

3. Unplug your amp from the wall.

He said the filter caps would not need any further discharging to be safe, altho there might be a tiny, tiny amount of voltage left in them.

Good luck!

Lew

I'm a little confused here...if the amp is on standby, how are you going to hear any sound?

Ryan

 

[Nightburst]

Re: Opening up my amp

It's NOT a tube amp!!! I apreciate the efford and the responses guys, but it's getting silly now...
Did I mention it is NOT a tube amp but a SS 2x12 combo...?
Any help apreciated

 

[Kent S.]

Re: Opening up my amp

It's NOT a tube amp!!! I apreciate the efford and the responses guys, but it's getting silly now...
Did I mention it is NOT a tube amp but a SS 2x12 combo...?
Any help apreciated

Look, like Lew, Bruce, amd MRID said (you too Ryan ), just do what they said, one ... Solid state amps do not use the as high voltages as tubes ...
second ... unplug the amp from the wall while strumming a chord drains everything to almost nothing,
three ... any remaining voltage is nill anyway, just as a good safety practice in general don't touch, and steer clear of the big capacitors, and thier leads.
if you are super safety concerned, then check the caps with a Meter set to read high DC voltage , then check it a lower and lower voltage ranges ...if it's an auto ranging meter you are good to go period.
I do this all the time with my SS stuff, sometimes I don't even discharge them (I'm very used to my stuff, I don't recommend this procedure though), you should be just fine ... also use the one hand rule ... that means stick one hand in your back pocket or waistband at your back and keep it there, probe around with your other hand, if you're looking for loose componenets a wooden chopstick is great as a mechanical probing tool. If you have to turn the chassis up side down (to unlodge som loose part), then grip it away from the caps, normally grabbed near the front controls is safe. It's not that big of a deal, do the affore mentioned steps, and everything will be fine. It's probably a loose nut or screw.

 

[Nightburst]

Re: Opening up my amp

Look, like Lew, Bruce, amd MRID said (you too Ryan ), just do what they said, one ... Solid state amps do not use the as high voltages as tubes ...
second ... unplug the amp from the wall while strumming a chord drains everything to almost nothing,
three ... any remaining voltage is nill anyway, just as a good safety practice in general don't touch, and steer clear of the big capacitors, and thier leads.
if you are super safety concerned, then check the caps with a Meter set to read high DC voltage , then check it a lower and lower voltage ranges ...if it's an auto ranging meter you are good to go period.
I do this all the time with my SS stuff, sometimes I don't even discharge them (I'm very used to my stuff, I don't recommend this procedure though), you should be just fine ... also use the one hand rule ... that means stick one hand in your back pocket or waistband at your back and keep it there, probe around with your other hand, if you're looking for loose componenets a wooden chopstick is great as a mechanical probing tool. If you have to turn the chassis up side down (to unlodge som loose part), then grip it away from the caps, normally grabbed near the front controls is safe. It's not that big of a deal, do the affore mentioned steps, and everything will be fine. It's probably a loose nut or screw.

Thanks man, I really apreciate it!