Delberthot Posted December 11, 2012 Share Posted December 11, 2012 My Gallien Krueger 1001RB II has developed a scratchy input jack so I'm going to replace it. The taking apart and soldering work does not bother me but I've never worked on an amp before -is there anything I should know before opening it up so I don't get electrocuted or something? Quote Link to comment Share on other sites More sharing options...
gjones Posted December 11, 2012 Share Posted December 11, 2012 Either unplug it first or wear rubber gloves. Quote Link to comment Share on other sites More sharing options...
Delberthot Posted December 12, 2012 Author Share Posted December 12, 2012 I don't fancy trying to win this year's Darwin award so the amp was always going to be unplugged and not been used for several days before opening it up. I vaguely remember reading something about discharging the caps or some such thingies before opening up. As I said, many time bass modder/repairer, first time amp repair. Want to make sure I don't end up as a charcoal briquette Quote Link to comment Share on other sites More sharing options...
flyfisher Posted December 12, 2012 Share Posted December 12, 2012 If the amp has been switched off for a few days then the caps are likely to be discharged anyway. Some designs have a bleed resistor across large caps specifically for this purpose. Also, in general, the input side of things will usually be kept away from the PSU side of things. But none of that is a reason for not being extremely careful, especially with valve amps. Have you tried a quick spray of switch cleaner inside the jack socket? Might be worth trying before going to all the trouble of taking the amp apart. Quote Link to comment Share on other sites More sharing options...
paul_5 Posted December 12, 2012 Share Posted December 12, 2012 If it's mounted on a printed circuit board then I'd recommend (insist is closer) a temperature controlled iron and some desolder braid. I've used desoldering pumps on PCBs before, but what you want to do here is avoid melting the copper tracks on the board. The trick is to get the iron hot enough to melt the solder, but cool enough to leave the PCB undamaged. I've found braid more successful for this. Top tip No1 though is that when you're removing solder from a board apply a little bit more solder to the joint as this helps the other stuff melt easier, and you're less likely to damage the board. Quote Link to comment Share on other sites More sharing options...
flyfisher Posted December 12, 2012 Share Posted December 12, 2012 The melting point of copper is over 1000C, so I don't think you need to worry too much about melting PCB tracks with a soldering iron. But you're right about being careful to avoid damaging the PCB (more likely lifting a copper track, rather than melting it) by leaving the iron applied for too long, which is easily done when removing large components. In this respect I've always found a solder sucker much quicker than desoldering braid. Just place the solder sucker near the joint, apply the iroin and as soon as the solder melts 'pop' the sucker and the job is done, taking all the hot solder with it. Braid needs to have the iron applied for much longer while the solder wicks into the braid. Also a solder sucker does a pretty good job of removing solder from plated-through holes. Having said all that, if a PCB track is damaged when removing components there's no need to panic as it can be fairly easily repaired by using some suitable wire soldered to the next PCB component along the track. Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted December 12, 2012 Share Posted December 12, 2012 Big question: Is the socket solely panel-mounted (i.e. only connected to the PCB with flexible wires) or PCB-mounted (soldered into the PCB and poking through the front panel, may also be locked to the panel with a nut). In the latter case (which on modern kit is much more likely unless it's an expensive all-valve job), you will need to find a new jack socket with exactly the same arrangement of 'legs' on it - theses are pins or flat tabs that locate into the PCB. Otherwise the job will be impossible, or if you're lucky, just freakin' difficult. I have carried out this procedure on my Hartke A35 when the input socket died, so I speak from experience! I was lucky enough to find a direct replacement Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted December 12, 2012 Share Posted December 12, 2012 Just to double up with the safety advice. Unplug the amp, don't trust the switches. Beware the big power supply capacitors. they store charge for a long time after the amp is turned off and I can testify that a 4,000uF capacitor at 70V is considerably more shocking than a mains jolt. This is how to discharge them http://www.acmehowto.com/howto/appliance/refrigerator/check/capacitor.php Turning the amp off whilst it is still playing will show you when most of the power has gone as the amp will fade for a few seconds as the voltage falls. A volt meter across the capacitor terminals will confirm it is discharged. Normally they discharge naturally across the circuits they are connected to so it is unlikely much charge if any will remain after the time it takes to get the case off the cab but it is better to be safe so check. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.