If the client's cabinet horn/tweeter is blown/damaged/intermittent, it could have likely fried the chip. Either way, it would be a good idea to test it as well as the speak-on cables/cabinet connections beforehand. Nice catch on the visual inspection as well as the work performed.
Excellent video Stuart! I’m not as tech savy as you but I have tried (and sometimes successfully) fixed a few amps and tv’s and similar musical items in my life so i love to tinker. Awesome video and your narration of what was going on and why was superb. Highly enjoyed and appreciate you taking the time to share your wizardry!
This tech video was AMAZING to me!!!! Your understanding of the "ins and outs" of the GK unit I found to be astoundingly sound, Stuart. The level of patience you display along with your experience and knowledge was honestly a satisfying spectacle to behold. I'm not a tech-head so I didn't understand all of what you were getting at. But because of your exemplary explanation of what you were facing and doing... man, I just found it to be mind-bogglingly AWESOME!!! It's just too bad I can't subscribe. That feature seems to be no longer available on YT the last few days (on my laptop). All that's available to me now is "Like", "Dislike" and "Share". Oh! Wait!!! Subscribe has been moved to the left of the screen. But I'd really like to be able to "Save" this video to my Library. But the "Save" feature isn't available any more. Doggone shame if you ask me. Anyway, I'm definitely subscribing because I want to see more of your videos!!!
Overall looks like you had a good go of it. I don't mind working on GK gear, at least it's not surface mount like Mark bass (yikes). As usual I enjoy your repair videos.
GK amps are unbelievably well known for this. The issues, unfortunately, are extremely hard to track. Had the same thing happen to two of mine: one from a combo, one head that I had hit my bench. They're extremely difficult to work on, as you've said, and seem to melt down for no reason. I actually had one that had fried so badly, that it burned the traces off of the board. Total loss.
Re: stuck screws..... heat (from a heat gun or soldering iron) and/or cold (from "freeze spray", or an upside down can of "keyboard duster"), or a cycle or two of alternating heat & cold, will usually loosen the screws, breaking the anodizing bond or the paint on the screws and cover sticking to itself. Better than stripping out the screwheads! A small, manual impact driver (the type you tap with a hammer) is also helpful. And of course it has 18 screws! It's a bass amp and you don't want it to rattle!
As an audio salesmen and repair tech with a lot of experience at setting up and repairing old turntables, I've seen British turntables with Whitworth screws!
That has always been typical of Gallien-Krueger; to not have available schematics, or even a parts matrix. The artists I worked with all gave up on the manufacturer's lack of serviceability. When the gear worked they sounded great, otherwise they failed in the most nonsensical manner. At any rate, well done as usual, Stuart. Enjoy the weekend, and remain secure from this ever-mutating pestilence. Cheers!
You have a new subscriber and fellow UA-cam. Hoping to learn about amplifiers this year so enjoying your back catalogue. Planning on building a Mullard 5-10 and maybe play with some fake China quad stuff. Best regards Chris
Gk 700RB and 1001 RB are BIAMP amplifiers (uses one amp for the woofers and another amp for the hf driver) to use the Biamp function GK biamp heads use a 4 pole speakon cable. This cable works ONLY with GK RBH, SBX and NEO cabinets. pin +1 and - 1 for the woofer signal and pin +2 and - 2 are for the hf driver. If you connect this 4 conductor cable to a regular cabinet... You will burn the hi frequency amp of the GK. ( i know because I made this mistake conecting my GK 1001 RB to a hartke hydrive 1x12 with the 4 pole gk speakon).
Excellent job. I would have tried desoldering it with JBC rubber pear desoldering iron, I got used to them. The problem is when the printed circuit is double-sided, then everything gets complicated. Maybe the chip only overheats when it has the tweeter load, it is also possible that the customer tweeter may have some kind of problem, because it seems strange that it does not get hot at all. By the way, the black plate looks like a grounding barrier to eliminate electromagnetic noise from the toroid. Cheers
The burned device has likely been operating on the ragged edge for quite some time, and finally gave up while idling. The speaker it's normally connected to is likely the cause of the problem.
Well done Stuart.. That looked really tricky.. A bit of a white knuckle ride as it were. It's a problem in so much as most of this type of equipment is reparable but in the end it comes down to the economics. There is no NHS for sick amps ! It has to be the private hospital.
@@stuartukguitarampguy5830 ... Indeed Stuart.. You are a good, honest and 'real' person that is an example of who we should all strive to be in this f..ked-up world.
You are the man to ask about refurbishing an Earth Amp. '72ish. Blatant copy of a Peavey Musition? Sorry got to get back to you on that, but definitely dig your vids. Cheers from Utah!
tbh I forgot! But there are no high voltages here and that sort of carbon arcing problem would normally only happen to high voltages (e.g. in a valve amp).
Did that cooling fan ever spool up? I had a Behringer bass head that reportedly smoked. The fan had stopped working, and the power chips had no cooling. Replaced the fan and all was well.
Hi Jim. No it didn't. I kind of assumed it has some sort of stat which only turns it on when the heatsink gets hot. Also, this amp failed whilst just sitting there doing nothing!
@@stuartukguitarampguy5830 It would have been smart to use a hair dryer or heat gun on the heat sink to see if the fan eventually kicked on. If the fan or the circuit that drives it is defective, that amplifier will eventually blow up again.
Exactly what I was thinking, I also wonder whether there is some switching circuitry that enables the tweeter only when a 4 pole lead is connected (there'd be no point driving the tweeter amp with no load) although the final minute of this video (which has just swung by as I'm typing this!) has probably debunked that theory.... I agree with his initial assertion however that the script usually goes you change these chips and whatever caused it to blow will just cause it to blow again....hopefully all goes well!
Stuff some shop towels or an old t-shirt between the board and the front panel to help keep the board standing upright as you heat the pins to pull them out. Also, a piston-type solder sucker would work better than solder-wick braid for clearing solder from the rivet-like plated-thru holes: heat the "rivet" from one side of the board and suck the solder out from the other side.
Like the towels idea! But I find that solder braid is magic and also doesn;t over heat the pads. Solder suckers tend to 'bounce' off as you trigger them.
@@stuartukguitarampguy5830 , adding flux before desoldering is helpfull. If the device was made with lead-free solder, adding ordinary lead solder *before desoldering* is pretty much a necessity in my experience (even when you have access to a vacuum-pump desoldering station, as I do).
It's not PCBs that is the problem, but bad design. And most of the time cheap components used. Take a thick Rogers with 100uM Cu, design nice just the right thickness traces and make it in a multylayer with a protective ground plane on each side, with crucial holes not just plated thorugh but riveted. Add premium components adequately fastened in place. No PTP design will be able to compete and be so reliable and sturdy. Most of the times you can tell good quality PCBs from bad ones from one glance.
Stewart, before you complain about oddball or non-standard thread sizes, I need to have a word with you, just one word: *Whitworth* 🤣! Anyway, although G-K is an American company, it is common to see US manufacturers source screws and hardware from Asia. Even though the US still.officially uses the Imperial or SAE system, I see lots of American made stuff with metric hardware ---- and even metric hardware can have all kinds of weird thread variants.
Ah yes, good old Whitworth! I wasn;t complaining about oddball threads I was complaining about having screws with near identical but subtely different threads to hold the case cover on! SO typical of GK's perversity!
@@stuartukguitarampguy5830 , I am also compelled to ask, how come you don't have a current-limiter of the series-wired incandescent light bulb variety, on the output side of your variac? In my experience as a tech it is absolutely a necessity, even for tube gear, but especially for solid state amplifiers.
Hi Chris I have one of course. I used to use it a lot (and still do on certain jobs) but it's actually a lot quicker using wick. I have the get the desoldering gun out (I don't keep it on my bench) plug it in wait for it to warm up. Then after about 5 uses it needs stripping down and cleaning etc. Bit of a hassle really!
All I hear is complain, complain, complain… That metal piece is a heat shield… Suggesting to return the amp to the customer without it being repaired is ludicrous! and you wanted to charge them? unreal! Yes, amp repair is a lot of work most of the time… you spent more time complaining then you did repairing the amp… It wasn’t that difficult of a repair… save yourself some time and buy a solder sucker… and stop complaining and get to work! Oh, and good job with the repair.
Great job. Just shows how important that first visual inspection is.
If the client's cabinet horn/tweeter is blown/damaged/intermittent, it could have likely fried the chip. Either way, it would be a good idea to test it as well as the speak-on cables/cabinet connections beforehand. Nice catch on the visual inspection as well as the work performed.
Interesting video Stuart. I am enjoying exploring these amps that are unfamiliar to me. Happy New Year.
Thanks Otto.
Hello from Utah! Cheers and thanks for posting.
Great fix Stuart..! Interesting amp, another success..Thanks for sharing..Happy New Year..Ed..uk..😀
Thanks Ed Happy New Year to you also.
Excellent video Stuart! I’m not as tech savy as you but I have tried (and sometimes successfully) fixed a few amps and tv’s and similar musical items in my life so i love to tinker. Awesome video and your narration of what was going on and why was superb. Highly enjoyed and appreciate you taking the time to share your wizardry!
Thanks Ben. I learned a lot from watching videos like mine on UA-cam. There's such a lot of knowledge out there.
I thoroughly enjoyed this! Cheers!
Great! Thanks.
This tech video was AMAZING to me!!!! Your understanding of the "ins and outs" of the GK unit I found to be astoundingly sound, Stuart. The level of patience you display along with your experience and knowledge was honestly a satisfying spectacle to behold. I'm not a tech-head so I didn't understand all of what you were getting at. But because of your exemplary explanation of what you were facing and doing... man, I just found it to be mind-bogglingly AWESOME!!! It's just too bad I can't subscribe. That feature seems to be no longer available on YT the last few days (on my laptop). All that's available to me now is "Like", "Dislike" and "Share". Oh! Wait!!! Subscribe has been moved to the left of the screen. But I'd really like to be able to "Save" this video to my Library. But the "Save" feature isn't available any more. Doggone shame if you ask me. Anyway, I'm definitely subscribing because I want to see more of your videos!!!
Glad you enjoyed it Nathaniel.
Wow you are lucky. Whenever I try to replace a burned out semiconductor without finding something that caused it the replacement usually smokes too
Yes, same here!
Looking forward to new vids! Cheers!
Thanks KEvon Just working on one now.
is it possible the amp was alerting him of a new pope?
Hmm... I hadn't considered that...
Yep, this is the channel for me. Subbed & thumbed up.
Overall looks like you had a good go of it. I don't mind working on GK gear, at least it's not surface mount like Mark bass (yikes). As usual I enjoy your repair videos.
OMG Mark Bass - nightmare. I always end up just swapping the whole board out.
GK amps are unbelievably well known for this. The issues, unfortunately, are extremely hard to track. Had the same thing happen to two of mine: one from a combo, one head that I had hit my bench. They're extremely difficult to work on, as you've said, and seem to melt down for no reason. I actually had one that had fried so badly, that it burned the traces off of the board. Total loss.
Very interesting thanks!
Re: stuck screws..... heat (from a heat gun or soldering iron) and/or cold (from "freeze spray", or an upside down can of "keyboard duster"), or a cycle or two of alternating heat & cold, will usually loosen the screws, breaking the anodizing bond or the paint on the screws and cover sticking to itself. Better than stripping out the screwheads! A small, manual impact driver (the type you tap with a hammer) is also helpful. And of course it has 18 screws! It's a bass amp and you don't want it to rattle!
Yes I might get a small impact driver. It's quite rare though for me to get a stuck screw.
I've worked on plenty enough of Triumphs, MGBs and Jaguars to know that no Englishman has any right to complain about thread sizes....
As an audio salesmen and repair tech with a lot of experience at setting up and repairing old turntables, I've seen British turntables with Whitworth screws!
That has always been typical of Gallien-Krueger; to not have available schematics, or even a parts matrix. The artists I worked with all gave up on the manufacturer's lack of serviceability. When the gear worked they sounded great, otherwise they failed in the most nonsensical manner. At any rate, well done as usual, Stuart. Enjoy the weekend, and remain secure from this ever-mutating pestilence. Cheers!
Interesting, thanks Alex.
You have a new subscriber and fellow UA-cam. Hoping to learn about amplifiers this year so enjoying your back catalogue. Planning on building a Mullard 5-10 and maybe play with some fake China quad stuff. Best regards Chris
Good job!
Gk 700RB and 1001 RB are BIAMP amplifiers (uses one amp for the woofers and another amp for the hf driver) to use the Biamp function GK biamp heads use a 4 pole speakon cable. This cable works ONLY with GK RBH, SBX and NEO cabinets. pin +1 and - 1 for the woofer signal and pin +2 and - 2 are for the hf driver. If you connect this 4 conductor cable to a regular cabinet... You will burn the hi frequency amp of the GK. ( i know because I made this mistake conecting my GK 1001 RB to a hartke hydrive 1x12 with the 4 pole gk speakon).
Ok thanks for the heads up!
I've found GK bass gear to be the best tonally, and generally bullet proof.
Excellent job. I would have tried desoldering it with JBC rubber pear desoldering iron, I got used to them. The problem is when the printed circuit is double-sided, then everything gets complicated. Maybe the chip only overheats when it has the tweeter load, it is also possible that the customer tweeter may have some kind of problem, because it seems strange that it does not get hot at all. By the way, the black plate looks like a grounding barrier to eliminate electromagnetic noise from the toroid.
Cheers
Ah ok,. I wondered what that was!
The burned device has likely been operating on the ragged edge for quite some time, and finally gave up while idling. The speaker it's normally connected to is likely the cause of the problem.
Well done Stuart.. That looked really tricky.. A bit of a white knuckle ride as it were. It's a problem in so much as most of this type of equipment is reparable but in the end it comes down to the economics. There is no NHS for sick amps ! It has to be the private hospital.
Yes that's about right! I often do extra work unknown and uncharged just to save an amp from landfill.
@@stuartukguitarampguy5830 ... Indeed Stuart.. You are a good, honest and 'real' person that is an example of who we should all strive to be in this f..ked-up world.
You need a smoke replacement kit
Lucas used them for their motorcycle electrics
Lucas, the Prince of Darkness.....lol!
You are the man to ask about refurbishing an Earth Amp. '72ish. Blatant copy of a Peavey Musition? Sorry got to get back to you on that, but definitely dig your vids. Cheers from Utah!
I've never heard of one of those! Happy to help if you have any questions.
I prefer chem wick too. Some cheaper brands OK if you coat with flux.
Correct me if I’m wrong, but did you test the “treble” main transistor by just listening to the “woofer” output?
No idea I'm afraid, its been ages.
Brilliant job! But why didn't you clean the carbon off the PCB ? Just curious. 🙂
tbh I forgot! But there are no high voltages here and that sort of carbon arcing problem would normally only happen to high voltages (e.g. in a valve amp).
Did that cooling fan ever spool up? I had a Behringer bass head that reportedly smoked. The fan had stopped working, and the power chips had no cooling. Replaced the fan and all was well.
Hi Jim. No it didn't. I kind of assumed it has some sort of stat which only turns it on when the heatsink gets hot. Also, this amp failed whilst just sitting there doing nothing!
@@stuartukguitarampguy5830 It would have been smart to use a hair dryer or heat gun on the heat sink to see if the fan eventually kicked on. If the fan or the circuit that drives it is defective, that amplifier will eventually blow up again.
Exactly what I was thinking, I also wonder whether there is some switching circuitry that enables the tweeter only when a 4 pole lead is connected (there'd be no point driving the tweeter amp with no load) although the final minute of this video (which has just swung by as I'm typing this!) has probably debunked that theory.... I agree with his initial assertion however that the script usually goes you change these chips and whatever caused it to blow will just cause it to blow again....hopefully all goes well!
@@trefwoordpunk2225 Seems to be holding up so far. A bit of a mystery,.
That amp has a thermal shut down circuit if the fan stops working. My fan stopped working and the protection circuit kept it from burning up.
Kapoom! Yeah you're right. That's why I won't plug it in untill I check with you first...
Stuff some shop towels or an old t-shirt between the board and the front panel to help keep the board standing upright as you heat the pins to pull them out. Also, a piston-type solder sucker would work better than solder-wick braid for clearing solder from the rivet-like plated-thru holes: heat the "rivet" from one side of the board and suck the solder out from the other side.
Like the towels idea! But I find that solder braid is magic and also doesn;t over heat the pads. Solder suckers tend to 'bounce' off as you trigger them.
@@stuartukguitarampguy5830 , adding flux before desoldering is helpfull. If the device was made with lead-free solder, adding ordinary lead solder *before desoldering* is pretty much a necessity in my experience (even when you have access to a vacuum-pump desoldering station, as I do).
Why I'm so glad none of my amps have any printed circuit boards.
Ha ha! Good choice!
It's not PCBs that is the problem, but bad design. And most of the time cheap components used. Take a thick Rogers with 100uM Cu, design nice just the right thickness traces and make it in a multylayer with a protective ground plane on each side, with crucial holes not just plated thorugh but riveted. Add premium components adequately fastened in place. No PTP design will be able to compete and be so reliable and sturdy. Most of the times you can tell good quality PCBs from bad ones from one glance.
@@jernejkurincic9050 Yes agreed. But of course it's all just money. £10 saved on production is £30 saved on retail price etc.
Stewart, before you complain about oddball or non-standard thread sizes, I need to have a word with you, just one word: *Whitworth* 🤣! Anyway, although G-K is an American company, it is common to see US manufacturers source screws and hardware from Asia. Even though the US still.officially uses the Imperial or SAE system, I see lots of American made stuff with metric hardware ---- and even metric hardware can have all kinds of weird thread variants.
Ah yes, good old Whitworth! I wasn;t complaining about oddball threads I was complaining about having screws with near identical but subtely different threads to hold the case cover on! SO typical of GK's perversity!
@@stuartukguitarampguy5830 , I am also compelled to ask, how come you don't have a current-limiter of the series-wired incandescent light bulb variety, on the output side of your variac? In my experience as a tech it is absolutely a necessity, even for tube gear, but especially for solid state amplifiers.
A desoldering gun with a vacuum attachment seems like it'd be worth the money given how much time you spent with the wick.
Hi Chris I have one of course. I used to use it a lot (and still do on certain jobs) but it's actually a lot quicker using wick. I have the get the desoldering gun out (I don't keep it on my bench) plug it in wait for it to warm up. Then after about 5 uses it needs stripping down and cleaning etc. Bit of a hassle really!
Horrible amp! You have the patience of a Saint Young Stuart!!!!
Yes that one did try my patience I must admit!
#74_NothinToAdd_RespectForEeducateingMe_OnWhyProfessionals_DeserveTheirWages_AndMore🇺🇸🇮🇱✝️
All I hear is complain, complain, complain… That metal piece is a heat shield… Suggesting to return the amp to the customer without it being repaired is ludicrous! and you wanted to charge them? unreal! Yes, amp repair is a lot of work most of the time… you spent more time complaining then you did repairing the amp… It wasn’t that difficult of a repair… save yourself some time and buy a solder sucker… and stop complaining and get to work! Oh, and good job with the repair.