Amp repair descoveries.

Keith Hilton · From: 248 Laurel Road Ozark, Missouri 65721

I had a friend give me a Gallien-Krueger amp that was not working. I am "NOT" a amp repair guy. Just for fun I thought I would discover what the amp's problem was.
Fuse was OK, but probably had been replaced. I soon discovered a trace on the circuit board had been torched for about 3 inches. I noticed coming out of the rectifier that the plus and minus were connected somewhere. It wasn't the rectifier,or the filter capacitors. My search is continuing next to some didoes as I must find what is connecting the plus and the minus. All the while I am thinking--what a cheesey falure protection design in this Gallien-Krueger amp. The 120AC volt incoming line to the transformer was protected with a 3 amp fuse. From the output of the transformer nothing was fused. There was "NO" protection on the circuit board. I can't understand why the designers of this amp would not of fused both the positive and negative rails shortly after coming out of the rectifier? Do all the amp makers just fuse the input to the transformer and leave the circuit board unfused. Seems to me this is a ticket to disaster. I thought Gallien-Krueger was a good name in amps,but I am thinking different now. If a company fails to do the basic failure modes in their design, what does that say about their product? Maybe I am wrong, do all the amp makers fail to fuse the circuit board? I can't understand not fusing the circuit board plus and minus rails. I would not be dealing with burned up parts, and burned traces on the Gallien-Krueger circuit board, if some designer had designed in a couple of fuses. What are these people thinking?

Tim Marcus · From: San Francisco, CA

Profit. That's what they're thinking.

GK makes terrible amps. Back when I used to do repairs I eventually threw my hands in the air when it came to repairing popular GK RB700 amps. They were a ticking time bomb - and once they went off, repairs were very costly and difficult to do. I always advised people to forget about it rather than pay me for the work.

Now a lot of steel players are using GK amps with class D power supplies. More ticking time bombs... Fortunately the amps are inexpensive enough to replace rather than repair.

However, that's a terrible model! Electronic recycling is kind of a myth - if you've ever seen pictures of people in Africa and china burning electronics to get the copper you'll think twice about buying disposable equipment.

I always think it's worth it to spend a little more on something that can be repaired. Buy one thing, make it last forever. And it will probably sound better too...
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Milkmansound.com

Mike Wheeler · From: Delaware, Ohio, USA

Keith, as far as fusing the power transformer output goes, it's not done in transistor amps because semiconductor failure happens so fast, the fuse wouldn't have time to blow before the damage was done.

There are other methods of protection, but they tend to be expensive. Nowadays, everything is moving toward disposable products. Sad! Crying or Very sad

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Best regards,
Mike

John Palumbo · From: Lansdale, PA.

Not sure if this is related, but I have a GK MB-200 in for repair, it worked ok for about 6 months, til I went to turn it on one time and it would never fully power up, the red light on the power switch would not change from red to blue. GK told me to take it to an authorized repair center, the repair center tells me that it needs a power amp and that its back-ordered, they have had it for almost 5 weeks and I'm still waiting, sure glad I have kept my reliable N112, there's a lot of great talk about the MB200 on this forum, but I'm kinda dissapointed and much so. Sorry to go on about this, guess I need to vent some frustration about GK.

Tim Marcus · From: San Francisco, CA

Keith Hilton · From: 248 Laurel Road Ozark, Missouri 65721

Mike said---"Keith, as far as fusing the power transformer output goes, it's not done in transistor amps because semiconductor failure happens so fast, the fuse wouldn't have time to blow before the damage was done." Mike I was not talking about fusing the output of the transformer. I was talking about fusing the plus and minus rails. I respectfully disagree with you Mike, when you say, "It's not done in transistor amps because semiconductor failure happens so fast." I hope it is OK to disagree. When I design a circuit, I figure out exactly what a circuit will draw in current. I then allow some mili-amps over what I figure the circuit will draw, and that will be the current rating of the fuses on each power rail. In addition to fusing current, a designer needs to rate all part voltage well over what is required to run the circuit. If I am running a 24 volt circuit, the minimum capacitor voltage I will run is 35 volts, and most of the time 50 volts. Other things besides fuses could of protected this GK amplifier circuit. For example: Current limiting resistors on all inputs and outputs. Also--Peavey Electronics and Hilton Electronics are the only companies I know of that boot strap the inputs and outputs of all transistor junctions with protective diodes, that prevent transistor junctions from rising above the power supply voltage. I think a lot of electronics today are being manufactured with little failure protection. Part of it may be cost, but many times I don't think the designers know about, or care about, failure mode protection in their design work. In the long run, if you don't do your homework on failure modes when you are designing, it "WILL" come back and bite you in the rear end. Most electronics today can't be fixed because it is SMT--surface mount technology. It is so small you can't rework failed parts. I have to stand behind what I manfuacture and sell, and that is why I still use IC sockets, and through the hole parts. Yes, it is more work, but you can fix it. I can't get away with what I see the music stores and the manufactures in China getting away with. The Music Stores and China manufacturers can sell you something and if it blows up in a short time they make you eat it. My products are made in the United States and I can't get away with making people eat it when there is a failure. I have to fix what is wrong. Why do people expect me to fix stuff when Music stores and stuff made in China can be tossed and everyone is supposed to be happy. I am not buying that concept. I am also not buying into the concept that quality has to be really expensive. I have seen some really expensive electronics stuff that was crap. I have also seen some low cost electronics that was built to last. Just my opnion.

David Collins · From: Madison, North Carolina, USA

Yeahhhhhhh Keith.
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David Collins
www.chjoyce.com

Ray Anderson · From: Jenkins, Kentucky USA

I like the way that was worded, striaght, truthful and to the point. Way to expound Keith! The trend has shifted, we no longer build for a reputation of quaulity to be rated for the top spot, but rather build cheap for big profits and force our way to the top. If we become large enough who can challenge us for a warranty claim and for that matter who cares if you're out of pocket. Yeahhhhh for Keith. Wink

Jack Stoner · From: Kansas City, MO

It's not just "today". A lot of companies have been making "throwaway" for a long time.

Most computer parts are in that category as it would cost as much or more to repair than replace. I saw that back in the 80's with IBM keyboards. At the time, it was costing IBM less than $25 to build a certain commercial model keyboard; if there was a problem on the keyboard, even just one key, they would replace the keyboard and throw the old one away. I asked them about repairing and was told it would cost as much to ship it and process it in at a repair center, excluding any repair, than what it costs new.

I have a 10 year old Peavey XR600F PA amp and it is US made and has SMT. It went out and as I don't have the equipment to work on SMT I had to send it to Peavey for repair.

Boutique equipment such as what Keith builds can be designed and built properly. This type of equipment costs a little more but is worth it. Most big companies, as he pointed out, are only looking at the $$.

Rich Santucci · From: Perkasie Pennsylvania USA

I think it says a lot when a manufacturer would rather do a swap and return on a piece of equipment that is under warranty, then to allow an authorized service center to actually repair that same piece. This is the case with some lower wattage Marshall amps (under 30 watts) and the entire Fender Front Man series as well as some of their GDec stuff. Yes all are solid state. Think about what that say about the cost of manufacturing and the quality of the gear!

I don't think tube equipment will become disposable any time soon. It's just too expensive to build and purchase.

Many repair shops won't even look at a piece of solid state gear these days, which I just don't understand. I see more solid state gear thru my shop than anything else. It's really my bread and butter and the tube gear is the icing on the desert! I'd like to sit and work on tube gear all day, but it just doesn't pay all the bills.

Keith Hilton · From: 248 Laurel Road Ozark, Missouri 65721

Here is a couple of other things I question about Gallien-Krueger. This amp is rated at 100 watts. From what I see on the circuit board, I don't see how it can possibly put out anywhere near 100 watts. Who is doing the rating on amps? Can you just claim anything you want to claim? Also, I looked up the owner's manual on the computer, and it said the fuse was a 2 amp fuse. Printed on the back of the amp by the fuse it says 3 amps? Does anyone care about getting ANYTHING right?

Rich Santucci · From: Perkasie Pennsylvania USA

Keith,

You never mentioned the model number of the GK amp.
Is the rating listed in RMS?

Rich

Tim Marcus · From: San Francisco, CA

Keith - you may want to just stop going down this rabbit hole. Its not going to get any better or less frustrating!

If you keep making your products to your standard, people will know the difference in time. My guess is that in the next 6-12 months we are going to be seeing a lot of negative posts about these new GK amps - but we'll never hear anything but good things about your products because you go the extra mile.

Same goes for ken and my amps, and Sarno's products. Once the dust settles from this current infusion of inexpensive Chinese made products and they all crap out, our products will still be there working reliably and standing the test of time. Our customers will be glad that they spent some extra money to avoid frustration.

Either that or we'll be picking through mountains of discarded electronics in a post apocalyptic zombie wasteland Very Happy

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Milkmansound.com

Ken Fox · From: Nashville GA USA

Well said, Tim! I am with you on that for sure!!! Very Happy

Keith Hilton · From: 248 Laurel Road Ozark, Missouri 65721

Rich, the model is a Gallien-Krueger 200MK. In the Operating Instructions I downloaded from the Internet, it just says Power@400HZ-- 100 watts into 4 ohms at 1%THD. Nothing is mentioned about RMS If the 100 watts were true it would be easy to figure--Root Mean Square. This amp looks to me like it would be lucky to put out 30 watts. I don't have a dog in this fight. I was just given an amp that didn't work. Thought I might learn something in the process of fixing it. Thus far I have not learned anything about electronics, just about people and how they build and sell stuff.

Mike Schwartzman · From: Maryland, USA

David Mason · From: Cambridge, MD, USA

Having a working computer is a necessity to me, but you simply CAN'T buy a "good" one by spending more. You can buy a decent hard drive and a good power supply, but at numerous places all through the thing, you have to depend on some low-grade throwaway parts. If you want and pay for a "great" computer, all that means is multiple hard drives that back up automatically, not better quality. I sure hope the planes flying overhead and the nuclear submarines have better access to better widgets than the average consumer.

Mike Wheeler · From: Delaware, Ohio, USA

Keith, I apparently hit a nerve with my post. I'm sorry I misunderstood your question. I was not referring to your electronics in any way. I have the greatest respect for your methods, designs and policies.

As far as my fuse comments, what triggered my response was your statement "From the output of the transformer nothing was fused.". Standard fuses don't blow instantaneously...But you probably know that...and thus aren't sufficient to protect solid state components from damage. They really only protect against deadly short circuits, extreme overloads, and such. The methods you mentioned, and others, are much better, and do reflect best design practices.

My apologies for taking your thread in the wrong direction. It won't happen again, my friend.

And, yes, of course, it's OK to disagree.
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Best regards,
Mike

George Macdonald · From: Vancouver Island BC Canada

I'm not sure exactly which GK amp it is that Keith took apart, But the GK amp I am using is the MB200. My amp weighs 2 lbs and according to Brian Clark at Gallien-Krueger it is 200 watts RMS into 4 ohms. I have had mine for 8 or 9 months now trouble free. I am using a cab built by Tommy Huff with either a 15" Sica or 1501-4 Neo Black Widow. I have used Fender and Peavey amps for over 40 years, and this light weight combination sounds as good or better than anything else I have used. I still have a Nash 112, Hilton and Goodrich pedals, and I have experienced Keiths outstanding customer service first hand. Is this little amp likely to last 20 years? Probably not, but likely neither will I ha,ha. George

Tim Marcus · From: San Francisco, CA

Pit Lenz · From: Cologne, Germany

Jack Stoner · From: Kansas City, MO

Rich Santucci · From: Perkasie Pennsylvania USA

Keith,

PM sent.

Rich

Rich Hlaves · From: Wildomar, California, USA

Ray Minich · From: Bradford, Pa. Frozen Tundra

I have been hoarding the old stuff for over 45 years just because of these issues.

My most favorite "speaker protection" circuit appears in Self's book about high power amplifiers. The outputs of the final stages each go across a crowbar circuit that turns on if the average voltage on the output to the speaker deviates from zero by very much for very long... (indicating rail voltage going to the voice coil). The powered mixer board I own has just such an arrangement.

The circuit is supposed to blow the output transistors before the speakers get cooked, but, usually they all get taken out.
I really suspect that the true purpose of this circuit is to prevent a fire. If the appliance or equipment overheats and catches fire the manufacturer's liability goes up by an order of magnitude or two. They really don't care about your speakers or output semiconductors.
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Lawyers are done: Emmons SD-10, 3 Dekleys including a D10, NV400, and lots of effects units to cover my clams...

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