B&K 200.7 blown up capacitors

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Brendan944

Enthusiast
Ratings
2
#1
Hi guys, first time posting and feeling pretty stupid right now honestly, so please try to be kind.
I picked up a gently used B&K 200.7 for a great price from a guy locally who was selling it "as is" it had been sitting in climate controlled storage for 5 years but says it worked properly when he put it away. The thing is flawless, no scratches, took the cover off, beautifully clean inside, no dust anywhere, no visibly leaky caps that I could see with an untrained eye, no bloating or scorch marks, perfect inside to the naked eye... You could tell this guy was OCD about his gear.
Well like an uninformed rookie I went home and hooked up the power cable to a completely unused outlet with no speakers hooked to it and kicked it on quick then off. Let it sit until blue light dimmed and went out then tried again real quick on and off. Seemed ok, did a sniff test for electrical smells and nothing... so I became dumb as a rock and turned it on. Within a minute POP! sparks and smoke... instantly unplugged and let it sit and breathe for an hour.
Took the cover off and started inspecting. Looks like something on channel 1 board exploded in glorious fashion.
How fu@ed am I here? Did I just shoot myself in the balls here? After some reading that I obviously should have done first, I have realized I've made a crucial mistake by not using a variac and dim bulb tester to start out with... I really screwed up here guys. I could cry...
I have an email in to the local high end audio repair shop here in St Petersburg florida but wont hear anything from them until Monday at the earliest since they are closed over the weekend. What are my odds here? Will I even be able to get parts?

I'm not home right now but I can upload some photos of the suspect burnt board when I get back.

Wish me luck guys, I couldn't afford to buy new and took a chance with this amp which I understand. Unfortunately, I didn't do any research on powering this thing up and it has bitten me right in the behind... Feel free to say I'm an idiot...
 
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Brendan944

Enthusiast
Ratings
2
#2
So I have now been told about stargate in NY. I will give them a call but still looking for some insight on how bad I've messed this beast up. Anyone else have sparks fly out of a single channel board and get away with it with a simple repair.
 
H

Hetfield

Audioholic Chief
Ratings
180 3 3
#3
I don't understand exactly why you are beating yourself up? You didn't do anything wrong to cause this it seems to me?

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Brendan944

Enthusiast
Ratings
2
#5
I read it's best to run a dim bulb tester or use a variac to bring voltage up slowly to help reform caps that have been sitting. Dim bulb tester helps if there is a short, the bulb will take the load instead of the circuitry. At least from what I have read that's how it seems... I'm not necessarily beating myself up as much as I should have done some more research on starting up an old amp before powering it up all the way. I'm just sad she popped like a fire cracker..
 
H

Hetfield

Audioholic Chief
Ratings
180 3 3
#6
I have a Parasound amp that had been sitting in my garage through all seasons for probably 8-9 years. I fired it up about 2 years ago without doing a thing to it and it has been flawless. I actually emailed the owner of Parasound before I fired it up and he said there is nothing I need to do before firing it up the first time.

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Brendan944

Enthusiast
Ratings
2
#7
I have a Parasound amp that had been sitting in my garage through all seasons for probably 8-9 years. I fired it up about 2 years ago without doing a thing to it and it has been flawless. I actually emailed the owner of Parasound before I fired it up and he said there is nothing I need to do before firing it up the first time.

Sent from my Pixel using Tapatalk
I too thought that solid state amps either work or dont... but actually looking into how capacitors work it does seem that a process of reforming "can" help the circuitry to ease itself back into operation, but under further investigation it doesn't visually appear that a cap has blown up. It appears to be isolated to the channel 1 board.

I appreciate all of your responses and hope to hear more of your thoughts. Your insight is very important to me, I know there are some seriously smart people on here.
 
B

Brendan944

Enthusiast
Ratings
2
#8
I too thought that solid state amps either work or dont... but actually looking into how capacitors work it does seem that a process of reforming "can" help the circuitry to ease itself back into operation, but under further investigation it doesn't visually appear that a cap has blown up. It appears to be isolated to the channel 1 board.

I appreciate all of your responses and hope to hear more of your thoughts. Your insight is very important to me, I know there are some seriously smart people on here.
And as I dig deeper it looks like channel 2 is about to blow as well. I just got back to the house to look at the damage a bit more.
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20181208_182535.jpg
 
B

Brendan944

Enthusiast
Ratings
2
#10
I will take more photos of the rest of the channels tomorrow. I dont plan on anymore disassembly tonight. I will be reassembling the amp properly and taking it to a repair facility next week. Keep comments coming, I will also keep this thread active with more possible damage photos and information. Dont worry about my skills on handling this hardware, I'm very familiar with the dangers of circuit boards and high voltage capacitors. Just dont feel like I could diag this amp on my own and get it right the first time. I will search for the right person that is capable of doing the actual repair work. Any extra help from the community here is obviously very helpful.

Thanks everyone so far who has contributed to this thread. Please keep the information flowing. I'm going to need all the info I can get here.
 
AcuDefTechGuy

AcuDefTechGuy

Seriously, I have no life.
Ratings
6,778 16 6
#11
@TLS Guy and @PENG can tell you a lot more.

But even if I bought an amp from eBay (which you did not do),and it popped when I turned it on, I wouldn’t blame myself.

You didn’t audition the amp first before buying locally?
 
B

Brendan944

Enthusiast
Ratings
2
#12
Think I just found my amp on another forum... it was purchased as is and I expected it may have some issues. I was not able to audition this amp because now I'm learning that the owner knew this thing was blowing up and did not tell me about his findings...

You can google B&K 200.7 blowing caps and find the thread on the other forum. I was told it was working when it went into storage and its current condition is unknown since he did not have the equipment to test it...

I'm not mad but do value honesty which I feel I was not given.
 
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TLS Guy

TLS Guy

Audioholic Slumlord
Ratings
7,281 17 25
#13
I read it's best to run a dim bulb tester or use a variac to bring voltage up slowly to help reform caps that have been sitting. Dim bulb tester helps if there is a short, the bulb will take the load instead of the circuitry. At least from what I have read that's how it seems... I'm not necessarily beating myself up as much as I should have done some more research on starting up an old amp before powering it up all the way. I'm just sad she popped like a fire cracker..
You are correct. It is best to bring gear that has been sitting up slowly with a Variac. You usually get away with it, but not always. It is an essential part of any repair desk.

I have one just like this.



I learned the hard way as a kid. I started up an old Sobell radio of my late grandmothers, and the power supply cap exploded on turn on, peppering me with shrapnel. I was lucky not to be badly hurt.

So yes, when I obtain an older unit I always bring it up on a my Variac, slowly and cautiously.

I would just replace those two components. There are lots of Variacs to be had on eBay for little money.

After your repair I would bring it up very cautiously on the Variac.

This problem of caps exploding after not being used for a long time, is well known.
Think I just found my amp on another forum... it was purchased as is and I expected it may have some issues. I was not able to audition this amp because now I'm learning that the owner knew this thing was blowing up and did not tell me about his findings...

You can google B&K 200.7 blowing caps and find the thread on the other forum. I was told it was working when it went into storage and its current condition is unknown since he did not have the equipment to test it...

I'm not mad but do value honesty which I feel I was not given.
I think your major problem was not researching the amp before hand. Not an amp I was familiar with. However it was a disaster from day one apparently now find.

Not only does it spectacularly blow those Tinatalum caps with abandon, but worse the output MOSFET devices become leaky and the units are known for variable DC off set as high as 70 volts. I get the impression there is no DC offset protection so they are known for burning up speakers.

Those output devices are no longer available.

My strong recommendation is not to repair that amp, but send it promptly to the recycling center.

The sad fact is that will be your cheapest solution, as if you persist more likely than not you will be out more than the cost of that amp.

In future remember that when buying second hand it is easier to spot duds than buying new. Old units have a paper trail and your unit has a disaster trail in its wake.
 
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Brendan944

Enthusiast
Ratings
2
#14
Ugh. I'm really feeling like crap right now. Thanks TLS guy. I know now I was taken advantage of and bought a time bomb masked as a diamond.

Lesson learned the hard way unfortunately.
 
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Brendan944

Enthusiast
Ratings
2
#16
I did. Told him it blew up 2 channels as soon as it happened... he said well it was still a good deal for a now 5 channel amp. Pretty sure he just bent me over and knows it.
 
Dmantis10

Dmantis10

Audioholic
Ratings
38 1
#17
Thats a shame and sorry you have to deal with it BUT the amp is a good one when in working order. I strongly suggest you get it repaired and properly looked over by an experienced B&K repair amp shop. Most good quality repair shops can fix it no sweat. But I'd also get the entire amp looked over from head to toe to make sure there is no other issues with it.
I may have missed it but out of sheer curiosity what did you pay for it?
 
TLS Guy

TLS Guy

Audioholic Slumlord
Ratings
7,281 17 25
#18
Thats a shame and sorry you have to deal with it BUT the amp is a good one when in working order. I strongly suggest you get it repaired and properly looked over by an experienced B&K repair amp shop. Most good quality repair shops can fix it no sweat. But I'd also get the entire amp looked over from head to toe to make sure there is no other issues with it.
I may have missed it but out of sheer curiosity what did you pay for it?
Thats a shame and sorry you have to deal with it BUT the amp is a good one when in working order. I strongly suggest you get it repaired and properly looked over by an experienced B&K repair amp shop. Most good quality repair shops can fix it no sweat. But I'd also get the entire amp looked over from head to toe to make sure there is no other issues with it.
I may have missed it but out of sheer curiosity what did you pay for it?
I disagree with that advice totally. First off it insane to spend money on an amp when the output devices are NLA. Also those amps are known to have fried speakers from DC offset. That basically means they should all be removed from service as that is a fire hazard.
 

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