Reckhorn A-402 subwoofer amplifier - Warning!!!

Following positive feedback from users, I bought a Reckhorn A-402 subwoofer amp earlier this year.

As soon as the amp arrived I plugged it in and noticed a significant amount of transformer humm. I decided to open the amp to see what could be done. The mains tranny is impressively large and it was easy to add some sticky feet to the exposed top so that it would be clamped into place when the base was replaced (this worked a treat - all audible hum disappeared).

While I had the case open I noticed that one of the six 10000uF caps had a swollen top. It also had a swollen base and some electrolyte had leaked onto the pcb. I removed the cap and it measured open circuit - I think the cap terminals must have been separated from the internal connections when the swelling forced the body of the cap up and away from the pcb. This was very fortunate, as no further damage had occurred as the cap was effectively disconnected.

When I first noticed the swollen cap I contacted Reckhorn and agreed with them that they would send me a replacement cap for me to fit (I bought the amp from Germany so it would have cost us both a lot of money to send it back and forward for repair). Reckhorn kindly sent me two replacement caps, and told me that they would have to remove caps from existing amps as they didn't have a stock of spares.

The replacement caps arrived last week and I decided to measure them both to select the best one to use. One of the caps measures 6640uF and the other measures only 4340uF. Both are NCC KMH 10000uF 100V caps!!!!!!!!!

I've reported this to Reckhorn and await their response.

Irrespective of their answer, I will probably replace all six 10000uF caps with better quality alternatives (probably costing me £120 plus a couple of hours work). I will not be happy using the amp while the KMH caps are still there.

I don't report this to the forum to have a go at Reckhorn - I am sure they have not deliberately used crap parts (and performance wise I'm very happy with the amp). I report this to warn other A-402 (and possibly A-401 & A-400...?) owners that they may have an issue to deal with.

Hopefully Reckhorn will respond to this problem in a professional manner - we will see....
 
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IMO it is about time some kind of import check/tax/restriction be placed on goods from China. It is despicable how much low quality knockoff stuff comes from there and how it is doing good honest workers in the EU and US out of a job.
 
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taj

diyAudio Member
Joined 2005
Sadly, that won't happen Jaycee.

All countries are clamoring to open better trade ties with China in order to cash in on export opportunities. China has a huge buying potential that no country will jeopardize by imposing import restrictions. China the importer, means we're stuck with China the exporter.

Most Chinese manufacturing/selling practices depend (almost entirely) on naive buyers. But there are a few (rare) Chinese companies that have grown up and learned how to be responsible, honest businesses, usually (virtually always) at the insistence of foreign traders who want better value -- a better balance of price/quality, not just a low price.

The government there may eventually be persuaded to grow up too, and force industry to reform (not just the token gestures they make now to appease naive foreigners.)

They will learn, eventually. In the meantime, it's up to the rest of us to not be naive buyers. Caveat Emptor.

..Todd
 
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There is something very strange about these amplifiers

I have both an A-402 and an A-403 and they both have the same NICHICON 10000uF/80 volts capacitors.

They are used to drive two EDGARHORN Seismic Subs so the duty is quite light and both of them have had failure of the supply caps. What is surprising, to me at least, is that the positive rail caps in one case literally exploded and the other one, which I took apart after the frist one failed, has caps ABOUT to explode, again, on the positive rail.

Whether it is a heat problem or a voltage problem is not known to me.

I am replacing the caps with computer style caps from APEV JR with a 100 volts rating and hope this solves the problem.

It is an attractive package in many ways but this is quite unusual.

On the 403 which I purchased recently from the North American distributor I thought it was my fault since on initial set-up I had a problem with my speaker cable and there was a short. The amp were not on for very long and after fixing the cable it seemed to work just fine. Two hours later and I hear a hissing sound and experience my first electrolytic explosion!

Any ideas as to what would cause MORE failure in the positive leg?

Looking for an answer and a bit of a warning.
 
a schematic would be nice, I was trying to get my hands on these wreckhorn:D subwoofer amp. Now I am thinking twice. In my experienced exploding caps means that the rail voltage of the amp has exceeded the voltage rating of the caps, It can happen since subwoofers are inductive load. The back EMF generated by the voice coil of the speaker could easily exceed the rail voltage, this will get dump on to the filter caps via the baker clamps on the output of the amplifier. Second the bridge rectifier could get leaky in time due to the high inrush current, passing a small amount of "AC" on to the "polarized" electrolytic cap. Well just my two cents.
 
Will send to you tomorrow

The schematic is on my work computer.

I have no idea if I have blown the output transistors since I know next to nothing about solid state stuff. I certainly hope I have not.

If you could advise me how to check I would be GRATEFUL!

I am afraid I will not be able to add much to the discussion of how to improve the amps but I would be glad to try changes and let you know what I think fo them.

There does not seem to be much different between the two amps. The 402 did have some kind of filter at the output jacls, a disk ceramic cap from the negative terminal of the output that connects to the chassis. Since it is not on the 403 I plan on leaving it out.

Look for the note tomorrow. I will title it RECKHORN SCHEMATIC.

Thanks,
 
child labor can happen anywhere.
a responsible manufacturing facilities happens in every part of the world.
but when u go to cheapest bid or offering to OEM your parts, be ready for compromise.
there are hundreds of thousand manufacturing facilities in china. basically there are some irresponsible owner and employer.
i visited about more than 50 factories in china, have never met child labor even once. i visit mostly small to medium scale, and some are not yet in the map. So i know if there are many child labor, the factories i visited should be potential ones.
I admire to the chinese dedication on working in their facilities, some owner are hands-on, and sometime work somewhere between 12-16hrs a day to meet the lead time.

cheers
henry
 
there are hundreds of thousand manufacturing facilities in china. basically there are some irresponsible owner and employer.
cheers
henry

China has good and bad suppliers.

I bought in some cheap pcbs from China and they were very good, however the turn around time varied from 1 to 2 months.

I tried another chinese company and they were very good but had an 8 day turnaround and were even cheaper !

UK pcb companies just cant compete with chinese ones on price.
I was quoted £300 in the UK for some pcb's and £70 in china.

Its simply not possible to make a profit using UK pcb makers, no wonder uk maufacturing is in such a mess.
 
Yeah, and the next thing you know, your 'name brand' toothpaste will be found to have ethylene glycol in it instead of propylene glycol. Oh wait, that already has happened. Did the 12 year old Chinese kid not know the difference? What I don't understand is how someone could mix them up, and furthermore why a factory manufacturing toothpaste would even have ethylene glycol around in the first place. I suspect that if this were to happen in the US, OSHA would have their keesters in a sling, as they would be out of business for something like that, or in jail if people were killed from it.
 
gentlemen I don't want to get involve in a non technical discussion. Poverty is one of the main reason that drive this children into child labor. In our culture, family comes first, we do anything just to help our father and mother put food on the table and help younger siblings go to school so that they can have a better life than we have. Its a sad fact of life. There are two things that a child can go; child labor or prostitution. I would choose the lesser evil. We do have a law here that prohibit employing a minor, But some of them do lie about their age just to get a job even to the extent of tampering their birth certificate.
 
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audiomachines,

good point.

some people aren't notices this conditions, specially from a develop countries.

CBS240,

yes its astonishing how those things can happen. some manufacturers and brand owner in china just trying to be a smart *** to choose ingredients or raw materials that is easily obtain and cheap to produce their products.

they simply dont care enough to do some R&D, especially for consumer products that can directly affect lots of people.

cheers
henry
 
Second point, China has just recently open up to world, they have less command of the English language (You can see these on their websites when you read it, spelling and grammatical errors abounds) and understanding the English alphabet can be difficult, there is around 4 thousand to 5 thousand Chinese characters each represents an idea or an object (ideogram) and the combination of these form the whole essence of what is being said,Now how do we transliterate propylene glycol or ethylene glycol into a Chinese character, So that a Chinese child could understand.

I thank the Americans for educating us with their language, actually English is our second language here in my country, everybody speaks it. Now my Chinese friends who wants hire me as an English proof reader =) Ha Ha Ha
 
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Pity the Americans abused OUR language ;) hehe

To be honest, I would hope the Chinese think to check chemicals not by name, but by formula. C3H8O2 is quite different to C2H6O2 and you dont need to speak English to know that those two are different! Personally I don't believe that it is stupidity, or lack of understanding, but pure and simple greed. China is all too quick to denounce Western life as corrupt and decadent, but they're only too quick to take our money and technology!

Also think, where is over 90% of the world counterfeit goods (and semiconductors) produced ? Oh yeah...
 
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