Reckhorn A-402 subwoofer amplifier - Warning!!! - diyAudio
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Old 9th August 2009, 10:51 AM   #1
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Join Date: Oct 2005
Default 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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Old 10th August 2009, 10:09 PM   #2
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Location: Metro Washington DC
Thanks for the warning!

I got an A-400 that I ended up having to rework the wiring, re-soldering the output transistors, and replacing some resistors that burned the PCB.

"All measurements are wrong! Thus, measurement is the art of handling errors."
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Old 10th August 2009, 10:58 PM   #3
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Location: Carlisle, England
Its always tempting when building an amplifier to obtain cheaper parts for it as this increases the profit margin.

With countries like China offering parts for peanuts its tempting use foreign inferior parts.

I design and sell amps myself and found PCB's to be a quarter of the price from China.
Murton-Pike Systems PCBCAD51 pcb design software.
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Old 11th August 2009, 12:43 AM   #4
jaycee is offline jaycee  United Kingdom
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Location: Norwich, UK
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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Old 11th August 2009, 11:47 PM   #5
taj is offline taj  Canada
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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.

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Old 4th July 2010, 09:10 PM   #6
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Default a-403

my new reckhorn exploded after a few hours. leaking fluid in my main amplifier. so never put it on top of other electronics. not much changed. i didnt ask my money back, i still want a new one.
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Old 4th July 2010, 10:44 PM   #7
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Location: Smoky Mountains , Tennessee
IMO it is about time some kind of import check/tax/restriction be placed on goods from China.
That's not to mention the child labor..
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Old 19th November 2010, 06:31 PM   #8
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Default 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.
Rick McInnis
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Old 20th November 2010, 12:24 AM   #9
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a schematic would be nice, I was trying to get my hands on these wreckhorn 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.
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Old 20th November 2010, 02:16 PM   #10
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Default Thanks for the help

I am going to try higher voltage rated caps and hope for the best.

I do have a schematic if you would like it I would gladly email it to you.

Rick McInnis
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