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How not to build amps...


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As many of you know, I for one have stopped releasing all new designs for a few years now after I got fed up with people building crap and claiming it was somehow connected to Kevin or I.  Now this also means I don't release the PCB's for many of the older projects as I want to change something and often... make them smaller.  So this hasn't stopped people selling crap with our circuits but at least they don't get any of the updates. 

Now here is an amp I saw come up for sale in Japan a while ago.  The new owner contacted Kevin to try and trouble shoot it but yeah, we don't offer any real help with these things.   Something about the PSU did peak my interest so when it popped up again for sale for not a whole lot of money, I snapped it up.  So here it is: 



Standard KGSSHV here with some version of the offboard PCB's but the build... it is just so bad.  All the wires are the same color which is just nuts.  Also just cheap PVC China wire and I'll check if it is actually real copper in there.  Here are some of my favorites: 


Support the sinks properly... that is for suckers.  Also I don't know why the volume extender is wrapped in Kapton tape... 


The amp shipped like this, the sinks are just attached by the components.  It takes no for to bend them like that.  


I think this is some form of the GRLV but shit is is cheaply made. 


Transformer wires thinner than 24AWG... yeah pure quality there. 


Terminal blocks clearly cost too much but stuff like this at +580V can arc over. 

Last but not least, no repairs are possible....


What I find truly fascinating about this thing is the PSU board as... well... they cloned my smaller KGSSHV design.  That one was never released into the wild but I have posted plenty of high res pics of both sides and they seem to have made a new board from those.  See this: 


Now all the written markings or most of them, look real.  What is not real are all the part numbers as Rxx or Cxx is not a system we use.  The packages are all also a bit wrong so the board is clearly a clone.  I'll dig it out and post some pics next to the real thing. 

More coming as I strip it down.  :) 

Edited by spritzer
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State of the art of the heartless bitches...

But, cmon, your designs are so bulletproof, that can resist such a build!

Now there are only one approach in public linear design. Boards splitted to cheap 100x100mm and opened to order through jlpcb or similar. Kit of the reliable parts are available through ebay. This will result in a small quantity of badly copied fakes but keeps badly assembled/builded. Also SMD machine-assembled design could be a way to minimize those fake capacitors and trannies with 100 pF collector-base capacitance.

Times when one can pick well-known design and sell 1k builds are finally gone.

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What the hell is Kapton used for on the potentiometer shaft?

I miss the DIY activity that was here until a few years ago but I can understand that, due to this type of thing, the intention to create and give new designs to the DIY community has decreased.




Edited by jose
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due to this type of thing, the intention to create and give new designs to the DIY community has decreased.

Let's be honest with each other.
Not to this kind of ugly build.

The bicycles are already invented and now we can only polish their lacquer or grease their chains.
Level achieved already a way higher of common soldering skills or schematic understanding.
Let's confess, no need to run further and we stomp at the spot.
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...wait, there is more!!  ;)  I woke up early so what better than strip this shit down.  First off was to remove the transformer and I found this: 


Notice the wire coming off the IEC and into the end of the fuse holder...and another wire connected to that pad?  Yeah...


I don't see any evidence that there had ever been any solder on that end of the fuse holder and the insert which holds the fuse is indeed missing.  That would explain why, when the PSU blew it left this mark on the chassis


At least the IEC input is nice... 


Gotta have that gold plating.  I also don't understand how anybody could put "copyright" on this PCB with a straight face:



It's two traces between two terminal blocks... ok.  ;)

Now the real price, lifting the amplifier boards:


Notice the nice line of standoffs...yeah not connected to anything:


The heatsinks just sat on them, not connected in any way.  So this thing has been shipped and the only thing securing the sinks are the transistor legs!!  Spoiler alert but what could possibly happen...


So 3 screws hold the amplifier boards to the chassis but no lock washers anywhere and everything was loose.  What a great way to support some of the heaviest objects in the amp.  

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the capon coated volume volume extender shaft is the fuse....

all my lt1021s from mouser have a 2 digit code at the top right of the chip (most have e3) running vertically downwards... so im sure those voltage refs are legit too.

P.S. talking of fakes dont buy from little diode on ebay in the uk... I got 2 sets of 4 2sa1486  from him fake.. C to E breakdown voltage a massive 360V... specsheet 600V... and 10 2SJ79, on a peak dca75 transistor identifier it shows D and S are swapped compared to the spec sheet! I would not want to see what happens with that in a circuit... Breakdown voltage using the specsheet pinout 0V!  breakdown voltage using the pinout the dca says <100V... spec sheet 200V...

and the "best" one so far from nikkolec on ebay $200 of 2sa1968s. Peak dca75 detects them as npn but spec sheets says pnp! breakdown voltage is 190V not 900V guaranteed firework display if used....




Edited by jamesmking
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8 hours ago, jamesmking said:

and the "best" one so far from nikkolec on ebay $200 of 2sa1968s. Peak dca75 detects them as npn but spec sheets says pnp! breakdown voltage is 190V not 900V guaranteed firework display if used....

When I was building my KG T2, I bought C3675's from Nikko. There were actually sparks from the board. Testing one of the unused devices on the curve tracer revealed they broke down at half what they should. Collateral damage was extensive. The horror story is all buried deep in the T2 thread. 

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