Yep, it's audiophile quality 🙂 The clue is in the word audiophile. Someone who loves listening to music is a musicophile. Audiophile just means lover of sound - they just listen to their system....
The output spec is there to accommodate very power hungry headphones. Some fancy headphones need a LOT (maybe not quite this much). The sad thing is the case itself would have worked as a heatsink far better. The engineer should know better.
@@peterlarkin762 I kida get the idea that they tried to engineer the mosfets as 'tube' devices, hence the high voltages, which are for headphone output uncommon. FET's often sound nice when warm -70 degrees centigrade und up-. A more common solution is just an arrangement of good op-amps for headphone use, which drastically reduces the amount of components and more importantly, coupling over caps and worse, resistors. Yet, I have never designed an headphone amp nor do I like headphones, so I can be very wrong. In general I would stay away from hard to drive headphones, the same for non-efficient loudspeakers, though there are always many reasons to oppose that.
Burnt mosfets, overheathed PCB .. and there is no ventilation holes in that chassis.. My guess,, It will happen again soon. Anyways.. Great repair on this, Mark!
That's my immediate thought too. Not only that but isn't capton tape meant to insultate agsinst heat? I get it's being used to insulate between the heat sink but surely that would also trap the heat and not transfer it? I'd seriously remove it, get a better tranfer medium and a better heatsink too.
Great video as always! Regarding those power transistors; Kapton tape has poor thermal conductivity vs thermal pads - perhaps the root failure was from someone trying to use this as a regular speaker amplifier, overheating to short? But as @pantelisEVs noted, using the chassis seems like a much better idea too (with thermal pads 🐱).
You're dead right - Kapton tape isn't designed as a thermal conductor. No way would I use it in place of silicone pads or thermal grease. It's the sort of cheap-ass shortcut that I see in china stuff all the time and just another reason I tell people not to buy this stuff.
thats what i thought and possibly wrong impedance speakers . made that mistake myself used my bi amp speakers (paralleled 🙄) on my rotel 931 amp , like a divi and cooked the o/p transistors
Without doubt the best electronic fixing channel on TH-cam please please longer videos I have learnt so much from watching your videos please keep the vids coming
@@radicalaudiodesign I doubt it makes good contact thermally. And the lack of vent holes... Those transistors shouldn't be getting really hot to begin with but still, it just looks dodgy.
@@radicalaudiodesign kapton tape instead of thermal paste is an indicator of someone who was asleep at school that day when they explained how to make heat sinks.
Those fets are based on the Hitachi 2SK1058 series, but the UK manufacturer never seems to have solved fundamental maufacturing problems. What seems to happen is that wafer or packaging impurities migrate into the channel due to heat, resulting in shorts or at least low resistance episodes that cause a positive heat feedback loop. What you see there is a charred board, you can imagine what happens in a big amp and +- 100V rails. They were touted as an equivalent, and superior replacement to the Hitachi audio fets, and they do provide excellent performance on the bench. But they are not reliable. You will see this kind of failure with them over and again.
wonder if someone ran high impedance mode into low impedance headphones = loads of heat then eventually mosfet failure i dont think that was a heatsink but just a way of thermally ballancing the high and low side mosfet pairs , like those little alluminium twin to92 clamps for input differencial pairs we used to see in the 90,s i didnt see any switching relay to select a lower rail voltage by selecting a lower voltage secondary winding just a protect relay for high and low impedance modes
All the thermal mass of the over-built chassis and they choose to mount TO-3P lateral mosfets which are no doubt biased into class A to a tiny piece of metal as a heatsink! You can tell they’ve been getting excessively hot by the board discoloration. Even the cases of the MOSFETs have discolored. And scraped part numbers on the components! This amp is over-engineered except for where it counts. Good for the warranty period and then will give you a bunch of trouble afterward. The company scraping part numbers and not providing even a simplified schematic screams stay away… Great work on the repair, Mark 👍🏼
@@PrimeHiFi ...And yet I wonder if the manufacturer even has a repairs department if miracle Mike wasn't there to mend it? I'll bet not! I just HATE it when manufacturers scrape off part numbers!😠😡🤬🤬! It seems almost CRIMINAL!
4 mosfets for a device with has an output of just a few watts, the FETS should stay extremely cold, yet they decided to large packets, I'd suppose at least.
@@edmaster3147 These lateral FETs have their Rds on the high side and benefit from sensible thermal arrangement, especially that they should ideally be run with high DC bias.
On holiday with my wife in Puerto Rico. She's taking a nap and I'm sipping a gin and tonic watching your vids and listening to the waves. Does it get better?
Talk about overkill. Just shows what extremes some people will go to just to listen through headphones. God knows why you need so much power. As always your video's are educational and entertaining.
Funny to see all the comments that assume that the design here isn't a true balanced amp & is flawed due to lack of cooling & will fail again. 😆 My guess is that the "balanced output stages" is actually the 8 much smaller SMD MOSFETs. 🧐 The 4 large 8A MOSFETs are only intended for keeping a steady temperature inside. 👍 This explains why this design isn't utilizing the massive chunks of aluminum for cooling, but just strapped these to a "radiator" in the middle of the closed chassis. 😉 Bottom line. "There is no spoon!" 😎
Thank you Mark for another highly entertaining video, so well produced. When that resistor measured 3.9 Ohms I thought you were going to find out it was one of those chokes that looks like a resistor! I’ve been in power electronics for 35 years and not seen a resistor fail short either!
i love mosfets in audio output they often blow up a little more gracefully than bipolar fire mongers and the usual 100r gate resistors protect the driver stages (usually)
The trouble with MOSFETs in audio output stages is that 30 years after the unit was made and you need to change out some transistors, they are obsolete and impossible to obtain. A good example are the 2SK1058 and 2SJ162 pairs. Used in many amps, they are now obsolete. BJT transistors are much easier to find - I have large stocks of genuine ones, many more than the MOSFET stocks that I have.
@@darrenmurphy6251 The Hitachi 2SJ and 2SK series MOSFETs are pretty much bulletproof. I had an amp come in for service that the owner replaced the fuses with nails and drove the thing to max - yet the MOSFETs didn't die. In fact, in the past 40 years I have only replace ONE of these Hitachi devices. They just don't fail. I have good stocks of them.
Impressive the difference in build quality comparing this and the Tom Evans piece. I guess I'd rather have something proudly made in China than ashamedly made in the UK...
Another great video Mark, could the damage have been caused by some piece of external equipment being connected wrongly, I guess we will never know. Looking forward to next video , keep up the good work.
It wouldnt. Mica is rather poor thermal conductor, as kapton is. Also, the power dissipated there shall be so small, it would work sufficiently even with 5 layers of the kapton tape. The problem here is, that by design, it is wrong, as there is no temperature feedback for bias control. As the fets heat up, bias current creeps up. Until it sh!ts itself. Overloading the amp in some way would only help this happen faster.
Mark great video as always. I might be a bit sleepy, but I thought the second from left Exicon was loose in the part where you were installing the beads. Maybe it was deliberate to aid alignment of the pins to the board… if not. It needs to be tightened 😅
Hi Mark I look with great pleasure at your videos they are very inspirational and I think I will made my own videos in audio repair soon, I learned a lot from you. Thank you!
love the metal back to the mosfet, with a metal screw into a combined metal heatsink.. (I have a set of these same fets). I'd probably want insulating inserts or plastic screws..
WOW. Thats the definition of an overkill output stage for headphones! Notes: -These power MOSes could be mounted and take advantage of this chunky bottom plane. -Is this high impedance mode protected in case someone plugs low impedance headphones or overcurrent and damage to the output devices Really interesting design anyway!
Call me an oddball but I think all videos of the unscrewing fast forwards would make a good ASMR compilation. Another great video Mark, it made my day after work to relax and watch. Cheers future watchers and enjoy.
Etching the transistors while selling replacement parts is an interesting choice. It's a shame they couldn't go full on right to repair but looks like a decent device overall.
Those Exicon outputs are excellent devices; some of the last really good power audio transistors. Based on the old Hitachi LatFet (and made in UK). However, the Kinki engineer is relying too heavily on how forgiving these FETs are with thermal runaway and breakdown, considering the size of the heatsink. If they ran the output at +/- 40 volts it would still have buckets of power and probably not overheat.
Good to see you're back Mark! You've set the bar very, very high when it comes to electronic repair videos. Different camera angles, zoom-ins, lightening, post-production and so on. I wonder how much time did you spend making this, relatively short one. ;)
In this amplifier, you can simply place the output transistors on the bottom side of the printed circuit board, bending the leads and fixing them directly to the bottom of the case. The main thing is to use an insulating thermal pad. As is done, for example, in the Burson Soloist HA160 amplifier.
@@arenaengineering8070 The Kapton tape used here seems like a bad idea, seeing as it's best known for its thermal insulating properties. A thermal pad would definitely be better. What's the reason for the transistors being unable to make direct contact with the chassis?
@@jamescollins6085 The case of the used output transistors is not insulated and in direct contact with the aluminum chassis a short circuit will occur between the + and - power supply. Kapton tape is used in this amplifier more as an insulator.
As usual, the Chinese doesn't know how to spell. But I was surprised by the build quality and the component selection. At least the ones that survived the anonymisation process.
The heat sink for the transistors appear to be no larger area than the transistor backs themselves… so there might be some thermal lag but there isn’t going to be much heat dissipation after about 15 minutes of use… looks like that heat sink could do with some fins or thermal coupling to the chassis (which looks a bit awkward given their position!)
It was quite common for low value carbon resistors in TVs in the 70s to reduce in value - the cathode resistor in valve frame-output circuits were notorious for it. One always checked the resistor in the case of valve failure - if neglected it could cause premature failure of the new valve.
Quality balanced connectors possibly the reason they are used but it does seem strange. Nice unit, made in China! It would have been nice to have done a performance test, i.e. frequency sweep at various gains and THD to see if it was worth the money... Great video at usual, thoroughly enjoy them but this was a bit short!
The Engineers that designed the thing clearly didn't want the likes of my novice hands to go gleam inside it's internals, what with all of those different sized screws and what not!
I wonder if one of those MOSFETs had gone unstable? In earlier days of MOSFET power amps Ihad a few go like that. They can osciliate in the GHz region, too, so you see nothing on your scope. The ferrite beads on the legs are a hint that it might be an issue. With one brand of power amp in the 80s, I resorted to the old radio amateurs leak testing trick of a wire loop with a PIN diode and a small bulb to see if the power amp I was looking at had turned into a transmitter.
Looks like the balanced output will only be truly balanced if you give it a balanced input - in that case it's acting as a passive preamp and grabbing what it needs to drive the headphone amp only when you have phone selected. It looks like a nice piece of kit, but given that it sells for £1100 you'd rather hope so!
I have an Allnic preamp which certainly looks good and works well, but when you actually look at the way it's been made, you find issues, such as you discovered with this Kinki not being balanced.
@@sw6188 Allnic is a small Korean family firm who, for example, hand wind their own transformers. They are not associated with shoddy workmanship although their design choices can be unorthodox. Also, not Chinese.
I'm not sure Kapton tape is a good thermal conductor. It has fantastic thermal stability and a great electrical insulator, but I don't think it is a good thermal conductor. This could be part of the failure mode, if heat can't be removed from the semiconductors it will hasten their demise.
You're right, but kept it to the audiophile factory spec. There is such a high voltage across those transistors, it wouldn't take much current to get them toasty!
You would think if they were throwing that amount of money at it you would have transformers feeding the XLR outs. Also I think it’s a bit overkill sanding off the component text. I think if someone was looking to copy the idea they would not copy this design!
A good balanced output stage can be done cheaply and well with op-amps but yes, for the money this thing costs I would expect to see transformers in it!
Great channel, one of my favorites. Just one observation: Mark, when you did put the four fets back together, mounted on that aluminium plate, one of them seemed to turn and shift. Second one from the left. Like it wasn't torqued down? Worth checking the video possibly.
Nice one, Mark. Interesting that the XLRs were not truly balanced. I also wonder if the owner inadvertently shorted one of the outputs. The overheating of the PC board didn't look good either.
I don't understand the use of kapton tape on the heatsink. Is it a good conductor of heat? I always thought it was a _bad_ conductor of heat, and hence why it is used to cover components where a hot-air gun will be used. I'd have used thermal pads on those FETs instead.
People are saying why have a large piece of thick aluminium as a case, and not fit the power transistors to it, well i will explain, the transistors collector is live,+- 80volts ,and your relying on a piece of very thin kapton tape,just think of the shock risks,if the tape broke down,swarf etc,the case would be sitting at 80 od volts (enough to give a shock) ,its that simple,it wouldnt meet the safety specs,even though its made in China.
@@enoz.j3506 We just used the regular mica washers & silicon grease under our power transistors that have 1200V on them with no problems! The pcb should NEVER get so hot that it discolours like this one did. It will eventually become conductive. The uniform discolouration under all the mosfets means they've ALL been overheating. $1000 for a piece of 💩 that just looks good, feels heavy, but WILL fail! Kinky CRAP!
@@nevillegoddard4966Yes ,as a qualified electronics engineer,for 40+ years,mica washers and silicon grease was & still is, widly used,mica withstands 1000 deg c,Kapton 260 degs c,big difference,got to look at worse case cenarios,to blue the legs on those fets,i dont know ,as you say the fact that the pcb is burnt means,bad designe & will conduct eventually. I dont know why they didnt use insulated fets,then bolting to chassis would be the way to go.Its made in China,nuff said.Make it look good and it will sell.
I use kapton tape to STOP heat transfer. Does the kapton tape behind the mosfets actually stop the heatsink from acting like a heatsink? That'd be my guess why it failed.
For sure, that tape should not be used in that application but also those transistors shouldn't get anywhere near hot enough to fail even without decent heatsinking.
I Always buy Japanese products, whether they are are vintage or brand new! I have vintage Japanese audio going back to the 70s and 80s which has never failed! The only works I have carried out to them, is replacing the capacitors, a few transistors, few resistors and update the speaker terminals and RCAs! Chinese amplifiers look nice, but they use very cheap components, is grossly over engineered, and very poorly ventilated! The same fault will occur due to poor ventilation! The customer should work with Mark, to fit a fan on the outside, and make some vent holes in the casing, because Mark is an exceptional, wonderful, talented gifted engineer!
Tom Evans should take inspiration from this chassis. Beautiful
He would enjoy the scratched out markings.
The internal layout and construction, as well! This one doesn't look like a middle-school science project.
If Kinki Audio ever teamed up with Schiit Audio they’d have a fantastic opportunity for a new brand name !! 😅😅😅
😂
😂😂😂😂
🤣🤣🤣🤣🤣🤣🤣🤣🤣
at least they would sell a lot of bumper stickers in certain parts of the usa...
inki pinky ponki💀💀
70K subs and climbing. We need to get Mark up to about 5 Mil
That amp is SERIOUSLY over-engineered. Something like 2 x 15w for headphones? I love it! Good to see you back Mark.
Yes, overengineered at the wrong Place. Massive enclosure, pippi heatsink plate 😂
Yep, it's audiophile quality 🙂 The clue is in the word audiophile. Someone who loves listening to music is a musicophile. Audiophile just means lover of sound - they just listen to their system....
@@borlibaerĺpp
The output spec is there to accommodate very power hungry headphones. Some fancy headphones need a LOT (maybe not quite this much).
The sad thing is the case itself would have worked as a heatsink far better. The engineer should know better.
@@peterlarkin762 I kida get the idea that they tried to engineer the mosfets as 'tube' devices, hence the high voltages, which are for headphone output uncommon. FET's often sound nice when warm -70 degrees centigrade und up-. A more common solution is just an arrangement of good op-amps for headphone use, which drastically reduces the amount of components and more importantly, coupling over caps and worse, resistors. Yet, I have never designed an headphone amp nor do I like headphones, so I can be very wrong. In general I would stay away from hard to drive headphones, the same for non-efficient loudspeakers, though there are always many reasons to oppose that.
Burnt mosfets, overheathed PCB .. and there is no ventilation holes in that chassis.. My guess,, It will happen again soon. Anyways.. Great repair on this, Mark!
Mark has the spares on the shelf ;)
I think in this case on FET failed and then cooked the others resulting in total failure
Last thing I’d have ever expected to see that is a headphone amp lol.
That's my immediate thought too.
Not only that but isn't capton tape meant to insultate agsinst heat? I get it's being used to insulate between the heat sink but surely that would also trap the heat and not transfer it? I'd seriously remove it, get a better tranfer medium and a better heatsink too.
Maybe drilling some holes on the top to eliminate the possibility of this happening again?
Great video as always! Regarding those power transistors; Kapton tape has poor thermal conductivity vs thermal pads - perhaps the root failure was from someone trying to use this as a regular speaker amplifier, overheating to short? But as @pantelisEVs noted, using the chassis seems like a much better idea too (with thermal pads 🐱).
You're dead right - Kapton tape isn't designed as a thermal conductor. No way would I use it in place of silicone pads or thermal grease. It's the sort of cheap-ass shortcut that I see in china stuff all the time and just another reason I tell people not to buy this stuff.
thats what i thought and possibly wrong impedance speakers . made that mistake myself used my bi amp speakers (paralleled 🙄) on my rotel 931 amp , like a divi and cooked the o/p transistors
Just got out of the shower, got in bed and thought let’s watch a few videos before bed.. and Marks video pops up!!!
Without doubt the best electronic fixing channel on TH-cam please please longer videos I have learnt so much from watching your videos please keep the vids coming
With Kinki and 'Ive got to get inside it' you had me hooked!
Such a chunky aluminium enclosure and they put the transistors on that little slab, I guess you could say that's a little... kinki, isn't it.
That heatsink connects to toplid when screwed down so not so little slab anymore.
@@radicalaudiodesign I doubt it makes good contact thermally. And the lack of vent holes... Those transistors shouldn't be getting really hot to begin with but still, it just looks dodgy.
I'd say there's an air gap@@radicalaudiodesign
An improvement would be a thicker longer block of aluminium that gets screwed to the lid and with the mosfets wider apart.
@@radicalaudiodesign kapton tape instead of thermal paste is an indicator of someone who was asleep at school that day when they explained how to make heat sinks.
Those fets are based on the Hitachi 2SK1058 series, but the UK manufacturer never seems to have solved fundamental maufacturing problems. What seems to happen is that wafer or packaging impurities migrate into the channel due to heat, resulting in shorts or at least low resistance episodes that cause a positive heat feedback loop.
What you see there is a charred board, you can imagine what happens in a big amp and +- 100V rails.
They were touted as an equivalent, and superior replacement to the Hitachi audio fets, and they do provide excellent performance on the bench. But they are not reliable. You will see this kind of failure with them over and again.
I literally threw my hands in the air when i got the notification 😂....Haven't even watched it yet 🤗
I know...Mark is the best. Love these videos.
I love these retro Phil Collins videos!
🤣
Phil Collins when he was 9.
wonder if someone ran high impedance mode into low impedance headphones = loads of heat then eventually mosfet failure
i dont think that was a heatsink but just a way of thermally ballancing the high and low side mosfet pairs , like those little alluminium twin to92 clamps for input differencial pairs we used to see in the 90,s
i didnt see any switching relay to select a lower rail voltage by selecting a lower voltage secondary winding just a protect relay for high and low impedance modes
Where is part 3 of the AIWA?
Yes mee soo eagerly waiting,Hungryfor that.But,sadly,Mark hates cassdecks....
Good point! Mark needs a rest on that one, but will suddenly strike back with it repaired in another video! I cannot wait for that one!
All the thermal mass of the over-built chassis and they choose to mount TO-3P lateral mosfets which are no doubt biased into class A to a tiny piece of metal as a heatsink! You can tell they’ve been getting excessively hot by the board discoloration. Even the cases of the MOSFETs have discolored. And scraped part numbers on the components! This amp is over-engineered except for where it counts. Good for the warranty period and then will give you a bunch of trouble afterward. The company scraping part numbers and not providing even a simplified schematic screams stay away…
Great work on the repair, Mark 👍🏼
@@PrimeHiFi ...And yet I wonder if the manufacturer even has a repairs department if miracle Mike wasn't there to mend it? I'll bet not!
I just HATE it when manufacturers scrape off part numbers!😠😡🤬🤬! It seems almost CRIMINAL!
I'm sorry but you're wrong. 🤭 I'm an electronics engineer my self with +30 years of experience in radio&radar. Look at my comment.😉
Hi Mark, these fabulous fets based on Renesas J162/K1058 have unusual pin-out; the beads actually went on the gate and drain.
Interesting you saying the MOSFETs not needing a heatsink considering how hot they’ve clearly gotten. Excellent video.
4 mosfets for a device with has an output of just a few watts, the FETS should stay extremely cold, yet they decided to large packets, I'd suppose at least.
@@edmaster3147 well then in reality they could have used TO220 devices then, regardless they don’t look like they’re staying too cold.
@@edmaster3147 These lateral FETs have their Rds on the high side and benefit from sensible thermal arrangement, especially that they should ideally be run with high DC bias.
On holiday with my wife in Puerto Rico. She's taking a nap and I'm sipping a gin and tonic watching your vids and listening to the waves. Does it get better?
Talk about overkill. Just shows what extremes some people will go to just to listen through headphones. God knows why you need so much power. As always your video's are educational and entertaining.
Best electronics channel, keep it up Mark!
that's is a superb job, nice to watch somebody who knows what they are doing ,thank you for the video
Funny to see all the comments that assume that the design here isn't a true balanced amp & is flawed due to lack of cooling & will fail again. 😆
My guess is that the "balanced output stages" is actually the 8 much smaller SMD MOSFETs. 🧐
The 4 large 8A MOSFETs are only intended for keeping a steady temperature inside. 👍
This explains why this design isn't utilizing the massive chunks of aluminum for cooling, but just strapped these to a "radiator" in the middle of the closed chassis. 😉
Bottom line. "There is no spoon!" 😎
Thank you Mark for another highly entertaining video, so well produced. When that resistor measured 3.9 Ohms I thought you were going to find out it was one of those chokes that looks like a resistor! I’ve been in power electronics for 35 years and not seen a resistor fail short either!
We missed you. Nice quick fix.
Nice repair. I wasn't expecting that amp to be so well made. Really good workmanship on everything, even the case!
Excellent as ever, it’s our pleasure to see you work through the problems and get them fixed. Thank you as always.
Came here just to see the electroshock in the intro again. Haha no, great video!
the best part for sure
i love mosfets in audio output they often blow up a little more gracefully than bipolar fire mongers and the usual 100r gate resistors protect the driver stages (usually)
The trouble with MOSFETs in audio output stages is that 30 years after the unit was made and you need to change out some transistors, they are obsolete and impossible to obtain. A good example are the 2SK1058 and 2SJ162 pairs. Used in many amps, they are now obsolete. BJT transistors are much easier to find - I have large stocks of genuine ones, many more than the MOSFET stocks that I have.
Yes iam running genuine hitachi 2sj50, 2sk135 and some of my spares will be fakes 😢
@@darrenmurphy6251 The Hitachi 2SJ and 2SK series MOSFETs are pretty much bulletproof. I had an amp come in for service that the owner replaced the fuses with nails and drove the thing to max - yet the MOSFETs didn't die. In fact, in the past 40 years I have only replace ONE of these Hitachi devices. They just don't fail. I have good stocks of them.
Yay!... new 'Mend it Mark' Vid... Happy, Happy, Joy, Joy!
Mark there you go again. Its an absolute joy watching you perform. Thanks and lots of love. 🎉
Impressive the difference in build quality comparing this and the Tom Evans piece. I guess I'd rather have something proudly made in China than ashamedly made in the UK...
Happy days when there's a new vid from Mark! Top notch work once again!
Another great video. I wish you posted more often but always a treat when you do. Thanks
Great to see you Electronic Zen Master
good to see you back, Mark! ciao from Italy!
I love listening to the sound of you working ❤️❤️❤️ great channel
Another great video from most positive technician on YT. Pure pleasure to watch your content Mark
You’ve been missed Mark. Thanks!
Another great video Mark, could the damage have been caused by some piece of external equipment being connected wrongly, I guess we will never know. Looking forward to next video , keep up the good work.
Hi, some micas and thermal paste should work better to dissipate the heat than capton tape on those mosfet, it is not suppose to break.
It wouldnt. Mica is rather poor thermal conductor, as kapton is. Also, the power dissipated there shall be so small, it would work sufficiently even with 5 layers of the kapton tape. The problem here is, that by design, it is wrong, as there is no temperature feedback for bias control. As the fets heat up, bias current creeps up. Until it sh!ts itself. Overloading the amp in some way would only help this happen faster.
Companies that grind labels off of components or cover them in goop need a slap.
Yeah this, kinda shady and makes me not trust them at all.
Mark great video as always. I might be a bit sleepy, but I thought the second from left Exicon was loose in the part where you were installing the beads. Maybe it was deliberate to aid alignment of the pins to the board… if not. It needs to be tightened 😅
I saw that as well. Hopefully he caught it in time.
All done as usual with the efficiency, finesse, and as usual the astounding knowledge you bring to this channel.
Great, but not enough uploads mark we love your content
Excellent as always Mark. Please dont keep us waiting as long for the next one! 😊
Hi Mark I look with great pleasure at your videos they are very inspirational and I think I will made my own videos in audio repair soon, I learned a lot from you. Thank you!
love the metal back to the mosfet, with a metal screw into a combined metal heatsink.. (I have a set of these same fets). I'd probably want insulating inserts or plastic screws..
I love the 555 timer in it's heavily guarded isolation 2:54
I think this amplifier looks good inside, it seems well designed and competently built. Nice device
It looks very well built but there definitely are some questionable design choices. Anyways, who comes up with those brand names these days 🤦
WOW. Thats the definition of an overkill output stage for headphones!
Notes:
-These power MOSes could be mounted and take advantage of this chunky bottom plane.
-Is this high impedance mode protected in case someone plugs low impedance headphones or overcurrent and damage to the output devices
Really interesting design anyway!
Using the bottom plane looks like a no-brainer.
This unit is £1199 street
@@thesleepstate Really, I knew it would be expensive, but that's mental!
Call me an oddball but I think all videos of the unscrewing fast forwards would make a good ASMR compilation.
Another great video Mark, it made my day after work to relax and watch.
Cheers future watchers and enjoy.
The front of that Kinki looks like it has been made with a scraper, what a beautiful piece of kit.
Danke!
Another great fix and Kinki look great build quailty :)
An electronics engineer would laugh his ass off looking at that thing. The case is impressive the rest not so much.
Etching the transistors while selling replacement parts is an interesting choice. It's a shame they couldn't go full on right to repair but looks like a decent device overall.
Excellent as always👍👍
Those Exicon outputs are excellent devices; some of the last really good power audio transistors. Based on the old Hitachi LatFet (and made in UK). However, the Kinki engineer is relying too heavily on how forgiving these FETs are with thermal runaway and breakdown, considering the size of the heatsink. If they ran the output at +/- 40 volts it would still have buckets of power and probably not overheat.
Thanks Mark,
I always enjoy your videos
Good to see you're back Mark! You've set the bar very, very high when it comes to electronic repair videos. Different camera angles, zoom-ins, lightening, post-production and so on. I wonder how much time did you spend making this, relatively short one. ;)
hear hear, Mark does a great job, smart and capable guy
Those that know, know how much thought & time this takes.
Excellent job Mark thanks for sharing 🙏
Ahh great content, thanks Mark
Wow, tidy bit of kit....Nice to see you back mark 👏
I'm surprised you didn't run it under load for a while and test it for hot spots with your thermal camera - perhaps if it returns in the future? 😊
Same thought . The burn Marks are below all 4 transistors, so all 4 overheated
This headphone amplifier have a big aluminium case, but output trasistor mounted on little heatsink. Case can be a good heatsink.
I would take advantage of that huge bottom plate and mount them onto there.
In this amplifier, you can simply place the output transistors on the bottom side of the printed circuit board, bending the leads and fixing them directly to the bottom of the case. The main thing is to use an insulating thermal pad. As is done, for example, in the Burson Soloist HA160 amplifier.
@@arenaengineering8070 The Kapton tape used here seems like a bad idea, seeing as it's best known for its thermal insulating properties. A thermal pad would definitely be better.
What's the reason for the transistors being unable to make direct contact with the chassis?
@@jamescollins6085 The case of the used output transistors is not insulated and in direct contact with the aluminum chassis a short circuit will occur between the + and - power supply. Kapton tape is used in this amplifier more as an insulator.
@@arenaengineering8070 Thank you for the explanation.
Nice to see you again, Mark!
Time to get KINKI with Mark! Let's do it!
As usual, the Chinese doesn't know how to spell. But I was surprised by the build quality and the component selection. At least the ones that survived the anonymisation process.
The heat sink for the transistors appear to be no larger area than the transistor backs themselves… so there might be some thermal lag but there isn’t going to be much heat dissipation after about 15 minutes of use… looks like that heat sink could do with some fins or thermal coupling to the chassis (which looks a bit awkward given their position!)
Thank you for posting 👍👍
It was quite common for low value carbon resistors in TVs in the 70s to reduce in value - the cathode resistor in valve frame-output circuits were notorious for it. One always checked the resistor in the case of valve failure - if neglected it could cause premature failure of the new valve.
Quality balanced connectors possibly the reason they are used but it does seem strange. Nice unit, made in China! It would have been nice to have done a performance test, i.e. frequency sweep at various gains and THD to see if it was worth the money... Great video at usual, thoroughly enjoy them but this was a bit short!
As usual, Mark is the best.. :)
Youre back , great episode Mark!
I understand very little, but holly cow is that beautiful!
The Engineers that designed the thing clearly didn't want the likes of my novice hands to go gleam inside it's internals, what with all of those different sized screws and what not!
Wow Mark, awesome stuff. Thank you
thanks for all the informative videos you make
By the time you were able to afford this sort of kit your hearing has deteriorated to the point a 1990s Aiwa all-in-one would suffice...
I wonder if one of those MOSFETs had gone unstable? In earlier days of MOSFET power amps Ihad a few go like that. They can osciliate in the GHz region, too, so you see nothing on your scope. The ferrite beads on the legs are a hint that it might be an issue. With one brand of power amp in the 80s, I resorted to the old radio amateurs leak testing trick of a wire loop with a PIN diode and a small bulb to see if the power amp I was looking at had turned into a transmitter.
Like always, great work!
Mend it Mark notification. Ah! the parts have arrived for the AIWA tape deck. Nope, we've gone all KINKI from China.
Looks like the balanced output will only be truly balanced if you give it a balanced input - in that case it's acting as a passive preamp and grabbing what it needs to drive the headphone amp only when you have phone selected.
It looks like a nice piece of kit, but given that it sells for £1100 you'd rather hope so!
That’s one chunky chassis! I hope it sounds good on the output side!
I have an Allnic preamp which certainly looks good and works well, but when you actually look at the way it's been made, you find issues, such as you discovered with this Kinki not being balanced.
China is all about 'look' and not about 'form'. They often produce products like this that have the appearance of 'expensive' but they cut corners.
@@sw6188 Allnic is a small Korean family firm who, for example, hand wind their own transformers. They are not associated with shoddy workmanship although their design choices can be unorthodox.
Also, not Chinese.
great vids mark . would be nice to listen to the repaired equipment operating in real world use
I'm not sure Kapton tape is a good thermal conductor. It has fantastic thermal stability and a great electrical insulator, but I don't think it is a good thermal conductor. This could be part of the failure mode, if heat can't be removed from the semiconductors it will hasten their demise.
You're right, but kept it to the audiophile factory spec. There is such a high voltage across those transistors, it wouldn't take much current to get them toasty!
I love your lab environment.
You would think if they were throwing that amount of money at it you would have transformers feeding the XLR outs. Also I think it’s a bit overkill sanding off the component text. I think if someone was looking to copy the idea they would not copy this design!
A good balanced output stage can be done cheaply and well with op-amps but yes, for the money this thing costs I would expect to see transformers in it!
Great channel, one of my favorites. Just one observation:
Mark, when you did put the four fets back together, mounted on that aluminium plate, one of them seemed to turn and shift. Second one from the left. Like it wasn't torqued down?
Worth checking the video possibly.
Nice one, Mark. Interesting that the XLRs were not truly balanced. I also wonder if the owner inadvertently shorted one of the outputs. The overheating of the PC board didn't look good either.
Top video this one ,! well done, enjoyable and knowledgable ( as always )
Very entertaining and educational! Thank you.
I don't understand the use of kapton tape on the heatsink. Is it a good conductor of heat? I always thought it was a _bad_ conductor of heat, and hence why it is used to cover components where a hot-air gun will be used. I'd have used thermal pads on those FETs instead.
My thoughts too.
People are saying why have a large piece of thick aluminium as a case, and not fit the power transistors to it, well i will explain, the transistors collector is live,+- 80volts ,and your relying on a piece of very thin kapton tape,just think of the shock risks,if the tape broke down,swarf etc,the case would be sitting at 80 od volts (enough to give a shock) ,its that simple,it wouldnt meet the safety specs,even though its made in China.
@@enoz.j3506 We just used the regular mica washers & silicon grease under our power transistors that have 1200V on them with no problems!
The pcb should NEVER get so hot that it discolours like this one did. It will eventually become conductive. The uniform discolouration under all the mosfets means they've ALL been overheating.
$1000 for a piece of 💩 that just looks good, feels heavy, but WILL fail! Kinky CRAP!
@@nevillegoddard4966Yes ,as a qualified electronics engineer,for 40+ years,mica washers and silicon grease was & still is, widly used,mica withstands 1000 deg c,Kapton 260 degs c,big difference,got to look at worse case cenarios,to blue the legs on those fets,i dont know ,as you say the fact that the pcb is burnt means,bad designe & will conduct eventually. I dont know why they didnt use insulated fets,then bolting to chassis would be the way to go.Its made in China,nuff said.Make it look good and it will sell.
I'm sorry but you're wrong. 🤭 I'm an electronics engineer my self with +30 years of experience in radio&radar. Look at my comment.😉
I use kapton tape to STOP heat transfer. Does the kapton tape behind the mosfets actually stop the heatsink from acting like a heatsink? That'd be my guess why it failed.
For sure, that tape should not be used in that application but also those transistors shouldn't get anywhere near hot enough to fail even without decent heatsinking.
well,aiwa is ,i think, way pain ina ass. HOPE THAT we see that soon enough,thumbs up. Thanks,Mark,top guy in repair business.
Mark is my hero ❤
Well done!
I Always buy Japanese products, whether they are are vintage or brand new! I have vintage Japanese audio going back to the 70s and 80s which has never failed! The only works I have carried out to them, is replacing the capacitors, a few transistors, few resistors and update the speaker terminals and RCAs! Chinese amplifiers look nice, but they use very cheap components, is grossly over engineered, and very poorly ventilated! The same fault will occur due to poor ventilation! The customer should work with Mark, to fit a fan on the outside, and make some vent holes in the casing, because Mark is an exceptional, wonderful, talented gifted engineer!
Mark can you make a video on testing balanced outputs on the oscilloscope ?
Capton tape is terrible as transferring heat. No wonder they cooked themselves - Mark get it back and put some mica or silpads in do a proper job
0.1 to 0.3 W/m•K ish versus 400 ish. Nah... be fine...what's several orders of magnitude between friends...
I was wandering about that! Not being an engineer I assumed Mark knew best and let it go. Thanks for the info.