I used to fix the STK'S Modules back in the 80's thanks to the ECG replacement book .

I recall when I used to do these projects.... Extra cautious and precise with the builds and use over designed parts like Teflon insulation.... Then the heart stopping moments when it does not work as planned and then the endless hours of fault diagnosis.... Then finally the hallelujah moment when it all comes together.... And it always does

I love your videos! You're very thorough and in electronics that can mean the difference between life and death! My name is Andrew and I live in Melbourne Victoria Australia! Cheers!

Very timely! - I got an SX-780 for free from a ceramics clay studio where it had been abandoned for over seven years - it was filthy and full of dust and clay spatter - anyway one of the STK-0050 modules was bad and I happened upon this solution about a week ago - I just got my PCBs and was ready to solder down the transistors when I called it a day and saw that you posted this video - I picked up a few tips that I will definitely use - Thanks Tony!

i really enjoy the videos, very fun to watch tony, thank you.

Another excellent, dependable video, many thanks! Peter

First of all Thank you Thank you Thank you Thank you !!!! This is a video I was hoping you'd do Anthony. Beautiful stuff. The idea came about, i believe, by both Rick and H Brown from A.K and another member Zebulon had the actual PCBs made. Nice collaboration with the thread reaching an epic proportion of interest. You can get the kits on ebay from Zebulon directly. Hardware including PCBs and mounting blocks with the BOM. I got mine when they were 22 bucks. I have purchased two sets for myself as I do have a Minty SX-780 and incase they were required, I'd make the upgrade. But for now, It is running the original STK-050s so no need just yet. I was thinking about purchasing another 780 with bad outputs so I can do this project. You're the man Anthony !!

Great presentation - very viewable.

Great Video Tony Liked the bias setup and the use use hantek I just got the hantek 6052BE Thanks again

Awesome video! I have two 780s and one has the output modification and one is stock. They both sound very similar. The one with the output mod has been fully recapped as well.

I think living in the UK has distinct disadvantages when sourcing these kind of components, especially for tube gear. if you can source them they tend to be extremely expensive, and when ordering from the US you get hit by excessive shipping costs and UK customs fees. if I wasn't so ancient I'd move there. Rant over! Anyway, I love the video's and am still learning new ways to do stuff. Keep up the sterling work.

Thank you for this complete technical video. These new modules are neat! Back in the end of the 80’s i was servicing amplifiers for a big store in Montreal. These STK modules where in a lot of models and brands. One brand in particular was problematic. It was Fisher. I don’t know if it was a flaw in their circuits designs, but 99% of the « STK shot cases » where with that brand. Few where Sanyo though. At the time it was a big disappointment to see them in Pioneer receivers, but in fact, not one Pioneer ever got to my bench. Note: Fisher’s quality in the mid-80’s was already not the same as what it was in their golden era. In any case, back then we where dreaming for such replacement solution to become available. 😊

I wish someone comes up with something similar for the great kenwood kr-9600. Great video. Thanks

Thank you for such a comprehensive video!!!

1st job in 1982 was working in an electronics repair shop, replaced many of those STK's back in the day!

EXCELLENT VIDEO - Huge amount of good info. THANKS!!!

How true and what a nice replacement kit. An amp only dumps power from the power supply to the speakers.

Amazing video, very clear and explicative. Thank you!

I've always been against IC power amplifiers because of thermal issues and reliability(especially stereo IC's)it seems there's too many high power components in a small space for my liking- but this looks like a good "cure".Good video Tony - Thanks. All the best from the UK.

Awesome work and video!

...I'm late to your video but would just like to say thanks so much for your detailed instruction. I have an SX-780 which I purchased new and am in process of getting the necessary components for this upgrade. This will be a fun project indeed! One comment in regards to solving your camera situation; you should look into an overhead camera mounting which would eliminate working around your camera setup as it is. They are not expensive and readily available on Ebay and Amazon...

Excellent video! Almost confident to do this myself!

I bought an old Sony N-220 4 channel power amp which is based on two stereo hybrid amp modules. I use it to drive a pair of 2 way loudspeakers via a cheap digital frequency dividing network. This sounds surprisingly good, warm and sweet yet having a tight bass and high frequency response if required.

Never apologize! I knew you would fix the camera shake. Good job!

I think you will really like the Leader generator. I have 2 of them and was lucky enough to get the optional remote mount control head for one of them. Used them for several years before upgrading to more modern generators. Collecting dust now but plan to dig them out one day and put them on another bench. I bought out a consumer electronic repair centers inventory many years ago. Got piles of the vintage STK modules. LOL, since I got them I haven't needed one of them yet. Can guarantee you if I sold them all today I would need one tomorrow. You never seem to need the rare parts when you have them. The silpads have far better thermal characteristics than the old school mica wafers. Buy high end reinforced ones. The ones I have here are impossible to tear.

I really liked the video. Very good informations .

Tony, Thanks for drop-kicking that old camera mount. This looks MUCH better!

i never had a doubt in stks i had old aiwa amp 50 wts. per channel mind blowing sound at high power levels too bad sanyo s gone they made some great products .

X ray tony hits another grand slam. Great video and thanks for the tip on the Leader LSG-216. I have been looking for something affordable that can send a multiplex signal for aligning many of my Pioneer SX receivers. I picked up the first Leader i saw on Ebay and at half the price of the sencore and other brands. Now I look forward to a tutorial on how to use it for aligning FM multiplex as the user manual is not very informative.

Very nice your tutorial

MAN... I'd kill to have that signal generator. Great find!

I picked up a 780 from the original owner, has never been opened or worked on. I ordered these assembled from the guy in Canada. when the time comes, I will install them but right now the thing sounds so good that I do not want to touch anything.

great to watch you work. thanks for making this. Once my new (1950 east german radio) is out of the shop ill be doing little work myself fitting a bluetooth module to it something like this could be the next project for me if I am allwed the space.

Hurray for that camera mount! I will shoot fireworks in your honour tonight! Just last week, JohnAudioTech posted a video testing and comparing the performance of different sorts of heat sink pads. Mica was the absolute winner, hands down. The differences in heat transfer speed are quite impressive.

Awsome, thanks for sharing

A lot of these STK modules are now over 40 years old. Reliability in now a issue, this kit looks like an awesome replacement option

The kit talked about from Bob is top flight. Well worth the money. Get the BOM and buy your own parts.

👍🏻😎Luckily, I was able to find a genuine Sanyo NOS, STK 2038 for my project.

The Kenwood KR-5010 also uses the STK0050. In similar fashion the Kenwood KR-4010 uses the STK0040 Darlington Power Packs. :)

I have an SX 780 with one working channel and one dead one, so i was pleased to run across this video. I'm considering the pre-assembled ones as it's gonna be a big job for me as it is. Thanks Tony!!

I have one of these old chips, if i remember it was B+/- was 24v. They crank good! Not sure of the # on it, it was 60 (real) watts a channel. Came out of a 'Project One' car EQ-Booster. had an inverter on one side, and the amp on the other. Got so hot it cooked the black paint off the heatsink fins.

The STK 8250 modules in my Aiwa AA8500 have given up. I'm gonna go for new copies of the modules. I'll find out if they're any good 😄 It's gonna need a recap too. Lol the repair will cost more than the amp is worth but I love the sound it has particularly from the headphone out.

You rule, Tony! Mr. Carlson rules too, but...you rule, Tony! : )

I bought several sizes of Cooper strips on a small roll it's peel and stick ,I think it should work you can get what size you need ,@and I bought some stuff in a tiny syringe,or a liquid version ,I haven't tried either yet ,I had radio traces that has come loose or off ,mostly I ju no it with a piece of desired wire.

@35:00 I agree about not using the fibre washers. Apart from the thread penetration, I was hoping you would change your mind. I have seen this type of washer deform and relax with time and you don't want the transistors to be half tightened onto the heatsink.

I put buckshot and silicone in the hollow area of tuning knob to add weight, much smoother

Thousands of receivers were thrown out because of Sanyo STK failures, including my Yamaha R-100. These things die from lack of power cooling ( Fans ). Each module was rated for 100 watts.

13:10 Nitpick: Q5 (BD139) is obviously *not* a phase splitter, it's just a plain Vbe multiplier for bias generation, i.e. a constant voltage source. A phase splitter is a follower at the bottom and an inverting amplifier (usually Gv = 1) on top and would be driven from the base. A complementary emitter follower output stage is driven in unison, so it does not require one. If you were to parallel the Vbe multiplier transistor with a capacitor, it would keep on working like nothing ever happened (and potentially make for a better, more wideband constant voltage source). The same clearly cannot be said about a phase splitter.

Realistically you could do this for any STK module as long as you have the schematic with the values of the capacitors, resistors, and the diodes! The transistors can be worked out by the operating voltages and load requirements.

It's a good thing that the STK-0050 is only a partial amplifier. Quite a bit of additional circuitry is needed to get it going. If you had to replace a more complete power amplifier then you probably wouldn't be able to do it with discrete components.

Odd, I have ordered several various STKs from UK and China, making sure the supplier has a positive feedback, and have not had an issue. The repaired amps work and test out fine.

Hi, I love your channel. I am going to do this to mine. I was wondering if there are any other upgrades like maybe transformer or anything else that would also give a noticeable increase in fidelity? thanks again for the video!!

be nice for a stk459 alternative may be ..great video so hope i find a tech to be friend i have a plethora of old thins to restore and ant the best tech

Nice!!

Many people will increase the size of the filter caps. Would that change the results of the last test that you did? And how much would you increase the size if you were to do that? Tuners are still my weakness so I be waiting for the next video. Thanks for sharing.

Dude Mothers Mag And Aluminium polish, steel wool than rag. Just a suggestion of something you can do in the lab without too much hassle. My first tunnel up snowmobile I built I used this method it didn't take that long and when it was done it looked like the tunnel and bulkhead had been dipped in chrome.

Regulators Q25, Q,20, Q19 get very hot. At very least resolder as they commonly develop a bad connection. New larger heatsinks help a lot.

I bought some stk modules from my secret sources in Silicon Valley Cali and they work 1000% i payed $23 each

This was dragging until I remembered the 2x speed option...much better.

A nice tripos to have...do you hang a weight from the center post to steady it..this is done alot in photography ........so it wont shake.

ficou show de bóla

Great video!!! Where do you order a Walnut (or other wood) case? I have a SX-580 that I'd like to have an actual wood case for. Thank you!!!

Great video, X-ray. Question kinda off track from module repair: at the end of this great video, you mention that you hoped the fella that owns this 780 would invest in a nice wooden cabinet for it. Did he? And where can a fella like me find one for my 780? I just had mine serviced and repaired recently and would like to invest in a nice walnut cabinet too. Thanks X-ray!

Question: You mentioned the higher voltage/output capacity of this discrete STK 0050 kit. Would the circuit also work for an STK 0060 or need to be changed in some way?? Datasheet shows the same circuit design as the 0050 but runs at slightly higher voltage and amperage.

Also what do u think about that analog discovery audio suite looks very interesting basically dynamic signal analyzer, thd vs power, fft and goes on found it kinda interesting.

Great video, thank you.

Greetings: since the ac voltage input setting of 110VAC produces a higher power supply output, it would be interesting to see what audio output will be then! Just curious; maybe the previous owner was seeking more output power.

When I try to do the test you do at 59:20 with my Fluke DMM on the diode setting I get 1.058V on pins 1 to 3(+) and .909V on pins 8 to 10(+). If I lift one of the probes and set it right back down I get around .1v higher reading on each very briefly, then it drops back down to the reading I get above. Both of the STKs I assembled give these exact readings when tested (installed in the unit, just like you show). I've checked for any arrant grounds or other obvious problems but I can't find anything. My solder joints are good, sil pads and shoulder washers in place. I haven't tested the receiver since installing them so I don't know if this is actually a problem, I just want to know why I'm getting different results before I plug this thing in. Any ideas?

I'd love to do that with my pioneer sx 780 And restore it. It's been in my family since new. Would you be willing to take on the job? Love you're work.

Thanks Tony. Great lesson! I always try to limit the stress of bending leads by supporting the leads close to the component. It might not matter but I just don't like to take unnecessary chances. Do you have a link for the nylon tubing?

Hi Tony. Excellent video as always, and perfect timing! for a question I have. It looks like you replaced those four MPC70 power resistors with the TWW series Ohmite wirewound resistors. I have four MPC71 0.47 ohm 5 watt resistors that are all measuring between 0.7-0.8 ohms. That seems out of tolerance enough so that I should replace them, correct? I can't find the MPC resistors, so I looked at the style you used. The question I have is this: the MPC resistors don't introduce induction because of the metal plate, but the wirewound would introduce induction. Is that not a concern, or is the amount of induction so small it doesn't matter? I've been waiting to make my order until I could get an answer to this, so thanks very much for your help.

Hi Tony. Do you happen to know how much current does the sx 780 transformer put on each stk0050 and also how much for the preamp section? I want to build a toroidal transformer, but I only have the voltages. Thanks.

Where do you get covers for these units? and is there anyone reworking the covers? all the laminate is gone from mine so its like a light peanut butter brown now :( Anyways, I fixed my unit long before these were available, I cut the STK pack open with a dremel, and soldered new wires in place of the shorted transistors, and ran the wires out, hooked them into new transistors mounted alongside the STK. I filled the STK in to protect it afterwords. Still working today.

What Oscope is that? Super nice!!

The rolls of stick-on copper foil meant for stained glass work are great for PCB land repairs. They're cheap, will stick onto your PCB with a bit of rubbing with a flattened popsicle stick and will easily withstand the heat of soldering. eBay sells them down to 3mm wide but you might find them thinner from electronics repair houses. You could probably make a whole one-off prototype board with the stuff if your design doesn't require very thin lands.

Where can I buy that module? Or are there any plans for self building?

I’d wonder what the capacitance is (we built a capacitor), from the transistor (collector) to the heat sink plate ...

just curious did you try matching or checking the transistor pairs to see how close they were?

You're right , they were clean sounding but had no bass.

Did you ever test the non-bias modules? Are they worth it?

During the burst test, the first half cycle was less than the second half of the cycle. Is that normal for that test?

unless I missed it its actually 3.26v not 32.6v as you state near the end of the video while looking at the clipping.. I'm hoping this was a mis-speak. The wave actually cleans up at around 2.64v not 26.4. I'm basing this on whats visible on the display for the Oscope. And the fact the 780 was factory rated at around 45 wpc (Maybe a little conservative). If I'm missing something do these up the output of the unit? I currently have 3 780's in mint condition but all have STK issues. Thanks!

1:12:10 - How about adjusting the bias for minimum crossover distortion?

So, Could this STK-0050 be used to replace a STK-0039?

They prop. thought they would get more power by doing that. As if you can get a free lunch! That is why the current limiting popped for sure!

sencore made a boombox way way back are they swiss ??

Will that bored work with other SX models like the 680...? Why don't you put a 0.1 poly film cap across the electrolytic filter caps terminals on the power supply? This will increase your wattage even more before distortion? I wish you'd leave links to these sites where to buy it. I was wondering if you can do a kit build from parts Express,, and test on it, these are the same modules using high-end amplifier costing upwards of 3 to $5,000 for about $300 400w they do 1000 watt as well they are 2 monobloc modules with a power supply board. They should be very good as they say high-end manufacturers use them in their amplifiers made by Ice power, class D. I was wondering about having a valve front-end buffer stage put in as well. There called 200ASC power supply and 200 AC amplifier boards modules by ice. They should be really good for the price maybe an upgrade power supply I was thinking of ultra low noise linear power supply about $70. All boards come pre-assembled with components from parts Express. They have a PDF datasheet manual if you want to look at it. They sound like they would be a great build...? You have a choice of 200 Watts per board what you need 2 into 400 watt or 500 watt board what would be 1000 Watts. Into 4 ohms maximum output current 12.5 amps, frequency response 10 to 20000 Hz THD 0.2% dynamic range 110 DBA. I think this would be a great build and even modification upgrades if needed, as I say running a valve front end not sure what to go for there...? built into the unit. Any chance of doing this in the future don't think they will be available for long Tony. PN: 326-210 icepower.

Where can I get one of these mod kits?? Who was yours made by?

Hey Tony, this is a weird one: I’ve just received my 780 back from service. The STK packs were replaced, although not with those nice discrete style ones you assembled. I find that sources sound nice, although there is pronounced surface noise rumble when playing records. I’ve compared it against my other vintage receivers and with multiple turntables. Same result with the phono stage or aux with an external preamp. Have you ever heard of such a thing? How would that be possible?

sil pads, 50% transfer of good old mica

I have built three sets of these.The first one worked great. The last two I cant get to work. The unit will nit start up on DBT when I go full power the relay kicks in but I cant adjust the Bias. Then they get really hot.There are no shorts and all voltages are good. I just think they re cheap. When I put the STK's back in all is fine.

Okay Can I have the name and number of the amplifier ic in this Pioneer vs77

hi there ive been watching your videos for some time now i have a poineer sa 508 amp there are some capacitors have gone but i cant find the capacitors to replace so can you help do you have a listing of the capacitors thanks andy

Aha, the “magic tweaker” struck again .. set at 110V to boost the rails ...

would you do a onkyo tx 3000

What diameter hole did you drill in the copper pad replacement?

I think that a lot of the STK-**** modules have become obsolete and no longer available so maybe a module will have to be built from scratch.

Just looked, here in Canada a single one of these with the parts is $110 plus $20 shipping. The provider mentioned isnt' listed here.

I have no idea what this channel is about or how I got here, but your work area looks like a complete fire risk. You seriously need to purge and prioritise. A tidy ship is a happy ship as we say in the trade :0)

Can I use this ebay circuit to replace a blown STK2250