Technics SU-Z2 amplifier repairs

Fixing up a nice Technics amplifier. Since finishing the video I have had the amp running for a few hours. No more problems :)
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Also check out my other KZbin channels:
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[@sunspot42]

I loved the design language Technics used from the mid-80s thru the mid-90s. This little amp looks great, even if its internals are so-so.

[@hooben...5211]

I really enjoy your problem solving and how you walk us through the repair!

[@DrCassette]

I'm glad you liked the video :)

[@bob7872]

Nice dumpster save! Good to see you are able to repair and reuse equipment, and it was just right for your needs.

[@DejanTesic]

Used to have the exact same one 25-30 years ago (only silver). Sounded good and never had any problems with it...

[@petersimpson5859]

The first amp I bought in a second hand shop in the 90s. Quite a powerful little amplifier and definitely sounds better when warm.

[@benkrake3678]

I had a Technics amplifier very similar to this one back when I was in high school, it was an SU-V2. A few differences with mine, it was silver not black, and it had fluorescent VU meters instead of the needle VU’s. Only problem was that by the time my father handed this amplifier down to me, only one input worked and that was the AUX input. Would have liked to get that amp fixed but I just kept using the amp on AUX input until the amplifier stopped working all together. It was a great amplifier though, 40 watts per channel I believe. 🙂

[@msylvain59]

The tape monitor switch. It is always the tape monitor switch that creates problems, just like if it was its only purpose.

[@macdaniel6029]

Yes it is. I got so many Technics receivers/amplifiers in the past 10 years or so, all had this problem.

[@phill_strange_media_1980]

Yep, same as mine! Takes a bit of fiddling about with it to get it working/sounding rite.

[@SonnyKavanagh]

Thank you, as always great work.

[@vfdffdd2675]

I don't have any voltages on outputs, but left channel ihave distorted sound and low. Is that mean stk is bad? I clean all contancts

[@DavidBerquist334]

I have a optonica 40 whats per chanel this looks 35 whats p/c my opronica draws 160 whats from wall outlet what is the power consuption

[@Seiskid]

Nice looking amp. Looks smart. No speaker protection relay and a STK chip makes a scary combination tho!!!

[@DrCassette]

For as long as you don't short them out the STK circuits are quite reliable. So the missing relay is not too bad.

[@Fabiano64Berbenciuc]

I own the smaller Z1, beside 7300 (discrete out) . It has STK2028. It has no problem with low impedance speakers (4 ohms) as long as you do not short the output. It will just lower it's power on 4 ohms, while on 8 ohms it will go normally. It is "safe operating area" protection. Drive with it some jbl lx 55, and can go really loud, no overheat. So it is a good amp. 6 ohms are also good, will not forge The amp. Even a discrete amp with relay may be roasted by a short.

[@EastAngliaUK]

I now use a harman/kardon HK 980 Stereo Amplifier in my stereo set up this is a beast though your small amp is very nice to lucky it did not need much work.

[@eggshellskullrule7971]

Ah I see. This is a Sanyo STK hybrid based amp. I know how it sounds: open and sweet. Congratulations!

[@BondedMusic]

Very helpful video, helped me fix mine & it was the bass switch as well! Similarly, after a bit of contact cleaner & just putting it back together again - it worked! I didn't need to totally dismantle & check solder points but helpful nonetheless. Beautiful amps & looks good in black too! Cheers.

[@chylogurti]

Hi there does the vu meter just pull off the board that it is attached to to change the lamps please? Thank you

[@Skuglyft]

Okay. So both channels are working now after I rattled the tape switch a bit, right one is lagging a bit behind tho compared to the left at the DB watts level. Any solutions?

[@DrCassette]

That's probably caused by more bad contacts.

[@gasolin75]

Also had the tape monitor problem on my Techniocs SU-8600

[@harimelilepi]

Great video!thanks!ours is working fine,except from the one speaker.can this be fixed?

[@DrCassette]

This means one channel of your amplifier has a problem. Try to carefully move all switches and adjustments to see if there is a contact problem.

[@farfthi]

Dr Cassette, Do you think good old gear is being destroyed in Germany’s zeal to recycle old electronics? I saw some stuff go into the orange recycle container in my town that didn’t look broken. I thought then that interesting stuff is going to disappear.

[@DrCassette]

A lot of nice old equipment is being destroyed because in Germany it's very difficult to sell used electronics. They can't just simply take all the equipment that still looks good and sell it "as is". So everything that arrives at the dump just goes straight off to recycling. But I also don't think there would be much of a market for selling used electronics "as is" locally.

[@00mouse000]

Did you know if it's possible to use a 2x4mmq speaker cable? Mine won't insert in the speakers output, simply it don't lock...maybe some plug or adapter? Please help thanks

[@DrCassette]

The speaker outputs indeed are only designed for thin wire. Use short pieces of thin wire in the connector and connect the other end to your good speaker wires.

[@robertdrinkall8947]

Needs 4mm speaker posts. Too many of these type of amps use those Block power amp modules from that time. They have built in protection, but can still blow & you can't get them.

[@sergiomiranda5831]

Hello! I have buy one. But last week, the left power left stop.. the sound is normal, but the indicator stoped. Any sugestion? Thks.

[@DrCassette]

The sound output is normal, but the meter does not display anymore? That's probably a mechanical problem with the meter.

[@RG-ls2db]

Thanks for the helpful info. I might give this a try. my left channel starts to fizzle out once it is warmed up, would this issue change your diagnostics?

[@DrCassette]

The fact that it happens when the amplifier gets warm would hint towards something like a bad solder joint, or something else that is a temperature dependent problem

[@RG-ls2db]

@@DrCassette thankyou, I'll look at it closer. I'd love to be able to repair it, it's quite a nice sounding amp.

[@dykodesigns]

But, is the pot of the bass control still good? I guess it wouldn’t be that simple as to replacing that single component.

[@DrCassette]

Let me put it this way: The bass control potentiometer must still be good. Replacing potentiometers is very difficult as there are so many different mechanical designs. I don't think I would be able to find a replacement that fits. All I could do is try again with contact cleaner and if that fails I'd have to disassemble the entire amplifier to get out the potentiometer to then disassemble it to hopefully repair any mechanical fault that may be present. However, at the moment the amplifier seems to work fine, so I am optimistic that I won't have to do that.

[@danvanlandingham3854]

Where you have no speaker protection,can you wire in fuses in the audio circuit?

[@Pro1er]

I believe he was referring to any power-on transients.

[@DrCassette]

Some amplifiers have fuses in series with the speaker outputs, but the fuses are often too slow to really prevent damage. They will keep the speakers from blowing up completely, but they probably won't help the tweeters, and they won't protect the STK circuit from shorted speaker outputs.

[@ceinodowd1841]

Does anyone know where to get replacement speaker outputs? Mine broke when I moved them

[@DrCassette]

These speaker outputs unfortunately are very fragile. To my knowledge, there unfortunately is no exact replacement available, so you will have to get creative.

[@coletrick8748]

Dr. I sure do wish you would’ve showed us spraying the cleaner on the pots.

[@ITTFami]

Technics really was into making some really short components back in that time... My RS-B18 tape deck is as short as this amp, and I recently got one of their amps from the same time period in for repair, and it was really short too. Saves a lot of space it you have an all-Technics system, but it's pretty much impossible to stack these together with different gear.

[@WaltonPete]

That's where the judicious use of sticky feet comes in handy!

[@vdochev]

Dr. Cassette's magic repair, LOL!

[@Pajo97]

I got the same amp and i got a problem There is no connected speakers and when i turn amp on pointer of left channel jumps at 100db and stands there, after i turn amp off right channel also jumps at 100db and then both are slowly going back to 0 I m not sure is it burned or what. Sorry for asking, maybe it s stupid question, i m beginner in this so i have to ask someone.

[@DrCassette]

First check for the presence of both DC and AC voltage at the speaker outputs.

[@Skuglyft]

I have this one but the right channel seem broken. Won’t work at all and nothing moves in the right DB window. Have to use left channel for both my speakers and play via main/remote at the same time. Wish I could repair it because it looks so neat

[@joriszsz95]

Maybe i have the solution for you. Do you still have this problem?

[@chylogurti]

I have the same problem with the left channel. Regards@@joriszsz95

[@haydenhoneyfield6155]

what bulbs do the vu meters use as i need a replacement

[@chylogurti]

Hi there Did you find the answer? Mine are dead. Not replacing. Cheers

[@chylogurti]

Another great video, Doc. This amp is very similar/same as my Panasonic SU 2700. I have one with the same left channel problem. It is when I use both speakers and headphone jack. I've just squirted the balance, volume bass and treble pots...or tried to. Problem is still there. Would it be worthwhile spraying everything inside or is that just hopeful thinking? Thanks . Keep the videos coming.

[@DrCassette]

If there is no trace of audio even after spraying the controls, the problem most likely is somewhere else.

[@chylogurti]

@@DrCassette Thank you for the reply. Just picked up one these , filthy. All working except the power vu bulbs. Not sure how to change them. The inside has 40 odd years of dust/grime. Big job if I decide to clean. Great videos, amigo.

[@breezebenitses397]

​​@@DrCassette hi there my Z2 had the same tape monitor issue as yours. Sorted. Both the vu do not light up. Any suggestions or videos please would be gratefully received. Love your commentaries. Keep up the great work.

[@rogerw9840]

Watching this and playing the audio via my su-z22 (the generation after). It also needed a fader lube shower. ;)

[@tonybalm1513]

No speaker protection relay but there is some sort of transistor switched muting circuit which I have never come across before.

[@DrCassette]

The problem is this electronic circuit may prevent a 'pop' coming from the speakers when the amplifier is powered up, but in case the output stage shorts out, it will not protect the speakers.

[@tonybalm1513]

Yes that's right but I have known speaker protection fail as well. This amplifier is clearly from Technics budget end obviously trying to save on manufacturing costs.Technics did adopt a belt and braces protection system were they removed the drive from the output stage which protects it and the speaker system.This was used in the SU3500 an earlier amplifier from around 1976.They also went back to this system on much later amplifiers as well. I have however replaced output chips which have blown even with this system on a Technics SUA900 from the 1990's.

[@andxx0r_the_second671]

I admit I've never been a fan of Technics' amplifiers, especially their masonite-chassis receivers, but this one has a very handsome simplicity to it.

[@cyelannford4735]

Looks like a Philips IAmp I had back in the day. Incredible sounding unit.

[@killmore75]

Be good to it. Good luck looking for a replacement for the "intergrated ouput" : (

[@DrCassette]

The STK circuits indeed are quite difficult to get these days, and those that are available are very expensive. Apparently the Chinese are also selling fake STK circuits.

[@fiero2]

​@@DrCassette Yes, I agree with you on the fake STK 2038 (specially series 1 with 16pins - because there is version 2 with 22 pins), I have two STK 2038 B, 16 pins , based Technics SU-Z55 and I cant find real replacement for the IC. I bough 3 IC's from different sellers (Alliexpress, Ebay and local electrical parts store ) and all of them are fake ! And the bad thing about this particular STK 2038 16 pin hybrid IC is that there is not schematic or PDF document, from which I can see what is inside and to try to replicate it on a new PCB board with discrete components...

[@electronicwaves]

@@fiero2 Hello, I recently fixed my Technics SU-Z45, it had blown right channel on STK2038B. I found replacement STK from ebay and after I installed the new STK, the amp works fine. I know that the STK I ordered is probably fake, after all they have been discontinued more than 15 years ago. I would like to ask you or anyone who might know, what is the problem of using a non original STK amplifier?

[@javierdece]

Does this amplifier have pre-amp integrated?

[@DrCassette]

Yes, this amplifier has an integrated pre-amp with inputs for line level sources and a phono input for record players with moving magnet cartridge.

[@mister1der]

STK2038 50 + 50 w min...good wattage for a room listening music amp.

[@jamescollins6085]

That is a beautiful amplifier. From the front, at least.

[@killmore75]

hehe!

[@ronbradshaw7404]

Has the Sansui colors and vibe...

[@jamescollins6085]

@@ronbradshaw7404 Now you say that, I can also see it. It's minimalistic, yet it still lookss quite densely populated.

[@polykarposz]

Ah Technics.... You are always the same. I have one su 810 and the tape button messes with the L R output. I currently don't have any contact cleaner. Can you suggest me something that will do the job?

[@DrCassette]

I usually use Kontakt Chemie Tuner 600 for cleaning switches and potentiometers.

[@polykarposz]

@@DrCassette I used a wd 40 contact cleaner it did the job ok now I have sound at both chanels

[@Fabiano64Berbenciuc]

What speakers are you using

[@DrCassette]

The test speakers on my workbench are just some random Eltax brand speakers I picked up at a flea market for 5€. You don't want any nice speakers for testing, in case something goes wrong and they burn out.

[@differentname8051]

I had the same amp only in silver, the right channel shorted out.

[@harimelilepi]

And can you fix thiw somehow?

[@pabloosvaldopenizzotto1098]

Pretty similar to the Sansui A40, A60 and A80. The front is almost the same design, and the back is totally the same.

[@pabloosvaldopenizzotto1098]

calee4nyaboy what Sansui are you talking about? The A40 I have used for decades was a model that got problems with overloading and overheating, and was repaired a couple of times after I changer the heatsink for a bigger one. Then lasted in use till early 2017 !! I bought it when I was 17, so I used it for more than 30:years!!

[@priestblood]

I noticed when you had the bass problem you where connected to tuner input and when you where problem free you where back in aux ,might be nothing but worth a check over .

[@DrCassette]

That was actually a part of the fault finding process, I noticed the problem when the CD Player was connected to the AUX input, so I moved it to the Tuner input to try and make sure there was nothing wrong with the input selector switch.

[@ImmortalDuke]

Have one of these. If it sounds good, do not touch it. If it sounds weird, just wiggle the tape monitor. Some say that with RS-M5 casette deck and an electric guitar you can blow out speakers and record it.

[@RUfromthe40s]

hello, i have the model that came next ,with this alternative colour scheme from technics without needles on vu meter but crystal liquid meters but without any tape monitor it as tape inputs but no monitorazing and a rec selector it seems to be the 1980 model so it might be worse than that ,the problems you´ve find are the same as mine that problem with the bass volume always on maximum is the same problem you found on other switches not auto repair , maybe you didn´t try to move the potenciometer inside to be cleaned or free it from being stuck, with mine i left it working ,this before cleaning it and some only from being working they start to work again normally as you refered the dust won´t came out because the moist through the years acts like glue with tiny particules of dust, this is the basic integrated amplifier from technics at the time. I own one but with a higher reference ,this one always worked on my home office so it only start to make some noises on the volume control and tone also in a switch like the loudness one but on a filter, this only to arrive to the conclusion that technics is a good brand but with the passage of time doesn´t seem to endure that much ,i own a turntable maybe from 76 the SL-3310 direct drive full automatic (mechanical) witch is great to see how they manage to have so many functions working on this turntable, later it came out with a quartz engine and renamed SL-5000 ,this i´m using it till today since i bought it ,i have others but this and a pioneer from 74 bought in japan are the ones i use them almost everyday, so not everything is that bad ,i think sanyo it´s the winner on get damaged with time only, when new very good after some years all wrecked, at least in my experience ,i bought a what they call now a boom box ,although there was ever no boom coming from that box, when in the first week it started to give problems, so sanyo was a brand i put on the no more list, regards

[@xhabirzejnuni6652]

Complimenti.

[@CVH72CHANNEL]

I like these video clip because it's very helpful

[@m80116]

What kind of electro-CRIMINAL would send such a beautiful unit to the dumpster? And I appreciate a nice compact vintage looking amplifier in such a small package. The fact that's using an STK integrated hybrid just speaks for the advancement in technology and integration of the day. Great little unit that I am confident can be miles better than anything on Amazon in the 250 EUR range.

[@DrCassette]

The STK hybrid circuits are not bad, I never had an issue with how they sound. However, I did find they run rather hot, and there is no protection at all. If the speaker outputs ever get shorted, the output transistors inside the hybrid circuits will fail and finding replacements for STK circuits that are not counterfeit is difficult these days.

[@m80116]

​@@DrCassette Ah-ha, maybe also because they've probably stopped producing them... didn't they? I am wondering if these Chinese copies are really that bad. I have one SONY that has such STK... well, at one point pretty much the whole line-up had STK so... unless you went QS or ES that was it.

[@DrCassette]

@@m80116 The STK hybrid circuits were made by Sanyo, and Sanyo does not exist anymore. But many of these circuits have not been made in decades before. So far I have only heard warnings of the Chinese copies. They don't have the output power they are supposed to have, or don't work at all. Many are not new, they are old, untested circuits salvaged from e-waste in recycling facilities. You can never know what you get, but they are still quite expensive.

[@DavidBerquist334]

I just googled it its 35 whats perchanel 1981 nice unit

[@HDXFH]

STK 2038, 2x 50 Watt, not bad

[@myturkishlife1777]

Friend of mine had one new, it was silver and cost £80 in 1981 😁

[@andyboa8107]

Excuse me, which exactly National Panasonic receiver model in wooden case did you trade for this Technics amp. I want to know how loud I should laugh at you :)

[@DrCassette]

I wanted this Technics, I didn't care for the National Panasonic. It was a good deal.

[@andyboa8107]

@@DrCassette OK, just tongue in cheek :) So which model of N Panasonic was it? If you prefer the sound of this Technics then good for you. Oh and I forgot. Technics amps of this vintage have sometimes broken traces so that it can't be seen. When you check continuity from solder point to solder point you may find out. But here it could be that bass potentiometer that cleaned itself by soaking and some use.

[@DrCassette]

I don't remember the model number of the National Panasonic receiver. Sorry.

[@ManoelSilva-xc8dn]

Que maravilha de Receiver

[@joseph9770]

This series by Technics looks suspiciously similar to a few Sansui units I have in storage....

[@DrCassette]

It does, but I don't think they are entirely the same.

[@owndragon2154]

Good vid, although i would have never bought an amp on STKs (as power ending) for obvious reasons.

[@DrCassette]

The STK circuits are okay, just be careful not to short the speaker outputs.

[@jackturtle131]

Good on you mate love your old Sennheiser headphone from the 70/80 s

[@DrCassette]

To be honest I don't like those headphones. The foam earpieces only last a few years until they start crumbling. And they don't sound that great. Better than some Chinese junk earplugs for sure though.

[@zerostacker2k00]

Ich hab den in Silber.. die Potis wurden mit dem selben Tuner Spray gereinigt. 😄 Irgendwann werd ich mit nen Kollegen die Lautsprecher Terminal wechseln, damit wa einfach unsere Bananas nutzen können, da es nervt immer ne dünne Strippe rauszukramen. Ich han das ganze Gehäuse in der Wanne gereinigt und nen Tag draußen Trocknen lassen. Die Platinen in Isopropanol gebadet. Schade an dem Technics ist das die Schalter als Plastik sind, die Drehregler nen Plastikinlay haben. Da ist mein Kenwood KA-3300 besser verarbeitet mit Rasterung im Lautstärkenregler

[@dayakarnadipalli5315]

This type we required amplifier

[@tonymontana897]

DeOxit my friend..

[@DrCassette]

I have never had any problems with the Kontakt Chemie products I use, they are easier to find and cheaper.

[@dannyjaar]

replace some caps al problems are gone

[@DrCassette]

I hope you are joking :)

[@705johnnyboy]

if this generation knew about vintage gear we would never get a chance to get this stuff ,all you nead is spray and a little knowledge ...

[@arnieworkoholik6883]

Kontakte vom Tape-Monitor Schalter einsprühen !!

[@DrCassette]

Video vor dem Kommentieren zu Ende anschauen!!

[@matrempit2885]

STK again...! Oh Lord......

[@raymondleggs5508]

Mitsubishi transformer

[@DrCassette]

No, that is the Matsushita logo on the transformer. Matsushita was the parent company of National, Panasonic and Technics. Now they are calling themselves Panasonic.

[@RWL2012]

@@DrCassette my tutor in college asked my class in late 2008 "which company is Technics a brand of" and I said Matsushita, and him and my classmates laughed and he "corrected" me and said "no, it's Panasonic". After looking it up later I was kinda annoyed, because the company legal name had literally only just been changed to Panasonic Corporation to reflect the Panasonic brand, following talks with the Matsushita family...

[@DrCassette]

@@RWL2012 Interesting, I thought the name change had happened a lot more recently.

[@keter1234]

Jump to 3:45 to skip over the useless back story and the dump story.

[@dennisduran8500]

Unless you're a technician stay clear of old stereo equipment.

[@DrCassette]

That's nonsense. A lot of the smaller faults in old stereo equipment can easily be repaired. Of course, all safety rules must be observed carefully. Unplug the device when working, make sure to stay well away from any parts carrying mains voltage when testing.