Technics SU-V90D Amplifier Service & Repair

[Music] today i'm going to be servicing a technics amplifier this is from 1988 to 90 sort of period it's a technics suv 90d this is a 200 watt amplifier stereo it's got a digital input quite a first of the time and this is quite a sturdy unit let me tell you built properly well for a technical let's get some power into this and get some equipment on oh that baby rush on that thing wasn't there oh well this doesn't look too promising well this isn't uh responding to favorably this is a bit crusty this one here this is a bad one oh crikey yeah this is gonna need all the front panel taken apart such joy let's get this lid off for the reveal but it's a good lid very solid perhaps they don't want me to get in it [Music] look at all that filth in here yeah yeah i think it's been in a smoker's home it's all very yellow i've done about a service this thing he said booming bath let's get all these knobs off here this one's a bit that good solid knob that is so [Applause] [Music] screws on the bottom should be about right to get this off now so just a little little twist and that's revealed a bit more i got to clear a bit of room up here i think snip that off there bit of slacks needed so these balls are held with some bizarre connectors if you press them or lift them no this is not good oh that's not how they're supposed to come out well that's annoying yeah look at that this up and down down i think this has been in there for far too long what if it's corroded in or what another one what if there's any chance these wires are on plugs now that one's not around this end that goes into there here we reveal where all the digital stuff goes on yeah this cable just get this dealt with so it is on a plug [Music] plug that works for once we can disconnect the front panel a bit more pull these plugs out this input board that's still a load of them yeah that's coming out next not a ridiculous amount of screws in this that's nice for a change what does that do for us let's keep yanking away there's one there's another i think that's got the front panel loose maybe there's not more connections surely yeah there is under there now will you come out [Music] we're getting there slowly a few more screws to go now it's free it's going to liberate these boards now [Applause] nothing but a couple screws to take out i think these are just little plastic clips oh good don't break anything mark [Applause] same with this board here i can see that there is [Applause] let's get in there oh hello what's this here that's the pots broken the scenes actually broke i've never seen that before well i guess that's got to come out as well so look at this board here this these are the push buttons behind this board for selecting the different inputs and it seemed to all work when i tried it but ah okay no buttons on this board it's hiding underneath there we go what a design i'll whip these out as well not much to see here these little push switches they sometimes go a bit bad so once it's all apart we'll check them out quite impressive none of the buttons it fell out i used to be lucky final thing to remove from the front panel is the phono select switch because this is a flashy amp it lets you switch between the moving magnet and moving in coil cartridges for those with more money than cents so here we are most of these sams troubles are on these boards here just these two dodgy knobs dodgy buttons i'm tempted just to chuck the whole lot in the ultrasonic cleaner apart from the pot that's snapped get that off yes it's looking a bit sad isn't it a bench shaft on there i think that might get damaged if i try and put it back i need to get this apart so see if i can just prise these little tabs up oh crikey that's the back off there's the tracks just don't look at that at all and there's the wiper wipers should i say there's a lot of bits there they don't look damaged which is encouraging hmm we'll see if i have to replace this which i'm not keen on i'm wondering as well is that a cc taper oh well i wasn't pondering what to do with that little pot this is going for a bath ooh i swear down i will change this cleaning fluid very soon but not today looks more like it oh can i get this in as well yes stay there stay there and cleaned let's get these out of here now nice and warm we'll just get those a rinse off under the tap and then dry them i've had to think about how to handle this broken potentiometer i'm thinking i need to file this little collet down and then probably glue this back in i think the whole thing when it's soldered in the circuit board and clamped in it's all going to hold together anyway so it doesn't need to be the best but that's something to do you can just see the little tiny little notches in here i think what they do is push this this into there and then they must use a machine to stake these over you can see it's being banged up there's no way of re-engaging that [Laughter] haha we got it yes put a bit of glue on what could go wrong assuming it will sort of run where it needs to we'll leave that alone for a bit just considering my strategy now if we're cleaning the rest of this up it really is in a horrible mucky state i mean this looks like a cathedral our filth the waist is built though it's just not on plug so if those horrible plugs wouldn't come apart and then we've got all these other wires just directly soldered on irritating so i think i'm going to take the plunge and chuck the main board in the ultrasonic cleaner as well there's a few things i want to do before i do that i might want to take the big caps out because part of that process is to dry out afterwards and i don't really want to put those in the oven it wouldn't do them any good yes get this out we've got a bit to do there's a couple screws here there all generally everywhere of course it's stuck to the heatsink for the transistors but the heatsink itself comes off with one two three four screws there yeah but also my favorite thing all these cables the bloody cable tie on there making my life difficult so this goes to the transformer i don't fancy dragging that around hmm power terminals there this cable here goes to this panel here which to be honest these have got these speaker select switches it wouldn't hurt them to go in the cleaner either we'll leave that on ah putting this cable at the back blimey see now this is moving i think oh that's moving i do unscrew these transistors now [Music] so don't drag the weight of the heat sink around and snap their legs off so if these come loose yes they have we can look at unsoldering these wires let's sort of pull these wires off come on soldier iron do your thing there's one out another i'm going to just fill these up with fresh solder and that allow me to get a lot more heat into them quickly so i try and heat the whole up in one go there we go they pulled out nice and cleanly see if i can do that twice right to the caps on breaking out the big guns now let's let that melt there oh good i just remember the caps are glued down as well just to make life bloody awkward so take the relay out as well [Music] these little plenty poster aren't they 12 000 microfarad caps technics branded i bet they didn't make them and i also bet they're still in fine working order after all this time well check that out at least now we have the board covered in hair and fluffing to be honest it stinks somewhat it smells like an ashtray just dust the worst off otherwise it'll just float in the top of the stuff they've got to clean out anyway let's set this off sailing in you go murky i can really start cleaning this chassis up now gold heat sink compound stuck on this and it's basically turned to like um oh i don't know what to describe it as yes it's gone like window putty that's what i was thinking of yeah i'm gonna take this top board out this is the digital board i might as well take the whole module out so i can get it nice and clean there's not much left of this amp there we go very early digital input now that's out of the way i can actually get in and clean this it is really really nasty in here i think i'll get a brush and a bit of foam cleaner i think i'll start off just brushing the worst off this it is leaving behind a bit of a nasty residue look at that running off down there he asked filthy [Music] [Applause] oh crap there's been a lot of writing on here it's all gone what's really weird is it's only taken the writing off this sort of brushed aluminium bit the plastic facial it's still perfectly good it's not taking that off at all how strange i'm bloody annoying i'll have to be a bit creative with this one whoops now i got these back out of the ultrasonic cleaning and they're all dried off looking lovely gotta put that potentiometer back in so we've got this that i've already glued back together just looking rather neat really what you do is put the shaft back in that turns really like that sitting there nicely then put this metal whatever it is this plate back in there we go now the nerve wracking part is to squeeze this back up without smashing the circuit board so not too much force at all looks pretty good flip it over well that's not solder does it there we go it's always worth checking these over for any loose parts especially after i've had the ultimate clean i can rattle some loose and um oh yeah like here look at that like wobbly teeth this is not at all uncommon in technics equipment that most of the troubles are down to dry joints in fact the more i look at this the more dry joints i'm seeing yeah they're everywhere i just don't need a little bit of a touch up little crack connections still a bit loose but i think that's just uh i think the tracks have actually lifted a bit a good idea just to check the continuity around that area well this ends easy how's that snake round here yeah it's okay no broken tracks just checking this board as well the push buttons so there's nothing untoward on here this doesn't look too bad at all just want to check now that the the um switches are functioning properly so i do is just make sure that they're all safer all pushed in and just check from this side that we've got the right sort of continuity now whether they top the bottom pins so the two pins this side and here pop them back yep they're all good let's now give all these a little tiny bit of light lube same on this board here this is the push button panel from the front of the amp and these are all the channel select switches it's a good idea to check that they work okay let's get the meter on these i think it's one you can go from corner to corner and press the button oh yeah that's not a good sign is it that one's bad that one's bad that one's bad oh this doesn't look good no they're all luckily i keep these sort of things in stock it's just a matter of getting them out new switches so if i'm going to get them to go in the board or they're going to fight me one in oh that nicely snap into place now let's give them a test make sure not put rubbish switches in that's better much better that's all the front panel boards working nicely well there should be what i can do now is put them back in the front fascia pop a few screws in there and then this can go in those just lamps on here nothing too complicated this just snaps into place [Applause] okay pop a few screws in pop this little led in that clips there and the volume knob just sits like that hang on a minute i've got to put the button caps on oh gotta come out again two little buttons one another little button and a vowel please carol that's the front panel back together apart from this board here but that's still attached to the main board which they'll do next here's the main board nice and clean missing a few parts so but i did that yes we'll give this a check over but i wanna just check the parts we took out especially very curious about these old caps 12 000 microfarads let's see if they still are these are certainly nice looking let's put the capacitor test on there so you have a positive lead on there negative lead on there now press the go button this might take you a while to measure these quite a while look at that twelve thousand two hundred and eighty microphones test dc i'm not surprised that's a good one and we'll do the same one here and they're good as well beautiful the other part we uh took out was the relay this is the mute relay this connects to speakers and we'll check that that's good so this is according to this it's a 24 volt coil on here so let's stick 24 volts on so what have we got here one ohm and zero ohms it's only got one ohm what have we got when i cycle this a bit yeah one ohm don't sound bad that but it's it is a problem in relation to most speakers being eight ohms that's significant it's a good job i've checked that isn't it so relay is no good in the part of scrap fortunately they're fairly common and let's not forget about these parts that fell off earlier yes they need to go back on i think this is gonna be for the dry joints as well let's flip it over and have a look there we go everybody there's bound to be some it is a technics after all little wiggle test oh straight oh there we go there's one winking it here well quite honest we are missing some holes where those came from those sockets pulled out at the top corner here and then to desolder all that let's get some of these dry joints like this one these are always for the dry joints now you can pull some of these connectors back in start with a small one mushroom let's see if i can do both at once put this new relay in so how's that looking nice okay last part to add let's put those capacitors back in negative to the left [Applause] these i need loads of solder on so these extra pins are just for a bit of mechanical support because the caps are quite heavy on the board stops them coming loose because we've already seen how technics parts like to come loose on the board so the main board is pretty much back together now it should work pretty well not getting this much attention yet this is the digital audio input board um this has got high frequency digital circuits in yes it would be hiding behind this tin lid i happen to know that some of the parts under there run pretty hot as well it's another favorite place for dry joints you can't leave it alone right now just looking how to get this out i don't think we need to take this top board off we do need to take the screws out start this end one out there of course you've got a self-tapper machine screw technics you do like to mix things up don't you the whole board's gonna be wiggly now so there we go comes out oh move that smelly bands right let's take those screws right before i completely lose them it's around here i'd be suspicious of dry joints again and things have all burnt up when i tested it this did actually work so probably don't need to go too far into it just give it a good old look over nothing we'll just touch up around there got the cleaned up chassis ready to put bits back together first i want to put in is the heatsink but i've just noticed something rather unpleasant about this it's not flat you can see here there's a raised part right there it's as if what i think's happened is someone's over tightened this this screw here um yeah that's pretty bad that's going to stop the heatsink connecting properly to the transistors because the back of the transistors i can show you here they've got these metal plates on there and they need a nice flat surface which is exactly not they're not having that here and how bad is this i've put a straight edge on it and you can see this it rocks on it it's definitely not good but i've put a feeler gauge under here that's not good at all i have to address that i've got this aluminium clamps in the vise now it's a soft metal so i'm going to hand scrape it with a carbide scraper and just get the high spots off unfortunately the carbide blades machine really sort of flat and accurate it's pretty good just do it carefully painstaking job right this is fixed up now let's get it back in the amp chassis so this just goes back on its little mountings there pop the screws in right now i'm going to put the input boards in whilst it's a bit easier to get to always a good idea to check these boards for any broken joints because the sockets get a lot of abuse a lot of wiggling and pulling and yanking yeah so this ground one's got cracked solder joint there yeah we'll touch that up before we put it in actually i might as well do them all when i'm here so let's get a couple screws in there before i put the main board in i've got to put new um insulators on the heatsink because odd ones are a bit knackered and crushed as we saw so these ones i've got a little bit smaller i think they're the exact size of the transistors so i need to place them quite accurately but this is a mucky job because we're using this heatsink on pan which is just gets everywhere i try to be very neat and deposit it with a syringe and sparingly prefer a system of little dot i'll put the first bit on my thumb though little dots because you don't need a lot that's probably too much to be honest so if we put it down on there the good news is it sticks itself quite well i'll push those in a bit more at the end same again on this one now i'm getting a little bit ahead of myself now before i start screwing this thing down i need to solder the cables back in that i unsoldered earlier ones off the transformer and the speaker connections and the same with the other cable [Applause] no more hates in compound filthy stuff so so it all lines up these long ones in and on the other side get a few threads turned in there [Applause] that's better i nearly forgot i need to put some heatsink compound on these little transistors here because these have to track the temperature of the heat to the to compensate for the gain of the transistors as it all warms up it's all lined up right i'm not going to do them up too tightly yet because i'm going to have a bit of a challenge with these ones because the capacitors are in the way start that off by hand oh that's threaded in nicely that has it's on the start of the thread sometimes you have to reverse it there we are [Music] finally [Applause] just wait for the click there we go snip that up see that heatsink compound sort of splurge out make some room for the front panel to get involved again i won't make that mistake again i forget to put the button caps on you can make sure the right way up as well [Applause] fiddle together see if i can get this cable to stretch all the way here right from the back panel to the speaker slits which that is that's tricky on that one i solder that in first then just push it we're nearly there with this get the front panel on the screws are on the bottom of this if i recall yes support them all back putting some of these cables back in what and they're going a lot nicer than they come out shall we get on with these this time round not much space in here works better now it's a small matter of what to do with all these ah we know where they came from number five this is took all the way back there goes into that that board there for the tape player looking j1 and then j2 a j13 in there and j4 now is a good time to put the digital module back in [Music] sits on there i think it was j11 must be right got this three pin connector here that just leaves this one if it'll reach well it's looking nice if nothing else oh yes right at the point now where i need to power it back on it doesn't blow up look i'm having with this okay nothing's blown up relay's engaged that's protection relates happy yeah seems to work what i need to do now is check the bias current and just general things about the amp just make sure i've not disturbed anything after it's been in the ultrasonic cleaner and all that stuff now these are the test points for the voltage control lamp one there and one on there we've got the left channel test points negative connection there the positive connection here i've got the two meters engaged now this is the left channel that's the right channel let's get the power on we're shooting for 25 millivolts apparently and it's there there about right it's not too bad we'll see how it settles a little bit of a waiting game now they're holding about steady about 30 millivolts a piece i'm tempted to increase the right hand channel a bit because it's a bit on the it's a bit lower than the other one so we figured we better tell them balanced just tweak this one up a bit they're pretty close to each other now i'm quite happy with that next is to check the current drive amplifier in the same way let's move these test leads over measure across these resistors i mean positives on the outside on this one just to confuse me we're now looking for about five millivolts i don't think they're too bad at all that's how warm this amp is still stone cold i imagine they get to five millivolts but the range is four to seven millivolts officially and there we are five millivolts or so can't complain at that i nearly forgot because this is an early digital amplifier it's got um quite a clunky digital to analog converter or dac as they called i need to check the offset voltage on that as well that's going to be really tight less than one millivolt put the red lead on there and then black lead then i've got the yellow cable there and then blue one on there then just power this up what have we got a naught point 0.16 millivolts to 0.18 well inspect that is perfect now give it a signal test just put some test leads in we'll go with the cd input first my favorite come on look at that lovely check some of these controls there's the balance there oh yes treble bass it's doing stuff i need to set the phono stage because that's an extra bit of circuitry in here that you never know if it's working so i'm gonna knock the amplitude right down on here to five millivolts on both channels i'm shooting five millivolts let's turn the volume down a bit on this and put the phono on whichever channel it was uh that one i think oh one of the channels he's down hmm it's not this switch is it no oh god this arm never stops getting surprises yep supposed to work this thing was anyway the preamp leaves on this board down here so this is where they preamp live so the very low signals coming from the ends here go after this selector cables here backward switch comes back then it's processed around here could be oh oh i'm knocking it it's oh there you go another wobbly part there look at that place this on the top just touch that up with some solder and back on with it that's better more like it the look i'm having with this amp i'm going to most definitely check the digital side of it i think it worked before and i checked it but you never know dry joints keep appearing so got me a little fibre optic thing toss link i think they call it any ideas that i find it though i don't know so is it um power amp direct digital oh lucky fine there we are oh look at that beautiful output now you can put the lid on this thing finally what a nuisance i've got the lid to go on here so that's normally when i finished the job but there's this outstanding little issue can't tell any of the buttons are i printed off a big label to put all the markings back on this so let's see how it goes on let's drop this ample just in a perfect perfect viewing position so so i'm quite happy with that i think it'll do it's better than no letters isn't it catch you next time

Channel: Mend It Mark

Views: 193,617

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Id: TZ6Xf70GtZs

Length: 55min 0sec (3300 seconds)

Published: Sat Apr 09 2022