Dynacord DDL 12 digital effects repair

[Music] and today in the workshop I'm working on a dyna cord ddl12 digital Delights from 1983 and it's a little bit bashed up but we'll see if we can fix it and this was built back in the good old days when they used to put the block diagram on the lead it's not a full schematic so we can't do the Full Repair with that but I like the way it's going what this diagram does show us is it's using a digital processor and memory this will make this far more repairable well there's certainly plenty knobs on this keep paper plane stained hours of fun and the back of the unit shows this is a professional bit of kits using balanced inputs and outputs wow and single-ended you got the choice it only tells me it's got no output but turns on so let's test it so we'll give it an input let's listen to the output on there and of course it needs some power so we're feeding this input of one kilohertz 500 millivolts that's quite a large signal and we got very little coming out of it what's that a little bit of a ripple there maybe okay so it's not very well like they said I think the lid's gonna come off next oh it's not too many screws on this foreign digital wasn't always easy they used to have to put quite a lot of stuff in there the block diagram gave us some insight into this but can we see here we see power supply section this is quite obvious with large junkie caps fuses and Regulators if we follow the signal path you can see the sockets coming in come out around the side so we've got some sort of analog circuitry here just sort of amps and just standard stuff they've got some fancy chips here this one here is actually the analog's digital converter so that converts from your analogs audio signal into the digital formats which gets stored on these memory tips here these chips here are actually the same memory chips as used in the Sinclair spectrum and probably a lot of other Home computers of the early 80s this long rower pins here is where you connect to memory upgrade you can actually double the memory in this to create deeper effects the delay effects work by cycling your waveform stored on the memory chips all the way through and of course you can change how fast that happens just by adjusting this and after you're done twiddling and mixing signals together the output comes to this chip here this DAC 80 converts it back to analog with any electronic fault finding power supplies is the place to start despite that red light coming on and it's a very convenient place to measure all the voltages all together so we've got plus 12 nothing there plus five that's working 5.1 volts that's not labeled up nothing on it anyway and we've got minus five also dead hmm and we've also got a minus 15 volt rail we have 0.5 volts on not healthy I guess we should check these fuses before we go any further dead also dead that one's okay and that's dead huh pop those up then Dad Dad that's quite a lot of problems and the fuses don't blow on their own so we've got to inject some voltages and see why they've gone I'm gonna start with the plus or minus 15 volt rail we've got the power supply set up to the appropriate settings so we've got the negative 15 volt regulator here the output pin on the right there and a positive one and we'll pick a ground up on the 12 volt regulator there we go let's see what happens oh oh they're very ill oh blimey and it's times like this so I'm very grateful to have a thermal imaging camera will be able to see where the energy is going come on where are you what though we got one is that the only thing I think so and then my friends is a knackered tantalum capacitor just there there's our short it's not uncommon for a transition capacitor to go short circuit like that so I'm hoping that's all there is but you never know I'm gonna just cut one of the legs off just to make sure oh wow we've still got problems is there more shorts I think I need to crank the power up on this should we give it all one amp that should warm things up 15 watts each side there's another one which one's out that one chop that one out try that again oh we've still got trouble what now something glowing there but it's not much that much with the core of a chip that might be okay I ignore it for now because I'm losing you know there's an amp flow in a one volt it's only like one Watts but no what's going on here and we've got a zener diode and resistor in series that's getting quite warm you see some of the chips coming alive I hope they're not all knackered all this negative regulator is getting a bit warm I think we've got a problem there's some weird things going on here I tell you wow let's get the meat on this because I think they're shorts all over the place I can't really get any power into this and the only thing getting warm it's a regulator a bit weird this minus 15 volt regulator I'm just checking here between the ground and the input it's dead short that's that is what about the output output's not shorted so I've got about a killer on there it's probably about right on the positive regulator that looks good yeah no problems there the firefight one works I'm about this 12 volt one whilst we're measuring things oh wow that's short as well crikey well I didn't think it was going to be this broken luckily the back cover comes off here because I don't fancy taking all these knobs out I think it's just a few screws and I can get it a lot [Music] trying to spot them black screws on a black surface and of course I will undo some screws on this side which have been glued down they've filled them up for the glue it's not very nice the brightness screwdriver I think revenge is called for see if it likes a bit of heat oh I'll leave that there be a bit warm so I'll take this screw out here because I'm going to take this negative regulator right because either it's shorted or the bridge rectifier shorted [Applause] and the 12 volt one I don't think the heatsink was coming off with it surprises I'll just check these and there's no shorts no short on that one and not on this one hmm oh that's just me touching the leaves back here's the AC side of this one okay shorted let's just take you down find out still shorted well we run out of things it can be I'm suspecting main filter caps so measuring shorts across here shorts across here as well you never know I need to cut that off though [Music] so these fair then oh Deadshot line this one yeah oh something's leaks hmm has that clear default on the board yes that's clearly a bit of a wild goose chase and I popped The Regulators back in and that bridge Rectify because I think they're fine clean it up a little bit foreign rectifier I'm gonna put the 12 volt rig back in let's see if we fixed it now yes that's better because there's a proper test I'm actually going to take these fuses out of the way and feed the power in on the AC side I need to crank the voltage up a bit say 20 volts per side and let's go so over here we've got minus 15 volts perfect over here we've got Plus 15. great and the minus 5 volt rail regulated by this little thing here is fed off the minus 15 like well and yes that's working now you can do the same test on the 12 volt rails disconnect that and just shift this over to this views here 11.9 closing off foreign foreign I've got 200 milliampere not sure how he's supposed to get them out without tipping them all over the place on there there are 500 milliamp fuse here let's replace these two shorted capacitors foreign cap in there I think they're not quite so troublesome and the same with this one down here foreign 's power well there was such small fuses and I don't know I can protect those if they're going to blow they're going to blow here goes oh bloody hell I thought I saw the fuses glow but maybe they didn't pop I've got minus 15. about Plus 15. it was five plus twelve it's all there not to mention we've got more in action got lights on there and stuff like what's going on I'm not sure we've got some crazy crap coming out of this why is it peaking oh so this seems to work okay delay what's this button do oh interesting I see what's happening this is actually working might turn that input down a bit this thing will probably make more sense if I connect it to a speaker oh we've got a dirty pot there that one's okay oh what was that doesn't do anything hmm I think I'm gonna give this quality going over I'm going to take the pots out and give those a good clean and uh I'm thinking with it's run a bad look I might replace all these capacitors I'm not a fan of doing that but this thing seems to be a plague with them and I've also just found the reason the pot didn't work it fell apart oh no oh they're funny size shafts ah oh it's all going to come off anyway I'm strain this as well when I put it off oh God these don't look good they're all variants oh corroded hmm no I think I take these other little nuts off the side I'll disconnect a few wires set this led off let's take this end off the board so I don't confuse myself that could do is slacking enough as well I think we can undo these yes and that one well this gives a bit of a clue as the condition of the parts you can see this one is it's pretty tarnished they're all going to be a bit grubby and you can see here it's just a bit covered in mock but yeah this just snapped off I don't know how that's come to happen because it had a nut on there I'm not don't know hmm let's just get him out anyway foreign how has that happened the wires need to come off anyway and to make matters worse this is a 100K positive log and this one is a 100K negative log ah we're small shafts having just realized what a horrible proposition that is to replace these I've just managed to push the negative log pot back together hmm I'll put it in the old Sonic cleaner with the others and then I'm going to give this a glow up in there it might be okay for the positive log tape I've got this part here which I'll do nicely but I need to um just modify a bit but grind that little Tang off there and then it shafts too long let's just trim it down a bit [Music] foreign just need to Tin the outer legs like that I'm just going to glue this stop it falling off so easily just a spot of glue on each little sort of rivet I'm going to give this a little bit of a wipe in before we go too much further spray the board anyway s shouldn't do any harm that looks a bit better I'll start so we won't put the pots back in there I'm just going to lift the board up a bit and just put a couple little blocks underneath to hold it steady let's see if I can put this front panel back on before I solder them [Music] now I can put these little screws back in and hopefully hold it all still that'd be good put the nuts on them so these will be held in the exact right place before I solder them in foreign [Applause] [Music] now the pots are sorted I'm going to change the caps and there's 42 in total it's got a lot well I've rounded all these up out of the parts bins so hopefully that's enough to go around foreign foreign s are actually non-polarized which means I'll be in the signal path so they're not a hazard to the supply rails so I'm gonna leave them alone because they are a bit harder to get older well the next stops to put the knobs back on [Music] another little drops too straight in this little thing do it in the Vise I think foreign foreign [Applause] [Applause] s on there just don't happen to have something fairly good just a little Dash we'll just wait for that to destroy the glue and then it should just crumble up and fall out it's time to save the screws where's stuff quickly evaporates it's a bit wiffy as well but yeah let's clean these out nicely yeah these will be fine foreign but it's safe to say it's working twiddle some knobs and all sorts of actions oh now the speed controls work the voltage controlled oscillator it's good let's put the amp on [Music] that's a good time to put the lid on it's working well I didn't think there'd be that much wrong with this but yeah well it might be a bit Bust Around the Edges still but it works like a new one catch you next time

Channel: Mend It Mark

Views: 86,008

Keywords:

Id: arO2npsNkLc

Length: 32min 36sec (1956 seconds)

Published: Thu Sep 08 2022