The community repair thread

midlifecrisis

Our singer has a similar keyboard. The input plug on the dc got wrenched out, similar situation. I offered to have a look at it at home to see if it could be soldered if a pulled out wire. it was exactly that, fairly simple repair. It take me about an hour to undo the hundreds of screws and take apart. Quite satisfying for me to fix and re assemble, just a little bit worried when i re assembled it having about half a dozen screws left over and unable to locate where they go. best not mention it to her.

Danny1969

midlifecrisis said:

Our singer has a similar keyboard. The input plug on the dc got wrenched out, similar situation. I offered to have a look at it at home to see if it could be soldered if a pulled out wire. it was exactly that, fairly simple repair. It take me about an hour to undo the hundreds of screws and take apart. Quite satisfying for me to fix and re assemble, just a little bit worried when i re assembled it having about half a dozen screws left over and unable to locate where they go. best not mention it to her.

Another way of looking at the extra screws is you have improved and streamlined the manufacturing process saving money on materials and time as the extra ones aren't needed.

midlifecrisis

Danny1969 said:

midlifecrisis said:

Our singer has a similar keyboard. The input plug on the dc got wrenched out, similar situation. I offered to have a look at it at home to see if it could be soldered if a pulled out wire. it was exactly that, fairly simple repair. It take me about an hour to undo the hundreds of screws and take apart. Quite satisfying for me to fix and re assemble, just a little bit worried when i re assembled it having about half a dozen screws left over and unable to locate where they go. best not mention it to her.

Another way of looking at the extra screws is you have improved and streamlined the manufacturing process saving money on materials and time as the extra ones aren't needed.

i look forward to her using it on stage and falling apart as she lifts it off the stage lol

menamestom

Rode NT-USB Mic. My mate was struggling with intermittent input.  Turned out to be the USB Type B socket.  The pins had broken but could make contact in certain positions.  So he spent hours setting the lead up in certain positions rather than address it.

But an easy fix.  Remove the stiff buttons.  Unscrew the circular nut at the bottom.  Loosen the main CB so that the small input board can be pulled out, after loosening grub screw.  De solder the 4 pins.  Install new socket, re assemble and good as new.

£3 fix has saved a £150 mic.

Danny1969

@menamestom ;
That's excellent work, be really useful for others too. Wiz and wow awarded. 

Danny1969

So this caused a bit of head scratching. It's a newish high end Lenovo which won't turn on. Customer reported power button didn't feel right leading up to this sudden death. So there's a clue right there I thought. 




Here's how it's built in Macbook Pro fashion reverse loaded onto the palm rest. Only not as well





So motherboard out, which is a complete pain on the arse on these machines as some connectors are under the board and if your unaware of that then you can easily tear a cable or a connector off the board. Once the offending board is out though you can see why it won't turn on, the whole top of the on / off micro switch is missing ... f#ck knows where it is now, must have got sucked out the fan. 



This is actually a problem because you can't just but the same exact switch from Mouser. Even if you could it's undersoldered with  such tiny amount of pad showing  trying to do it with a micro iron will be very very difficult and attempting it with a heat gun will destroy the membrane before the lead free solder melted. 

So I need another switch in exactly the same position as the old one, trouble is there's almost no room as it needs to be in the exact same spot as the faulty one. Then I had an idea. What has a tiny very robust micro switch with easy to solder on connectors ... an Ipad 1, 2 or 3 does and when you have fixed as many ipad screens as I have you tend to have loads of them in the work shop. This is why I can't throw shit away. 9 months after it had it's screen changed the old home button on the smashed LCD get used to save a £600 Lenovo






So here's our brave little soldier here removed from the smashed iPad screen. 

Now 3 or 4 attempts to wired this switch to the board in the exact place it needed to be ended in failure. And every failure meant the board had to come out again which meant unscrewing everything and disconnecting about 15 ZIF cables. Then I had a better idea. Secure the iPad switch to the palm rest lined up exactly with the Lenovo On switch. Then connect 2 wires 
Then connect 2  wires to the motherboard on the terminals of the broken micro switch, install motherboard and join wires




Now I have a switch  exactly where I want it, pop the plunger in and boom, it lives again. 

Chris.B

10/10 for perseverance and determination for that one. 

Brio

When I take anything apart - I had to put SSD's in a dozen Mac Mini computers at work - I put a strip of doubled over masking tape on my desk surface. If I had doublesided tape I'd use that.
Put small components on it in order from left to right. Assembly just go back along the line.

menamestom

Danny1969 said:

@menamestom ;;
That's excellent work, be really useful for others too. Wiz and wow awarded. 

Thanks Danny, much appreciated!

I should have recorded this one as I did it at the same time but it didn't  really constitute a repair.  But may as well post it anyway.  This is a 90's Rode NT1.  I think it was mine originally but sold it to a mate.  He said it didn't work after it had a fall.  The grille was dented and I assumed capsule damage.  I thought if that was the case it might be an interesting project to install an after market Neuman capsule clone or something.  

The mic was filthy, covered in gaffa tape and looked sorry for itself. I cleaned the body with sticker remover and pushed the grille back out a bit.  The mic looks pretty good now.  The capsule was quite dusty/dirty.  Not much you can do really, I gave is a very gentle blow with a camera air blower, from a shallow angle.  When I put the mic back together and tried it is seems to work fine. Perhaps it was just a bit if moisture that caused issues previously, but either way it's back from the dead.
Incidentally, looks and feels nicely built with good components.  Not sure what they are like now but this is well made.

Danny1969

@menamestom ; I had one of those, great mic and as you say very well built. Doug Ford used to be head of design at Rode and he certainly knows his stuff, very, very clever electronics designer. I watched a talk he did for EEV blog on Youtube where he talked about some of his tricks.

Danny1969

Brio said:

When I take anything apart - I had to put SSD's in a dozen Mac Mini computers at work - I put a strip of doubled over masking tape on my desk surface. If I had doublesided tape I'd use that.
Put small components on it in order from left to right. Assembly just go back along the line.

Very wise when it comes to anything Apple as they tend to vary the shoulder and head size of the screw as well as the length and width of a screw in their designs. Every screw needs to go back exactly where it came from. 

The blue antistatic mat I using in most of these pics has sections for just that purpose, a grid of tiny boxes for following the pattern of where screws came from. Useful for phones and laptops. 

Chris.B

Bang went the old microwave, it is so old that it has a mechanical timer, but I thought I would open it up and see if there was anything to be done. Replaced the internal fuse, all was well for a week then the same thing happened.  Research suggests a problem with the door switches, in particular one of the switches will short the supply voltage to ensure the microwave does not operate with the door open.

Further investigation showed that a couple of the switches (standard Omron microswitches) were able to move a little in their plastic mounting brackets (no screws).  Spent some time applying Araldite to fix the switches in position and 2 weeks later all is well. 

If it fails again, I'll have to admit defeat and buy a new one, but I couldn't resist having a go. 

Danny1969

Chris.B said:

Bang went the old microwave, it is so old that it has a mechanical timer, but I thought I would open it up and see if there was anything to be done. Replaced the internal fuse, all was well for a week then the same thing happened.  Research suggests a problem with the door switches, in particular one of the switches will short the supply voltage to ensure the microwave does not operate with the door open.

Further investigation showed that a couple of the switches (standard Omron microswitches) were able to move a little in their plastic mounting brackets (no screws).  Spent some time applying Araldite to fix the switches in position and 2 weeks later all is well. 

If it fails again, I'll have to admit defeat and buy a new one, but I couldn't resist having a go. 

That's quite useful to know Chris, nice repair work. 

Danny1969

I've been busy but it's all been boring stuff recently. This job isn't interesting but the way I find the offending failed component is a trick you can store up for your own use. 

So this laptop came in as won't turn on, completely dead. It's a Dell Inspiron, not an expensive model but customer has only had it a year so not keen to buy another. Another engineer had looked at it and says it needs a board. 

Plugging the charger into the mains and then into the laptop reveals something right away. The charger light goes off. This means there is a direct short to ground on the board and the charger is turning off to protect it's self and avoid a fire. 
There can be many, many things that cause a direct short, anything from a failed I.C to a shorted cap or diode or MOSFET.  

So get board out and examine it under magnification. Any signs of a spill ? any tops of chips bulging up, if so declare it dead because a machine this cheap won't stand a £200 repair bill. If though, everything is lovely and clean and all chips look good and all diodes test for good junctions then 9 out of 10 times it's a shorted cap. The hard bit is finding it as this motherboard only has a direct short to ground when it's receiving power, so that tells us it's not a smoothing cap right on the DC input, it's further down the board and could be anywhere. But here's how you use a car battery charger to find it. 

The basic trick here is if as I suspect it is a shorted cap to ground then when I apply a current source that's quite happy driving into a direct short then the shorted cap will absorb the full current and destroy it's self. For this a standard car battery charger is ideal as these are designed to connect to a mega low resistance car battery, basically they are current protected internally. 

So connect the neg terminal to ground on the board, all USB ports chassis and HDMI  connecter  chassis will be ground,  then connect the red lead to a small metal body of a screwdriver to give you a 12V probe and connect probe to laptop positive DC input until you see the cap light up. 



Sure enough i saw it right away. If you don't then stop and turn the board over as both sides are covered in components. 

Here's the little bugger, no longer a short as the current destroyed it. Very hard to take a picture of something this small 



When it comes to replacing it there's 2 choices. Either nick one from a dead donar board which I don't have or guess the value if you can't read it from the working voltage and it's physical size. The working voltage can be measured and just chuck on another 40% to be on the safe side. 



So all back up and running. As nice as it is to have a proper constant current supply in cases like this a simple lead acid car battery charger will do the trick and most of us have one of those ... or at least anyone remotely interested in my thread would have. 

Emp_Fab

My repair / music room has become a bit of a dumping ground over lockdown.  I really need to get in there and tidy it up then finish my repair bench.  Your thread has inspired me to think about doing it.



*Note, there is a difference between thinking about doing it and actually doing it !

Danny1969

So been a while since I've put anything on here, been doing nothing but laptops, iPads and data recovery recently. But heres an ol skool bit of kit I've just done and a design I rarely get to see nowadays. 

So a Laney powered monitor. Customer says it's got hardly any volume. 



So apart it comes. This is how everything used to be made. Large transformer lowers the 240AC down to a centre tapped 47V - 0 - 47V ... that goes into a bridge rectifier to convert to DC, couple of bulk capacitors act as a reservoir and form the crude DC supply. 
Circuit wise it uses 2 dual opamps ... one as a differential amplifier for mic / line pre amp and one for the tone control. The output stage at first glance looks like a couple of IC's but is in fact a complimentary pair of Darlington transistors in a classic push pull config. 



So you can see I've got an iPod hooked up to it and a test speaker. There's volume but not much and turning the volume knob up actually decreases the volume with full volume available in the volume off position. Now straight away that gives a clue to what's going on. 
A typical opamp diff amp config like this one has the gain \ volume set by varying the negative feedback back from the output to input. What's happening here is the opamp is doing nothing and the input signal is going to the output of the opamp via the feedback which is why there's hardly any volume (no pre amp gain) and why turning up the volume decreases the volume (turning up volume increases the resistance between our input and the power amp section. 

So an intelligent person at this point will first measure the power rails on the opamps. A complete idiot like me however will decide the opamps faulty and change both without so much as measuring the rails on either and then be disappointed it didn't achieve anything

Ok so now I decide to measure the rails and sure enough ones missing. One a design like this pin 8 will be around +15 and pin 4 will be -15V in respect to audio ground at 0V. There's no +15V on either opamp. 

So now I check to see how the opamps get 15V from the transformers 47V and they get it in the most basic way, using 2 large ceramic resistors to drop the voltage much in the same way a Fender Hotrod does to generate it's opamp rails. 



So measure each side and sure enough there's -15V on one but almost nothing on the other. That tells us the one with nothing on it's output is shorted to ground. It's not a direct short to ground from the transformers point of view as it's passing through the resistor but then it's going directly to ground depriving our poor opamps of their +15V rail. 

Here's the easy bit now, a quick look at the rail leading to the opamps from the resistor show 2 caps and a diode as the only possible suspects. So naturally I take the diode and one cap out of circuit by lifting their legs before I check the final cap and find that's the culprit. It's actually the bulk 470uf cap right by the resistor. If I had engaged my brain I would have looked at the cap and saw it was a 16V cap being used in a position where there's an unregulated 15V supply. That's asking for trouble. 

So I take that cap out and it's buddy on the other resistor. I wouldn't use a 16V cap on a 15V line, I change both to 25V versions, and all is well again. 

So when checking a circuit like this always check your rails are present first, could have saved myself a good half hour if I had used my brain a bit more. 

Danny1969

So this was this mornings job and quite handy too as a few people have asked me how to replace the hard drive in this type of iMac. This is the newer type introduced around late 2012, early 2013. Rather than have a removable cover held with magnets over the LCD this type has the LCD and cover bonded as one, and then bonded into the frame with adhesive strip, much like a giant iPad. Internally they use a Fusion drive assembly which is a small SSD and a normal rotational drive. The idea is the OS and anything that gets constantly used goes on the SSD while the rotational drive has large capacity for storage. Inside this one is a faulty rotational drive of 3TB ..... I know it's faulty as I recognise the little clanging noise when the drive spins up and the heads swing back to the stand. 
So if you buy a used iMac of this type have a good listen to the drive while it's spinning up as replacing it is not as easy as it is in the older iMac design or a basic PC



So I've removed the screen on these in various different ways and the method I use now is to cut the adhesive using a scalpel. This means I'm not prying the screen with a plectrum to cut it, I'm simply cutting through it using a sharp scalpel and because the blade is so thin the screen isn't being moved at it really. Before I start though I measure 8mm and then put some tape on my scalpel so I don't insert it too far. Most of the way round there's nothing you can hit but this ensures I don't anyway. 



I do the sides and the top, I've got a cushion under the iMac stand meaning it can't tip forward. When the sides and top have been cut through I gently tip the panel forward around 45 degrees and unclip the LCD connector lock from the motherboard and then slide the LCD connector out. The I slide the BL driver cable out, that one isn't locking. Then I tip the panel all the way forward. Look in the corners around 1 inch from the bottom and you can see they have left that adhesive there so you can get hold of it and pull it which cleanly removes it from the bottom edge and now the panel is completely free.



So panel out now all we need to do is remove the old faulty drive and replace it with an SSD BUT a generic SSD doesn't have a thermal sensor in it like the old drive so if you just replace it the SMC won't be able to read the drives temperature and will ramp the fan speed up constantly. On the older iMac's the temp sensor sat externally on the drive and could be put on the new one, on these models it's built into the drive so you need a special adapter cable which sits between the iMacs Sata cable and the new SSD. You also need a 2.5 to 3.5" drive adapter and it needs to be a certain type. Basically you need these parts. 



So at the top are the new adhesive strips to put the screen back in. These come with the temp sensor cable. On the left we have the hard drive adapter bracket and on the right is the temp sensor SATA cable adapter 

https://www.amazon.co.uk/gp/product/B00UN550AC/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

https://www.amazon.co.uk/gp/product/B00J42D5MK/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

So £45 worth of parts plus the SSD. I'm fitting a 4TB SSD which probably cost the customer a fair bit. 

Bolt the drive in the adapter then unscrew the 2 T8  screws holding the left speaker and slide it to the left slightly so you can remove the old hard drive in it's brackets. Then remove the 4 T8 screws in the old hard drive an fit them in the bracket adapter and screw the SSD in the adapter and then that can be installed in the iMac making use you use the temp adapter cable and you put the sensor on the SSD like this. Don't forget to put the speaker back in place with the screws back in. 



Then temporarily fit the screen back in, tape it to the chassis  so it can't fall out and hold cmd plus R to boot into recovery mode. Then use disk utility to partition the new drive and then either install a fresh version of OSX or ghost an image or use time machine to install your OS. The main thing is you want to know everything is fine before you install the new adhesive strips and close the machine up for good. 

Once you know all it good it's just a question of LCD back out, making sure all surfaces are clean before applying the new strips which are numbered and can't be installed wrong really. Keep your cushion in place so it can't move on the stand. Then remove the coverings, offer the screen back up. Reconnect both cables remembering to relock the LCD connector then look at the bottom edge, make sure you have the LCD back in line at the bottom by feeling for any overhang on both sides then when good tilt it up and make sure it's sat firmly against the adhesive all the way round, pressing gently all the way round the edge of the LCD. 



So job done, I put some tape around the top edge to make sure it can't tilt while the strips are bonding and the iMac is being moved back to the shop. I have heard reports of others having the screen tip out at the top and then fall and smash with the bonus of ripping the LCD connector socket from the board so I don't take any chances. A panel for one of these is around £450 so it's not worth the risk.

So there you go, not that difficult but does require a bit of thought to avoid making costly mistakes. 

Chris.B

That's a fascinating read and a great repair - good work. 

I can't help feeling that this is a design over substance product, having to remove the screen just to replace a drive seems to be a very poor design. 

Thanks for keeping us entertained with your work.

roundthebend

I love these repairs. I get a buzz out of them in a similar way to ASMR. It's soothing. I'm not particularly handy myself, but whenever I have a job like this I do enjoy it when I can follow a structure approach and do things with precision.

This weekend I need to extend the power cables on two outdoor heaters so they can be plugged into separate outdoor sockets rather than an extension spool. That is kind of the limit of my skills.

Emp_Fab

This is the best thread on the forum!  Thanks @Danny1969 ;