Any fellow Elektronauts have a Korg MS10? & time to help?

The Lounge Other Gear
#21

I’m gonna sound boring here but a bit of practice on something old and scrap to hone your soldering/desoldering skills and you should be fine with just a half decent iron, some braid and a sucker. That Hakko looks great and I do enough bits to prob justify the expense of one but if you’re just doing the odd repair it is quite an outlay especially as you’ll still need to buy an iron and a few other bits if you don’t have them already. As has been mentioned Hakko and Weller make plenty of irons to cover most budgets. I use a Weller WTCP and have done for years and I’m happy enough with it. You’ll also want some small snips/sidecutters. I’ve got a pair of Knipex ones that are fab. Not the cheapest but worth every penny to me. (I’m my day job I use Knipex pliers and I’ve had the same pair in my own toolbox for over 20 years and still going strong even having been blown up a couple of times over the years :rofl:)

These are the ones I use for electronic repairs. From bitter experience I found that cheap cutters are just a false economy with soft jaws that blunt after pretty minimal use. I’ve had these a few years now and are still tip top

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And for a laugh my trusty pliers after 20 odd years of hard work! Still going strong!

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#22

Ok so I’ve got it in pieces and trying to work out whether to replace the ic or the PW/PWM pot. Don’t know how to test the chip with multimeter but the reading from the pot starts (200k on meter) 25 then up to 60 and back to 15 when it’s turned does that seem strange?

#23

It can be tricky to test some components in circuit as you can be testing trough other components. For instance R70 is in parallel with the pot and R48 in series to the positive rail. Although pots can get scratchy and develop dead spots that tends to happen over time. I’d venture to say the pot is prob good. To be sure you could desoldering it then test it out of the circuit. My guess is it’s the op amp if you’ve reflowed the joints in that area. You can test continuity between components to ensure you’ve got good solder joints and no damaged/lifted tracks.

Don’t forget the positive rail is supplied via the external PWM jack (via R48). There’s always a chance that the normally closed contact in the jack socket is open and you’ve lost that positive supply to the circuit.

#24

I’m gonna start by removing the 4558 ic and installing a socket so I can try a new chip as that seems to be the most popular problem

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#25

Do you have a DVM/multimeter or a scope? Although the op amp is a likely candidate I’d deffo check around that socket and make sure you’ve got the voltages you expect especially at the ‘top’ side of the pot on the schematic. It could save you a bit of work. If you are going to swap out the op amp anyway it’s always a good idea to socket it, which you’re doing. Just take care with the PCB as some of those old boards don’t stand up to much in the way of heating when it comes to repairs. It’s not hard to lift a pad or trace.

It’s also worth checking the connector from the socket onto the board. Those can go bad too. I’d deffo test continuity trough the connector

#26

The readings from the op amp as follows:

pin 4-1 411
pin 4-2 305
pin 4-3 304
pin 4-5 305
pin 4-6 305
pin 4-7 409

Does that mean it’s not the chip after all and I’m looking in the wrong place? Don’t want to do any unnecessary desoldering on a hunch

#27

Fixed, ic6 popped out with a bit of braid and flux then installed socket for future proofing. Square wave and pwm back!

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