Can't seem to get a MicroKorg part

emberdark · Post by **emberdark** » Sun Mar 11, 2007 8:50 am

After my MicroKorg stopped working, I finally tracked the difficulty to the 3.3 volt switching regulator circuit and the fuse. Unfortunately, when those components go, there is often damage done to the CPU.

So it was in my case.

So I got new switching regulator parts from Korg. Very quick. Very easy.

But I cannot seem to get the CPU. I'm sure this part is not often requested, since removing the old IC and installing a new one is a very finicky and specialized chore (it's a 128 pin ultra fine-pitch chip).

But I've managed to remove the old chip, and I'm sure I can install a new one - if Korg would just supply me with one!

I've had one backordered for a while, but I get the feeling the order will never be filled. Does anyone know if there is someone at Korg who might be able to help me to get this part? I really would like my MicroKorg back.

BTW, the part is:

IC18 CPU HD6412320VF25 320004686

The last number is the actual Korg part number.

Thanks

gmanca101 · Post by **gmanca101** » Mon Mar 12, 2007 11:37 am

The only thing I could think of is partsisparts aka Korg Parts aka Gibson Parts. From a couple of dealing with Korg Service, they won't give you a part because they want you to deal with the authorized service centers as part of a contract/fee deal.

I'm curious though, what part was the 3.3 v regulator and fuse? I got a microKorg that was missing a couple of components and had a blown component.

emberdark · Post by **emberdark** » Mon Mar 12, 2007 9:18 pm

Thanks. PartsisParts is where I've got the part backordered. They seem like really good people, but even they can't get a part from Korg if Korg claims it is out of stock. And my suspicion is it is never in stock.

The 3.3 switching regulator is IC5. Its associated mosfet is F1. And the 3.3v fuse is FU1. These are all located in the upper right quadrant of the board, between the Release pot and the Attack pot. These are all surface mount components, so be careful out there.

gmanca101 · Post by **gmanca101** » Tue Mar 13, 2007 12:58 am

uh oh, looks like I may have a damaged cpu as well. I have a blown IC5, and C9 and C107 are missing. Do you happen to have their values?

Through a continuity test, looks like the FU1 is blown as well. Darn.

Hopefully it's not a busted CPU.

Anyways, thanks for the awesome info! Do you happen to know if a CPU is undamaged if the Korg does the Audio 1/2 orange light routine when you turn it on?

emberdark · Post by **emberdark** » Tue Mar 13, 2007 1:32 am

C9 is an 'optional' - it is not installed. C107 is a 1000uF 16v electrolytic.

When no 3.3v power is getting to the digital circuitry, you get that Audio light routine when you turn the unit on. When 3.3v power is restored, often, as with mine, the machine springs to life and you do a little happy dance. Lights light up and the machine will play demos and woo-hoo you think it's fixed. Unfortunately, much of the time, the CPU has been damaged, and many things won't work. The service manual even mentions this - saying that if the switching regulator circuitry is damaged, it is likely that the CPU is whacked. A sure sign is the lo Bat indicator staying on all the time, and sporadic or non-existent input from the pots - just generally uber-flaky operation. I think the main A/D part of the CPU silicon is the part that gets whacked hardest, while some of the rest of the chip may keep chugging.

But who knows - maybe you'll be one of the lucky ones. If not, removing and replacing the CPU is pretty much out of the skill range of most people.

Daz · Post by **Daz** » Tue Mar 13, 2007 1:39 am

That CPU is a Renesas H8 ... I thought the number looked familiar

Are Korg they use a ROMless version and storing the OS/software on a separate flash ROM chip ? If that was the case you might be able to buy the CPU somewhere else.

Daz.

Daz · Post by **Daz** » Tue Mar 13, 2007 1:50 am

Just checked on the Renesas site and the HD6412320VF is a ROMless part.

More info here :
http://eu.renesas.com/fmwk.jsp?cnt=h8s2 ... 328_group/

emberdark · Post by **emberdark** » Tue Mar 13, 2007 1:51 am

Yes it is a ROMless version, and Korg does indeed store data on a separate Flash RAM chip. But danged if I can find the silly processor chip anywhere else, at least in quantities of one or two.

And I want one now, dad-gum-it.

gmanca101 · Post by **gmanca101** » Tue Mar 13, 2007 3:23 am

Sorry if this seems simplistic, but I see that it is on Digikey as far as corresponding NO's. However, I didn't compare datasheets to see if there was an underlying difference.

http://www.digikey.com/scripts/DkSearch ... 72&Site=US

Thanks for the component values; now I can start to put in an order for the parts as well as the CPU just in case. I'd like to get the Korg fixed sooner than later

Daz · Post by **Daz** » Tue Mar 13, 2007 3:50 am

Looks like the same part to me ... it's not RoHS compliant, I wonder if they will still sell the part.

Daz.

emberdark · Post by **emberdark** » Tue Mar 13, 2007 4:49 am

Yep, that's the part. I never thought to check Digi-Key. But it is not in stock and the estimated ship date is July 2nd.

I kinda wanted the widdle chip before then.

Oh and here are the component values for the switching regulator circuit. The number on the end is the Korg part number, in case you order from a Korg parts distributor.

MicroKorg Switching Reg Circuit Parts
--------------------------------------------------------------
(1) F1.....FET CPH6302.....304060250
(1) IC5.....IC-S-8520F33MC-BNS-T2(TS).....324023008
(1) FU1.....Surface mount fuse CCP2E20.....184090000

emberdark · Post by **emberdark** » Tue Mar 13, 2007 4:59 am

Whoops! Looks like an RoHS version *is* in stock. Just gotta check data sheets for pin4pin compatibility. Geez, I'm getting dumber every minute. Thanks all!

gmanca101 · Post by **gmanca101** » Tue Mar 13, 2007 5:00 am

Wow, that really sucks; I just noticed that Jameco has their Renesas stuff as 7/02 as well, albeit incompatible MCU's.

I guess that's why your chip is on backorder; I saw that from Daz's link that there are other uses for the chip, if only we knew what digital cameras had em, you could get a broken one, or broken anything and get the chip.

Edit: dang sounds like you may have hit the jackpot, good luck on the datasheet comparison.

emberdark · Post by **emberdark** » Sun Mar 25, 2007 7:27 am

Heh - I know huge throng of probably one or two people have been waiting with bated breath, so here is a pic of my microKORG's newly installed CPU:

<img src="http://images.andale.com/f2/130/124/142 ... nu_cpu.jpg" width="400" height="277">

This repair along with the replaced power supply components has allowed the little guy to resume working like a charm.

I know the soldering on the FP128 package looks a trifle ragged, but it's not bad considering the whole repair was accomplished with a 20 dollar Antex soldering iron, a bit of flux, and a bit of wick.

(Oh and of course, a steady hand, a keen eye, and a BIT OF LUCK!)

Please don't try this if you've had no experience - it isn't as easy as I make it sound. Really, it isn't.

Musical Cheers!

Daz · Post by **Daz** » Sun Mar 25, 2007 2:44 pm

Way to go, ember