Vintage Synth Repair

Had a look at the Radias SM and there are a few things that I noticed relating to the DSP, according to TI’s manual on the 5502 it has limited on board masked ROM that is used to hold a Bootloader program, based on the information on the schematic it looks like it loads via the HPI (Host Port Interface) from the flash, for more info this is the TI documentation http://www.ti.com/lit/ds/symlink/tms320vc5502.pdf

 

I can’t find anything on the other DSP but since power issues are the most likely to cause problems I would be inclined to check that the 2.5V rail for the FXD03 core is stable without any ripple, the same goes for the 1.26V for the 5502 cores (this one in particular could be prone to problems due to the relatively low voltage).

 

I would also be inclined to check the frequencies of the 3 divided clocks coming from the FXD03 that go to the 5502’s and the Codec as this could give a clue as to which of the 3 DSP’s may be at fault.

 

Just some thoughts from what I can see.

 

Is there any chance if the passwords for the M3 docs as these could be useful.

 

Many thanks

 

John Rose

 

(www.astrodevelopments.com)

 

From: vintagesynthrepair@yahoogroups.com [mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of euklides69@...
Sent: 04 October 2013 04:55
To: vintagesynthrepair@yahoogroups.com
Subject: [vintagesynthrepair] RE: Korg Radias - checksum error

 

  

I think its time of second part of my sad story :)

 

Since I have enough desperation , some electronic background with PC mainboards repair , access to SMD rework station and eprom programmer I started looking for DIY solution.

I was able to find Korg Radias service manual. 

 

Its has been posted on Korg forums.( link below - if this will help anybody)

 

 <https://www.dropbox.com/sh/1pmscfmrtp9ykdn/izuYC5TjWT> https://www.dropbox.com/sh/1pmscfmrtp9ykdn/izuYC5TjWT 
password is: "&radiasr" without the quotes

 

I obviously checked all the voltages and connectors. Everything seems to be exactly like service manual described. Looking at the CPU board schematics and CPU PCB itself i assumed that most suspicious parts are IC12 Flash memory , and IC27 SDRAM 128M.

 

Looking for cold solder joints I checked their traces for data and address bus. ICs voltages also have been checked. Everything seems to be ok. My best bet for know are either corrupted flash and (or) sdram working with that flash.

 

I already contacted Parts is Parts. Very nice people working there but unfortunately they have no electronics parts for my Radias at all (hence my later call to KorgUSA). I asked them if they can provide me programmed flash chip ( it has even part no in Korg parts catalog),  whole CPU borad or even if they can program blank flash memory chip, which I was going to send them. I got no answer for this....

 

All the ICs are slodered on radias CPU board ( see links with PCB pictures)

I already ordered SDRAM chip and will try to replace it soon but honestly I doubt if this will help. 

 

I have no access to working Radias CPU board or the one with non damaged flash. Therefore I cannot get copy of working flash. What I thought (since there is no other way visible on the horizon) is to order few blank flash chips (they are fairly cheap), desolder my existing flash from Radias, read it with eprom programmed and try to find area where chekcsum error is calculated. Fix that checksum (caculate it again and enter to bin code) program new flash chip, solder test scoket TSOP48 to CPU board and place there programmed flash chip.

 

I know it sounds desperate but I dont see any other way for now.

 

Do you thing this plan has any sens?

Can you advise me something based on your experience ?

 

Radias CPU board pictures:

http://obrazki.elektroda.pl/1692988900_1378904376.jpg

 

http://obrazki.elektroda.pl/9737250700_1378904379.jpg

 

Radias (flash) test mode results:

 

http://obrazki.elektroda.pl/7067918200_1380253022_thumb.jpg

 

Thank you for all your help

 

BR

Chris 



---In vintagesynthrepair@yahoogroups.com, <narfman96@...> wrote:

Not to worry! You're not spamming the group so you're in like flint.

 

I am worried about your Radias though. Your only bet may be John from Korgparts.com. I'm not sure if he can get a main board for you but if anyone can it will be him. He ordered a main board for my MicroSampler when Korg and none of their dealers would help. The only other problem will be cost and since it's special order there will not be any return. 

 

From what you describe for a problem somehow the flash has been corrupted. I'm pretty sure this is what happened to the MicroSampler. The CPU is in interrupt mode bacause the DSP will not run. Watching it try to boot on my scope the flash for the DSP never does anything.   



---In vintagesynthrepair@yahoogroups.com, <vintagesynthrepair@yahoogroups.com> wrote:

Hi

 

I'm new to this forum so please forgive me if I'm doing something against your forum posting rules.

 

I have problem with my KORG Radias which during startup, after the loading progress bar and the Logo of Radias hangs. The logo remains on the screen and 

a text appears at top of the screen saying : DRUM Checksum Error!!!.
Synth is then totaly frozen and doesn't respond to anything.

I updated the firmware to version 2.0 but this doesnt change anything. I found also test menu, which (for  FLASH memory test) says: SYS ok, USR ok, PCM checksum error!.

 

I tried contact Korg Service, Korg Product and Customers support. All are saying that this product is no longer supported and they have no parts for it. I also tried to find synth repair service that can help me but this was even more challenging. 

Looks like nobody (even authorized services I contacted ) really worked on that specifc synthesizer. Most technicians I talked to stated they have to contact KORG for diagnosis.

 

Somebody from Korgforums recommended me to reload flash with factory PCM still sound data. I don't know where to get such thing. Korg support page provides for Radias only firmware (no additional binary files there ) I also ask for that Korg but no answer for this at all. 

 

I dont know if I m so unlucky or really this synth is coursed and nobody wants to touch it even its vednor. I'm starting loosing my faith that this synth ill ever work again. 

 

Can you help me and advice what to do ?