Repairing an SP404 need help - Page 1
Forum section: electronics / repair

author: Psqwall
author_rank: Contributor
timestamp: June 30, 2013, 03:57:26 pm
content: Hello EEV folkshave not posted in a while... I am back with a new project and a request for some help. I recently bought a broken Roland SP404 off a lad who plugged in the wrong power supply and since that time it has not powered on. I immediatly thought blown fuse and rushed over to snatch it up. I got it to my bench and opened it up to find 3 surface mount fuses melted and one processer chip with a little bubble in it. I am guessing that the chip is not effected and if I replace the 3 fuses I will have a working unit. My questions are1. Where do I purchase the proper fuses for this unit?2. How do I figure out the proper value I need only one fuse is readable and it reads M2W ?3. Do you think the chip was effected? I think its just residue from the fuse blastHere are some pictures of my findings

author: SeanB
author_rank: Super Contributor
timestamp: June 30, 2013, 05:21:27 pm
content: Bad news.Those weren't fuses.........They were the input voltage regulators, and it was a switching device, it's power switch and the diode, all cooked to death. The bubble on IC13 is fatal damage, but it is replaceable, providing you can get a new one. It was the main RAM for the micro. The EEPROM above it looks like it survived, along with the main microcontroller.

author: marshallh
author_rank: Unknown
timestamp: June 30, 2013, 05:32:01 pm
content: The bad news is that whatever killed the RAM probably nuked tons of other stuff on there also. Probably the 3v3 was shorted to the input voltage.

author: Psqwall
author_rank: Contributor
timestamp: June 30, 2013, 05:59:44 pm
content: Thank you all !So the odds of me repairing this and it being worth it ?The unit new costs about 400will the parts cost more than that?Will I a novice be able to repair all the burnt components?

author: Psqwall
author_rank: Contributor
timestamp: June 30, 2013, 06:02:31 pm
content: I should say replace not repair the burnt components ?

author: SeanB
author_rank: Super Contributor
timestamp: June 30, 2013, 06:07:53 pm
content: Sadly no...... Not the cost of the spares ( Ram is cheap, the regulator chips as well) but the tools and knowledge is expensive.

author: Psqwall
author_rank: Contributor
timestamp: June 30, 2013, 06:23:01 pm
content: Oh well I have a decent iron and a halfway decent scope and most toolsI am asking how hard will it be for me to desolder the 3 input voltage regulatorsthe IC13 and solder in those 4 parts. I am willing to buy those 4 parts and solder them in to practice. What are the odds of me replacing those 4 partswill fix the device? If slim to none do you think that there are other parts I should look for that will be cheap?My main question is thisI bought this to repair it and get practice and feel all proud of myself when its fixednow I just feel like a moron lolI would totally not mind pricing out the 4 parts we know of and if they are under $50 I would buy them and have a gobut what other parts should I be looking forand most important what website can I buy/price these parts from ?God I hate new gear ! It's so not repairable !

author: SeanB
author_rank: Super Contributor
timestamp: June 30, 2013, 06:38:34 pm
content: If you have the tools and look for a service manual online so you know what the cooked chips are then they will be cheap, and you can desolder them and replace them. The ram is a cheap part, so you will come out under the $50 probably by quite a bit. You might even find them on old dvd writers. If you are willing there are plenty of tutorials here about chip replacement. All involve a lot of liquid flux, a steady hand and good light, which are simple. As you have nothing to lose go for it.

author: PA0PBZ
author_rank: Super Contributor
timestamp: June 30, 2013, 06:43:23 pm
content: I wouldn't bet that the only damage done is visible. The voltage regulators are cooked and so is the ram chip, so you have to ask yourself what else will be killed from overvoltage. I think that the chance that the main processor is still ok is less than 50%.

author: Psqwall
author_rank: Contributor
timestamp: June 30, 2013, 06:57:08 pm
content: Ok so what would be a check list of what I am looking for when it comes to other parts that might have been destroyed ?What is an estimated parts list and cost listkeep in mind this is a learning project for meCan I repair a toasted SP404 for under 100 bucks ?main processor is that a replaceable chip?Can anyone recommend a good website where I can part out this repair ?Also I have looked for a service manual online and it just seemed to bring me to sketchy websitesany goto source for Roland products service manuals?

author: SeanB
author_rank: Super Contributor
timestamp: June 30, 2013, 07:23:38 pm
content: As the ram died short circuit it likely protected the other chips from damage. You will have to put up the writing or a clearer pic of the crispy chips.

author: Psqwall
author_rank: Contributor
timestamp: June 30, 2013, 07:28:48 pm
content: OK will dowhen I get to my bench tomorrow I will take more pictures that are more clearI can make a video using a macro lens so all can see. Good news I just downloaded the service manualand as a reference for anyone else looking to fix a sp404 I am going to post the link herehttp://elektrotanya.com/roland_sp404.pdf/download.htmlThanks so much for your help EEVersI am gonna try and conquer this one first and then get back to my over my head drum machine rebuildbad news is I have to find a new home for my lab and that might derail my learningAnyone on here live in NYC ?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 30, 2013, 10:20:46 pm
content: Probably worth pulling that RAM off and seeing of the power draw from the rail it runs off (via an external supply) looks sensible, but if that much power got to the RAM, chances are very high other things are smoked as well.

author: Psqwall
author_rank: Contributor
timestamp: July 01, 2013, 12:36:49 am
content: Oklike what other things?What could get smoked ?Are you all familiar with the Roland SP404 ?the only thing I think that could make me not go forward with this repair is if the partswill cost me over $100 bucks or if a whole board is firedif its a matter of replacing 4 service mount componentsor even 10 that are replaceable I think it is worth itWe all can spot 4 things that need replacingI guess if I open it up further and take more images or video and post it herewe all can better determine if its worth itIs that safe to say?Forgive my newbieness I only just begun repairing audio gear and have fixed a few simple things so farbut I really want to be able to fix things like this so that is why I am so eagerI am not looking to do the imposible though