Kurzweil K2500X Repair Project - Page 1
Forum section: electronics / general

author: dexters_lab
author_rank: Unknown
timestamp: July 09, 2014, 12:35:15 pm
content: just picked up this basket caseprevious owner sent his kurzweil k2500x keyboard synth in for repair to a local pro-audio repair shop, it came back 7 months later in bitsWill be interesting to see if it can be revived, i'll probably blog this one my youtube channel after i'm back from holiday

author: Yago
author_rank: Frequent Contributor
timestamp: July 10, 2014, 04:27:09 pm
content: Look forward to blog, a lovely instrument.Looked at something similar some time back, found the PCB tracks very eager to part company from the board!

author: Kjelt
author_rank: Super Contributor
timestamp: July 10, 2014, 06:12:23 pm
content: nice! if you can repair it. Those synths probably have a lot of customs chips I hope for you that the failure lies somewhere else.

author: dexters_lab
author_rank: Unknown
timestamp: July 10, 2014, 08:06:53 pm
content: just had a quick look at it, it went in to a pro audio place with intermittent issues believe, freezing etc, which got worse.I just tried to power it and i do get some leds lighting but no display and flicking / dim leds so this sounds like a power supply problem to me.it is enormous, 88 weighted keys with the top case made from extruded aluminium, too big for my little lab so i'm working on the floor in the living room!!i'm sure SWMBO wont mind my scope and multimeter as well

author: 22swg
author_rank: Frequent Contributor
timestamp: July 10, 2014, 10:00:37 pm
content: Great looking instrument , I had a very old Elka e19 made several mods to it fortunately i got hold of the schematics , great fun . be interesting to see how you get on..http://www.wdgreenhill.com/manu/kurzweil.htmsay they have service manual ?

author: dexters_lab
author_rank: Unknown
timestamp: July 10, 2014, 10:29:50 pm
content: right, i found an online service manual for itnothing seems amiss on a visual checkbeen all over the power supply and pretty much every test point is way out of spec so looks like the power supply, thankfully they are all either low or a just a few % over so i would hope there's no damage beyond the power board

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 11, 2014, 05:03:20 am
content: If some unobtainable ASIC is bad, what about stuff a PC in it running some MIDI software?

author: dexters_lab
author_rank: Unknown
timestamp: July 11, 2014, 07:19:30 am
content: some pics, more to come once i remove the power board and transformer

author: Kjelt
author_rank: Super Contributor
timestamp: July 11, 2014, 08:09:23 am
content: Ah you must love those conventional linear 20 year old PS's with standard 78xx's. Piece of cake to replace and repair

author: dexters_lab
author_rank: Unknown
timestamp: July 11, 2014, 08:46:21 am
content: yes hopefully, there is some control in it, without the power connector to the audio processor board some of the rails are 0v apart from a 5v line so suspect the audio board enables the remaining rails. The backup batteries also run through this board.it looks like the previous repairer replaced the main filter cap (and left flux everywhere) i cant see anything else that might have been touched by them.the story was the guy doing the repair decided to go on tour abroad after he'd taken it in and just left it as it was!

author: 22swg
author_rank: Frequent Contributor
timestamp: July 11, 2014, 01:26:46 pm
content: You may need to load some the power outputs to get a voltage...

author: dexters_lab
author_rank: Unknown
timestamp: July 14, 2014, 08:11:39 pm
content: ok small update on this, turns out i can order a new PSU from kurzweil for £25 inc shipping so i will be ordering one.i will hopefully still be repairing the apparently defective PSU and having a working one will certainly help.

author: dexters_lab
author_rank: Unknown
timestamp: July 17, 2014, 08:24:12 pm
content: Will post more on this after i am back from japan in a few weeks but for now...Kurzweil K2500X Repair Part 1:

author: 22swg
author_rank: Frequent Contributor
timestamp: July 17, 2014, 08:49:00 pm
content: Synth usually have a split keyboard setting available and instrument assignments to each section it may have lost some of the voice settings for the keys that are not responding.. or split may be set up wrong , it will be on the display somewhere

author: dexters_lab
author_rank: Unknown
timestamp: July 17, 2014, 09:10:13 pm
content: Quote from: 22swg on July 17, 2014, 08:49:00 pmHmmm, yea i should have mentioned i checked for key splits in the video, the keys are not working on any any mode, its not even outputting midi from those keys

author: SeanB
author_rank: Super Contributor
timestamp: July 18, 2014, 07:46:17 pm
content: Probably a broken scanning line to the half keyboard. The backlight might also be associated with this if there is a trace for it running near the board break.

author: dexters_lab
author_rank: Unknown
timestamp: July 18, 2014, 09:40:37 pm
content: Lcd should be easy fixed, its a standard 240x64 graphic module, the backlight is EL so would suspect an issue with the backlight driver. I might just replace the whole lcd module with one that has an led backlight and remove all the hv stuff as there does appear to be a line of pixels out on the display as wellThe keys run into a separate board so suspect another issue there, i will need to remove some of the keys to access where the idc cable connectsBoth jobs for when i return from japan!

author: dexters_lab
author_rank: Unknown
timestamp: July 20, 2014, 11:30:50 am
content: update 2all keys now working, the backlight is still dead and i have now spotted three horizontal lines of pixels out on the LCD so i'm debating if i should just swap the screen for a new one.They are just standard 240x64 graphic modules so i could pick one up on ebay for about £25 with an LED backlight like this:http://www.ebay.co.uk/itm/231138248717or i could try and retro fit a LED backlight into the old display, check the zebra strips to try and fix the dead pixels but something tells me i will be cursing it!i have also started replacing some of the maybe 20 or so missing screws! So at least now i dont have 27kg of bits trying to depart company from each other when i move it.

author: SeanB
author_rank: Super Contributor
timestamp: July 20, 2014, 12:05:52 pm
content: The screws should be easy if you have an old DVD or VCR as a screw donor. Old CRT monitors also have a surprisingly large number of screws inside as well.

author: dexters_lab
author_rank: Unknown
timestamp: July 20, 2014, 04:10:36 pm
content: normal set-top-box screws too wimpy i'm afraid, it's all M4 bolts, thankfully i have plenty on hand.

author: SeanB
author_rank: Super Contributor
timestamp: July 20, 2014, 07:16:38 pm
content: Older VCR decks with metal transport typically had 300 plus screws in the unit. When I take apart that UMATIC player ( havent forgotten I will have to post you the head from it) you will see a load of M4 screws in it.

author: 22swg
author_rank: Frequent Contributor
timestamp: July 20, 2014, 08:27:42 pm
content: I am guessing that the way you 'stabbed' the keys you are not a player,So i suggest you consider having a go , I did at the age of 55 and its a great pastime / interest... Here's you first piece...Happy Hols...

author: dexters_lab
author_rank: Unknown
timestamp: July 21, 2014, 08:20:34 am
content: no i dont play, will likely be selling this on when its finished, its too big for me to keep or learn on anywayi'm going to try and clean it up as best i can, make sure everything is working. The keys and weights could do with a clean so need to decide if i want to disassemble all of the keys. I do have a set of the last generation PLDs to install onto the engine and audio boards which fix a few hardware bugs. The PLDs in this seem to be the original release.i have seen someone selling the sampling option board on ebay which would be a nice upgrade but perhaps a step too far...