[KL] Re: K2500XS HD Behaviour

[[e-mail] [KurzList]]

...............because the color code of the wires is not red for 5 vdc and black for ground on the cable.


Yes, I almost did it. It could still use it. I hard wire it to Dig ground and Dig 5 vdc.


Since the K2500R uses a K2000R power supply that needed several extra big current jumper tacked to bottom of the circuit board to handle the extra currents drawn by the addition big LSIs, and even more on KDFX.


And while you at it, disconnect the analog 12VDC that goes to the program pin of the flash ROMs on CPU daughter board. The 12V analog goes thru the CPU daughter board to the sampler. It is used to erase the flash roms. Using the 12 V analog was a mistake. It should have been connect to the digital 12 VDC.


You can then run a separate wire from the digital 12VDC on the power supply to the flash ROMs. THIS MISTAKE IS THE CAUSE OF 98% OF THE DREADED BLUE SCREEN OF DEATH (by erasing of all flash Rom data when a static electric charge get feed in via the audio jacks and discharge through the flash roms).

[[e-mail] [KurzList]]

You know, it's great you have all this knowledge - but without a schematic or labelling I would not know where to begin. I must be missing a level of documentation.

So, is there a webpage with photos and commentary as a step by step guide to how to do this, and other commone corrections?

If not, I have a feeling that that would help a lot of K2500XS owners out there, prevent repeated forum questions, and help to keep more machines from the scrap merchant!

I have time this week to look at the boards in my K2500XS so and would be happy to create some photos of the PSU overhaul as I go along, if I am able to work out what I supposed to do to get it on its feet.

A Skype session with video and audio might be a good way to work through problems like this without people needing to take machines anywhere, if they are confident to open an older machine up to give it a go.

[Jon Hartmann [e-mail] [KurzList]]

are there any youtube videos of Kurz guts being worked on?

On Thursday, August 3, 2017 11:33 AM, "***@yahoo.com [KurzList]" <***@yahoogroups.com> wrote:


  You know, it's great you have all this knowledge - but without a schematic or labelling I would not know where to begin.  I must be missing a level of documentation.

So, is there a webpage with photos and commentary as a step by step guide to how to do this, and other commone corrections?

If not, I have a feeling that that would help a lot of K2500XS owners out there, prevent repeated forum questions, and help to keep more machines from the scrap merchant!

I have time this week to look at the boards in my K2500XS so and would be happy to create some photos of the PSU overhaul as I go along, if I am able to work out what I supposed to do to get it on its feet. 

A Skype session with video and audio might be a good way to work through problems like this without people needing to take machines anywhere, if they are confident to open an older machine up to give it a go. #yiv3820483982 #yiv3820483982 -- #yiv3820483982ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv3820483982 #yiv3820483982ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv3820483982 #yiv3820483982ygrp-mkp #yiv3820483982hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv3820483982 #yiv3820483982ygrp-mkp #yiv3820483982ads {margin-bottom:10px;}#yiv3820483982 #yiv3820483982ygrp-mkp .yiv3820483982ad {padding:0 0;}#yiv3820483982 #yiv3820483982ygrp-mkp .yiv3820483982ad p {margin:0;}#yiv3820483982 #yiv3820483982ygrp-mkp .yiv3820483982ad a {color:#0000ff;text-decoration:none;}#yiv3820483982 #yiv3820483982ygrp-sponsor #yiv3820483982ygrp-lc {font-family:Arial;}#yiv3820483982 #yiv3820483982ygrp-sponsor #yiv3820483982ygrp-lc 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[[e-mail] [KurzList]]

Hey Wink,

I just purchased another K2500RS, and when I receive it I'll go through this suggestion of the 12V digital replacement of the analog. I swear I wasn't being gauche with the connector, reading +5VDC with my meter with red as pos and white as ground.

Here's my "before" pic:

Loading Image... http://theluthers.net/images/K2500R-before.jpg

http://theluthers.net/images/K2500R-before.jpg

http://theluthers.net/images/K2500R-before.jpg http://theluthers.net/images/K2500R-before.jpg


View on theluthers.net http://theluthers.net/images/K2500R-before.jpg
Preview by Yahoo




... and after:

Loading Image... http://theluthers.net/images/K2500R-after.jpg

http://theluthers.net/images/K2500R-after.jpg

http://theluthers.net/images/K2500R-after.jpg http://theluthers.net/images/K2500R-after.jpg


View on theluthers.net http://theluthers.net/images/K2500R-after.jpg
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Note the PSU/audio board needed a replacement capacitor (actually two). Much nicer now, with plenty of nice open space for airflow. I even taped the mounting bracket for the transformer back in, just in case anyone ever needed it -- the replacement I got from Alex was for the "early" style rack units which required me to mount it using 75mm bolts. And yes, that's a Noctua fan. Highly recommended -- much more airflow than the Panasonic, and *so* much quieter...

[[e-mail] [KurzList]]

I've been thinking about this, and have a suggestion.

What you're describing sounds like your CCFL is dying (it happens, and for the 2500 series it's due), but could also be related to the power supply. Were you able to obtain the K2500 service manual from the "Kurzweil-K2600" group's files section? This group doesn't allow uploads, otherwise I'd post them here. Let me know if you need me to send them to your Yahoo address.

Here's an image of the two pages describing the PSU test and calibration for the K2500X:

Loading Image... http://theluthers.net/images/K2500X-PSU.jpg

http://theluthers.net/images/K2500X-PSU.jpg

http://theluthers.net/images/K2500X-PSU.jpg http://theluthers.net/images/K2500X-PSU.jpg


View on theluthers.net http://theluthers.net/images/K2500X-PSU.jpg
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What would be even better, after verifying the PSU is good, you were able to put a meter down the pins of J512 (LCD backlight connector on the I/O board), which is the 16VDC unregulated input. Pin 1 is GND and pin 2 is +16V, and see if there are any fluctuations in input supply whenever your display is fluctuating. This can be difficult with a digital meter if the sampled display isn't "fast", which is why I usually use an analog meter or a scope to watch for voltage fluctuation. If all is well there, check the AC output voltage at pin 1 (ground) and pin3 of J513, the backlight power connector, which should be ~100VAC (and please be sure to switch your meter to AC voltage.) All this is to verify you're getting correct power to the CCFL backight.

If all is well at this point, you're confident the power supply is not the issue and you still see display fluctuations as you've described, then it's probably a sure thing your CCFL backlight is failing, and you have to either replace the entire display (wasteful) or the CCFL backlight tube. I don't recommend tearing the display completely apart by bending the board mounts and delaminating the contacts, but you can remove the CCFL module itself and expose the CCFL tube with minimal damage:

1) Remove the display module from the unit
2) Remove the four retaining screws from the component side of the display module
3) Clip the nylon cable tie from the edge of the board holding the power connector in place
4) Using the edge of a small common screwdriver, push up the bottom of the two friction retainer pins and remove
5) Remove the friction retainer pin shoulders from the display
6) Slide out the CCFL module

There will be a small raised plastic retainer for the diffuser that will be bent back and/or break. Work it out slowly, knowing that you're bending plastic. Once free, use a small set of flush-head cutters to trim this piece off. The diffuser face is held in place with some double-sided tape at the friction pin holes, pry this off with a small flat-blade screwdriver and you should have the CCFL tube exposed, and it should be pretty obvious how this is held in place. Those rubber boots have a small amount of glue down in the lamp bases, which will need to be worked out to slide the boots down the wires.

You can order a replacement 157mm CCFL tube from "lcdparts.net" for ~$10.00US:

http://www.lcdparts.net/ccfldetail.aspx?ProductID=1592 http://www.lcdparts.net/ccfldetail.aspx?ProductID=1592

You will have to clip and solder the original wires back on.

- or -

I have a supposedly good unit I could ship you to test. Contact me at this ***@yahoo.com email address and we can work out the details if you're so inclined...

[[e-mail] [KurzList]]

Hi Dan

Thanks for such a thorough email.

Yes, I have downloaded the manual and schematics, so with the right guidance I am about ready to dive in and sort it out.

I have been wondering about the integrity of the PSU - recap? Dry joint? The machine locked up late last week, so the comment about 5V fluctuations upsetting the microprocssor perhaps is another clue it has to with the 5V rail. I guess it's all connected, so we need to find a way to discern which line of enquiry is correct.
So I think we are into following the manual to test the PSU board, and then over to your display tests?

I picked up that I need
1) a "non-KA" part no IC
2) to sever the 12V flash wire mistake while I am about it (and solder in the fix)

Advising, I am picking up faint electrical odour too, when the case is closed.

All advice welcomed at this point. I'll record what I can as I go as photos.

[[e-mail] [KurzList]]

David,

Post by ***@yahoo.com [KurzList]
Advising, I am picking up faint electrical odour too, when the case is closed.

Okay -- this is probably going to require major surgery. Check the AC bump transformer on the digital I/O board for the smell -- if the CCFL backlight is actually failing, it's cycling that little transformer and you're probably going to want to get your nose around that and see if that's the source. If so, time to replace the CCFL.

If that's not the source, unplug all the power connections to your power supply and completely remove it - the PSU board, transformer, AC rail selector and plug/fuse assembly. Re-assemble these components on a workbench with some non-conductive surface (big cutting board), and perform the tests on the power supply. Smell the transformer -- if it's going, you'll need to replace that because there's no way to get into the windings even if you were so inclined.

You could have some swollen caps, this is a common failing on the K2500 series. If you see any of those electrolytics either leaking or bulging off the top (mostly the big one), time to replace with some nice Nichion 105 degree versions.

Are you located in the US?

[[e-mail] [KurzList]]

David,

Any progress?

[[e-mail] [KurzList]]

Hi Dan, sorry, been up to my eyes in a EF6/SQL database problem this week so far, so I am hoping to start Kurzweil K2500 PSU fixes Thursday morning. I'll do the photos on the way through because I am sure that will help others. Skype call can be arranged if you're about and want to join in when I get to the nitty gritty of measurements and soldering. Liking the Nichicon cap idea. And to answer your previous, I am UK based (GMT timezone, +1hr currently).