Krell Kps 25 sc problems
- Thread starter Cognard
- Start date
Thank you very much Lagonda , you are the man !!!!Your welcome !
well , i shouted "hurrah" before testing the analog part .....variable output works fine , but fixed output does not work , plus when i touch the xlr fixed output when the rca`s are connected on the fixed output i hear some mass loss noise ......the fixed output is on a permanent mute condition .....any advice here ??
Do you have light in the red output mute indicator lamp ? Try toggling between the different analog output setting. The trim setting for the CD output could be set at low. Go into the menu and check. The capacitors on those analog boards go bad every 10 years or so too
Have you tried the balanced fixed outputs ? Are they working ? Alternatively try the tape out rca's, the machine could have been wired wrong from the factory, and has probably never been used on fixed outputs before. If balanced connectors are working, use a conversion plug, or make a conversion cable.
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I do not like the idea of shorting the inverting output phase in a XLR -RCA adapter - in cases of low output impedance it obliges the output circuit to supply a lot of current from a shared power supply. Some quality adapters connect the inverting phase (pin 3) to ground using a 10 kohm resistor. Surely this only applies to XLR output to RCA input.
When making a RCA output to XLR balanced input cable the resistor should have the value of the output impedance of the output stage.
When making a RCA output to XLR balanced input cable the resistor should have the value of the output impedance of the output stage.
well , still dealing with the lack of signal at the fixed output ....in the mean time , i have found that the unit becomes crazy when cueing , ( back or forth) fixed the fork that moves the laser , now fwd cue is ok , but back cue is still crazy .....any clue of what could be happening ? thank you !!
Stop being so picky, be happy its playing again ! Who needs cuing back
anyway ?
It sounds like the laser is weak, or adjusted wrong.Laser is new !! I have bought 2 More NIB units !! Picky? That piece of hardware costed the same as a brand new Mercedes when it was new !! And a 2000 cedes still works ok !!! Lol !!!Stop being so picky, be happy its playing again ! Who needs cuing back
anyway ?
well , looks like i am almost done with the kps25sc .......found the lack of sound at the fixed audio output ....someone stole the preamp boards , and they were surprisingly present at krell in Argentina........... , $500 tossed the boards in my pocket, big pocket by the way .....capacitors were almost dead , replaced them all , tested analog part , worked perfect , fixed , non fixed , mute , etc ......some distortion came from the digital section .......all the smd electrolytics from the dac are fried .....ordered nichicon units from mouser .....let`s see .......btw , fwd and rew cue is fixed now , just a broken piece at the laser fork .......let`s see when mouser sends the caps .....
By now you have almost built a new KPS 25sc
Careful, if it's the older 20 bit model, the dacs go bad and start making weird noise, the 24 bit ones just fail one at a time, and you loose half the output in one channel as they are stacked 2 per side.
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Dac is 24 bits , i heard distortion on 1 channel , caps were fried .....replacing caps on both sides ....By now you have almost built a new KPS 25sc
Replaced smd caps on the DAC board , still hearing some clipping on bass and volume is higher on one channel ...... this beast is driving me crazy .....maybe the 24 bit black module got bad ?
How big is the difference in output between the two channels ? I never had a problem with the clock (black module). The KPS 25 sc often has problems with volume boards or the control chip for volume, my brothers unit sometimes freezes and has to be turned off and on to work again. Try sending a analog signal into the preamp section, it will tell you if the fault is in the volume board or the dac board. If the drop in output in one channel is substantial it is probably a burnt BurrBrown PCM1704U chip, the dac board holds 4 of them, and i have had 3
go bad until now. If the problem is in the volume board,re-soldering the resistors can sometimes fix the problem, other times the problem is in the circuit board itself, and a new electrical path has to be created. The repair guy in Holland described the problem/fix pretty well, i will see if i kept it. I think it was in a eBay add he posted last year.
well .....How big is the difference in output between the two channels ? I never had a problem with the clock (black module). The KPS 25 sc often has problems with volume boards or the control chip for volume, my brothers unit sometimes freezes and has to be turned off and on to work again. Try sending a analog signal into the preamp section, it will tell you if the fault is in the volume board or the dac board. If the drop in output in one channel is substantial it is probably a burnt BurrBrown PCM1704U chip, the dac board holds 4 of them, and i have had 3 View attachment 75655go bad until now. If the problem is in the volume board,
re-soldering the resistors can sometimes fix the problem, other times the problem is in the circuit board itself, and a new electrical path has to be created. The repair guy in Holland described the problem/fix pretty well, i will see if i kept it. I think it was in a eBay add he posted last year.
DAC : left channel sounded at normal level , too much distortion , one pcm 1704 worked very hot . right channel sounded low , not many distortion , one pcm1704 worked hot , not as hot as the left one , but abnormally hot .
damaged ics were crossed , they were not taking the same task on L&R boards .
i have removed a working ic from the right channel and welded it in place of the real hot ic on the left channel .
TEMPERATURE CEASED AND LEFT CHANNEL IS WORKING PERFECT NOW.
now i will have to find a set of pcm1704 ic`s ......there are several offers with many letters behind the 1704 number , which one would be the correct one ? the 1704 i have here , all of them , have no letters behind the number ......any reliable source ??
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I think the K is the best and my original dac where all K, but finding any these days is good, they have been out of production for some years. Did you try if there was a difference in channel volume with a analog signal ?
Analog signal is perfect now , either on fixed or variable outputs .....lack of fixed output was the result of 2 stolen boards at krell sudamericana , maybe the result of an estimate not accepted ....they were waiting for me .....sooner or later the new owner should land there .
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