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Old 15th September 2013, 06:26 AM   #1
Leeds is offline Leeds  Singapore
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Default High missing from phono stage

I need some advice to troubleshoot the problem.

The high is missing from both channels and sounded soft and muddy when playing turntable through my integrated amp with a built-in phono stage. The same turntable sounded good with my two other integrated amps so the problem must be from the phono stage.

What could go wrong with the phono card? Do I need to replace the two L/R capacitors and the single bigger capacitor (1000 uf, at 10v). Are these 3 caps causing the problem. The amp in question is a 1980 British made Nytech receiver. CD, and tuner sound good.

I am tempted to replace the 3 caps but have no confidence that they are the cause of the problem.
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Old 15th September 2013, 06:41 AM   #2
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Hi, if you can try to draw a schematic ...
Since you have to access the down side of the PCB, to solder or de-solder...
You are referring to some caps but an active stage
( like a phono amp) has more parts; of course you can put new caps, and
you can use higher voltage ones if you don't have the same exact voltage.

I did a restoration on an old amplifier with a 1 transistor phono stage from the early '70s
and I ended subsituting the output cap of the phono stage; it was an Elna 0.47 uF/50 V
and I put an Ero MKT ( the green ones) 0.47/63 V

Last edited by picowallspeaker; 15th September 2013 at 06:58 AM.
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Old 15th September 2013, 10:02 AM   #3
Leeds is offline Leeds  Singapore
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I will try to take a photo of the phono card the next time I open up the receiver. It is quite a challenge to open up the casing. Here is the receiver in question.

Click the image to open in full size.

I am wondering do these caps of the phono card affect the high or low if they are faulty.
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Old 15th September 2013, 10:20 AM   #4
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Is that a receiver ? Very strange -I don't see the scale for the tuning frequencies- does
it have an electronic display ? All the buttons suggest that it's more than just an integrated amplifier .
So as you say, you have to open it again.
Oh! I made an error: my phono pre has 2 transistors
So I see : 10 uF/10 V input caps; mica precision caps in the Riaa network ( equalization ) which works by adding NFB taken after the 0.47 uF output cap, which I changed. A 100 uF cap is for supply decoupling.
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Old 15th September 2013, 11:04 AM   #5
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Default Nytech CTA-252 XD ??

Quote:
Originally Posted by Leeds View Post
I need some advice to troubleshoot the problem.

The high is missing from both channels and sounded soft and muddy when playing turntable through my integrated amp with a built-in phono stage. The same turntable sounded good with my two other integrated amps so the problem must be from the phono stage.

What could go wrong with the phono card? Do I need to replace the two L/R capacitors and the single bigger capacitor (1000 uf, at 10v). Are these 3 caps causing the problem. The amp in question is a 1980 British made Nytech receiver. CD, and tuner sound good.

I am tempted to replace the 3 caps but have no confidence that they are the cause of the problem.
I think it is the CTA252XD - go to product list about
http://www.pinkfishmedia.net/forum/s...d.php?t=107603
Nytech Audio / Ion Systems Appreciation Thread [Archive] - pink fish media
and look also here:
Ugliest Receiver Made - AudioKarma.org Home Audio Stereo Discussion Forums
check additional this thread:
Nytech Audio / Ion Systems Appreciation Thread - Page 13 - pink fish media
Nytech CTA-252 XD II... MC haut gain... • LS3/5a le forum

All electrolytic caps in the signal pad you must replace. Don't use 10V, use in general 63V for lower ESR. Additional use bypass caps like WIMA MKP and if space an issue, MKS.
Attached Images
File Type: jpg Nytech CTA252XD-I.jpg (177.3 KB, 109 views)
File Type: jpg Nytech CTA252XD-II.jpg (24.8 KB, 107 views)
File Type: jpg Nytech CTA252XD-III.jpg (5.8 KB, 107 views)

Last edited by tiefbassuebertr; 15th September 2013 at 11:12 AM.
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Old 15th September 2013, 11:56 AM   #6
Mooly is offline Mooly  United Kingdom
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Both channels affected suggests to me that this is not a "hard" fault as such. Is there any user (or factory option) adjustable components to match the cartridge. Or has someone been there before and attempted this.

Is there an obvious audible problem or just a "subjective" feeling that it sounds a little soft ?
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Old 16th September 2013, 04:37 AM   #7
Leeds is offline Leeds  Singapore
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Quote:
Originally Posted by picowallspeaker View Post
Is that a receiver ? Very strange -I don't see the scale for the tuning frequencies- does
it have an electronic display ? All the buttons suggest that it's more than just an integrated amplifier .
So as you say, you have to open it again.
Oh! I made an error: my phono pre has 2 transistors
So I see : 10 uF/10 V input caps; mica precision caps in the Riaa network ( equalization ) which works by adding NFB taken after the 0.47 uF output cap, which I changed. A 100 uF cap is for supply decoupling.
The tuning is at the bottom of the sliders. The electronic display is right at the top with the 3 little windows.

I am attaching the photos of the phono card. The larger cap is 1000 uf 16v and the two smaller caps are rated 47 uf 16v.

I am hoping that it is the caps that is causing the problem.
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Old 16th September 2013, 04:41 AM   #8
Leeds is offline Leeds  Singapore
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Quote:
Originally Posted by tiefbassuebertr View Post
I think it is the CTA252XD - go to product list about
Nytech Audio / Ion Systems Appreciation Thread - pink fish media
Nytech Audio / Ion Systems Appreciation Thread [Archive] - pink fish media
and look also here:
Ugliest Receiver Made - AudioKarma.org Home Audio Stereo Discussion Forums
check additional this thread:
Nytech Audio / Ion Systems Appreciation Thread - Page 13 - pink fish media
Nytech CTA-252 XD II... MC haut gain... • LS3/5a le forum

All electrolytic caps in the signal pad you must replace. Don't use 10V, use in general 63V for lower ESR. Additional use bypass caps like WIMA MKP and if space an issue, MKS.
Thank you for the link. I have posted the problem to pinkfishmedia and hopefully, someone there could help.

I have posted more pictures of the phono cards.
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Old 16th September 2013, 04:44 AM   #9
Leeds is offline Leeds  Singapore
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I remove the casing and here are the photos.

This photo shows the phono card assembly
Click the image to open in full size.

This photo shows the phono card
Click the image to open in full size.

This photo show the top and bottom halves of the circuit boards
Click the image to open in full size.

This photo show the Nytech CTA252XD receiver
Click the image to open in full size.
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Old 16th September 2013, 05:39 AM   #10
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have you tried with another pickup ?
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