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Old 29th September 2010, 02:43 PM   #1
Lucas_G is offline Lucas_G  Netherlands
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Default Display problem with Pass X1

After having built a couple of Pass DIY amps, my friends got enthusiastic too about the sound of Pass amplifiers.
Recently a friend bought a second-hand Pass X 1 preamp from 2004.
He is overjoyed with the sound. However after the acquisition we found a small defect in the preamp; the display is badly readable from a distance of two meters or more. Furthermore the left side of the display is less bright than the rest.
Yesterday we compared the display with the same amp from another friend. It turned out that the display is not as bright and clear as it should be.
I attach a photo of the display.
Meanwhile my friend got some information from the Dutch distributor. Repair would cost about 500 USD, and that seems a costly affair for an only 6 year old amp.
My question is: Does anyone have experience with this? Having some experience in DIY, could I try to mend it myself?
Any advice welcome!
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Old 29th September 2010, 03:07 PM   #2
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Default No Idea...

Looks rather irresolvable. I would say... : Take the easy way out and spend those US 500,--

Kindest regards! (And many thanks!)
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Old 29th September 2010, 03:36 PM   #3
Lucas_G is offline Lucas_G  Netherlands
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Quote:
Originally Posted by PHPentatone View Post
Looks rather irresolvable. I would say... : Take the easy way out and spend those US 500,--

Kindest regards! (And many thanks!)
That would be an easy way out indeed, but we are DIY guys, remember!
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Old 29th September 2010, 04:35 PM   #4
qusp is offline qusp  Australia
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ask papa if he remembers or has a record of the model of the LCD used, seems most likely that the screen itself would be the culprit, but I suppose it could also be the power supply to this section.
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Old 29th September 2010, 05:32 PM   #5
Mooly is offline Mooly  United Kingdom
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It looks like a VFD from the picture (Vacuum Fluorescent Display) and faults fall into a couple of categories.

The display itself can suffer from low emmision giving dull uneven illumination. Sometimes this can actually improve if it's caused by lack of use, the duller segments recovering if left illuminated.

Is the display clean ? and the polarising tinted window clean on the inside... because that makes a big difference if not. They attract atmospheric dirt easily.

Power supply problems... the displays use a negative rail of around -28 volts. Dried up caps can be a real issue here depending how that supply is derived. Any ripple on the supply can cause illumination problems too.

Looking closely at the pictures I suspect the display may be low emmision because there is noticeable brightning in horizontal lines which coincides with the heaters in the display.
Whether the dull segments would recover with use is impossible to say.
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Old 29th September 2010, 09:43 PM   #6
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If you can remove the display, you could try hooking it up to a lab power supply.
Then you could determine whether it is a power issue or a display issue.
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Old 2nd October 2010, 08:23 PM   #7
Lucas_G is offline Lucas_G  Netherlands
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Quote:
Looking closely at the pictures I suspect the display may be low emmision because there is noticeable brightning in horizontal lines which coincides with the heaters in the display.
Whether the dull segments would recover with use is impossible to say.
Hi Mooly and thanh1973,

Thank you both for your suggestions!.
We have had the display on for some while now, but it hasn't really improved, so I guess it's not low emission...

I will try the power supply. It would help if I knew how much voltage it should supply to the display..., but I am too shy to ask Papa

Has there ever been a service manual for the X1?
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Old 3rd October 2010, 12:10 AM   #8
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There should be a model number for the display.
Once you have that simply look for the technical data sheet.
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Old 3rd October 2010, 06:59 AM   #9
Mooly is offline Mooly  United Kingdom
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It could still be low emmision... it's more when they have been unused that they seem to recover over time.

Voltages... can't give exact details but all VFD follow the same principle. Have a read at this,
Marantz CD5000 - display very dull - help?
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Old 28th January 2011, 07:56 PM   #10
gotoma8 is offline gotoma8  United States
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So, I was thinking of the X1 as well... is there a unanimous "approval" for this pre? Is it as good as they say?

I am currently using a Bent NOH transformer based preamp.

Thanks
T
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