Display problem with Pass X1

Lucas_G · 29th September 2010, 01:43 PM

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!

PHPentatone · 29th September 2010, 02:07 PM

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

Kindest regards! (And many thanks!)

Lucas_G · 29th September 2010, 02:36 PM

Quote:

Originally Posted by PHPentatone

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!

qusp · 29th September 2010, 03:35 PM

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.

Mooly · 29th September 2010, 04:32 PM

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.

Melon Head · 29th September 2010, 08:43 PM

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.

Lucas_G · 2nd October 2010, 07:23 PM

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?

Melon Head · 2nd October 2010, 11:10 PM

There should be a model number for the display.
Once you have that simply look for the technical data sheet.

Mooly · 3rd October 2010, 05:59 AM

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?

gotoma8 · 28th January 2011, 06:56 PM

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

29th September 2010, 02:07 PM	#2
PHPentatone diyAudio Member Join Date: Sep 2010	No Idea... Looks rather irresolvable. I would say... : Take the easy way out and spend those US 500,-- Kindest regards! (And many thanks!)

29th September 2010, 04:32 PM	#5
Mooly diyAudio Moderator Join Date: Sep 2007	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. __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

3rd October 2010, 05:59 AM	#9
Mooly diyAudio Moderator Join Date: Sep 2007	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? __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

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29th September 2010, 03:35 PM	#4
qusp is choosing a less facetious title... diyAudio Member Join Date: Oct 2009 Location: Brisbane, Australia	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.

29th September 2010, 08:43 PM	#6
Melon Head Banned Join Date: Nov 2006	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.

2nd October 2010, 11:10 PM	#8
Melon Head Banned Join Date: Nov 2006	There should be a model number for the display. Once you have that simply look for the technical data sheet.

28th January 2011, 06:56 PM	#10
gotoma8 diyAudio Member Join Date: Apr 2006 Location: SF/Bay Area	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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