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HP8568B on screen text intensity
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I have 2 of these analyzers and both demonstrate exactly the same
problem - the trace intensity becomes inreasingly less visible as the trace line lengths get shorter. On screen text, consisting of short lines, is barely visible (unless I really turn up the intensity control). Has anyone else seen this? I have posted a pic here of the signal on TP301 (Z axis output) with 0 volts being the bottom graticule. The intensity control is adjusted for a low intensity (but clearly visible) trace. I'd appreciate hearing from anyone that might have seen this or can compare my scope trace with thiers? David. KM5TZ |
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Hi David,
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You have a low emission CRT. Most HP CRT's are on RF instruments where the operator feels inclined to leave the instrument on 24/7 to keep it warmed up and stable for use at a moment's notice. This wears out the cathode in the CRT's gun assembly, and makes it become increasingly dim, and blurry. There are only two fixes for this problem: 1) replace the CRT, something that is becoming more and more difficult, and 2) restore/rejuvenate the CRT, a process that sometimes extends the useful life of the CRT for a good while. I have restored several HP CRTS (I have never needed to do a tektronix CRT) using my Sencore CR70 CRT restorer. The Sencore CR70, and CR7000 are about the best that are routinely available. They were made for the television/ computer monitor repair market, but are equally applicable to scope, and test equipment CRT's. After you have restored/rejuvenated a CRT, you should avoid leaving the instrument on 24/7. If you only turn it on when you need it, it will last you for many many years. If you use it 24/7, it might last you only another couple of thousand hours. Each additional time you restore/rejuvenate the CRT, you get less of an improvement, and less additional life, until it just quits. -Chuck Harris david_woodhead wrote: I have 2 of these analyzers and both demonstrate exactly the same problem - the trace intensity becomes inreasingly less visible as the trace line lengths get shorter. On screen text, consisting of short lines, is barely visible (unless I really turn up the intensity control). |
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Didier Juges
Chuck Harris wrote:
Hi David,There is a third fix: a company (I forgot whom, but they should not be too hard to google, or John Miles can post it here) makes a color LCD replacement for the entire display. Pretty neat, and great use of color. It's not cheap, but worth it, considering what these instruments are worth in good condition. This replacement makes it better than new! Didier KO4BB |
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That would be Test Equipment Plus which I pointed out to the group some
months back when we were having a discussion on weak/failing CRTs in 856x units. Web site: <BLOCKED::> Not inexpensive however. - Greg _____ From: hp_agilent_equipment@... [mailto:hp_agilent_equipment@...] On Behalf Of Didier Juges Sent: Saturday, January 13, 2007 7:44 AM To: hp_agilent_equipment@... Subject: Re: [hp_agilent_equipment] HP8568B on screen text intensity Chuck Harris wrote: Hi David,increasingly dim, and blurry.There is a third fix: a company (I forgot whom, but they should not be too hard to google, or John Miles can post it here) makes a color LCD replacement for the entire display. Pretty neat, and great use of color. It's not cheap, but worth it, considering what these instruments are worth in good condition. This replacement makes it better than new! Didier KO4BB |
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thats the way i would do it too and i think the kit is worth $1495
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im not familiar with the 8568b but if it dosent have a vga output then it is a fairly complex project to design a product like that. "im sure their sales volume is small "100s of units" ----- Original Message -----
From: Greg Werstiuk To: hp_agilent_equipment@... Sent: Wednesday, January 17, 2007 3:19 AM Subject: RE: [hp_agilent_equipment] HP8568B on screen text intensity That would be Test Equipment Plus which I pointed out to the group some months back when we were having a discussion on weak/failing CRTs in 856x units. Web site: <BLOCKED::> Not inexpensive however. - Greg _____ From: hp_agilent_equipment@... [mailto:hp_agilent_equipment@...] On Behalf Of Didier Juges Sent: Saturday, January 13, 2007 7:44 AM To: hp_agilent_equipment@... Subject: Re: [hp_agilent_equipment] HP8568B on screen text intensity Chuck Harris wrote: > Hi David, > > You have a low emission CRT. Most HP CRT's are on RF instruments > where the operator feels inclined to leave the instrument on 24/7 to > keep it warmed up and stable for use at a moment's notice. This wears > out the cathode in the CRT's gun assembly, and makes it become increasingly > dim, and blurry. > > There are only two fixes for this problem: 1) replace the CRT, something > that is becoming more and more difficult, and 2) restore/rejuvenate the > CRT, a process that sometimes extends the useful life of the CRT for a > good while. > There is a third fix: a company (I forgot whom, but they should not be too hard to google, or John Miles can post it here) makes a color LCD replacement for the entire display. Pretty neat, and great use of color. It's not cheap, but worth it, considering what these instruments are worth in good condition. This replacement makes it better than new! Didier KO4BB |
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