HP 859x CRT replacement - Page 1
Forum section: electronics / repair

author: hjf83
author_rank: Contributor
timestamp: September 21, 2025, 10:49:01 pm
content: So I have an 8595 with severe burn in, and pretty worn too since it barely focus (it's legible but needs to have low brightness).The CRT is a Teletube Electronics Limited S1501P31N1 and I found a replacement that fits exactly, has the same number of pins (7) and the code is a bit debatable: it's either S1503P31N1, or it could be that the 3 is overwritten with pen to be a 1. It also has a code 150BGB31.The module code is Omni Vision LP0615E3Y, HP P/N 2090-0539It does two weird things:1) it's extremely bright. It's as if the screen control is turned way up. but adjusting BRT controls (int or ext) can only do so much and retrace lines are still visible.2) in the bright part, the image looks out of focus but darker than what should be black. it's like reverse video but completely unreadableCould it be that this picture tube has a different pinout? Different voltages? Maybe the filament voltage is different ?I put the old tube back and it works.

author: hjf83
author_rank: Contributor
timestamp: September 22, 2025, 04:25:08 am
content: So I compared the tubes and the guns are similar but a couple of pins are different. There are two pairs of "shorted" pins, one is the heater at 20ish oms, and the other is a short, which i suppose is some sort of grid inside the CRT. But that "dead short" is in different positions in both tubes.So I guess the tubes aren't compatible.I don't know if it could be used anyways by rewiring the CRT connector?

author: Uunoctium
author_rank: Frequent Contributor
timestamp: September 22, 2025, 07:37:12 am
content: Have you tried to adjust the focus with the old tube? (tiny hole in housing located near left handle, accessible without opening).If it dos'nt react and you have an Omnivision chassis, check R27 on second pcb. Don't remember exact value, possible 1 MOhm? Belongs to focus voltage divider.Mine 8591 showed same behavior, was in accepable sharpness only by extreme dimming the brightness.Runs now with reftrofitted LCD, the afterwards repaired tube-chassis is sharp again as new (exept the burnt in graticule).

author: hjf83
author_rank: Contributor
timestamp: September 22, 2025, 11:43:07 am
content: The focus control on this one doesn't work at all, but I haven't checked the rest of the circuit as I'm assuming it's probably a worn tube issue. The burn in is severe.But I'll check the focus circuit anyways. Maybe it's fixable and it'll be good enough to use as is.

author: Uunoctium
author_rank: Frequent Contributor
timestamp: September 22, 2025, 12:04:21 pm
content: Image of the chassis, i found in mine SA......& the location of open resistor in focus voltage divider

author: mikeson99
author_rank: Newbie
timestamp: September 24, 2025, 03:35:58 pm
content: Quote from: hjf83 on September 22, 2025, 11:43:07 amMakes sense with severe burn-in and no focus control, a worn tube is definitely a strong possibility. But yeah, worth checking the focus circuit just in case it's something simple like a bad resistor or a cracked solder joint. Even a weak tube can still be usable if focus improves a bit. Let us know what you find!

author: hjf83
author_rank: Contributor
timestamp: September 24, 2025, 03:58:02 pm
content: Last night I fixed the focus, it was the resistor mentioned by @Uunoctium. I was able to crank the brightness higher and still keep things in focusIt's not eye-searing bright but it's bright enough. It makes me wonder if these tubes are driven very hard so they're easily burned in, and it's not really a a worn out gun.

author: hjf83
author_rank: Contributor
timestamp: September 24, 2025, 03:59:57 pm
content: Also: I determined the pinout on the tubes is different. I thought of rewiring the CRT socket to match the new tube but ultimately decided it was too risky... I may make a wrong move and send 800V focus voltage to the video input and kill everything.So now I have a NOS CRT that I have no use for. Maybe some day I'll buy a compatible vintage device.

author: Uunoctium
author_rank: Frequent Contributor
timestamp: September 24, 2025, 05:02:06 pm
content: It's great to hear about your success.You can hide the burnt-in graticule a little by shifting the complete picture a couple of pixels in menue with H-align and V-align.Once open, you could have a look at SRAM's backupbattery which stores your Cal-data. If never before replaced, its time to act. And don't trust the manual - the Goldcap in parallel to battery is'nt capable holding the data! Better feed it with external PSU + resistor during excange.