AnsweredAssumed Answered

HP-8590A Omni Vision Display Schematic

Question asked by LarrBeard on May 3, 2011
Latest reply on Apr 11, 2016 by AgilentHpSpectrum

Like • Show 0 Likes0
Comment • 7

I have a perfectly good HP-8590A (Ser No 2618AXXXXX) that has an absolutely dead display. (Another display works perfectly in it.) I don't have any of the complex software or hardware problems a lot of other guys describe - but I still can't see it!

I've poked around in it - looked at the usual suspects (dried out/leaking aluminum electrolytics..etc) and nothing yet.

I've had pretty good luck repairing the Panasonic TR-60S1A monitors used in some 8590A's, but this unit uses a more complex display. The display has a tag "Omni Vision; Glendale Heights, IL P/N LP0615EVC", with some addition numbers that are probably Lot or Date codes. There is a tag on the chassis "Hewlett Packard P/N 2090-0514". I have not found any support data for this particular monitor.

Omni Vision has disappeared without a trace - no lingering artifacts hiding on the internet.

Any help with a schematic or manual?

No one else has this question

Outcomes

7 Replies

LarrBeard Jun 4, 2011 7:05 AM
Mark Correct
Correct Answer
This is a follow-up to my previous post concerning an Omni Vision display in the HP-8590A. After a lot of looking and pure blind luck - I've found out a bit more about this display.

There is a possibility (I can't verify this) that the Omni Vision display was not an HP-8590A display - it was used in the later 8590's, but maybe not the "A". The unit I have has had the display replaced.

Two things make me suspicious:

A. The screen has a burned-in imprint "SRQ 140 Ref Fault" (or to that effect - I don't have the CRT in front of me) This is not an error message that the 8590A can generate - so that points to the display having been in another model for a long time.

B. Once I got the display working (although badly), it was way out of horizontal sync. The Horizontal Hold control would only barely stop the display from rolling. I found documentation for the display (Panasonic and Omni Vision) in an ArtekMedia CD-ROM support manual (08590-90008). The Omni Vision manual - although sketchy - seems to indicate that the Omni Vision display was intended for 15.75 KHz horizontal sweep, not the 19.2 KHz of the 8590A. This would explain why the display rolled so badly and had limited adjustment margin. Reselecting a capacitor will probably cure this - if anything is ever that simple. Later versions of the 8590 used the standard 15.75 KHz horizontal sweep - go figure - it probably seemed like a good idea at the time.

C. Oh, by the way - the Panasonic and Omni Vision displays use different CRT's - same size - different pinouts. They don't interchange. If you look hard enough (think eBay) and get lucky, Panavision CRT's can be found in green or white phosphor, Given the choice, I'd get white for a replacement. Omni Vision CRT's seem only to be available in green - about $220 US if you find them..

So far - it's still been a worthwhile project.
Like • Show 0 Likes0
Actions
LarrBeard Jul 23, 2011 6:44 AM
Mark Correct
Correct Answer
I didn't intend to have this turn out as a blog, but this project has turned out to be one thing after another. It's one of those you work on for a week, then put the job aside so you don't end up talking to yourself - and giving wrong answers. Fun, but only in small doses.

The display on the Omni Vision monitor wasn't right. To get display intensity high enough, contrast was all the way up and intensity controls were so high that the background raster was obvious. Additionally, focus seemed to be off. The small dots that form the graticle were sharp, but adjacent characters would run together - e.g two "T's in ATTEN blurred together at the top of the crossbar.

Since the old CRT had several layers of imprints on the phosphor, I decided to replace the CRT. This was straightforward, but the display with the new CRT had the same problem. Time to go poke some more. I checked the Focus circuitry - found a 2-meg resistor that measured 20+meg. Replaced it - no real change. Conclusion, Focus voltages are not terribly critical on this CRT.

The bias voltage on the base of the video driver was way off. One cause of this was a missing ground on a group of components - probably my fault by lifting a plated through ground while replacing electrolytics. Once I got the ground replaced, still no real difference - bias was still way off. Go poke some more. I finally decided that the video driver (cascode driver) transistor was breaking down. There is no way that current should be coming out of the base of an NPN transistor. I called in favors from the local group and finally found a replacement for the MPS-U07. As I got the iron hot to change the part, I noticed that the outline of the transistor in the board silk screen didn't match the outline of the part. (The MPS-U07 is symmetrical with the base in the middle). The transistor was in backwards - the emitter and collector were reversed - verifying something I learned years ago. Reversing EC terminals will, sometimes, almost work. How did it get in backwards - ??????.

I turned the part around - and son of a gun - the display works! Great contrast, good Focus.

Lesson: Trust Nothing on a "Parts or Repair Only" unit.

Now, I can get on to looking at the other problem with the instrument - CAL signal drifts up about 6 - 8 dB as the instrument warms up, but the CAL out is still at -20dBm. This should be easier.

Hint to other users: Replace R15 (originally 9.09K) with a 7.5K resistor to put Horizontal Hold in mid-range of adjustment. This takes care of the 19 KHz/15.75KHz sync difference.
Like • Show 0 Likes0
Actions
- sreaves @ LarrBeard on Oct 17, 2014 7:03 PM
  Mark Correct
  Correct Answer
  Hello,
  
  Would you please provide the link or put the manual of the display up on www.ko4bb.com
  
  Thanks,
  
  Sam
  W3OHM
  Like • Show 0 Likes0
  Actions
- AgilentHpSpectrum @ LarrBeard on Apr 11, 2016 4:52 PM
  Mark Correct
  Correct Answer
  Trying to replace the dead CRT module in my HP8590a 1.5 GHz Spectrum Analyzer with an LPO615E3Y.
  
  I obtained a new-in-box OmniVision LPO615E3Y 15.75 KHz CRT and understand there are several possible modification routes for the OmniVision CRT module to move it from 15.75 KHz to 19.2 KHz; to work with the HP 8590a.
  
  - However, I also understand that some later HP 8590a S/N's worked with a 15.75 KHz CRT ?
  I understand (but may be wrong), that the HP 8590a SA originally had OmniVision CRT model: LPO619EVC (HP part #:2090-514 or 2090-0826; both at 19.2 KHz ?)
  
  - Does anyone know when (what S/N's ) the specification changed for the HP 8590a ?
  
  - Can anyone clarify which CRT modification works well ?
  
  A] replace: C11 with a 4300 pf; R15 with a 7.5 K; and possibly C18 with (? unknown) ?
  
  B] Only replace the R15 with a 7.5 K { is this the only mod required } ?
  
  C] Are there any cable-wire changes required on the E3Y OmniVision module to make it work in the HP 8590a ?
  
  D] What specific adjustments are necessary with either modification.
  
  Simply trying to clarify the mods.
  
  thank you,
  Like • Show 0 Likes0
  Actions
LarrBeard Aug 9, 2011 6:27 AM
Mark Correct
Correct Answer
Well - I guess its time to cut this thread.

Omni Vision is alive and well and still in business in Illinois - but if you don't Google their name just right - their web site doesn't come up.

The display is still available - at a reasonable cost if you're using the display in an industrial or engineering application where time really does matter.

A .pdf service manual is available from Omni Vision.

Good luck folks
Like • Show 0 Likes0
Actions
LarrBeard Aug 9, 2011 6:28 AM
Mark Correct
Correct Answer
Well - I guess its time to cut this thread.

Omni Vision is alive and well and still in business in Illinois - but if you don't Google their name just right - their web site doesn't come up.

The display is still available - at a reasonable cost if you're using the display in an industrial or engineering application where time really does matter.

A .pdf service manual is available from Omni Vision.

Good luck folks
Like • Show 0 Likes0
Actions
JohnMiles Aug 22, 2011 10:43 PM
Mark Correct
Correct Answer
"
The transistor was in backwards - the emitter and collector were reversed - verifying something I learned years ago. Reversing EC terminals will, sometimes, almost work. How did it get in backwards - ??????. I turned the part around - and son of a gun - the display works! Great contrast, good Focus.
"

Great story -- as you point out these things sometimes "work" when they have no right to. Even HP's own hardware sometimes left the factory with undetected screw-ups. I worked on an eBay-special 11848A awhile back in which an LM338K was installed where a fixed TO-3 regulator was supposed to go. It worked after a fashion and must've passed the production tests, but if you turned on too many internal features at once, the supply rail would brown out.
Like • Show 0 Likes0
Actions

HP-8590A Omni Vision Display Schematic

Outcomes

Related Content

Recommended Content