HP 8590A spectrum analyzer repair

[feedback.loop]

Repair of 8590A analyzer, which turned out to have bad mixer diodes in the first converter:



I wonder if anyone has a better service manual. The one from Keysight seems to be incomplete and has many corrections in handwriting. Some adjustment procedures are not clear at all.
I would appreciate a better one.
Thanks.

[SaabFAN]

Nice! I always thought that a fault in the first Mixer was the death-sentence for these Spectrum Analyzers.
Good to be proven wrong

[MadTux]

Interesting video! Didn't knew, those 8590A are build that noob friendly. I would have expected some wirebonded magic instead of discrete, soldered glass diodes.

Good work

Some pics of the 2-22GHz YTF-Mixer assembly of one of my 8566 spectrum analyzers. Mixer diode is under a extremely fine gold wire mesh in the assembly in the center, close to the blue blue blob.

 The YIG filter is also in there, 3 YIG balls mounted onto ceramic rods for fine adjustment. In the back you can see the large magnet coil used for tuning those YIG filters. If you decide to take it apart, you need to mark the rotation of those magnet coils relative to the case, as the magnetic poles are slightly slanted, so they can be aligned to get the most homogeneous magnetic field between them.

Fry that and you're done. Instrument works perfectly now, btw. YTF tuning current vs frequency was misaligned, which caused the amplitude to drop at higher frequencies.

Anyone some pics of the 8568 1th mixer? Haven't had that one open, but would be quite curious, since that is my everyday use SA.

[AF6LJ]

Nicely Done...
I think I would have bought the diodes with 15V breakdown.
Still that is great to have a working analyzer for such a reasonable price. 

[feedback.loop]

Nicely Done...
I think I would have bought the diodes with 15V breakdown.
Still that is great to have a working analyzer for such a reasonable price. 

It seems that 282x family (15V breakdown) has higher noise. Here is a quote from the datasheet:
"The HSMS-281x family is a hybrid Schottky (as is the HSMS-280x), offering lower 1/f or flicker noise than the HSMS-282x family."

[MadTux]

......offering lower 1/f or flicker noise than the HSMS-282x family."

Wouldn't worry about that. 859X goes down to only 10kHz and doesn't have narrow RBW, so that the low frequency range, in which the 1/f (pink noise) is relevant, has high noise by the LO anyway.

[xrunner]

Excellent work and video. I have a HP 8595E myself.

[chris_leyson]

Nice repair, and a mini teardown as well, thank you 

It's always nice to see teardowns for analyzers at this sort of frequency range, at least some of the RF stage is repairable. I like the way HP put the low pass filters into the first mixer box, saves on external filters and connectors, and that's the first time I've seen ferrite used to absorb harmonics. Was surprised to see a matched pair of diodes I was expecting a to see a bridge for some reason. Nice design 

[feedback.loop]

Followup - experiments with different diodes in the mixer:

[tggzzz]

Followup - experiments with different diodes in the mixer:

Is there a TL;DW summary somewhere? I'm not going to spend 40minutes of my (remaining) life finding out whether or not you have done something that would be useful to me. If the results are good then I will watch.

[DimitriP]

Followup - experiments with different diodes in the mixer:

Is there a TL;DW summary somewhere? I'm not going to spend 40minutes of my (remaining) life finding out whether or not you have done something that would be useful to me. If the results are good then I will watch.

Heeeey...it takes one click on the Youtube logo to see the summary you are seeking ....

[tggzzz]

Followup - experiments with different diodes in the mixer:

Is there a TL;DW summary somewhere? I'm not going to spend 40minutes of my (remaining) life finding out whether or not you have done something that would be useful to me. If the results are good then I will watch.

Heeeey...it takes one click on the Youtube logo to see the summary you are seeking ....

I see a link to this thread, a service manual and some datasheets. From that I can infer "he did some work", but cannot infer the results.

[feedback.loop]

Is there a TL;DW summary somewhere? I'm not going to spend 40minutes of my (remaining) life finding out whether or not you have done something that would be useful to me. If the results are good then I will watch.

I see a link to this thread, a service manual and some datasheets. From that I can infer "he did some work", but cannot infer the results.

You must be referring to the first video. I believe that the summary there describes what was done:
"A replacement was found and installed. The analyzer seems to be back in business. Perhaps, it will need some adjustments though."

By the way, what is "TL;DW summary"?

If the results are good then I will watch.

Would you watch a failed repair attempt?

[DimitriP]

There are plenty of timewaster videos out there to complain about, this is not one of them.
Not sure what the issue is, or why it is with this one in particular.

If it were a video about comparing soldering tips, or DMM probes I'd understand

[PA4TIM]

Hi feedback.loop. I like your channel (and your accent  ) One of the better ones I know. Always nice to see how others think and do when it is about repairing measurement gear. 

[nidlaX]

Hey feedback.loop, keep making videos! I've watched a few of your other ones such as the Keithley electrometer repair and the Agilent 66309D repair. Good work!

As a bit of feedback (), I suggest you record the whole teardown and play back the less interesting bits at increased speed. This way, someone else who is working on the same instrument can see the entire teardown procedure, while you can avoid boring the viewer.

[Shock]

Been watching your channel since it started, great videos.

[tggzzz]

"A replacement was found and installed. The analyzer seems to be back in business. Perhaps, it will need some adjustments though."

I'd like to know what he means by "business". For some ebay sellers it is sufficient that "it turns on and the trace wiggles"

By the way, what is "TL;DW summary"?

Too long; didn't watch

Would you watch a failed repair attempt?

Yes, if I had reason to believe I could learn something from it.

If there's no visible reason why I might learn, well there are many many many other things where I can see I will learn something. Guess what will get my attention.

Always remember the "elevator pitch" concept - and go on to back that up with solid information.

[Shock]

I send an email to the youtube standards committee, they will investigate this matter thoroughly. 

[AF6LJ]

Just a point of observation; every SA I have used that had a first LO out had it terminated in a 50 ohm load when it was not in use.

[feedback.loop]

I wonder if anyone has a newer version of firmware. My unit has 9.1.87. According to service manual, there are at least three more versions: 31.7.87, 29.7.88 and 14.10.88.

[DimitriP]

Firmware jungle....before you conclude the wrong thing, ask over at  https://groups.yahoo.com/neo/groups/hp_agilent_equipment/info.

[azer]

Firmware can be had from here ftp://ftp.bluefeathertech.com/electronics/testgear/HP_Agil_Keysight/firmware/8590A/
The version number is just the revision date, 14.10.88 is the latest one before they changed to 8590E series.

[feedback.loop]

It turned out that there was another issue. I found that the input attenuator Wavetek 0955-0329 was defective in a strange way: the 20 dB pad in it attenuated lower frequencies only by 15 dB, but worked fine at higher frequencies. I wonder if it is possible to take it apart without destroying it. I found a replacement for now, but I would love to fix it. The replacement is Wavetek 0955-0453, which I borrowed from another non-working HP 8590A unit. It is slightly longer physically, but has the same mounting holes, and otherwise seems to be identical.

Part 3 video:

[Shock]

Well done, nice detective work.