Author Topic: HP-8569 Spectrum Analyzer Repairs  (Read 9560 times)

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Online AF6LJ

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HP-8569 Spectrum Analyzer Repairs
« on: March 22, 2017, 02:24:33 AM »
Finally it's time to start this project.
A friend acquired not one but three HP-8569B, and one HP-8569A spectrum analyzers.
One 8569B would not power up, that was an easy find a bad tantalum cap on the supply module's -15V rail. The power supply module was borrowed from one of the A model and all four analyzers appear at this point to have no electrical issues, however..........
All of them do have one or more of the rotary switches, damaged.

The front panels were removed from the two that are most likely to be easily fixed.
 
And a rear view...

Oh and then there are these...

The one on the left has been straightened and is ready for re installation.

Since the freely available manuals online were garbage, to put it nicely, I want to Artek Manuals http://artekmanuals.com/ and picked up the three volume set for a very reasonable price (under $20.00USD) and received a wonderfully scanned manual set.
These guys are great and the price is so reasonable....

Moving along to the immediate problem...

The switch rotor is a piece of what feels like ether nylon or delrin plastic. They have hot stakes that secure the contact fingers to the rotor, pay close attention to the inner pair of hot stakes, they were never used in this switch rotor, the outer ones as can be seen are sheered off, no doubt from the decades of pressure on the hot stakes....

At this point laziness kicks in, and I am going to ask if anybody has ever repaired these switch rotors before and what did you use to attach the contact fingers?



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Offline SeanB

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #1 on: March 22, 2017, 05:09:34 AM »
Small PCB drill and a tiny nail, with the drill diameter being a little smaller than the nail diameter. The nail is a push fit into the hole, after cutting it to size, filing the head round and the shank to round, and to leave a small chamfer to the leading edge to allow easy entry into the hole.  Leave some ridges on the rivet shank, round the diameter, so it is harder to pull out.

You cannot use any glue or such, unless you know for sure it will not attack the plastic material, and if it is nylon in any case many do not work nicely with it. Some cyanacuralates might be compatible with nylon and delrin, but YMMV with it.

Done many a repair with rivets, including making new pins recently for my glasses to replace a stripped screw, and to replace worn pins in my watch strap. Of course also helps having used so many solid rivets in repairing airframe parts, and getting to know how to form them in places where it was impossible to get to them with a power riveter, but a small ball peen hammer was a perfect fit, plus i made a few mandrels to get the head shaped.
« Last Edit: March 22, 2017, 05:12:44 AM by SeanB »
 
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Online AF6LJ

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #2 on: March 22, 2017, 06:41:51 AM »
I have some ideas, there are adhesives made for Delrin and Nylon.
It feels like Delrin and MEK (yes I still have some) will not attack the plastic, which confirms that this is not one of the more reactive plastics.
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Offline SeanB

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #3 on: March 22, 2017, 06:58:20 AM »
If you are wanting MEK simply look for Linx solvent or a generic clone, which is MEK in a bottle. Used in continuous jet industrial printers, and a consumable there.

Still the rivet idea will work better than heat stakes, simply because it is a lot more area to hold them.
 
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Online AF6LJ

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #4 on: March 22, 2017, 07:17:16 AM »
If you are wanting MEK simply look for Linx solvent or a generic clone, which is MEK in a bottle. Used in continuous jet industrial printers, and a consumable there.

Still the rivet idea will work better than heat stakes, simply because it is a lot more area to hold them.
I have all the MEK I need.

I am thinking I am going to end up using glue...
I don't have a drill press and it's going to take a #60 or smaller drill.
I have a lot of these to fix.
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Online xrunner

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #5 on: March 22, 2017, 09:22:03 AM »
Don't have any better ideas on the switch, but I'll be following this thread with interest.  :popcorn:
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Online AF6LJ

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #6 on: March 22, 2017, 10:00:29 AM »
Don't have any better ideas on the switch, but I'll be following this thread with interest.  :popcorn:
Good I am thinking the glue is the way to go.
I just have to find something that sticks.
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Online AF6LJ

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #7 on: March 23, 2017, 03:03:36 AM »
I do plan on exploring the possiability of using both glue and a small screw to anchor the contact fingers in place.
Anybody know where I can get more of those fingers????
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Offline donmr

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #8 on: March 23, 2017, 03:19:10 AM »
Does the slot for the fingers extend to where the inner pair of stakes is?

When I worked for HP some time ago, they made products to be repaired.  They might have made contact fingers with a longer tail on them for attachment with the inner stakes.  Of course you would have to get or make some like that to use them.
 
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Online AF6LJ

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #9 on: March 23, 2017, 04:22:05 AM »
Does the slot for the fingers extend to where the inner pair of stakes is?

When I worked for HP some time ago, they made products to be repaired.  They might have made contact fingers with a longer tail on them for attachment with the inner stakes.  Of course you would have to get or make some like that to use them.
I haven't been able to find any.

The switch set up is like I have seen in some HP scopes, the same type of rotatory switch configuration.  Still looking while I wait to get the items to fix what I have. 
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Offline mmagin

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #10 on: March 23, 2017, 04:27:58 AM »
I do plan on exploring the possiability of using both glue and a small screw to anchor the contact fingers in place.
Anybody know where I can get more of those fingers????

Some of the high temperature hot-melt adhesives are amazing (and will stick to a lot of things), though you have to be careful when applying them to plastics with lower melting points (polyethylene, polypropylene, etc).  Nylon may be okay, I dunno.
 
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Offline cncjerry

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #11 on: March 23, 2017, 05:12:45 AM »
two options:

1) Put the fingers on the posts and melt them around it with a soldering iron.  Find some of the excess material and use it as filler mixing it around with heat.

2)  Send the delrin/nylon material parts to me and I will drill them for you for the cost of return postage.  Then use two small screws to hold them down.
 
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Online AF6LJ

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #12 on: March 23, 2017, 06:35:35 AM »
two options:

1) Put the fingers on the posts and melt them around it with a soldering iron.  Find some of the excess material and use it as filler mixing it around with heat.

2)  Send the delrin/nylon material parts to me and I will drill them for you for the cost of return postage.  Then use two small screws to hold them down.

I am going to give option two serious consideration.
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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #13 on: March 27, 2017, 05:27:57 AM »
Today I did a test drill in the one rotor I had already removed, I think I am going to drill, tap and install 0-80 retaining screws on the switch contacts that I can, a dab of Epoxy will secure the screw head to the edge of the contact base...
This should work...
Here is one of the good ones I pulled from the same module I am working over..

These contacts are working loose as can bee seen below.



For those who may not be sure how these switches work the contacts slide across the plated tracks on the circuit board. On the left as seen above is the resolution bandwidth stationary contacts, the broken rotor and contact assembly came from that switch.
The switch on the right is the sweep selector switch contacts. The wide contact in the center is the ground contact.
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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #14 on: March 27, 2017, 05:43:31 AM »
Looks good so far. Maybe put a smidgen of epoxy on the pair that are loose too. Good work.
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Offline SeanB

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #15 on: March 27, 2017, 05:46:36 AM »
Tap will work, especially a thread forming one, but that is one seriously tiny tap there. Especially the price of nearly $30 each. Tiny screws as well, and a 0 Phillips as well, but at least they will hold better than the stakes, and less stress on the material as well.
 
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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #16 on: March 27, 2017, 06:01:16 AM »
Looks good so far. Maybe put a smidgen of epoxy on the pair that are loose too. Good work.
I am going to try that on the one you see in the last picture, while it is still intact the contacts are working loose. The only issue is the piece is made of ether nylon or delrin. and the epoxy will stick but not too well. I also have some CA glue and was thinking about trying it on the other rotor in a location where it won't matter if it should stick better than I thing it would.
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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #17 on: March 27, 2017, 06:06:37 AM »
Tap will work, especially a thread forming one, but that is one seriously tiny tap there. Especially the price of nearly $30 each. Tiny screws as well, and a 0 Phillips as well, but at least they will hold better than the stakes, and less stress on the material as well.
Next month I plan on ordering the screws, a few drills and a tap.
I have 1-72 screws but I believe they are a little too large for this application.
As for taps, I had not thought about using thread forming taps, I can use thread cutting taps and use a little soap or silicon oil to lube the tap. Because of this being plastic petrochemicals are to be avoided.
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Offline cncjerry

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #18 on: March 27, 2017, 02:49:14 PM »
Tap will work, especially a thread forming one, but that is one seriously tiny tap there. Especially the price of nearly $30 each. Tiny screws as well, and a 0 Phillips as well, but at least they will hold better than the stakes, and less stress on the material as well.

You can buy taps that size in a hobby store for cheap.  They aren't made for steel or aluminum but work in plastic.  Also, you don't even have to tap them;  just let the screw form the threads.  Use socket head cap screws so you can put a lot of pressure on them while twisting them in.
 
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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #19 on: March 27, 2017, 10:40:13 PM »
Tap will work, especially a thread forming one, but that is one seriously tiny tap there. Especially the price of nearly $30 each. Tiny screws as well, and a 0 Phillips as well, but at least they will hold better than the stakes, and less stress on the material as well.

You can buy taps that size in a hobby store for cheap.  They aren't made for steel or aluminum but work in plastic.  Also, you don't even have to tap them;  just let the screw form the threads.  Use socket head cap screws so you can put a lot of pressure on them while twisting them in.
I am going to tap the threads, my reason for doing so is to lower the stress on the thirty plus year old plastic.
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Online AF6LJ

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #20 on: March 28, 2017, 02:19:56 AM »
Just a quick update;
I took apart the front panel module for the 8569A Someone repaired the switch rotor with epoxy, I'll post pictures later on, I have to get the day started and will have pictures up later today or tomorrow.
EDIT;
Here is a picture of the glue job that was done on this rotor.

I think I can make this work........

This is good news.
I have some fresh JB Weld and my trusty hair drier....
For the time being I am going to get one good front panel assembled for my partner in this project and get him a working analyzer.
I should be able to make one good front panel from the remaining parts.

Sometimes I like Mondays
 :-+ :-+
« Last Edit: March 28, 2017, 04:32:12 AM by AF6LJ »
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Offline cncjerry

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #21 on: March 28, 2017, 04:51:16 AM »
Use a little silicon oil or Vaseline on the tap.  You want it to cut and not stick. Depending on what is on the other side, it might be easier to just drill thru and use a bolt and nut instead of small screws.
 
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Online xrunner

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #22 on: March 28, 2017, 04:57:27 AM »
Just a quick update;
I took apart the front panel module for the 8569A Someone repaired the switch rotor with epoxy, I'll post pictures later on, I have to get the day started and will have pictures up later today or tomorrow.

When I first glanced at that pic, I was pretty sure you didn't do that repair.  :phew:

Is having a new part made with 3D printing an option? I know some of those systems are not that precise, but couldn't a laser 3D printer make a new part (if the file could be created) with new posts for the contacts? I don't know ...  :-//
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Online AF6LJ

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #23 on: March 28, 2017, 06:09:55 AM »
Just a quick update;
I took apart the front panel module for the 8569A Someone repaired the switch rotor with epoxy, I'll post pictures later on, I have to get the day started and will have pictures up later today or tomorrow.

When I first glanced at that pic, I was pretty sure you didn't do that repair.  :phew:

Is having a new part made with 3D printing an option? I know some of those systems are not that precise, but couldn't a laser 3D printer make a new part (if the file could be created) with new posts for the contacts? I don't know ...  :-//
I think that might be overkill, and I think I have found the right formula to make this happen. If Keysight had the parts I would consider ordering them.
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Online xrunner

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Re: HP-8569 Spectrum Analyzer Repairs
« Reply #24 on: March 28, 2017, 08:58:44 AM »
I think that might be overkill, and I think I have found the right formula to make this happen.

Yea but my middle name is Overkill, that's what I'm known for LOL.  ;)

Quote
If Keysight had the parts I would consider ordering them.

I bet you would be horrified at the cost though, even for that small part. I got an Agilent E4411B Spectrum Analyzer last year - great unit. It's B&W, but it actually can display colors if you go into the right menu and change all the assignments for traces and this and that different colors. Takes a while. 'Cept the problem is it won't store all those colors and next time you turn it on - it's back to B&W. I looked at what it would take to make it remember the colors. It takes a firmware upgrade - but to do that you have to get the software from Keysight, and then before that, you must upgrade the memory, and to do that would cost somewhere between $1k and $2k. All to make it display colors. The thing didn't even cost me that much. Grrrr.
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