HP-8569 Spectrum Analyzer Repairs

[AF6LJ]

More work on the way, I have a bunch of Radio Club paper work I have to get done. I will be back ASAP.

[AF6LJ]

Here is how to disassemble the bandwidth and frequency span switches.
I cannot stress the importance of proper tools.
A set of combination wrenches in imperial sizing.
Allen wrenches GOOD ONES! this is no place for cheap tools, some of the set screws are very tight and you don't want to have to drill them out and chase the threads with a tap.
Before I forget... the case screws are posidriv. not Phillips.
you will need a small pair of outside snap ring pliers for the reference level control group.
A copy of the service manual (volume 3)

With the proper tools, and a reasonable mechanical aptitude anybody, even someone partially sighted, like me can repair these switches.
Some operations may require not drinking that third cup of coffee.

The next post will contain pictures of the disassembly of the bandwidth and frequency span switches.

[AF6LJ]

I reposted the above picture in order to show the back side of the bandwidth / span switch..\
The shaft can be seen in the center of the module just above the blue connector.


Turn the two switches ether full clockwise (engaged) or full counterclockwise this will establish a reference to make reassembly easier. After you do that make witness marks on the side of the switch rotors to document their position. (you will regret not doing this.)
I did go back and scratch in lines with an awol just in case the marker rubs off. Also notice the position of the two support pillars on the switch rotors. If you have a camera take loads of pictures if you have any question as to how things go back together you will have them...
Next post...

[AF6LJ]

The wires connecting the sweep time board to the main switch board need to be un-soldered.
There are two screws holding the board to the top of the rear switch rotor, this rotor is the bandwidth rotor and has only one set of fingers.....



Here is a view of the bandwidth switch rotor, this one has its contact fingers intact. Take note of the spacers and washers under them. remove them and place all your parts up to this point in a safe place. I use Altoids boxes.
The screws used to remove the front panel assembly are in one. In another are all the hardware removed to disassemble the module. Now it is time to start one dedicated to this stage of the process.


Here is a view of the switch rotor removed. BE VERY CAREFUL OF THE BALL AND SPRING. These can get away from you if you are not careful.

You can see the spring and socket on the rotor where the ball resides when the switch rotor is installed on the shaft. Don't move anything just yet........
Take careful note of the pin protruding out of the side of the brass collar... and the location of the stop pin. This is where the grief can begin if you haven't documented their relationship to each other.
Next post............

[AF6LJ]

Here you can see a small scratch I made to indicate which hole the pin is point to. This witness mark is needed to orientate the pin which engages bandwidth rotor when the knob is pushed in. That pin is what turns the bandwidth knob. Likewise you will find a similar pin on the frequency span rotor which will disengage when the knob is pushed in, leaving the frequency span knob in its current position.
It is now okay to remove the spacers, washers and the bandwidth switch detent, note the position of the notch.

Moving on...


On the other side there is an E clip and washer that needs to be removed.
I use an awol to remove the E clip, be careful not to loose this or the washer.

The shaft will not come out just yet, you have to loosen the two set screws holding the brass collar the stop pin is located in. Now the shaft will come out but be careful.
The frequency span switch detent must be supported while this shaft is removed. Use your hand to support the switch detent and screws, there is another ball and spring you must keep an eye on.


Take note of the spacers and washers. Also take note of the collar location, at the end of the hallow shaft. In this picture I am supporting the switch detent and screws with my hand while loosening the second set screw on the collar.

Next post......

[AF6LJ]

Hardware from the bandwidth switch assembly.
You should have all this. for that switch plus the rotor and spring.



Here is the front view of the frequency span switch, note the position of our witness mark to the pin on the brass collar. also note the spring in its cup.



Here are the pieces from the frequency span switch.
You can add a witness mark to locate the pin position, or simply remember it is in the center of the rotor stop block.

Moving on.......
Next post...........

[AF6LJ]

In the above picture you can see the top side of the switch rotor. One set of contacts remain, the outside set has fallen off and these can be found inside of the analyzer if you are careful it can be recovered.



Above you will see the components from the frequency span switch. A collar that is held in place with a spring clip the spring, ball, spacers, screws, detent, and shaft.
The missing contact finger set was recovered when the analyzer was opened.



Here you can see where the missing contact finger set goes.
We will go into reattachment in a later post, I have to deal with other obligations for the next few days. Any questions post them and I will answer them as I visit this site several times a day.

[xrunner]

Great pics I'm sure they will help someone someday. 

[AF6LJ]

Great pics I'm sure they will help someone someday. 

Thee is an individual who has contacted me about the same repair, he may or may not post in this thread.
If he does he will want to start his reccmonded reading on page 8-25 of volume three of the manual.

[AF6LJ]

So after fending off life's oblations I now have a few hours to work on the switch rotor repair.
Using my Redneck engineering talents I rigged up a holding fixture for the switch rotor.
What I did next was to practice holding and landing the switch contact fingers in the proper position. (Keep a reasonable distance from the coffee pot before attaching these contacts.)


A bottle of CA glue was opened and a test drop applied to the body of the fixture to prime the spout... Then a drop was applied to the location where the contacts would be attached, the bottle sealed and the contacts which were preloaded into tweezers were applied and held in position for two minutes.

Tomorrow afternoon the surface of the glue joint will be scuffed and lightly cleaned. Epoxy will be applied to the joint to reinforce the joint, and provide enough bonding straight to allow for reassembly of the front panel module and installation this weekend.

[AF6LJ]

Okay the CA glue has set up and cured now it is time to apply epoxy.
The surface is roughed up, and cleaned.
Out comes the hair dryer the epoxy and cotton swabs..




The switch rotor will now sit under an incandescent lamp for several hours to speed up the curing process and to help drive off moisture.

Stay Tuned reassembly is next.

[xrunner]

Stay Tuned reassembly is next.

Interesting work! I'm going to be glued to this thread until the final results. 

[bitseeker]

Thanks for the detailed log, Sue. Very educational. Looking forward to reassembly and power up.

[AF6LJ]

Thanks for the detailed log, Sue. Very educational. Looking forward to reassembly and power up.

Thanks; I enjoy doing these...

[AF6LJ]

This morning the the resoluation bandwidth and frequency span switches were reassembled. Pictures will be posted later on...
I am going to take a moment and warn people about the assembly procedure in the manual....
It's not necessarily right, so far of the two 8569s I have rebuilt switches in the front panel assembly was slightly different on both. This makes it all the more important that you take photos especially of how the hardware stacks up on these switch assemblies.
The pictures I took were valuable in the reassembly process.

[bitseeker]

Yeah, I always take photos when doing stuff like this. They can always be deleted if the job turns out not to require them for reassembly. Fortunately, we don't have to rely on film cameras these days.

[AF6LJ]

Just an FYI
I finished repairing the second HP-8569B this morning, works well...
I have pictures to post and will be cleaning up this thread, to get rid of the empty place holders and such.

The thread will bet cleaned up later in the week, I will walk through the process of repairing these switches and I shall repost teardown pictures at some time in the future, given that I have a pair of hanger queens now (they really only need front panel parts and knobs. ) I can do the teardown pictures with a bit more detail.

[bitseeker]

Sounds great. Thanks, Sue, and congrats on the happy patients.

[xrunner]

Just an FYI
I finished repairing the second HP-8569B this morning, works well...
I have pictures to post and will be cleaning up this thread, to get rid of the empty place holders and such.

It's a bummer that you have to do that clean-up but it will be a great help to others in the future. 

[KD0CAC John]

Hay Sue , John KD0CAC here .
I have 2 parts units got cheap , and then bought one that was spouse to work , well partially .
With the 3 I have all options , including a riser board bolted in the 3 unit .
I have seen lots of these , mostly on line and most are missing a cover in the top right rear , seem to be a common part left out during ? whatever ?
Oh and have not seen you around another hang-out for some time , hope all is ok ?

[AF6LJ]

Hay Sue , John KD0CAC here .
I have 2 parts units got cheap , and then bought one that was spouse to work , well partially .
With the 3 I have all options , including a riser board bolted in the 3 unit .
I have seen lots of these , mostly on line and most are missing a cover in the top right rear , seem to be a common part left out during ? whatever ?
Oh and have not seen you around another hang-out for some time , hope all is ok ?

Everything is fine these days. That other hangout and I had differences and they decided we needed a divorce.

[KD0CAC John]

Good to know .
Ya stuff happens , some time I wonder if I'm getting close

[AF6LJ]

Good to know .
Ya stuff happens , some time I wonder if I'm getting close

There is a hand full of people over there who really don't like to see a woman who knows more electronics than they do. Then you have K6bbC; he single handily managed make that place one of the least desirable places on the Net. 

[KD0CAC John]

Sorry to see a good resource be lost to that site .
I haven't been hanging out here as much , so just having seen ya around .
It's too bad , I know the media in general is polarizing the masses , but there also seems to be more illness , hate going around .
To get back on topic , kinda - the thread title - spec. analyzer , I followed a Google search on the HP 8650B .
My newest one came from someone on the ZED , and did not have all functions , then more quit after looking into it more .
I've read that if in storage sitting on the feet on back / front facing up , that some lube ? in the main oscillator flows over time and you can loose the signal , have you come across this ?
   

[rob.manderson]

I'm guessing you mean the 8640B?  If so, yes, it's not good to store them on their front or back because the cavity lube flows.  I haven't seen it myself but I understand it can take months(!!!) to get back to normal.

Otherwise, a fine signal generator and you can have mine when you pry it from my cold dead hands!