HP 3410A AC Microvoltmeter Restoration ** In operation added**

[quarks]

Hello robrenz,

sorry for getting OT, but may I ask for a hint how you would clean and bring back the "black print" on keys like in the picture.

Thanks
quarks

[SeanB]

Nothing you can do there as those are screen printed onto the keys. Either you engrave the legends into the keys or you reprint using a screen and ink. Better keys use a 2 shot injection moulding that makes the contrasting colour that extends down through the key top.

[Dr. Frank]

Hi robrenz,

you've done a great job, I really admire that! 

Additionally, you present here a whole bunch of cleaning tricks.

The old, stinky and sticky HP plastic surfaces always need some facelift.

Maybe I rework my old gear after your presentation..

Frank

[plesa]

Wauu, thats awesome. Really nice work!!! It will just needs to add smell of new instrument 

[ecat]

A thing of great beauty robrenz, excellent work.

[chickenHeadKnob]

Making my own epoxy paint to fill recessed engravings is something I wouldn't have thought of. Noted and remembered, thank you for sharing.

[dannyf]

I got this almost a year ago

Nicely done.

[robrenz]

Thanks again all for appreciating this restoration. Its great that there are some techniques that you are finding useful.

@ lowimpedance  Yes I will be using it. A video should follow

@BravoV  The Autosol looks like it may be similar and probably work even though it is targeted at Aluminum.

@quarks  I would probably have a silk screen made and redo the keys like SeanB mentioned.

@Dr.Frank  Glad it inspired you, (don't forget to take the before and after pictures)

[BravoV]

@BravoV  The Autosol looks like it may be similar and probably work even though it is targeted at Aluminum.

Thanks, and other question on using the rotary fabric buff with this kind of paste when used at the bnc connector surface.

I know you've mentioned the words "slow speed", its just sometimes I'm so worry at this process, it may eat off the outer chrome (or is it nickel ?) plating too much, and will starting to expose the inner yellowish brass base metal, that will be my nightmare. 

Just stop when it is enough bling/shine ? or I'm just worrying this way too much ? 

Also once finished buffing, did you apply any extra coating at these metal surface to protect it ?



Hope I'm not bugging you too much. 

[robrenz]

You are not bugging me, I am glad to help where I can.

You could test/practice on a cheap adapter first so you don't toast your favorite instruments BNC. Simichrome is an extremely fine polish and would take quite a while to buff through the plating.  Simichrome is made in Germany so I would think you should be able to get it somewhere. Simichrome leaves a protective coating so I did not apply anything else.  it only takes a about 3-5 seconds of buffing to get that shine. Other metal polishes may be more aggressive so you should test first.

[simonmc]

I showed this thread to my daughter. As she was in the workshop with me 'learning', she pointed to my hp5326b frequency counter and said 'We have to do that to THAT, dad'. To be honest i had to agree. If it comes out half as good as your restoration then i will be pleased, and the project will give me some father daughter time..

[robrenz]

Glad it inspired you. I get a lot of satisfaction bringing these things back to life,

[robrenz]

Here is a quick test using the 3410A to measure the AC rms ripple at 60Hz, 120Hz, 180Hz, and 240Hz. PD2005 set at 10V and about 475mA (almost max current) The 87 is reading the oscillator output of the 3410A.  The values were about the same at 20V output and decreased about 25% at 1V

60Hz about 20µV rms


120Hz about 40µV rms


180Hz about 49µV rms


240Hz about 25µV rms

[robrenz]

I forgot about ground loop voltages at these levels. The manual actually tells you to float the meter when using the very lowest ranges. So I made a ground lead interrupter out of junk bin parts with a line switch on the ground lead only so it can be floated or not with the switch. This allows the meter to be grounded while safely making connections and adjustments then disconnect the ground only to take a reading.  There was only this much difference at 60Hz,  120Hz and 180Hz had no change in reading when floated.


60 Hz reading of 25µV rms with the ground connected.


60 Hz reading of 5µV rms with the ground disconnected.

[SArepairman]

now you just need to compare it to a DSA

[robrenz]

I would love to, please send me one and I will do the testing

[HighVoltage]

This is truly inspiring and I learned a lot, by reading your steps.
If I would have only looked at the "before" pictures, I would not have believed that such a restoration is possible.
Amazing.
Thanks for sharing.

[FrankenPC]

Any tips on removing dings and dents from the cover panels? 

[robrenz]

Concave side of dent down on flat compliant surface like a piece of rubber sheet on top of a rigid flat surface. then use a large radius body hammer gently on the convex side of the dent.  If you only have regular hammers place a piece of scrap sheet metal over the dent to spread the force of the hammer blows over a larger area and not leave smaller hammer dents. The compliant surface allows the hammer to slightly over bend which is necessary to get a flat surface.

[saturation]

Incredible work and documentation.     A model for everyone!

[bsgd]

A-M-A-Z-I-N-G 

Thank you for sharing!

[robrenz]

Thanks again all.

@ saturation,  glad to see you are still around

[TheRuler8510]

Thanks again all.

@ saturation,  glad to see you are still around

robrenz or anyone else,

Where can a guy buy toluene by the ounce? The only way I can find it on-line or in Home Depot is by the gallon.

Any Ideas?

Thanks,

[PedroDaGr8]

Thanks again all.

@ saturation,  glad to see you are still around

robrenz or anyone else,

Where can a guy buy toluene by the ounce? The only way I can find it on-line or in Home Depot is by the gallon.

Any Ideas?

Thanks,

Honestly, it's pretty low priced.  The price at the one liter volumes is low enough a liter should be fine. You would be hard pressed to find a smaller volume for much cheaper. Part of the problem is the shipping restrictions. 

[saturation]

my pleasure, and your restorations have few peers.

Thanks again all.

@ saturation,  glad to see you are still around