Restoration of a really old hp5065a

[syau]

For reason that I am not able to explain, I decide to try my luck to score this unit:

https://www.eevblog.com/forum/metrology/really-old-hp5065a-on-ebay-right-now!/

Now it start its restoration journey.

Battery has been removed by the previous owner 

Resistance measurement on the SMB connector in front of the RVFR = 3.33k ohm.

Just ordered some 100uF and 20uF capacitor from RS, will replace it before power up.

Note: Have difficult to pull out come of the cards, will attempt again when I got the replacement capacitor

[edpalmer42]

Congratulations on your purchase.

If you haven't already found them, there are a couple of threads on the 5065A:

https://www.eevblog.com/forum/metrology/hp-5065a-rubidium-standard-repair-log/msg2271831/#msg2271831
https://www.eevblog.com/forum/metrology/hp-5065a-lamp-oven-repair-details!/msg2440983/#msg2440983

There's also a few web sites with good info on repairs, modifications, and general info:

http://phk.freebsd.dk/hacks/HP5065A/index.html
http://www.timeok.it/hp5065a-corner-3/

There are others, but that's enough for now!

Good luck!

[syau]

Found R34 crack on the A11, the colour band show ORANGE GREEN GOLD GOLD which is 3.5 ohm but the manual show 1.5 ohm 

[dietert1]

Maybe orange is brown. Can't you check the other one to find out? Note: Those old carbon resistors may be off much more than 5 %.

Regards, Dieter

[testpoint1]

Found R34 crack on the A11, the colour band show ORANGE GREEN GOLD GOLD which is 3.5 ohm but the manual show 1.5 ohm 

there is no 3.5OHM resistor for normal, if that is 0.1%, maybe is different.

[5065AGuru]

Syau,

The 2 resistors on the A11 are 1.5 Ohm wire wound resistors.

Before you do too much repair you need to unplug  the A12 RVFR 9 pin jack and measure the following.

Measure the impedance between pins 4 and 5 and pins 3 and 4.

You should have 50 Ohms on each.

Then measure from those 4 pins to the threaded stud sticking out the end of A12.

You should not have any continuity!

If you do the lamp oven winding has shorted out.

Pretty much a show stopper but can with LOTS of effort and patience might be repaired.

Also what is the units serial number and what series number is your A7 module.

Cheers,

Corby

[syau]

Hi Corby,

The unit serial number is 808-00051 as wrriten on the front panel cover. Unable to locate other data plate on the unit

A7 part number: 05065-6010
A7 serial number: 916

There is also a stamp "1143" on the assy, not sure if it is the manufacturing date 

Attached see a photo with better resolution

Cheers,

Stanley

[edpalmer42]

It might be helpul to pull the 00105 OCXO and test it seperately.  Power it up and let it run so that it can settle down and provide good aging numbers while you work on the other preliminary tasks.  Knowing that it's working properly will help remove one variable.  It might be awkward to try to chase system troubles while the oscillator is aging rapidly.

[syau]

Resistance between pin 3 & 4 is 48.56 Ohm but short circuit between 4 & 5  May be this the reason why R34 on A11 get fired. 

Open circuit from those 4 pins to the threaded stud sticking out the end of A12.

Looks like I either need to try out Corby’s instruction

https://www.eevblog.com/forum/metrology/hp-5065a-lamp-oven-repair-details] [url]https://www.eevblog.com/forum/metrology/hp-5065a-lamp-oven-repair-details!/ [/url]

unless someone willing to sell me a RVFR

[edpalmer42]

unless someone willing to sell me a RVFR

Don't hold your breath on that.  I remember a number of months ago someone on ebay paid something like $1K for a RVFR.  I don't know what surprised me more - the fact that someone was selling a RVFR by itself or that someone paid that much for it!

[syau]

The P2332ADVFEP.009BL quoted by Corby out of stock Placed a 100ft order of P2332ADVFEP.005WT, same resistance per feet but with thinner insulation.

[james_s]

Looking at that other thread, it doesn't look like too bad of a project. As long as the thing can be disassembled without completely destroying it I don't think it will be hard to repair.

[5065AGuru]

Stanley,

If you have not already done so remove the lamp assy. and see if it looks like it got too hot.

Also once you get the oven cylinder free you might be able to wind the new heater without machining the slots shown in my post.

Let me know once it's out and I can take you through checking if that's feasible.

Cheers,

Corby

[syau]

Corby,

Found 1 screw missing (actually sheared) when I opened the cover, looks like someone has been there before 

Close examination of the light assembly found some greenish in the legs of several resistor (especially the 1k33) and some capacitor

Looks like the assembly has also subjected to overheat 

BRGds,

Stanley

[5065AGuru]

Stanley,

It does not look too bad as far as overheat.

The 1.33K will need to be changed as it frequently fails. I use a 1.3K metal oxide resistor.

Take the 3 slotted screws out of the lamp assy. to allow the front diffuser to come off.

This will expose the lamp. Take a closeup PIX of the spherical lamp with the small coil around it so I can evaluate it.

Also remove the 3 screws on the diffuser and remove the perforated lid.

I usually have to put it at an angle in a vise and apply pressure sideways to get it to pop free.

Then you should see a glass disc convection shield and also the surface of the mirrored portion.

If the mirrored portion is corroded and dull you will need to pop off the glass disc (you can push through with your little finger or use a wood dowel to force the disc out of the slot) and then use Aluminum polish to restore the mirror surface.

Take a PIX of the now exposed circuit board also.

The rest of the unit can  be powered up without the optical unit and you can check out the Quartz oscillator and power supplies.

Cheers,

Corby

[syau]

Corby,

Removed the diffuser & reflector as per your instruction, found it is more like a glass cup instead of a disc (it actually come loose when I removed the diffuser (no glue) 

BRGds,

Stanley

[5065AGuru]

Stanley,

The lamp assy looks pretty good although the reflector does need to be re-polished!

Cheers,

Corby

[syau]

My x’mas project 

[syau]

Corby,

Finally has sometime to continue the project, lamp heater removed, all the remaining resistance still within limit (remaining heater & thermistor x 2).

As I don’t have accessed to a turning machine therefore I am thinking of reusing the thermistor and wind the new heater on top of the aluminium housing with a thin layer of ptfe tape.

BRGds

Stanley

[5065AGuru]

Stanley,

Yes that is a good option. Rub off as much loose materiel as you can from the inner surface of the "exclusion zone" to give you a little extra room. It's usually powdery and you can at least go down the thickness of the original winding that you can see in the foam. Just don't go crazy as if you go too deep you could damage the remaining wires. Make sure the thermistor is covered in heat sink goop!

Cheers,

Corby

[syau]

Corby,

I also managed to drill out the broken screw from the heater housing, do you have any idea on the thread size / pitch? If not, I will “re-condition” the thread using a M2 tap.

Note: close examination on the thermistor found the sleeve still in good condition. 

BRGds,

Stanley

[5065AGuru]

Stanley,

I believe that the threads are 2/56 on the 3 lamp mounting holes.

Cheers,

Corby

[5065AGuru]

Stanley,

Could you post a PIX of your A15 power supply board?

Also before you power it up change the 2 non hermetic electrolytic caps on the A11 board, they almost always are bad.

Also open the A7 and A3 modules and check the single 100uf caps inside for signs of corrosion.
The A3 is a pain to open. you can shine a flashlight in thru the holes for the matching network and see the + lead of the cap. That's what I usually do instead of opening it up!

When you have the time could you maybe trace out the circuitry for the "adj mag field" position of the mode switch? Yours is the only unit I have seen with this switch position and I wonder what it's doing???

Good luck on the repair.

Corby

[syau]

Photo of the A15 board before repair.





Replaced 3 capacitor and 4 diode (with the schottky diode to lower the voltage drop).

[syau]

 Repaired the A11 board by replacing two 1.5ohm resistor (1 burnt out) and 2 capacitor