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Products => Test Equipment => Topic started by: CopperCone on December 17, 2017, 05:07:08 pm

Title: 6114a precision power supply switch problem
Post by: CopperCone on December 17, 2017, 05:07:08 pm
So my 6114A has a problem, if you gently hold the 0.x0 switch, on the bottom, the display is correct. If you let go, it shorts it out to the maximum value.

How can this be fixed? Bad switch? Bad contacts?

Like, gentle pressure on the bottom part of the switch fixes it. This is the type of switch that you press, and it moves the display. It's bang on accurate with light pressure.
Title: Re: 6114a precision power supply switch problem
Post by: Vgkid on December 17, 2017, 06:56:12 pm
I would first check the solder joints on the switch board.
Title: Re: 6114a precision power supply switch problem
Post by: Tomorokoshi on December 17, 2017, 07:42:06 pm
I've repaired those in two 6114A units, along with the similar switch used in an 8011A signal generator.

There may be a thread around here on the topic.

Anyway, there is a grease that was put on the gold-plated switching elements. It gets thick, and prevents the contact from taking place, effectively making that string go to the maximum value.

Take pictures at each step. Collect containers for the hardware. From I recall the repair procedure is something like:

1. Open up the unit and remove the switch assembly board. You will have to desolder a couple wires from the variable resistor. The front plate is a little tricky to remove.

2. Desolder the 4-gang switch assembly from the circuit board. A good desolder station is good for this. Use a lot of solder paste and solder wick.

3. The switch assembly is probably wrapped up with cloth tape. Peel off the tape.

4. The 4 units along with the two sides will slip apart from each other relatively easily.

5. The switching element board is heat staked in 4 places. Carefully cut through the mushroomed part and remove it.

6. Remove the rotating switch contactor and the element board.

7. Clean both the contactor and the element board with alcohol. There was enough that I needed to use a couple q-tips for each one.

8. I sprayed on a plastic-safe contact cleaner with silicone lubricant.

9. Reassemble, and do the next set.

It probably took 2 hours to work out to do the first machine, and probably an hour for the second.
Title: Re: 6114a precision power supply switch problem
Post by: CopperCone on December 17, 2017, 11:20:16 pm
shit, any idea where the brown and white wire goes?

It must have been fatigued, it ripped out when I removed the thing. Gotta find a manual...

ripped from the main board.

never mind, found it. this looks fun.. I think I will use alcohol to clean the switches.
Title: Re: 6114a precision power supply switch problem
Post by: Tomorokoshi on December 17, 2017, 11:25:29 pm
Here is the manual:
https://www.keysight.com/en/pd-1000001521%3Aepsg%3Apro-pn-6114A/voltage-source?pm=PL&nid=-536902299.536879741&cc=US&lc=eng (https://www.keysight.com/en/pd-1000001521%3Aepsg%3Apro-pn-6114A/voltage-source?pm=PL&nid=-536902299.536879741&cc=US&lc=eng)

The manual seems to not contain wire code colors. Later tonight I can open mine up and see where it goes.