I'm checking the capacitors currently and am facing some surprising things.
Disclaimer: This is true for my 6114A with a serial # beginning with 1928A. 6114A's with different serial # beginnings might be (as expected) different.
First of all, I had found capacitor C1 completely dead causing the 6114A to not regulate the output right and with a ripple completely out of Spec (see first posting of this thread).
I checked C2, C3 and C12 now (really hard to get them soldered out the PCB even with a desoldering gun..) and found C12 completely dead also (120pF left over from 490µF).
Having all big caps out I decided to bodge in capacitors like I did it before for C1 temporarily.
I'm keeping the good C2 and C3 for spare parts. Could be another 6114A or a 6104A be hitting my Test Equipment stack.
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/xwink.gif.pagespeed.ic.cldandycH0.png)
Upcoming TEA once more..
![Evil >:D](https://www.eevblog.com/forum/Smileys/default/xevil.gif.pagespeed.ic.tdrs7Uj5gu.png)
Inside of my 6114A it's now (temporarily) looking like this:
![](https://www.eevblog.com/forum/repair/hp-6114a-repair-(fault-regulation-seems-to-work-voltage-low-output-ripple)/?action=dlattach;attach=404818;image)
The failed capacitor C12 (with a 0.25Ohm series resistor) is connected between terminal A8 and -S(ense).
With A8 connected with a bridge to + and -Sense to - normally C12 is connected to the +/- output of the power supply.
In the manual it's function is described (error corrected..):
3-59 An internal capacitor (CI2) connected across
the output terminals of the power supply. helps to
supply high-current pulses of short duration during
constant voltage operation. To reduce current
surges. this capacitor can be removed by unstrap-
ping terminal A7 A8. Any capacitance added external-
ly will improve the pulse current capability. but
will decrease the safety provided by the constant
current circuit. A high-current pulse may damage
load components before the average regulator cur-
rent is large enough to cause the constant current
circuit to operate.A failed capacitor C12 is therefore nothing else then an open connection between A8 and + output.
![Grin ;D](https://www.eevblog.com/forum/Smileys/default/xgrin.gif.pagespeed.ic.QVVz6XIT20.png)
After I had replaced C1 (and with it repaired the main fault of my 6114A) there was still a crackling sound (50Hz) noticeable that was really annoying to me. After some exploring I found this guy across transformer terminals 12 and 14 making this annoying sound:
![](https://www.eevblog.com/forum/repair/hp-6114a-repair-(fault-regulation-seems-to-work-voltage-low-output-ripple)/?action=dlattach;attach=404820;image)
It's a foil capacitor 1µF 220V~ still measuring 923nF, 0.1% loss, 0,14Ohm ESR.
It's not getting hot, not even warm but I'll replace it anyway to get rid of that crackling sound.
Capacitors of this kind should be absolutely silent.
The legs were wound around the transformers solder terminals and it was a little difficult to desolder it before I found out.
![Banging Head |O](https://www.eevblog.com/forum/Smileys/default/bangheadonwall.gif.pagespeed.ce.8iLbFYV4Bc.gif)
The smallest replacement I found is
slightly bigger (31,5mm x 11mm x 21,0mm).
I wonder how Sprague managed to build this capacitor in such a small form factor. Perhaps that's the reason why it makes a crackling sound now.
![Huh? ???](https://www.eevblog.com/forum/Smileys/default/xhuh.gif.pagespeed.ic.6Nvt7O8a11.png)
Then I found a capacitor C1 on the A5 interconnection board that's not mentioned anywhere, not even in the change/errata notes I got with the manual from ArtekMedia:
![](https://www.eevblog.com/forum/repair/hp-6114a-repair-(fault-regulation-seems-to-work-voltage-low-output-ripple)/?action=dlattach;attach=404824;image)
(one pin desoldered for measuring purposes)
C1 on the A5 board is connected directly to + and - output. And it's nowhere mentioned/shown in the schematic nor the changes/errata section.
I discovered that in my 6114A C2 is not connected to the A3 terminal but to the A1 terminal.
Last but not least the output capacitor soldered directly over the front output terminals is C3 in the parts list but C13 in the schematic. I corrected the schematic for my 6114A:
![](https://www.eevblog.com/forum/repair/hp-6114a-repair-(fault-regulation-seems-to-work-voltage-low-output-ripple)/?action=dlattach;attach=404822;image)