Ok, some test equipment porn.
![Evil >:D](https://www.eevblog.com/forum/Smileys/default/evil.gif)
(Glad I missed the spam posting -things like that don't belong here. There are other parts of the internet for that.)
My HP 6114A arrived today.
For $41 + ~$90 shipping costs I wouldn't call it a real bargain but it's worth it, if I could repair it without bigger hassle.
That said I directly moved it from the cardbox package onto my bench.
The outer cardbox was damaged but the padding was very good, the 6114A didn't get hurt being shipped around half of the planet.
![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif)
After switching it from 115V~ to 230~ input I switched it on and it behaved just like the seller had described it. Ok.
Problem: It put out voltage some volts lower than the voltage dialed in even though the voltage and current regulation seem to be working basically. And it had 50mV ripple on the output.
Ok, first, I took it apart.
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/wink.gif)
Turned out that one rail for the control board was at ca. 19V DC with 9V AC ripple on it. The brave 6114A regulated that down to 50mV ripple on the output.
First I suspected one of the rectifier diodes to be dead -they all were intact.
After that I powered the faulty rail from my Oltronics B300D supply and -tada: The 6114A came back to life and worked as it should -despite being completely decalibrated by the seller -he must have tried to solve the problem through recalibrating. I'm glad he didn't touch anything else inside.
With this finding my next suspect was the electrolytic capacitor for the +28V rail.
Some further mechanical dismantling it turned out that it is completely dead:
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=403791;image)
I had checked the one for the negative rail and that had more than 800µF (490µF nominal value!).
Strange that one of two similar capacitors is completely dead while the other is as good as new.
![WTF? :wtf:](https://www.eevblog.com/forum/Smileys/default/wtf2.gif)
I only had a bunch of 220µF/400V capacitors available for testing so I bodged two of them in parallel into the 6114A:
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=403793;image)
That brought it back to life again. Winner!
![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif)
Some calibrating later (quiet easy with modern equipment like electronic loads and DMMs with >> 10megOhm input resistance
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)
the 6114A was spot on again and also the hefty ripple was gonski.
![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif)
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=403795;image)
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=403801;image)
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=403803;image)
This repair was a quick hack because I couldn't wait. I'll check all the other electrolytic capacitors as well as the tantalums and will replace some or all of them. Don't know yet.