HP 6111A power supply issue ? - Page 1
Forum section: electronics / repair

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: May 08, 2016, 08:36:08 pm
content: The power supply reads about .0003 off , the normal dial settings are 5 digit 00.000 so all readings up to 19.999 everything is ok except for .0003 off - that is just for information , not the problem I am looking to solve , unless there connected .The problem that I am chasing is that once I rotate the 1st digit to 20v - 20.000 the meter slowly creeps to about 34v [ slowly , the meter on PS and monitoring meter , is will 2-3 sec.s ] - for all voltage tests I am using a good multimeter , that match the meter on PS .So again if set to 20v it creeps to 34v , with the creep to 34v I wonder if its a cap charging , and then uncontrolled to the 34v .

author: sync
author_rank: Frequent Contributor
timestamp: May 08, 2016, 09:08:50 pm
content: 19.999 should be the maximum value. I'm surprised that you can dial the first digit to 2. That doesn't make sense. I think there should be a mechanical stop to prevent numbers above 1. But I don't know if the 6111a have this. I have a 6113a which goes to 9.9999 so there is no need for a limited first digit.The schematic show only one resistor (R231) for the first digit. It's for position 1. For 2 and above the switch is probably open without any resistors. That means the voltage adjustment resistor (the thumb-wheel block) is open which causes the voltage to rise.

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: May 08, 2016, 10:08:10 pm
content: The PS is spouse to go to 24v , there is a 4 position range switch up to 2.4v then up to 24v , then 2 more positions for current ranges .Got it used , so not sure , but all rotate sw. will go to 1 - 9 & stop .Thanks for schematic , I started to dig into the other day and stopped at repairing meter , pushed through & needle stuck , now on to the over voltage .

author: sync
author_rank: Frequent Contributor
timestamp: May 08, 2016, 10:35:41 pm
content: The meter is probably the same as in the 6101a. It's the 20V/1A version with potentiometers for voltage setting. From the 6101a manual:3-14 OPERATION OF SUPPLY BEYOND RATED OUTPUT3-15 The shaded area on the front panel meter faceindicates the amount of output voltage or current that isavailable in excess of the normal rated output.Although the supply can be operated in this shadedregion without being damaged, it cannot be guaranteedto meet all of its performance specifications. However,if the line voltage is maintained above 115 Vac, thesupply will probably operate within its specifications.On the 6101a it's possible to set a voltage above 20V. But the 6111a is limited to 19.999 due the resistors in the thumb-wheel block. Maybe you can add a resistor for 2X.XXX volts. It should have exactly the same value as your R231. These resistors are matched.

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: May 08, 2016, 10:42:03 pm
content: The label at top says 0-20v 0-1a , the switch says 2.4v , 24v meter 1.2a .12aThe meter I would not call shaded , but finer divisions .Thanks

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: May 08, 2016, 10:50:36 pm
content: So maybe no problem 20v , I wander if there was a stop for rotator ? so only 19.999 - they cheated me short on voltage by .001