Hp6227b regulated power supply

[Applemac]

Hi, was wondering if anyone could help, I have a hp6227b regulated power supply. When I switch it on with with independent and volts selected. With volts turned to the middle which should be 15volts the master side indicator shows maximum output 30volts and will not adjust, the slave fuctions correctly indicating 15 volts. Any ideas what I need to check?

[alm]

If it is set to independent, then the two voltage knobs should independently control the voltage of the two channels. Are you turning the left or right voltage knob? The left voltage knob should only affect the left panel meter, and the voltage knob on the right should only affect the right panel meter.

[Applemac]

Your correct I can control the right chanel nob and the meter reflectd what I adjust it too. However the left one swings directly to infinity without adjusting it. If i try ti adjust it is stays at infinity.

[alm]

Did you check with a DMM that the left output is indeed > 30 V, regardless of the setting of the voltage knob? Did you check that the strapping on the screw terminals on the back matches the standard strapping as shown in the manual?

[Tomorokoshi]

Did you check with a DMM that the left output is indeed > 30 V, regardless of the setting of the voltage knob? Did you check that the strapping on the screw terminals on the back matches the standard strapping as shown in the manual?

This sounds like the key. Can you take pictures of the terminal strapping with the protective covers off? They control the analog programming feedback circuits. If some are missing it can drive to the rail, oscillate, etc.

This part from Digi-Key fits the terminal block:
https://www.digikey.com/products/en?keywords=WM9711

Figure 3-2 in Section 3-7 on page 3-2 of the manual at Keysight shows the normal strapping pattern:
https://www.keysight.com/en/pd-1000001528%3Aepsg%3Apro-pn-6227B/power-supply?pm=PL&nid=-536902299.536879778&cc=US&lc=eng

[Applemac]

Thank you never thought about that i will take a look at the strapping and report back

[Applemac]

I hv check the strapping and both sides are strapped the same and in accordance with what the manual shows. Any other ideas?

[alm]

Then it sounds like a defect in the unit. Could be a shorted series pass transistor. Open sense connections, or a defect / bad connection to the voltage control pot. Defect component in the voltage comparator / or gate / error amplifier, e.g. one of the op-amps. I would start with the troubleshooting steps in table 5-4 of the manual on the Keysight website: Series regulator troubleshooting, high voltage condition.

[Applemac]

Strapping is the same both sides and as shown in manual. So decided to test the voltage out of the front binding post black probe in the black terminal and red in the red. The indicator returned to zero after there was a spark and bang from the terminal.Any ideas on what's causing my problems

[alm]

What jacks were the DMM leads connected to on the DMM side? If it was one of the current jacks, then you effectively shorted the output, which if regulation was not working properly (output pass transistor shorted) could have blown a fuse or something else. If the leads were connected to the voltage jacks, then I can't see how connecting them would have caused a spark.

[Applemac]

I did step one of the 5.4 series regulator troubleshooting high voltage. Shorted Q7 collector to emitter tp66 and the cable i used to short it started smoking but the indicator on the front instead of going straight to infinitive started raising slowly but i turned it off because of the smoke. Does this indicate bad q8 through q11 short?

[Applemac]

You were right, leads connected to dmm incorrectly my mistake. Connected test leads correctly and output terminals read 50 volts dc?

[Applemac]

Started the tests table 5.2 reference and bias voltages. Testing 1 voltage over 40 volts when should be 27.5 leads me to suspect shorts in cr21 and cr22 1n5059 diodes in power supply rectify circuit. Anyone know what equivalent I can use, and if im on the right track to solving this issues?

[Applemac]

Anybody?

[Applemac]

OK thanks for the help so far

[Tomorokoshi]

A couple questions to follow up:

1. Were you able to work through other measurements from Table 5-2? Given that the slave channel works, I suspect these are fine.

2. I have a 6227B that is currently outside of the frame. I will try to get some measurements within a few days. Let me know if there are any specific test points to look at. I will do unpowered resistance and powered voltage.