HP 6030A possible damages

[Fiorenzo]

I have bought an HP 6030A (0-200v, 0-17A)
Someone, when converting It from 120volt to 220volt, did not disable the voltage doubler and left the inrush current limiter in the 220volt configuration.

I am trying to check what kind of damages could have been happened to the power supply.

Strangely it was working and nothing exploded.
This is very strange.
I know that part of the same circuitry, rectifier for example and the FET board, is on its brother model 6035A that is rated for 500volt output.

I attach some part of the schematics the service manual PDF.

Thank you

[George Edmonds]

Hi

In all probability provided the link W1 was in the open position the power supply will have not sustained any damage from the application of 220/240 VAC.

Link W1 changes the Bridge Rectifier plus the six 1800uf electrolytic capacitors from a normal Bridge Rectifier on 220/240 VAC input to a Voltage Doubler for 100/120 VAC input, the incorrect setting of the Inrush current limiters will probably have caused no harm, but please make the full change to 220/240 VAC operation before any further use.

G Edmonds

[Fiorenzo]

The problem is that the link W1 was in the 120volt position.

The power supply was powering on, I don't know why It didn't blow up

[George Edmonds]

Hi

Hi

Neither do I, it usually proves quickly fatal for the bulk storage electrolytic capacitors and the input switching semiconductors at a minimum.  How long was it on for before the incorrect setting for W1 was found?

All I can say is that HP well over designed the AC input to DC stage, there may well be a long term reliability problem.

G Edmonds
.

[Fiorenzo]

Thank you Edmonds,
I don't know for how long It was left in such configuration.
I have personally started It up and left It running for about 5 minutes before discovering such problem and without a load.
Because I have paid it about 880 euro It could be better if I give it back and ask for a refund.

Just to give It a last chance, how could I test it to check if It is still good?

Thank you

[Fiorenzo]

I have spoke with the shop who sold me this power supply.
They said that It was from a military lab that was working with a 240volt supply... they should have set It with such configuration.

I do not understand why it is working.
Could be something that I am missing?

I attach some photo of the actual configuration.

[George Edmonds]

Hi

Having gone back and looked more closely at the schematic it is not immediacy clear just what W1 does and how it does it.  At first glance it looks like the normal dual voltage input Bridge Rectifier / Voltage Doubler configuration, this is in agreement with the statement on page 72 of the manual that you attached, but what is certain that if W1 is on J9 you should have serious damage to the bulk storage electrolytic capacitors with the supply on 220/240V mains.

G Edmonds

[Fiorenzo]

I agree with you, but the psu is working and i cannot understand why, after all this time.

Could you suggest me how to check it, maybe with an oscilloscope?

[George Edmonds]

Hi

I will try to make some suggestions later today.

Under no circumstance get a class 1(grounded) scope anywhere near the primary of the power supply,  To do so a mains isolation transformer must be used.

G Edmonds

[Fiorenzo]

in the afternoon I tested the output of the psu for the ripple peak to peak.

as for specifications it should have been less of 50mv, it was around 35mv at 1000watt output and at 1250watt was about 50mv p-p

at over 600watt the psu start to make a little 50hz hum from the capacitors bank, could be a sign of bad capacitors or is a normal behave?
at over 1100 watt some time the psu has made a louder and higher frequency tone... I don't know why.

ps: i had an isolation transformer but at the moment i am without it. also my scope is limited at 300volt maximum 10x probes

[George Edmonds]

Hi

First it would be nice to know if you are hearing 50Hz or 100Hz from the input stages when you load the power supply, if 50Hz it should be coming from before U1, the bridge rectifier, possibly from the common mode choke L1 in the AC input filter.  If it is 100Hz it should be post U1, which may indicate a failure or failures of the 1,800uf 200VDC electrolytic capacitors.  I do note that you say that the frequency you hear changes with load, this maybe a sub harmonic of the switching frequency or it may be a change to 100Hz from ripple on the DC supply.

The only way that I can see the power supply surviving with W1 set for 100/110VAC operation is if C4 and C8 have failed as these are the voltage doubling capacitors, with them open circuit the power supply will be set for 220/240 VAC operation irrespective of the position of W1.

I do not know the intended use for this power supply, but if it is for long term and at a reasonably high output load I would suggest that C4 + C8 and C1 + C2 + C6 + C5 all be replaced as a precaution.  In normal use C1 + C2 + C6 + C5 will be the first components to fail and it looks like your power supply has anything but normal use.  No doubt these will be expensive electrolytic capacitors (possibly screw fixing) which should be rated for high ripple current use at 105C.

I certainly would be looking for any slight distortion of the capacitor cases or any sign of venting electrolyte (can smell like fish or cats pee) then checking them for correct capacitance and most importantly ESR (although making valid ESR measurements is yet another saga fraught with problems).

As I have not seen this supply the above is based on my experience only.

George Edmonds

[Fiorenzo]

it is very interesting what you said.
i think your suggestions are right, probably the doubling capacitors could be failed.

i am going to desolder all of them to check if are in specs.

because they should be very high performance capacitors could you suggest a way to test them in the right manner?

i have a basically esr meter and a scope, not more...

[Fiorenzo]

Hi George, sorry for the late reply.

I have desoldered the 6 primary capacitors.
I have tested all off them with a cheap ebay esr meter.
All seem to have specs around these values:

1760 to 1840 uF
0,12 to 0,15 ohm ers at 50hz
0,6% vloss

Are these good values?
If they are good, why the psu is not broken by the voltage doubling effect?

Thank you

[JoeRoy]

I just bought an HP/Agilent 6030A, it seems to be in good shape, but it lacks the "black box" on the back, looking the service manual, it seems to be just an EMI filter.

There are a white-with-Gray-line cable (maybe Neutal) and a white-with-Gray-and-Black-lines (maybe Live). I measured resistance (between the white cables) and is only 8.3 ohms (in 120V would be close to 15A), I'm not sure if this is normal on off-state.

What do you think, would be safe to turn it on my 120 AC outlet?  Thank you so much.


https://ibb.co/G5PqDFq

[wasedadoc]

The service manual contains no detailed schematics but the text on page 74 strongly implies that this is a switched mode supply which would mean it does not have a mains transformer operating at AC line frequency.  As such I would NOT expect to measure such a low resistance as 8 Ohm and thus I suspect the unit has a fault and I do not recommend applying 120v AC.

[JoeRoy]

The service manual contains no detailed schematics but the text on page 74 strongly implies that this is a switched mode supply which would mean it does not have a mains transformer operating at AC line frequency.  As such I would NOT expect to measure such a low resistance as 8 Ohm and thus I suspect the unit has a fault and I do not recommend applying 120v AC.

Actually when I "turn it on-off-on" the resistance changes from 8R to 40R, 100R, 30R, etc...  I guess the DMM cannot read it correctly because of some internal variation.

I'll try to find an incandescent lamp to put it in series.  I also have a variac, maybe if I slowly increase the voltage, but I don't know if low voltages can harm it.

[wasedadoc]

I do not understand how but when I read JoeRoy's post I thought it was the opening post of a new topic.  Although the service manual I found at elektrotanya had no schematics, I now see that there are some schematics in the actual first post of this topic.  One of those does show a transformer connected across the AC line so the low DC resistance could be correct.  For 120 Volt operation there are two primaries in parallel.  I suggest you switch it to 240 Volt configuration and check if the resistance changes to four times larger, ie about 34 Ohms.  Then change it back to 120 Volt setting. 

[JoeRoy]

Thank you Wasedadoc, I'll do that but I think, if there is a 120/220 switch, maybe is inside.

I smelled inside (LOL), no problem, don't smell burn, actually smell like new, there is no dust inside.

All the screws were tight like from the factory, and one had a protection seal.

I'm attaching the service manual, I think page 113 shows this 120/220 switch.

[JoeRoy]

I did the 220V switch test and changed the internal resistance, everything seemed fine so I decided to use the Variac, with +- 50V it turned on, so I put in the 120V outlet.

It's working, Max Voltage 204V, Max Current 17.4A, good score 

Thank you all.