HP/Agilent 66312A (or others in the range) fan replacement and maybe other mods?

[wirewrap]

I have recently purchased one of these PSUs for the work I do at home (electronics final year student) and I am wondering if anyone has made any modifications to make the thing a little more quiet?

There is a chance that mine is louder than the norm, but either way I think it could do with an upgrade, so I was looking at a noctua NF-A6x25 FLX fan to replace the current one. My only concern is for heat dissipation. I don't expect this to be a problem as the psu only supplies 40W total, so the size of the heatsink is likely meant for higher power models, but there is always the possibility that a new fan will not deliver enough airflow and damage the power transistors. What I could do is wait for my 121GW (yes I bought one o: ) and then I will be able to measure the temps of the heatsink, although I will have to look into what temps are acceptable.

So has anyone done anything like this? or other mods for that matter?

Thank you

[TheSteve]

If it has the same fan as the 66309D's then it will be crazy loud. I swapped the fan out in one for a Papst 622L I had on hand. It is now very quiet as it runs the fan on 8 volts when cool. It will ramp the speed up if the temperature rises. I haven't loaded it fully to see if it will get too warm but so far it is fine. The Noctua fan should be a good option too.

[mweymarn]

I have two 66312A units, they are my most used power supplies.

On both of them I installed ebm-papst 612NLE fans. These are high quality, low noise ball bearing fans. Without load I can hardly hear them, even when they spin up the noise level is very low. Got the fans from Mouser. Careful with the part number, the 'NLE' part makes the difference.

A Torx screwdriver with narrow shaft is needed to remove the two mounting screws.

[nctnico]

I have two 66312A units, they are my most used power supplies.

On both of them I installed ebm-papst 612NLE fans. These are high quality, low noise ball bearing fans. Without load I can hardly hear them, even when they spin up the noise level is very low. Got the fans from Mouser. Careful with the part number, the 'NLE' part makes the difference.

You have to be carefull because the 612NLE produces very little pressure so it may not be a good replacement. OTOH I noticed HP/Agilent tends to mount fans which move way more air than necessary.

[wirewrap]

I have two 66312A units, they are my most used power supplies.

On both of them I installed ebm-papst 612NLE fans. These are high quality, low noise ball bearing fans. Without load I can hardly hear them, even when they spin up the noise level is very low. Got the fans from Mouser. Careful with the part number, the 'NLE' part makes the difference.

You have to be carefull because the 612NLE produces very little pressure so it may not be a good replacement. OTOH I noticed HP/Agilent tends to mount fans which move way more air than necessary.

Yes I was wondering that also..

If it has the same fan as the 66309D's then it will be crazy loud. I swapped the fan out in one for a Papst 622L I had on hand. It is now very quiet as it runs the fan on 8 volts when cool. It will ramp the speed up if the temperature rises. I haven't loaded it fully to see if it will get too warm but so far it is fine. The Noctua fan should be a good option too.

I have two 66312A units, they are my most used power supplies.

On both of them I installed ebm-papst 612NLE fans. These are high quality, low noise ball bearing fans. Without load I can hardly hear them, even when they spin up the noise level is very low. Got the fans from Mouser. Careful with the part number, the 'NLE' part makes the difference.

A Torx screwdriver with narrow shaft is needed to remove the two mounting screws.

Have either of you had any thermal issues? as I said at the start I really doubt it with a heatsink that size, and the estimated thermal power..

[mweymarn]

Have either of you had any thermal issues? as I said at the start I really doubt it with a heatsink that size, and the estimated thermal power..

No problems whatsoever, even when pulling high currents at low voltages. I believe these units were primarily designed for ATE use. Hence their thermal design is very conservative. They are specified for operation up to 55°C ambient temperature.

The unit also measures its heatsink temperature via a thermistor (RT301). I have never managed to trip the overtemperature error.

[peertux]

I have a 6612C (same housing as yours) that was really load as well. I put 68 Ohm in series with the fan and put a bits off rubber between the fan and the heathsink. Now its way more quit and there are no thermal issues.



I also put a piece of rubber between the transformer and the housing because there was a 100Hz hum.



 

[HighVoltage]

I have replaced the fan of my 66312A as well to slow turning ball bearing fan and have no problems at all with it. The PSU has been working perfectly for at least 2 years now.

[alm]

So has anyone done anything like this? or other mods for that matter?

Front terminals are an obvious addition. Recessed safety banana jacks fit in the holes designed for BNC connectors with only minor filing. Normal binding posts would require some sort of mechanical support to mount them to the front panel, like the solution HP used in the related 661xC bench supplies. You can loop wires from the rear connectors through one of the holes in the rear panel.

[wirewrap]

I also put a piece of rubber between the transformer and the housing because there was a 100Hz hum.



 

Yes I also have this issue but I didnt really know what to do about it, I hope something like this helps me as it is a very loud hum and its sitting on a wooden desk s:

Front terminals are an obvious addition. Recessed safety banana jacks fit in the holes designed for BNC connectors with only minor filing. Normal binding posts would require some sort of mechanical support to mount them to the front panel, like the solution HP used in the related 661xC bench supplies. You can loop wires from the rear connectors through one of the holes in the rear panel.

I actually have binding posts already, which from what Ive looked at seem professionally put in. Not sure if they are factory or an addition however, there have certainly been some aftermarket changes to the unit (there is a small "phone cap" switch on the back the appears to connect to the coms board for RS232 and HP-IB).
Both binding posts are red too which Im not a fan of

[peertux]

I also put a piece of rubber between the transformer and the housing because there was a 100Hz hum.



 

Yes I also have this issue but I didnt really know what to do about it, I hope something like this helps me as it is a very loud hum and its sitting on a wooden desk s:

The hum in my psu is the attracting and pushing away of the metal casing from the transformer, when you wedge a piece of rubber really tight in between the vibration becomes almost none existent. 

[chronos42]

Hi wirewrap,

yes, that was a really stupid idea to use two red binding posts for plus and minus. I have never seen such a nonsense at any other power supply.