HP Agilent 6033A Power supply teardown

[Cones]

Hi,

I've not seen any of these on here yet. Probably due to the ridiculous cost of the new units!  £3200 UK Pounds

These were second hand on ebay for a more than reasonable sum.

I bought two and the fan on one of them is almost seized solid. 80x80x38 115v AC 2700rpm 26.5cfm
I am wondering about replacing it with a lower rpm and cfm unit so I can run at low output with less noise? It is fixed speed and blows air into the case from the rear. A new PAPST fan to the same spec is about £40 (The Agilent one is £95) or go for the lower cfm one?

I bought them with the intention of using them to power a ham radio. As they were less expensive than even a very basic 13.8v 10A ham supply.

A few photos of the internals.









































The transformer windings are a work of art!













Thanks

Mark


 

[free_electron]

Ah, the resonant supplies. These things are a bitch to repair.

this thing is essentially a switching power supply. they have a first step down converter which is galvanically isolated. this is followed by a second step-down converter. this is why you find those two huge ferrite transformers.

if i remember correctly they sense the current through the fan in these supplies. get it wrong and the supply will not start.

there should be a huge choke somewhere aroudn the main power input as well to keep the switching noise off your power line...

[Cones]

Hi,

Thanks, yes 20KHz clock with 320KHz oscillator. Flyback like switching circuit. Regulation seems very good on these and no RFI on my HF radio. So I assume the filters are effective.

The fan is wired across the 110v transformer tap. I cannot see any current measuring?

Large mains choke, yes see below.



Thanks

Mark

[anotherlin]

That question may sound dumb, but for what sort of application would you need 30A at 20V ?

[Cones]

Hi,

The power supply will not give maximum current and voltage at the same time. You can have around 200 watts maximum.

So at 20V you get 10A. Or at 30A you get 6.66V

Mark

[nctnico]

I used to have a 6038A (60V 200W). The biggest downside of these power supplies is the noise from the fan. AFAIK Agilent has a complete  service manual (with full schematics) on their website.

Edit: I wouldn't mount a fan with less airflow. Many years ago I bought an HP6002A PSU (same form factor) from a fellow who had mounted a smaller fan and then he used it to charge a battery. Because the PSU overheated the temperature protection kicked in. At that point the PSU found the output voltage was higher than it should be so it engaged the crow bar. The battery started to battle with the crow bar and eventually the PCB traces burned away. I fixed the damage to the traces, several lose wires and added a temperature controlled fan. Under light loads the fan isn't even on but if the going gets though it kicks in.

[DeanThatcher]

Hi
Looks like a lot of work.

Would you have any idea what SEC error means? and how to clear or fix it
thanks