I found a great deal on a “totally faulty” 4352B, well, it is a bit a cat in a sack, as we say in Germany, you never know what you get. It shipped from Manila, even better! List price, I think it was close to USD 50k!

It’s a clean unit, except for about 100 stickers and seals!

All heavily shielded, many kinds of screws and metal plates to keep to good waves in, and the bad waves out.

The brain of the machine – quite sophisticated – Japanese engineering (this unit has been manufactured by HP Japan!).

After some study and test, it is clear, it is dead because there just isn’t any power. The power supply is a two-stage supply, first stage, a switchmode universal voltage to 24 Volt (190 Watt) supply, bz maker Artesyn, then a really top quality 2nd stage, made by Agilent. And guess what, the 24 Volt supply is faultly!

This supply uses power factor correction, and two IRFBE30 MOSFETs to drive the transformer – one of them is shorted shot. Otherwise, no damage to be found on the board so far, except the thermal fuse, which must have cut out immediately (even the primary fuse is OK – so there is hope that this will be an easy repair of the 24 V supply).

Ordered some spare thermal fuses and MOSFETs, quite common IRFBE30 type – low cost. Let’s see if this will let us get the power back, if not, worst case, we can always install a new 24 V 200 W supply – there is enough space in the case.

In any case, these VCO analyzers are a great deal – there is a 26.5 GHz (!! APC 3.5 !!) power splitter inside, value, still available today, EUR 1350, and a 13 GHz detector, value, 450 EUR. But let’s keep fingers crossed that this won’t become a parts unit anytime soon.