Seeking a schematic for the Fluke 406 power supply that followed me home from the Puyallup hamfest. It looks like a nice bench anchor, with parallel 807 regulator tubes but also has a bunch of selenium rectifiers and bumblebee caps begging for replacement.
Any assistance appreciated.

--Chuck

http://www.cedar--rapids.com/Industrial ... manual.PHP

-Matthew

I have one of these too. There is a 407 manual on BAMA thats close, but not really close enough. It has circuit board construction, and 3 807's. (this has 2 807's and rivets in plexiglas) It was better than no information at all...

It's one of my favorite and most used pieces of equipment, and remains unrestored. It was still in use by it's former owner when I got it, and working fine. There is one black beauty behind the panel in mine that would probably explode if I ever hooked up the grounding strap (I never use that). I will restore it eventually, but like you I have no manual.

What follows is all from memory, but I don't think it will be to far off. There are some 500v filter caps in series, with big wirewound balancing resistors. When I had this about a week, one of the resistors opened with a little pop. I thought the noise came from a screw i dropped on the bench, and continued using the supply for about a half hour, unaware that the noise came from the power supply. Later, i found a piece of green ward-leonard ceramic and opened up the supply to see where it had come from. The resistor had a hole blown in the side and was open. Now if you haven't alreadfy guessed, all of the voltage was across ONE of the series capacitors for about a half an hour. Not good. I tested the cap, and leakage was negligible. It remains working to this day.

One thing you may find surprising compared to some other equipment, like HP or Tek, is how hard some of the components are pushed. It turns out that these caps, and the resistors, are running OVER their ratings at the 117 volt line voltage listed on the data plate. It is even worse if there is any unbalance in the resistors, or at the 121v line voltage in my shop. I would inspect all those components carefully, because if a resistor fails. you will have about 1100v on a 500v electrolytic cap. To Fluke's credit, it held together like this for over 40 years.

The 407 (the one in the BAMA manual) improves on this by having part of the voltage switching on the primary of the transformer. This issue still exists on the 407, but only when the voltage is turned all the way up. It exists on the 406 whenever the power switch is on.

I replaced both of those resistors with ohmite brown devils, new ones, and the values matched perfectly, making this less worse than it could be. If you are going to change the filters, I would look for 600v parts.

One other issue it has is that the voltage runs away on startup. This might be normal, I don't know. I suspect this is due to the 6aq5 in the regulator warming up slower than the 807s. I cant get too excited about chasing this until I restore the unit, however it doesn't fit too well with my habit of hooking stuff up before turning on any power.

Have fun with this thing. I don't know how I ever lived without it.

John

.

I have a 407DR that quit on me. Bad filter cap. Replaced all other suspect caps and anything else that looked like it might fail.

Mine has two 6.3 VAC-5 amp outputs that did not have fuses, which I added.

My manual was a joke, so many differences from the equipment plus different capacitor values for different s/n ranges. Use schematic and parts lists as a guide, I don't think the capacitors were critical in value or, the circuits would not have worked in the first place.

Added a diode across H.V. output in reverse bias. I also added a 1N4007 diode each, (in reverse bias), across both C10 and C11, 100uf/500VDC caps that are in series, for what it was worth, in case some accidental short or something, would not allow, (hopefully) that one cap, reverse charge the other.

After rebuild, checked specifications and used mfg test procedure;...passed with no problems

Charlie