This is the last in a line of shop bench jobs I've had to do on shop bench equipment.

I built this supply in 1978 and rebuilt it in 1992. It gives 6.3v A+ voltage at 3 amps, variable regulated B+ voltage between 220 and 480v, fixed B+ at 580v, and C- (bias) voltage between 5 and 60v. If you work a great deal with tubes, especially in construction and rebuilding, a power pack like this is hard to do without. This one, unfortunately, often has to sit unused for long periods of time while I'm involved in other work, and that gives the caps a chance to go "soft" (develop high power factors, leakage etc). I call it "shelf rot."



The power transformer is a Thordarson 24R15 and the two chokes are Thordarson 20C54's. The tubes are the notorious potato-masher 5R4WGB B+ rectifier, 5932 regulator (losser), 6SJ7 regulator control, 0C3 reference, 6H6G C- voltage rectifier, and a 6AF6G eye tube. Its shadows track the regulated B+ level and close at 500v.

Circuits for such packs as this can be found in the tube-era ARRL handbooks, the Orr Radio Handbooks, and many other places.



Thankfully there are no tight places belowdecks. The chassis is fan-cooled since the 1992 rebuild; the silver power transformer is for the fan; the bias power transformer is mounted on the right-hand apron. Since I found a number of soft caps in the B supply, I replaced them all. Bias supply and fan supply caps were all OK, so I let them be.



The unit has main fuse, B+ fuse, AC and B+ pilots, a standby switch, and a crossthrow line-reversing mains switch. Power is taken from a 6-pin tube socket on the right apron; I use multimeter-type probe leads to bring the voltages from the socket to the bench.



Back in its place beside the Variac pack (built in the late 1960's) and the Heathkit HO-10 monitor scope, another recent shop job.

It's the first time in a while I haven't had issues with at least one piece of my shop gear. It's a good feeling and I hope it lasts awhile...

Cold 807 time!

Larry

This might be better in the "test equipment" category.

I also built and use a power supply like yours. I approached mine a bit differently. Since I don't usually use regulated supplies in the stuff I build, I used a 350-0-350 volt transformer supplied through a 1.75A variac, so I can vary the transformer secondary voltage from zero up to its rating. The secondary is available directly, if I want to feed an external rectifier, or through diodes or a tube rectifier in the unit. The tube rectifier can be any of the 5 volt 4-pin or octal rectifier tubes. The filament is powered from a separate transformer not controlled by the variac. I chose not to include any filtering in the supply; I use external filtering so I can tailor it to my needs at the time. There are no meters in the supply, I put tip jacks in the supply for measuring voltage and current with my DMMs and VOMs.

The supply also includes fixed voltage filament power at 2.5, 5, 6.3 and 12.6 volts and a negative supply of up to about 70 volts using a 25.2 volt transformer feeding a voltage doubler.

I am thinking of building a regulated add-on for it, sort of like yours.

A supply like these is very handy to avoid having to build a supply for every circuit you try.

I thought about putting this in the "test equipment" category, but decided it would be better off here. If a moderator wishes to move it, by all means, well and good.

Can you post pix of the supply you built? I'd certainly like to see it.

Larry

Here are photos of the front panel and a view from the rear. I originally built it on a 17 by 10 by 3 inch chassis box set up to hang on a wall above the bench. The transformers were mounted on the top of the box on one of the 17 by 3 inch sides. When I rearranged my bench I no longer had the wall space so I had to reconfigure it because with the transformers on the top edge it was too unstable. I moved the transformers to a chassis behind the front panel. The tube sockets are on the top of the front panel box.

Each section has tip jacks for voltage measurement and two tip jacks with a switch to open the internal connection for current measurement. The variac can be connected to either the plate transformer or to the filament transformers. Being able to vary the voltage to the filament transformers is useful for coming up with the appropriate series resistor for d-c heater supplies.

The coil of wire hanging out of one of the filament supplies is to use with a clamp-on ammeter. I found that the amp position of my DMM had too much internal and lead impedance to use with low voltage filament tubes, 2.5 volts fed to a 3 amp type 82 filament resulted in 1.9 volts at the tube.

The supply is also useful where you might normally use a variac to bring up the voltage. With this supply you can pull the rectifier tube in the device under test and apply normal power to the device to have the tube filaments at full voltage, and then bring up the d-c voltage incrementally.

Very nicely done indeed! Congratulations on a good job .

You may or may not have any immediate need for a regulated DC supply, but the experience of building one is worth having in itself. Truth to tell, I don't often need mine nowadays, except on specific service jobs and for "jigging" experimental or test circuits where fixed DC supply voltages are called for.

I don't do so much of that kind of work anymore, but throughout the 1980's, after I built my power pack, I was doing a lot of it.

Keep up the good work and best regards ,

Larry