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Restoration of the PSU

I have begun with the first phase of electrical restoration on the Marconi MK3 which is to get the power supply unit operating. I am following the restoration process through this MK3 restoration guide on the Museum Of The Broadcast Camera site and am in communication with the owner of that site who has wrote that restoration guide and has restored a MK3 to working order, he is kindly providing me with technical advice on restoring this camera.

So the first step is to reform all of the electrolytic capacitors which is a standard procedure in old electrical equipment. For this job I needed an isolation transformer, a variac, a high tension power supply, an analog meter and a digital meter. I got the company I use to work for to build the isolation transformer, I bought the variac and analog meter from Jaycar (the variac was expensive $230) and the high tension supply I had to build from scratch so I designed and built one based off the power supply circuit in my homemade vidicon camera and it works good! Here below is a pic and video of my homemade 450V HT power supply:
Homemade 450V HT power supply
A video demo on my 450V HT power supply without the variable pot at the output (I added that later)
Okay now that I have my high tension supply and the other gear handy it was time to start on reforming those capacitors. So firstly I have my HT power supply connected to my variac connected to the isolation transformer connected to mains, I then the HT supply to a capacitor with the analog meter connected in series between the HT supply and capacitor for current readings and my digital meter connected in parallel with the capacitor for voltage readings. I disconnect one leg of the capacitor from the circuit so the HT supply only powers the capacitor. Next I set the variable pot to somewhere between 5K and 10K and crank the variac up to about 50V for the 100V 1000uf caps and 250V for 200uf 350V caps and wait till the voltage rises to the set voltage, the current will start at a few milliamps and then will drop close to 0 amps as the voltage rises. Once the capacitors are charged to their set voltage, I then lower the pot to close to 3K and crank the variac to close to the capacitor's maximum working voltage and wait for the the voltage rise till it stops and then leave it for an hour to see if the capacitor retains charge and doesn't go hot. I did this to all 15 caps and most of them reformed nicely without a hitch except for one 1000uf 100V cap which took a long time to charge up close to it's max working voltage. The process took roughly an hour and a half per cap and so it took about a week on and off to get them all reformed. Here below are pics and a video of the capacitor reformation setup:
450V HT power supply connected to variac and output connected via analog meter to capacitor
Analog meter connected in series between HT supply and capacitor and digital meter in parallel across capacitor
Output leads from HT supply connected to one of the electro caps
Close up of the leads connected to an electro cap, as seen I disconnected one lead so only that cap gets powered by the HT supply
Video demonstration of my HT supply in operation reforming one of the electro caps
After reforming the electro caps I then removed all the valves and tested the first stage of the PSU which is the mains tranformer in which I checked all the secondary voltages and they were all correct. Also in the first stage is the blower fan which unfortunately is not operating so I'll have to somehow fix it. Being happy with the transformer being operational, I started on the second stage of testing which is testing the output voltages. I put the valves back in and then connected two 150W lamps to the 250V output and a 150W lamp to the 330V output and jumpered the interlock connection. I then gradually cranked the variac up and saw that the valves started to light up, but then I heard a "BANG" at one of the electro caps followed by smoke which was not a good thing. I pretty much jumped the gun without checking the PSU over more thoroughly.

So the next thing to do was to check for physical faults and test the resistors. First thing I noticed at the power output socket was one of the wires was broken off the pins and others were a little frayed, so I resoldered the broken and frayed wires to their pins on the socket. I then checked the resistors with the multimeter and found a number of them to be open circuit or out of tolerance so I replaced them, actually seeing there wasn't many resistors I decided to replace pretty much all of the carbon resistors, the wire wound ones were good so I left them. While I was at it I replaced the smaller paper caps as well with mylar caps as paper caps are unreliable. I also rewired all of the electro caps with new wires as I had to cut the old ones during testing. So I've pretty much given this PSU a bit of an overhaul.  Here below are some pics of the component replacement jobs I did:
PSU before replacement of resistors and paper caps
Replacement of resistors and paper caps with new resistors and mylar caps
All of the old resistors and capacitors I replaced in the PSU
Electro caps rewired with new wire and new resistors in place of the old ones
After replacing faulty components and fixing the broken wires at the output socket, it was ready for testing again. I rigged up the lamps once again to the high voltage ouputs and gradually cranked up the variac and to my delight no capacitors went bang and the valves were lighting up and one of the lamps powered up so I was getting power at the 330V output :D. But then I was getting sparking and crackling behind the front panel which means there's some breakdown of insulation somewhere in that area causing some arcing. I powered it down and then powered it up again and this time no sparking or crackling so I was happy. However I was then seeing some smoke coming from one of the large variable wire wound resistors so I wasn't out of the woods yet. Testing the resistor, it appears the variable wiper is not making contact as I'm getting an open circuit reading, so will have to look into getting this resistor working. Also I have to somehow get the blower fan working or the mains transformer will overheat. So that's where I am up to right now with the PSU, stay tuned for updates when I tinker with it next. In the meantime here are some pics of the PSU rigged up for testing along with a video I made of the PSU in action before the resistor went smokey:
PSU rigged up for testing
A video of the PSU powered up, during the video the big wire wound resistor went smokey
Stay tuned for updates!