[Mr 1936]

Hi Scotorvm

I have an 830 which I haven't restored yet. I also have its successor from 1934, the 834C, so I am familiar with this era of set. Some say there is the right way, the wrong way and the Philips way ! The 834C has the longest warmup time of any set I own, nearly 2 minutes.

The DC mains supplies in the 1930's would have been anything but clean, hence the common mode filter choke and the HT choke S3. Note that just to confuse, Philips schematics show windings as zigzags and resistors as castellations. The mains ripple and noise would probably have been at higher frequencies than 100 Hz. In those days large value smoothing caps weren't practical, so one sees modest values combined with series iron cored chokes to give decent overall smoothing. Nowadays a 100 uF HT smoother is nothing special but chokes are expensive.

The LT current demand is 180 mA, and with four 20V valves in series that tots up to 80V. The rest of the 190 to 260 V DC input voltage is "lost" in the barretter which acts as a constant current device to allow for some variation in supply voltage. Larger variations are catered for by fitting different types of barretter.

When it comes to the HT side of things, Philips didn't see fit to change anything for different mains voltages. At 220V DC input the HT drain according to the data sheet tots up to about 30 mA, and less at lower voltages.

Your outboard DC power supply therefore needs to source a more or less constant current of about 200 mA at somewhere between 190 and 260 volts. The ripple at 100 Hz will be smoothed a little by S3, so it doesn't need to be ultra-clean.

In the interests of low heat in the radio, I would be inclined to aim closer to the 190 volt end which will give it a dissipation of about 40 watts.

I confess I don't understand all the resistors in your simulation

Assuming you have a 2:1 ratio step-down transformer fed with 240V AC, that's 120 V AC on the secondary. You then have effectively one halfwave rectifier with a capacitor input filter which will produce DC at the peak value of plus 170 volts. You have another halfwave rectifier producing minus 170 volts. The total across both capacitors will therefore be 340 volts, a voltage doubler arrangement. To drop this down to 190 volts you would need lose 150 volts. If you used a series resistor it would need to be 750 ohms and would be dissipating 30 watts which does seem mighty inefficient. If you want to keep this rectifier arrangement I suggest you try and source a transformer with an isolated (safer) secondary winding with a voltage of nearer 65 volts, or maybe two secondaries in series of 30 volts each. Something out of an old transistor HiFi amplifier might suit.

Alternatively, a 120 V AC secondary feeding a bridge rectifier and single smoother cap will give 170 volts DC. Although this is a little on the low side it might be enough for the radio to work so could be worth a try. Bear in mind that the 120V autotransformer gives no isolation from the mains, so the radio must be treated as live chassis.

Regarding the B2043 output valve, I suspect that this was available with more than one type of base. Some pentodes have Grid 3 connected internally to the cathode, to reduce the number of pins needed. The types with a side terminal for Grid 2 are not compatible with a recessed valveholder. Grid 2 should connect directly to HT positive, as per the schematic.