The project cluttering my workbench (Project X) has many challenges ranging from actually getting it to work to how do you power the beast.
Tempo One FP-200
Weird and Strange are two really good words. As advertised Project X can be powered from a home (AC) supply or mobile from the DC Supply. In either case the HV is 750VDC, the LV is 210VDC, the Bias is -60VDC, the Filaments are 3.2 Volts at 3.2 Amps and 12VDC at 1.5 Amps.
So, at the N6QW Radio Ranch, I have a Heathkit HP-23, Drake AC-4, Drake DC 3, Collins 516F2, Collins PM2, National NCXA and a Tempo One FP-200. While all of these supplies cover some of the requirements of Project X, none is a drop in.
In looking at the herd, one supply is left over from a project called Resurrection Radio where I took a Tempo One (worse shape than Project X) and brought it back to life. I bought a FP-200 to power that radio and when I sold The Tempo One, I kept the FP-200 JIC that someday it is needed. Well, some day is here.
Resurrection Radio
The FP-200 will need some modifications to even come close but most of the mods are reversible and in fact in some cases improve the operation.
The 1st mod is the 117VAC input to the supply. I noted that the Project X power connector on the back panel for switching on the power supply was physically shorted. Oh, Oh I undid the short and the switch is OK. There is a function switch on the front panel that turns on the power supply, has an operate position and tune position. The switch is like that on the KWM2 where it is ganged on the shaft, it is an ON-OFF switch much like on a volume control. To replace that little switch is almost an impossibility.
The solution is to install a power relay in the Power Supply so that the switch in the radio is not seeing a huge inrush current thus increasing the likelihood of a failure. This solves another problem in that the FP-200 had a hot chassis since it was a two wire and not three wire like today's standard. It will be converted to a three wire.
The 150 VDC supply on the FP-200 is not used.
At 600VDC on the plate you will not see 100 watts output, but I can live with that as it will give something north of 50 watts which is OK. The LV supply at 300VDC is too high and my solution is to install two power resistors, one in each lead going to the LV bridge rectifier so the voltage supplied to the bridge is less than 270 Volts AC.
In fact, this is a TKT (Tribal Knowledge Tip) if you did this on the primary side of a HV Plate Transformer where only half the AC voltage is supplied initially and then using an Arduino to trigger a contactor to short out those resistors after a timed interval you have what is called a "stepped start" circuit. The 1/2 voltage on the primary enables the capacitor bank to charge slowly and then get a full charge after a short duration. In this case the resistors are in the circuit at all times.
The Bias Circuit has no adjustment at the supply so a dropping resistance in series with a pot using the center wiper will give you the -60VDC. The Bias is set so with the PTT tripped and no mic gain the static plate current on the 8042's should read 50ma.
The AC Filament circuit will need to be converted to DC so that now it will supply 12VDC at 1.5 amps.
The 8402 Filament supply 3.2 Volts (AC or DC) at 3.2 Amps at first was the long pole in the tent until I thought about a packaged supply. Mean Well sells a power supply that produces 3.3 VDC at 6 Amps with a 120VAC input and these can be had for about $12. It is an enclosed supply and small 3X2X1 inch. I might have to do some filtering in the event of hash. OR an alternative.
In the factory AC supply a trigger from the rig operates a relay that actually supplies 3.2 Volts only on transmit. Suppose we use that feature so that a relay inside the power supply turns on the primary power to the Mean Well. The 8042 has a 1 second warm up time so plenty of time as the 3.3VDC at the terminal is less than 1 second. BTW the 8042 specifies the Filament as 1.6 VDC +/- 10% so we are OK with 3.3 VDC as the filament supply.
There is plenty of room inside the FP-200 case for the added stuff. I also have a small 120VAC to 12VDC at 5.6-amp power module and just may use that versus building a 12 VDC supply from the 12.6 VAC filament circuit.
A Bonus as the FP-200 case has a built in speaker.
Never TRUST what you get! The Project X power connector has 10 Pins and is not a Jones type connector. One pin is broken, and ALL the pins have been touched by a soldering iron.
The Bastard prior owner burnt a lot of the insulation on the wiring to the connector and in one case the wiring didn't match the schematics. Then the dim light lit --- he converted the 3.2 Volt input with the 8042 tube filaments in series to a parallel connection thus needing to supply 1.6 Volts at 6.4 amps. Thankfully the power connector appears to be the only place where there is the obvious touching with the 80-watt Radio Shack soldering iron.
Thus, today we covered the power supply, and the modifications needed to the FP 200 so it can power the Project X transceiver.
Them that know can make it go.
73's
Pete N6QW