Hallicrafters SX-62 - low volume - Printable Version
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RE: Hallicrafters SX-62 - low volume - bridkarl - 05-17-2024
This is coming along. Found a misplaced wire and a capacitor. Still need to go through and finish cleaning this up, but I think it’s much better. A new side cutting pair of snips has helped. I’ve put in two Sprague electrolytic caps. Very nice solid units if expensive.
Just waiting for my NOS 5U4GB tubes to arrive.
I think it will be ready this weekend to bring up with just the rectifier tube and see how it goes. It is unclear to me how much current it should be pulling with just a rectifier in place.
RE: Hallicrafters SX-62 - low volume - Chas - 05-17-2024
Quote:I think it will be ready this weekend to bring up with just the rectifier tube and see how it goes.The B+ can soar without a load, possibly taking out the filter caps...
Set OFF, measure the DC resistance of B+ to B- at the power supply. That resistance will dictate the load current based on the highest published voltage in the schematic, usually at the screen of the output tube, if no rating the plate voltage figure would apply also. If the calculation exceeds 80ma recheck measurements and calcs. If consistent, check all B+ paths for miss-connections or shorts...
A resistance of from 15k and higher is good...
Any resistor/inductor in the main B+ line or B- can be used as a shunt to determine real-time current. Measure the devices resistance and record. Place a voltmeter across that device and power the set. the voltage measured calculates to the milliamps flowing in the B circuit...
Caution meter leads are live, avoid handling the meter...
The greatest consumption of B current is the output tube(s). Controlled by the grid voltage.
It is possible to alter the grid bias voltage as long as distortion is not introduced, doing so can save both tubes, output transformer and overall B current as well as a cooler operating receiver.
GL
Chas