06-20-2016, 12:52 PM
The replacement power transformer and restuffed filter capacitors were next re-installed. As mentioned before, the mounting centers of the original and replacement transformers were exactly the same, so no modifications to the chassis were needed. All of the wiring associated with the 115/230 voltage selector switch and Hi-Med-Lo line voltage switch was removed. The switches were left in place. The power transformer primary leads were connected directly to the AC power supply terminal strip. The existing AC power switch wiring was left in place (also connects to the AC power terminal strip). There was some fraying and wear where the wiring bundles passed through holes in the bottom transformer cover. The cover was removed and shrink tubing was applied to any wiring that was frayed to prevent future shorts. Some of the lead wires were very stiff and could break if bent. I used a heat gun to soften up the old insulation prior to bending the leads. There was no room inside the transformer covers to splice on new leads, so the existing leads had to be used.
The replacement power transformer leads exited the bottom cover, just like the original. However the positions of the primary plus 6-volt filament bundle and the high voltage plus 5-volt rectifier bundle were swapped on the replacement – they were on opposite sides of the cover. This meant that some of the replacement transformer leads were too short. These leads were spliced with appropriate new wiring and the splices insulated with shrink tubing (double layers for the high voltage secondary leads).
The wax/paper capacitors that were removed in order to gain access to the filter capacitor wiring, and were subsequently restuffed, were also reinstalled. A few out of tolerance resistors in the power supply and audio amplifier sections were replaced. I do not like to have too many loose parts at one time, so before doing any further recapping or resistor replacement I wanted to reinstall everything that had been removed up to this point. Once some of the (leaky) capacitors in the audio section were removed, additional resistors were discovered to be out of tolerance. And some had likely been damaged by soldering heat. I tried to make sure that all resistors in the phase inverter circuit were within 10% tolerance, as they affect the balance of the audio output stage, and thus the fidelity.
C100 and C101 (bottom center of bottom view) were replaced with 0.0027mfd 1600v dipped film capacitors. The originals (0.003mfd 1500 volts) had been replaced with 0.003mfd 600 volt paper caps as received. Since these are connected between the high voltage secondary leads and the chassis, I did not trust using 630 volt caps here.
Attached are photos of the top and bottom views of the power transformer area of the chassis. The AC power cord has not been installed at this point.
The replacement power transformer leads exited the bottom cover, just like the original. However the positions of the primary plus 6-volt filament bundle and the high voltage plus 5-volt rectifier bundle were swapped on the replacement – they were on opposite sides of the cover. This meant that some of the replacement transformer leads were too short. These leads were spliced with appropriate new wiring and the splices insulated with shrink tubing (double layers for the high voltage secondary leads).
The wax/paper capacitors that were removed in order to gain access to the filter capacitor wiring, and were subsequently restuffed, were also reinstalled. A few out of tolerance resistors in the power supply and audio amplifier sections were replaced. I do not like to have too many loose parts at one time, so before doing any further recapping or resistor replacement I wanted to reinstall everything that had been removed up to this point. Once some of the (leaky) capacitors in the audio section were removed, additional resistors were discovered to be out of tolerance. And some had likely been damaged by soldering heat. I tried to make sure that all resistors in the phase inverter circuit were within 10% tolerance, as they affect the balance of the audio output stage, and thus the fidelity.
C100 and C101 (bottom center of bottom view) were replaced with 0.0027mfd 1600v dipped film capacitors. The originals (0.003mfd 1500 volts) had been replaced with 0.003mfd 600 volt paper caps as received. Since these are connected between the high voltage secondary leads and the chassis, I did not trust using 630 volt caps here.
Attached are photos of the top and bottom views of the power transformer area of the chassis. The AC power cord has not been installed at this point.
