Heathkit TC-1 Tube Tester Restoration Part 8

Part 8: Initial Testing

The moment of truth has arrived.  Will it thrive, or go up in smoke??

I plugged the newly reassembled TC-1 into my variac to bring up the voltage slowly.  Before powering on the unit, I put the controls in the following positions:

  • Set Line: Full CCW
  • Filament Voltage: 0.75v
  • Lever switches: All in center position
  • Type: 1
  • Plate: 0 %

Then, I turned on the tube checker.  As I raised the voltage, there were no signs of obvious electrical problems, and the Line Voltage indicator slowly crept up.

I found that I could center the Line Level on the meter at any voltage between 107 and 130 vac line voltage.

I checked various filament voltages.  With the Line Level centered in the meter, I found that they were all around 10% higher that what was marked.  This is not too far off from the state it had arrived in, where filament voltages were high at that time, too.  But I figure that if some higher power tubes are tested, they may cause the voltage to drop a bit, so I can live with that.

Line Level Test OK

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Heathkit TC-1 Tube Tester Restoration Part 7

Part 7: Reassembly – Panel Wiring

It’s time to install the wiring harnesses that we made a few days ago onto the panel.  I started with the harness that runs from the 10 lever switches to the tube sockets on the top left of the panel (as viewed from the back).

Lever Switches Wiring

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Heathkit TC-1 Tube Tester Restoration Part 6

Part 6: Reassembly Con’t… Wiring Harnesses

The instructions for assembly in the TC-1 manual leave a lot to be desired.  It is one long, run-on sentence/paragraph that tells you generally what to hook up in sequence.  This was before Heathkit came up with its standard “check the box” format that they became famous for.

After looking at the TC-2 manual, I find that there is little difference between the TC-1 and the TC-2.  Since the TC-2 has a much better manual, that is what I will generally follow while reassembling the tube checker.

After assembling the major pieces to the front panel in the previous (Part 5) post, the next step is to rebuild the two wiring harnesses.  The originals have insulation crumbling, and are no longer reliable nor safe.

Top Wiring Harness (old)

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TS-430 Control Board: IC-1 Waveforms

IC-1 is the main processor chip on the Control Board of the TS-430.  It is a uPD8049c.  This 40 pin chip runs at 5.74 Mhz, and interfaces with virtually every control integrated circuit (IC-2 through IC-6) on the board.  You can see that it is central to the radio’s operation.

Digital Control System

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TS-430 Control Board: IC-3 Waveforms

IC-3 on the control board is an I/O expander chip.  It is a uPD8243c.  This chip is directly compatible with the 8049 processor, and uses instructions received from the processor on pins 8-11 to control 4 output ports. These 4 ports control the PLL Oscillators, and interface with the two data selector chips (IC-4 and IC-5) as well as the static RAM chip IC-6. It also provides BAND data to the RF board for control of filters.

8243 Pinout

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