Test Equipment For Main Pcb Testing; Repairs Following Power Fet Failure; Preparation For Main Pcb Testing; Preliminary Checks - TTI TSX Series Service Manual

Test Equipment for Main Pcb Testing

100Ω 5W wirewound resistance for discharging HV reservoirs.
Power supplies: 60VDC 2A limited, 5VDC 2A limited, 3VDC 1.5A limited. A single 60V 2A dual
lab supply should meet all requirements. A 4700uF 63V electrolytic capacitor is required across
the 60V output while checking overcurrent tripping.
A 4-pin 0.156" pitch socket with leads carefully wired for safe connection of external 60V PSU to
header PJ4 according to Fig 1.
A 2 pin 0.156" pitch polarised socket for connection of output terminals to sense input header PJ3
according to Fig 2.
A lead for earthing node VRECT-.
A light lead with an EZ clip at each end.
A light lead with a clip and pointed probe for tripping.
Oscilloscope, 20 MHz bandwidth with x10 HV probes.
General purpose multimeter suitable for HV use.

Repairs Following Power Fet Failure

Q1,Q2 must both be replaced. Survival of gate drive components, particularly R18,22 should be
checked. Triac TC1 should be checked for short circuit failure.

Preparation for Main Pcb Testing

Set mains voltage selector switch to 230 or 115VAC position to suit local supply.
Visual Inspection. C9,10 electrolytic polarities; all power semiconductors properly mounted and
correctly torqued.
Remove HV bridging connector from PJ4.
Earth primary side circuitry at Q1,2 mounting screws on SK1.
Link sense input from PJ3 to its corresponding output terminal using 2-pin polarised connector
lead as shown in Fig 2.
Connect EZ clip lead to link from 0V to C69 +ve to inhibit apparent primary overtemp trip.
If preset potentiometer settings are suspect, centralise all presets except VR10 (fully CW) and
VR9 (fully ACW).
Connect the Control Board via PJ1.
Connect the isolated AC supply to the main PCB pins P100,101.
Connect DVM to output terminals.

Preliminary Checks

1. Check Inrush Control and HV Rectification - This should be carried out if this section is
suspect. Adjust the Variac for about 15 percent of the voltage selector indication. Switch on.
Check that voltage across C9 and C10 are both about 25/50VDC for selector on 230/115V
and that voltage across PTC1 exceeds 3 VAC (meter on AC mains voltage range). Then
increase Variac to about 60 and then 100 per cent of the voltage selector setting. At each
voltage, check for equal DC voltage across C9 and C10 and that voltage across PTC1 is
less than 1.5 VAC (meter on AC mains range).
2. Check Auxiliary Supplies - The voltages from 0V to IC4 pin 3 and IC3 pin 3 should be
+5V and -5VDC within 0.25V. Note that the Control board draws approx 280 mA from the
+5V rail. The primary side auxiliary voltage between VRECT- and IC2 pin 3 should be 12V
within 0.6V.
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