VC3500/VC3700 Troubleshooting Manual
Valco Cincinnati
Page 19
12v Hold Supply
Transformer XF2 supplies 12vac to connector J2, Pins 4 & 5. Bridge rectifier BR1 provides
rectification. Fuse F1 provides over-current circuit protection. Voltage regulator U3 will
provide either a fixed 12v Hold Voltage (JP4, pins 1 & 2 jumped), or a variable 5v to 12v
(JP4, pins 2 & 3 jumped). A sample of this voltage exits this board via J1, pin 9, to drive the
12vdc coil voltage LED indicator on the front panel.
5v Logic Supply
A 7805 (U4) is supplied from the 12v Hold Voltage. Choke L1 provides current stability
during high demands of the Hold Voltage.
Valve Driver Control (Valve 1)
An active-low signal on connector J1, pin 1 triggers 556 timer U2 to begin the Peak Voltage
duration timing. The 556 timer active-high output turns on npn transistor Q2, which in turn
drives the high current IGFET Q6 to pass the Peak Voltage to the Valve output at connector
J3 for a period of 1ms to 5ms. Diode CR5 and capacitor C17 isolate the current demands of
this channel from the other channel. Resistor R17 provides a bleed-off path for the charge on
capacitor C17 when the VC3500 is turned off.
At the same time that the 556 timer is triggered to begin its timing, npn transistor Q1 is
turned on, which in turn drives the high current IGFET Q5 to pass the Hold Voltage to the
Valve output at connector J3.
Diodes CR11 and CR12 act as a gate to allow the highest voltage to pass through to the
output.
Zener diode CR7 limits the level of the negative voltage spike that occurs when the valve is
turned off (due to energy storage). Diode CR8 blocks the effects of a forward-biased zener
diode when the output voltage is positive.
Fuse F2 provides over-current circuit protection.
A remote purge button can be connected to connector J3, pin 1 (signal) and pin 2 (return).
This signal is fed back to the beginning of the valve driver circuit to manually enable the
valve. Filtering of noise spikes due to the capacitive coupling along the glue valve cable into
this board’s purge circuit is accomplished with a 1kohm resistor connected to 5v and a 0.1uF
capacitor connected to ground.
Summary of Contents for VC3500
Page 1: ...VC3500 User s Manual Software Version 3 X Manual Number MCO35 Manual Release Date July 1999 ...
Page 19: ...Installation VC3500 User s Manual Valco Cincinnati 16 Figure 8 Internal Connections Diagram ...
Page 88: ...VC3700 User s Manual Software Version 3 X Manual Number MCO34 Manual Release Date July 1999 ...
Page 181: ...VC3500 VC3700 Troubleshooting Manual Manual Number MC048 Release Date May 1999 ...
Page 185: ...VC3500 VC3700 Troubleshooting Manual Valco Cincinnati Page 1 System Level Documents ...