AFP Imaging Mini-Medical Series, Инструкция по установке, эксплуатации и сервисному обслуживанию

Страница: 84 / 132

Service
Mini Med Series
0000061122
Service Procedure 5-5
Theory of Operation
Solution Temperature Control
Temperature in the developer tank is sensed by an integrated circuit temperature sensor
which generates a current that is directly proportional to temperature.
The signal from temperature sensor is sent to I.C. U2, an LM 3900 quad current-
differencing amp. The amplifiers in this package amplify differences in current at its
inputs. Two of the amplifiers are connected as comparators comparing the current
generated by the temperature sensor with the current set by the front panel temperature
control. R20 sets the maximum temperature at which the front panel control can be set.
R20 is preset at the factory for approximatly 110°F maximum temperature.
When replacing the Logic board or when replacing U2 or the temperature sensor, R20
must be re-calibrated (see calibration Procedures). The other two amplifiers in U2 are
used as a triangle wave signal which is mixed with the current from the controls. This
gives proportional temperature control supplying less heat as the temperature approaches
the set temperature, and automatically adjusts the amount of heat supplied to maintain
temperature as closely as possible. The action of the temperature control is indicated
by the LED lamp on the front panel and L2 on the Logic Board. When the lamp is on,
the heater is activated.
As the tank temperature approaches the set temperature, the LED will begin blinking
and will remain on for less time as the temperature comes closer to the set temperature.
Drive to the heater is disabled if the solution level in the developer tank drops below the
level sensor probe.
Dryer Temperature Control
Temperature in the dryer transport is sensed by an integrated circuit temperature sensor
which generates a current that is directly proportional to temperature.
The signal from the temperature sensor is sent to I.C. U2, an LM 3900 quad current-
differencing amp. The amplifiers in this package amplify differences in current at its
inputs. Two of the amplifiers are connected as comparators comparing the current
generated by the temperature sensor with the current set on the board. R21 sets the
temperature for the dryer. R21 is preset at the factory for 135°F maximum temperature.
When replacing the Logic board or when replacing U2 or the temperature sensor, R21
must be re-calibrated (see calibration Procedures). The other two amplifiers in U2 are
used as a triangle wave signal which is mixed with the current from the controls. This
gives proportional temperature control supplying less heat as the temperature approaches
the set temperature, and automatically adjusts the amount of heat supplied to maintain
temperature as closely as possible. The action of the temperature control is indicated
by the LED L1 on the logic board. When the lamp is on, the heater is activated.
As the dryer temperature approaches the set temperature, the LED L1 will begin blinking
and will remain on for less time as the temperature comes closer to the set temperature.
5-18