Worked O.K.before but now gives no output. Led LD2 lights but I cannot see any output from “CLK” on IC20 opto-coupler. Have tried changing it. Any ideas?
The CLK is not continuous signal. It appears only periodically when the generator settings are changed.
[quote]Led LD2 lights [/quote]This indicates the communication from the PC to the generator is working OK.
You may check the voltages on pins 4 and 7 of IC13. Should be about -12V and +12V respectively.
If the output relay RY1 is defective you should still get signal from pin 6 of IC13.
You may use DVM to check the adjusted signal offset (-5V…+5V).
All the voltages are O.K., so is the relay. Anyway there is no input to it from IC13.
I am assuming CLK would be repetitive (although infrequent) if a repeated signal is set up on Wave Sequence.
I am getting about 2.6V relative to computer ground on T8’s collector. Is this enough to drive the photo diodes of the opto-isolators?
Indeed, when running Wave Sequence there is periodical CLK bursts.
The amplitude of the clock is 0.6V.
You may also check the clock on pin 12 of IC9. There is full 5V amplitude.
I think 2.6V is OK on the collector of the T8.
Do you see any waveform on pin 3 of IC13 ?
If nothing found, then check pin 6 of IC33.
Nothing on IC13/3 or IC33/6.
There is also no response to changing the offset voltage. IC24/6 is at -8.53V and IC13/6 is at 9.38V whatever the setting.
Looking at the digital part of the system, signals F1-F6 seem to be O.K. and appear on the inputs to IC22 but with no information on how it is programmed I cannot check its outputs. Can you provide this? Also, should this item turn out to be faulty can I get a replacement?
The LED LD2 is turning on and off when you click the signal on and off?
If yes, this indicates that the IC22 is working. The ENABLE pin 21 of IC22 goes high and low.
[quote]There is also no response to changing the offset voltage. IC24/6 is at -8.53V and IC13/6 is at 9.38V whatever the setting.[/quote]Does the DC0…DC7 signal change state on the output pins of IC2 when the offset setting is changed and signal is set ON ?
All should be high when offset +5V and all low when offset -5V.
If no change, then you may check the DATA signal on pin 14 of IC2.
Do you get there any clock bursts when the frequency or amplitude settings are changed?
There is all the time in this pin a periodic “refresh” pulse. High 104ms, low 6ms.
Yes, LED2 turns on and off and pin21 of IC22 goes high and low.
The DC0-7 signals are not changing. DC0-2 are low and DC3-7 high.
On pin 14 of IC2 there is a burst of pulses but no periodic refresh pulse. Also LD2 does not always come on again after signal is changed (i.e. sine wave to square etc.)
Is the pin 14 of IC2 low or high when stable?
What are the states on pins 6 and 8 of the optocoupler IC37?
Pin 14 of IC2 is at about +1V with regular pulses to 0V about every 110mS.
There are similar pulses on pin 6 of IC37 but +5V when high.
Pin 8 of IC 37 is at +5V
Please check the R61 (47k) value and soldering.
No problem with R61
Is there supply voltage on pin 16 of IC2 +5V ?
Pin 14 of IC2 should be about +5V with regular pulses and to 0V about every 110mS.
You got only +1V. It seems that the voltage is lost in R61. - Why?
I think there is a fault on input 14 of IC2 which is clamping it to 1V. It measures .93V with a multimeter on the diode test range. If I move the 74HC595 which was in IC5 position to IC2 I get a full 5V swing, but of course the system will not work like this.
Am trying to obtain a replacement 74HC595.
Many thanks for your help, patience and quick response in tracking this down. Hopefully this is the answer
Indeed, according to your tests it seems IC2 is defective.
I hope replacing the IC2 with a new one cures the problem.