I powered up one of my 7704As which worked fine the last time I used it several months ago. This time it worked for about 30 seconds and stopped with the power supply going into a rapid tick mode which I presume the frequency of the relaxation oscillator.
I opened it up and using an autotransformer to slowly take the voltage up, I observed DS3019 flashing in time with the ticks. At first, the ticking is much slower but as I increase the input voltage, the ticks get faster and are fastest at full input voltage. I checked across CR3015 and the voltage is getting up to what I remember as a normal level (don't remember what I measured but since that circuit develops peak-to-peak the line voltage value, it should be around 350vdc which I think is close).
I know what "normal" tick mode sounds like but this seems to be something that's occurring before the startup circuits are at work causing the the "normal" ticks. Is it likely that the inverter is never getting to the point of trying to start? If so, then I presume the inverter controller chip isn't working or, at least, isn't seeing what it needs to work. Is that a reasonable assumption?
Thanks,
Barry - N4BUQ
