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I don't see how that 555 timer circuit is supposed to work.
The output will never go below 25V and the LM317 can't sink current so the output voltage will rise and might even destroy it.
A more sensible option would be to run the 555s from 12V and use PNP transistors to switch the 25V and 35V lines.
The output of the LM317 isn't supposed to go below 25V, but maintain a constant output voltage. Using the output as virtual ground and +35VDC input as positive supply the chip will "see" just a supply voltage of +10V, nothing to destroy the chip. Of course it will also sink current, because it has a ground connection, which is just not used to supply the timer circuit.
Why switch a line which is already there? The OP wants a constant +25V voltage level, interrupted by 100ms +35V pulses at intervals of 180 seconds.
Hans
I'm not disputing that. The 7555 doesn't care if the negative rail is 25V and the positive rail is 35V, it will still see a potential difference of 10V.I guess the TLC556 doesn't care if it is supplied with +35V for VDD and +25V for ground. It will "see" just +10V at its VDD pin.
I've seen it with MCUs where VCC is connected to ground and VSS connected to -5V. The MCU "sees" a positive supply voltage of 5V.
To have a minimum load at the LM317s output a 1K2 resistor might be connected to ground.
Before you try, I strongly recommend looking at the internal schematic of the 7555 with a load connected from pin 3 to a lower voltage than VSS.
I don't want you to waste a 555 unless of course you're got 1000s of them at your disposal.
The CMOS and TTL ICs do behave differently.
If it's a CMOS IC it'll probably go into destructive latchup, if it's TTL, the base-emmiter junction of the output transistor will breakdown and be destroyed.