Softstart problem..

[rtate]

I have reached the testing stage for my softstart and have a problem.
When I apply 24vac to the bridge rectifier I hear the distinct 2 clicks but after about 5-6 seconds K2 opens up.
I traced the problem to a failure at T2(BC547B).
If I replace T2 the cycle will epeat itself.
R1 is 2 100 ohm 20 watt in parallel.

Where should I start to look for the source of the problem.

[peranders]

I write that you have 24 VDC. The curcuit is a bit special you see. I think the unit works.

[rtate]

I'm sorry P-A  I don't understand what you are telling me. The rectified voltage is 33 vDC, Is this going to present a problem to for the devices in the circuit?

[peranders]

I mean when you test the basic function (without killing yourself) use a DC (not AC) source. If the circiut seems to work, then you can apply your mains voltage. Capacitve voltage division which I use here is a bit tricky.

33 VDC is too much since you have a 27 volt zener diode.

[rtate]

If that is the case and 33v is to much would it make sense that T2 fails first?
I do not have a 24vdc supply handy at this point. I guess that I should buy one!!
When i was testing if I plugged and unplugged the 115vac supply quickly it seemed to work ok. It was only when I left the power on K2 opened and T2 failed after 5-6 seconds.

[peranders]

Have you changed C1, C2 to 680 nF? Which relays do you use?

[rtate]

I'm at work right now so I will verify the parts when I get home.
Thanks again for your patience and help!!

[rtate]

When I checked your schematic it calls for a 33 volt zener. In an earlier post you mentioned 27 volt zener could you comfirm this value for me?

[rtate]

For my proto type I have been using a transformer to feed the bridge rectifer. It is a 24volt ac centre tap which gives me 33vdc on the out side of the bridge.
The relays are Schrack # RP10024  24 vdc