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Softstart problem..

Started by rtate, April 04, 2008, 03:53:35 AM

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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.
7 Leach superamps, 3 shiva subs,Aria5R
Parasound AVC2500u, Sugden transport,
Bride of Zen preamp,home made Cat5 speakecable
and interconnects

peranders

I write that you have 24 VDC. The curcuit is a bit special you see. I think the unit works.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff

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?
7 Leach superamps, 3 shiva subs,Aria5R
Parasound AVC2500u, Sugden transport,
Bride of Zen preamp,home made Cat5 speakecable
and interconnects

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.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff

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.
7 Leach superamps, 3 shiva subs,Aria5R
Parasound AVC2500u, Sugden transport,
Bride of Zen preamp,home made Cat5 speakecable
and interconnects

peranders

Have you changed C1, C2 to 680 nF? Which relays do you use?
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff

rtate

I'm at work right now so I will verify the parts when I get home.
Thanks again for your patience and help!!
7 Leach superamps, 3 shiva subs,Aria5R
Parasound AVC2500u, Sugden transport,
Bride of Zen preamp,home made Cat5 speakecable
and interconnects

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?
7 Leach superamps, 3 shiva subs,Aria5R
Parasound AVC2500u, Sugden transport,
Bride of Zen preamp,home made Cat5 speakecable
and interconnects

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
7 Leach superamps, 3 shiva subs,Aria5R
Parasound AVC2500u, Sugden transport,
Bride of Zen preamp,home made Cat5 speakecable
and interconnects