Simple voltage regulator get crazy... and so am I

[Malefoda]

Hi guys,

they are brand new µA7810 from TI, TO220 package and right now with no load at all. (I want to make it work before plug anything!). And I've tried two, no heatsink here it's ice cold
As this 15/16V will feed LM317 wich can stand more dropout voltage (up to 40V in the datasheet!) it may be easier for me to give them lovely heatsink.
I still had no time to check as yesterday night I had to try to catch a bat wich came to check my bedroom and this morning a magpie try to steel a withe handkerchief, jump everywhere including my CDP pcb and parts etc...
http://img37.imageshack.us/img37/8323/dsc00052rki.jpg

What do really matter is sound, do some of you have experienced some sound behaviour difference with or without 78xx pre-regulator?

[Matt.B.H.]

Nice magpie

It must be something with the Loire Valley. We used to go there every couple of years, beautiful. We had a bullfinch type bird in the bedroom one night and another night some kind of small lizzard fell on the bed. Needless to say I thought it was hillarious, the better half was mortified ,which I guess is why I was so amused;-)

Anyway, regulators. Why do you think the 7810 is current limiting?

Having no load could cause a problem with the 7810. It will definately with a 317. Also check your rectifiers. If you have a bridge and any are short/open circuit (usually fail short circuit) this will give weird symptoms.

Some form of heatsink is a good idea. Charging that big cap. could cause it to overheat and go into thermal limiting, the cap discharges into the following regs then the 7810 recovers only to overheat again. I would think this would happen rather slowly though.

Cheers Matt.

[Malefoda]

Hi Matt,

well I must confess that when my wife was shouting to death for a lovely "couleuvre" in the living room (my translator says "grass snake") It was very funny
The big black spider on the wall is another story wich is not fun at all for me, I'll have to check under the bed several times and still feel bad... should have kept the bat!
Fellow DIYers are welcome when the come around Always something to fix/try or just listen to music!

As for the regulator I'll get rid of it and will go for direct feed from the main big cap. If and only if some regs get hot I'll may use the 7810 with no output cap but a small film one.
And yes 7805 were running fine there with the 15/16V... why bother?

With the 2200/25 ZL it was oscilliating seems as without it was working nice.

Thanks,
Matthieu