Heat sink issue with three regulators ?? KEEF ??

Just fired up my SSL 9k and board voltages look all good, however the regulators
are getting quite hot, almost too hot to touch after 5/6 mins !
They are all in a line next to each other, so my first thought was to use a big
piece of aluminium, drilled to fit across the back of them all .... until I read
the spec sheets :
LM317 - back plate has V out across it ( 44.9v dc ) NOT getting HOT BTW
7818 - back plate has ground across it
7918 - back plate has V in across it ( 24.5v dc )

How the heck do I solve this one ?? HELP !

Marty.

Marty, Use insulator kits.

They have a thin wafer of thermally-conductive (but electrically non-conducting) plasticky-stuff, and usually come with some plastic shoulder-washers and a nut and bolt.

How much current are you pulling to make them hot, and what's the unregulated voltage going in to the regulator chips?

Doesn't actually have to cover all three chips by the way... the 48Volt regulator will only get warm if you start pulling lotsa juice through it... which is uncommon for phantom applications. No need to warm it up by sharing heat from the two 18Volt regs which are carrying more of the load, but it won't do any real harm if you do, so whatever you prefer.

Keith

Hi Keef, sorry I'm a bit "green" so didn't know about the insulated reg kits !
Will get some, the 317 is running cold so that's fine ...

There's 28.2v unreg coming in, and 18.3 / 18.4 out for the +/- output.
Toroid is an 18/0 18/0 30VA which measures 20.5/0 20.3/0 at input to the power board.
I'm running just 2 x 9k boards and one balanced out board, JLM go betweens looking after the 48v switching and pad/phase.

It's all working perfectly , having just checked it for 10 mins

Just one issue, at the point where power enters both signal boards I have +/- 18.3v dc but at the chips on the + side (all pin 8 ) it's down @ 15.4v dc ?
The TLE2082 I have running instead of the TL052, I used 2 x 4148 diodes each rail
to drop that down, and it has a perfect 16.9v dc on each rail ( max rated @ +/- 19v dc )
Good to know that the LM394 works as a direct replacement for the MAT's too .
Thoughts on the positive rail small voltage drop.

BTW - they both sound FABULOUS and operate very well :green: :thumb:

There's some resistors in between the supply pins and the incoming power, IIRC.

28V is going to make them run warm, for sure. Not damagingly, but get a heatsink on there and things will be much more relaxed. -Use some thermal compound to seal the deal (white silicone grease or similar... Radio Shack may have the stuff: I'm not certain of their stock habits in the UK...

Keith

Thanks for the help Keith, picking up the special insulated stuff tomorrow, it
will allow me to use the heat sinks that I have with this sandwiched in between.
The pre-amps really sound terrific, thanks for your work on them, it was 4
full days work to get them done ... carefully.... and there is no de-bug
Cranked my system with them solo'd and there is virtually ZERO noise, just
my system's slight hum/hiss that's there anyway.

I'm pleased as punch with them !
Regards,

Marty.