3 Terminated regulator?????

[||| Philip Pilgrim |||]

Batz,

Those 78 and 79 series regulators are usually rated to 1amp output. It sound's like you have a thermal problem only.  There are lots of heat sinks available for those packages. The trick is to watchout for shorting the heat sink to other devices, leads, traces...etc since quite often the heatsink mounting flange on the device's back  is often at gnd or another potential.

My Waldorf MWII has this style of heatsink mounted to the circuit board:

http://www.aavid.com/datashts/pcboard/533402.htm

Checke here too (under products). These guys make a *huge* variety of heat sinks

http://www.wakefield.com/sitemap.htm

Philip


Philip Pilgrim                 The Lab
5 Evan's Drive              Synth Mods/Repair
Hammond's Plains        Software 
N.S. Canada                http://www.robotnik.com/the_lab
B4B 1M8

mailto:thelab at sprint.ca
+1.902.835.7844
----- Original Message ----- 
From: Batz Goodfortune <batzman at all-electric.com>
To: DIY <synth-diy at mailhost.bpa.nl>
Sent: Saturday, January 22, 2000 12:02 AM
Subject: 3 Terminated regulator?????


> Y-ellow Y'all.
> Ok so I've just spent the past month re-writing the mixer firmware from
> scratch. The vary moment I blow the firmware into the chip and plug it in,
> the hardware dies. Needless to say I went to bed before impulse took me to
> the garden shed. Where upon I would have retrieved the 10 pound Sledge and
> done my worst.
> 
> The morning brought a revelation. When powering it back up the system came
> to life. Then it dawned on me. The mixer had been turned on all the
> previous day. It was hot. The little 78L/79L regulators probably thermally
> shut down. With the addition of a quad op-amp package to the system for a
> balanced output, the little regulators were probably right on the edge. The
> whole thing should have been under 100mA but being on for a significant
> amount of time, saw them heat up just enough to go. "Ah Aar.  I'm just not
> going to play this game any more." And shut down. Obviously I need to put a
> bigger reg in there. A 78M at least. Should they still make such things?
> 
> The problem is that whilst I plan to totally re-design the boards for many
> reasons, and could accommodate the new regs on the new boards, I don't have
> room on the prototype. Vertically, horizontally, anyway you look at it, I
> just can't get a TO220 in there. 
> 
> Now I know that designs often call for TO92 transistors to be in thermal
> contact with something else for thermal regulation. Such as oscillators and
> biasing in power amps etc. What I'm considering is getting one of those
> little heat sinks from Can-package transistors (I don't know what they call
> those. they're like a TO5  with a built in radial heat sink.) and hijack a
> pair to try and retrofit them to the 78L/79L regulators. A kind of stop-gap
> measure.
> 
> They're TO92 plastic packages so I'm not sure how effective this would be.
> Whether it's worth destroying two perfectly good transistors (and all the
> associated trouble I'd have to go to) in order to try and cool 2 TO92
> regulators. Anyone have any comments on this?
> 
> There's virtually no air flow in the system... Am I wasting my time here?
> Remember this is just to keep the prototype running. I'll do it properly on
> the final item.
> 
> Thanks in advance.
> 
> be absolutely Icebox.
> 
>  _ __        _                              
> | "_ \      | |         batzman at all-electric.com
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>