Re: Ampliphone HV FAQ is done!!!

On Mon, 7 Jun 1999 10:26:36 EDT, you wrote:

><< You might want to re-think adding an insulator to VR1 (the 7824). The case
> of the 7824 is connected to GND. The heat sink on the Amplifone is also
> connected to GND, so there cannot be a short, or any current flow of any
>kind,
> between the case of the 7824 and the heat sink -- they're both already
>grounded!
> On the other hand adding an insulator *will* cut down on heat transfer,
>which is
> not a good thing. >>
>
>Hello Zonn,
>
> Thanks A Ton for the helpfull feedback!!
>On the 7824 - I thought that since the heatsink was painted, that it wasn't
>being a real good ground conductor, and that the 7824 and 7924 are using pin
>2 as ground.

Well, the 7924 uses pin 1 as GND, the 7824 uses pin 2.

>I didn't like the idea of having an uninsulated 7824 because
>I've seen a quite a few boards with the 1N4001's mounted to the solder side
>of the regs, and I don't think you can allways count on the insulation of the
>1N4001 leads - ( plastic tube insulation seems to get brittle and deteriorate
>over time).I figured if one 1N4001 leads crossed a trace on the solder side
>of the board, it would increase the likelyhood of blowing an uninsulated
>7824. I felt insulating the 7824 was a good way to avoid this potential
>problem. (I didn't really discuss this reasoning in the faq, I was starting
>to get out of hand with my ramblings anyways).

Yet the insulator serves no purpose here. On the HV board I looked at
(a beige board) the heat sink was rivetted and solder to gnd. Since
the tab of a 7824 is connected directly to it's pin 2, and pin 2 is
also solder to ground, there is nothing to insulate, they're already
electrically connected! If you remove the 7824 from the heat sink and
let if float, then connect an ohmmeter to the heat sink and the body
of the 7824 you'll get zero ohms of resistance. This being the case,
what does the insulator accomplish (besides cutting down on heat
transfer)?

> Also, I think anybody running a Amplifone HV board without the use of a
>fan would be crazy. True, an insulated 7824 is not going to transfer heat as
>well as one mounted directly to the heatsink, but I felt that the fan would
>do more than compensate.

The fan is a very good idea!

> I would love to get more feedback on the 7824 insulation issue, if
>enough Vectorlist guys feel that it's better to NOT insulate the 7824, I'll
>put it in the faq. So far I've got Zonn in at a "NOT INSULATE" vote.
>
<snip all my MC1 ramblings>
>
>I'd like to put this e-mail to the Vectorlist for more input. Thanks Zonn!!

No problem! ;^)

-Zonn
Received on Mon Jun 7 12:25:01 1999