Re: Re[2]: Amplifone rebuild kit

Mmmm, I actualy think the mica and silicone is a better and longer
lasting cooling option then thermal pads.
The Amplifone FAQ already suggest to replace the rubber thermal pads
used with mica and thermal grease on the existing power regulators
and transistors, because the rubber can deteriorate. Also the pads
have a worse heat conduction compared to the mica/grease.

Even so, I have to say that both the rubber pads and the mica/grease
on my Amplifone PCB's look to be fine still.

I have no problems replacing parts on the PCB's, even if it's just a
precaution and I did so on the HV PCB, but I don't see a point in
blindly replacing all kind of parts that are still fine and are not
subject to deterioration. I want to know that there is a reason for
replacing parts on a good working PCB.

Another thing along that line: The amplifone FAQ suggest to add a fan
near the HV board. Now, I've checked the temperatures of the various
parts after it run for about half an hour. The only things that get
really warm are R20 and R21 (the 5W, 50 Ohms resistors). The Cinelabs
HVT keeps very cool. The BU406D keeps amazingly cool as well.
The 7824 and 7924 seem to be loaded pretty much, but then they have
the largest cooling body I've ever seen for these kind of power
regulators. I am thinking of replacing the wire-wound ceramic 5W
resistor I use now with aluminum 10W types that can be mounted on a
cooling body. I'd mount them to the 7824/7924 cooling body so they
can dissipate the heat much better.

Then, I think, there would be no need for forced cooling.

The thing that really gets hot is the deflection PCB ! I think
cooling that with a fan would make much more sense...

Op 11-aug-2007, om 3:57 heeft peter jones het volgende geschreven:

>
> -----Original Message-----
> From: "MyPearl" <mypearl@dds.nl>
> To: <vectorlist@vectorlist.org>
> Date: Fri, 10 Aug 2007 17:30:44 +0200
> Subject: Re: VECTOR: Amplifone rebuild kit
>
>>
>> I never did fot the same obvius reason.
>>
>> I also don't replace any transistors. They fail because of wrong
>> use or
>> other bad components such as caps.
>>
>
> yes,
> but it's always good to remove them for a clean and put them back
> with thermal pads instead of mica washers & silicone mess(grease).
>
> ----------------------------------------------------------------------
> -----
> ** Unsubscribe, subscribe, or view the archives at http://
> www.vectorlist.org
> ** Please direct other questions, comments, or problems to
> chris@westnet.com
>

André Huijts
andre.huijts@wanadoo.nl

---------------------------------------------------------------------------
** Unsubscribe, subscribe, or view the archives at http://www.vectorlist.org
** Please direct other questions, comments, or problems to chris@westnet.com
Received on Sat Aug 11 04:17:09 2007