HP 2113B service manual / schematics

From: Bob Shannon <bshannon_at_tiac.net>
Date: Wed Nov 17 19:00:23 2004

Because these caps are there to suppress HF noise from inside the supply....


----- Original Message -----
From: "Joe R." <rigdonj_at_cfl.rr.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk_at_classiccmp.org>
Sent: Wednesday, November 17, 2004 6:54 PM
Subject: Re: HP 2113B service manual / schematics


> At 06:35 PM 11/17/04 +0000, you wrote:
>>Hi Joe,
>>
>>>One of the things that I noticed was that the computer kept running and
>>>even though I turned >off the power switch the cap kept sizzling.
>>
>>On the 2113 (and I guess from your description the 2117) the capacitor is
>>directly across the terminals on the mains input socket - i.e. on the
>>'always hot' side of the on/off switch. So turning the power off behind
>>the
>>front panel of the computer won't help.
>
> Yeah I sort of noticed that! But it's sort of funny that they don't seem
> to fail unless the machine is running.
>
> Joe
>
>
>>
>>In order to effectively control interference the capacitor has to be
>>mounted
>>as close to the point at which mains enters the equipment enclosure as
>>possible. Mounting it further away causes the input leads to act like an
>>antenna inside the enclosure.
>>
>>>I had to unplug the line cord to stop it.
>>
>>Yep, this is the only way to shut the power off to this capacitor, it is
>>always live when the equipment is plugged into a live mains socket.
>>
>>A good reason NOT to leave this sort of equipment plugged in but turned
>>off!
>>
>>Peter Brown
>>
>>
>>
>
Received on Wed Nov 17 2004 - 19:00:23 GMT