Re: 465 oscilloscope problem


Tewell, Kevin <tewell.ka@...>
 

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Saturday, April 02, 2016 8:26 PM
To: TekScopes@...; TekScopes@...
Subject: Re: [TekScopes] 465 oscilloscope problem

OK here is what I have starting over :) I got a 465 scope and the power would come on and that was it. So I took the cover off and found that the fuse was bad, I put a new one in and turned it on and immediately blew the fuse on the outside. So I checked the test points and +55 was ý.9 ohms and I was told to check the C1534 from the antique radio forum person so I did and I thought it was bad and took it off. And that is all I have done to the scope. And from what I hear so far was a mistake :( So where should I go from here besides ordering a new part for C1534. Thanks for the help. So how do you check the capacitors to see if they are bad? Since I messed one up already.

Sent from my BlackBerry 10 smartphone.
From: David @DWH [TekScopes]
Sent: Saturday, April 2, 2016 7:00 PM
To: TekScopes@...
Reply To: TekScopes@...
Subject: Re: [TekScopes] 465 oscilloscope problem




Thanks for reminding me John. I was only refering to C1419 in the high voltage inverter circuit.

There is a good free scan of the late 465 service manual out there.

On Sat, 02 Apr 2016 17:58:03 -0500, you wrote:

That about covers it.

A solid tantalum capacitor would be pretty expensive so assuming it
will fit, I would use a low impedance high frequency 105C aluminum
electrolytic intended for switching power supply applications. To get
an equally low ESR as a solid or wet tantalum capacitor, increase the
capacitance 2 to 4 times.

One of the capacitors on this list would be ideal but as a practical
matter, almost any 220uF aluminum electrolytic capacitor should work:

http://goo.gl/Oc2MBt

A new solid tantalum capacitor would be much more expensive. I almost
always buy NOS (new old stock) solid tantalums from my local
electronics surplus store:

http://goo.gl/A1ynvX

For once an aluminum polymer capacitor would work but they can be
almost as expensive as a solid tantalum capacitor and would not last as
long as the less expensive electrolytic. The capacitance would only
need to be 22 microfarads (or lower but I would need to make
measurements to determine how low). This would be the best choice if
the physically larger aluminum electrolytic will not fit but that seems
unlikely:

http://goo.gl/BPudsE

On Sat, 2 Apr 2016 21:32:40 +0000, you wrote:

So what do I replace it with?
On 02 Apr 2016 14:50:27 -0700, you wrote:

Usually common aluminum or solid tantalum electrolytic caps, depending on the application and ratings needed. As I said, I don't know the application here, but I'm sure others here with 465s will respond soon with advice. I can say that it's unlikely that the original cap even had to be wet Ta - they are special, but were more commonly used back then, usually to save space because of their high C-V product. They are essential though, in certain low-leakage, higher voltage, higher temperature applications, which are unlikely to be encountered in a scope.

Ed
On Sat, 02 Apr 2016 18:23:38 -0400, you wrote:

Aluminum electrolytic. Look for 105 °C rating.

http://www.ebay.com/itm/5x-Panasonic-FC-47uF-50v-low-ESR-radial-Capaci
tors-caps-105C-New-low-impedance-/251942149865?hash=item3aa8ec1ee9:g:~
1gAAOSwVFlT~K3t

One of many.



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