Re: Tek 2215


Or you could use a pair of ~ 500k - 1/4 watt film resistors standing off the board for each of the 1 meg resistors. That would spread out the HV stress a bit more.


----- Original Message -----
From: David @DWH [TekScopes]
To: TekScopes@...
Sent: Sunday, March 20, 2016 11:17 PM
Subject: Re: Fwd: Re: [TekScopes] Re: Tek 2215

Oo! Oo! I know this one! *raises hand*

This has been discussed on the list before and on EEVBlog by me at
least once but I will quickly cover my recommendation.

The problem is the voltage rating and not the power rating of the
resistors. Tektronix used a string of inexpensive Allen-Bradley
carbon composition resistors so the voltage across any individual
resistor is within its voltage rating although barely. Later these
were replaced with specialized film resistors made by Mepco/Centralab.

Now you can probably get away with using standard carbon or metal film
resistors but their voltage rating is marginal in this application.
Higher power resistors generally have higher voltage ratings so do not
use a 1/4 watt resistor where a 1/2 watt will physically fit.

A better and actually very good option is to use a modern film
resistors intended for high voltage operation like a Vishay 1/4 watt
HVR25 (1.6KV) and 1/2 watt HVR35 (3.5KV) series. 500 volt 1/4 watt
and 700 volt 1/2 watt film resistors are also available but I would
not use anything with a voltage rating lower than that by preference.

On 20 Mar 2016 18:13:39 -0700, you wrote:

>I am still working on the rebuild and someone mentioned the replacing focus resistors network and want to know what resistors need to be replaced ??? I found the parts in the schematic but trying to make sure I get the right parts..

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