Topics

Tek 2215

Jay
 

Has anyone completed the replacement parts list ??
Also should the 1.8k 75v cap be replaced and can't seem to find one ..

 

On 22 Feb 2016 11:25:08 -0800, you wrote:

Has anyone completed the replacement parts list ?
I have not had to rebuild any of my 22xx oscilloscopes yet so I just
have various notes without definitive replacement parts.

Also should the 1.8k 75v cap be replaced and can't seem to find one ..
The value of capacitance does not need to be exact although 1800
microfarads should not be a problem. Check lead spacing, diameter,
and height to make sure the replacement will fit.

<http://goo.gl/uOXcx6>
<http://goo.gl/z9UgiW>

Jay
 

Thanks
Right now I am have to make a parts list to place an order in order to start the rebuild ..I found most of the parts needed but have to read through the thread just to check the other parts are within tolerance ..
Any other suggestions

Jay
 

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..

 

The resistors are all 1 meg ohm and are R878, 879, 880, 881, 882, and 884. You can find them on the main board - A10 part layout - Figure 9-8. They are at coordinates 5-H.

HTH,
Tom

----- Original Message -----
From: jasontucker70@... [TekScopes]
To: TekScopes@...
Sent: Sunday, March 20, 2016 9:13 PM
Subject: Re: Fwd: Re: [TekScopes] Re: Tek 2215



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..

 

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..

 

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.

T

----- 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..

 

In a pinch that is a great idea. Using 1/2 watt resistors would be
even better.

I really think Tektronix ran the Allen-Bradley carbon composition
resistors too close to their voltage rating but apparently it worked
out well enough given that they lasted so long. Maybe they had
experience showing that they did not need to be voltage derated.

On Sun, 20 Mar 2016 23:38:57 -0400, you wrote:

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.

T

 

Ha. They probably didn't think someone would be using it 30+ years later. High voltage does do strange things over the long term.

t

----- Original Message -----
From: David @DWH [TekScopes]
To: TekScopes@...
Sent: Sunday, March 20, 2016 11:55 PM
Subject: Re: Fwd: Re: [TekScopes] Re: Tek 2215



In a pinch that is a great idea. Using 1/2 watt resistors would be
even better.

I really think Tektronix ran the Allen-Bradley carbon composition
resistors too close to their voltage rating but apparently it worked
out well enough given that they lasted so long. Maybe they had
experience showing that they did not need to be voltage derated.

On Sun, 20 Mar 2016 23:38:57 -0400, you wrote:

>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.
>
>T

 

I think reliability was the reason Tektronix used carbon composition
and then special film resistors for the focus resistor chain; normal
thin film parts would be been questionable unless significantly
voltage derated. Other oscilloscopes made during this time used a
custom thick film network which was only inexpensive because the same
network was used to regulate the cathode voltage which was not
necessary in the 2 channel 22xx oscilloscopes. I have never heard of
these thick film networks failing.

Carbon composition (and thick film) resistors are bulk devices so they
do not suffer from surface effects like in a thin film resistor. They
also tend to fail open rather than closed although at high voltages, I
suspect that is no advantage.

As far as I have been able to tell, the film resistors Tektronix used
later were specifically designed for high voltage operation and had
some type of special processing done after being trimmed to their
proper value to prevent the surface effects like electromigration
which would normally be a limitation.

On Mon, 21 Mar 2016 00:14:28 -0400, you wrote:

Ha. They probably didn't think someone would be using it 30+ years later. High voltage does do strange things over the long term.

t

Jay
 

Thanks everyone and I almost done with the parts list..Right now I have the caps,focus resistors,and damaged parts .. Are there any other parts that need attention ?? Also has anyone every completed the Tek upgrades like the trigger mod cause I already have the unit apart figured it might be worth doing ??
Would anyone be interested in the parts list for the Tek 2215 (Not updated)..

coresabmw@...
 

Since you asked, Jason, yes, I am interested in the parts list! If you would be so kind ... CoresaBMW@...

Thanks!

Norm

Jay
 

With this parts list you have understand what scope you have cause there are different variation..
The parts list I will post for if still requested is for a TeK 2215 without option 48 and has current limited power supply..