Old 'Scope inductor and cap help please

Down with water heaters and up with old tube oscilloscopes, that's
what I say.
Well, I picked up a couple of old scopes. One is a Dumont 241 and
the other is a DeVRY. No model number on the DeVRY. It's not a Bell
and Howell model 34, but it is similar, and older. As near as I can
tell it is also a B&H, but I can't tell much. It came with
construction manual as it was a kit. The manual is # 9027A. It has
some sections of the schematic for the scope but not the whole
schematic.
Though the scope sorta works it ignores all signals fed into it. I
can get a dot, a line, and a small waveform but those just come from
switching the dials. By small I mean it is not very tall or long on
the CRT. It is not a pure sine wave but instead looks like a jagged
triangle wave. Sort of.
On the front of the manual someone wrote that an inductor is bad.
It is a 35uH coil wound on a 10 meg resistor. It is called a peaking
coil and is in the signal path of the vertical amplifier.
I have not been able to find this style of inductor online. Maybe
I'm not using the correct search terms. Can anyone point me in the
correct direction? Maybe I could just wind my own. Anybody know what
the permeability of a carbon comp resistor is?
I also would like some advice on where to buy caps for tube gear.
Digikey or Mouser? Someplace better?
Finally, it looks like I need to get me a cap tester. One that can
check caps in circuit would be ideal. But since this is a hobby I need
to keep the costs down. So suggestions would be great.
Thanks for reading.
Cheers,
Eric

 

[Fox's Mercantile]

On 10/4/19 12:53 PM, etpm@whidbey.com wrote:

I have not been able to find this style of inductor online. Maybe
I'm not using the correct search terms. Can anyone point me in the
correct direction? Maybe I could just wind my own. Anybody know what
the permeability of a carbon comp resistor is?

The permeability is zero. It's "just a coil form"
Unwind the old one, count the number of turns, measure the wire
size. Wind new turns and replace.

--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

 

[pfjw@aol.com]

A few things:

a) I keep the Peak/Atlas ESR & Cap tester. There are much cheaper Chinese devices that test more things than it does, but for reliability and simplicity, I find it a better choice. Note that if all you want is capacity, any decent DVM/VOM will have that function these days. But having reliable ESR readings is very helpful.

b) I also keep a fairly vintage (maybe 20 years old) B&K LCR Meter, useful for measuring inductors. I see them on-line in the $$$ range, with Chinese LCR meters along side in the $$ range. I got mine from a retired Tech at a garage sale. Recently calibrated (then) and works fine.

c) Mouser and DigiKey are my first two choices, with Newark (Element 14) being next. Note that Mouser will answer the phone, typically by/with a knowledgeable person, typically also patient with amateurs.

d) LR networks are common enough and there is nothing magical about them. Winding one yourself is no trick either. The trick is to wind on a few more turns, then back off until it is where you want it to be. In the factory, that would not have been necessary, but with such an old device, pretty much nothing is as it was then, so you may need a bit of range. Nor does that coil have to be around the resistor if space permits. But, if you are lucky enough to be able to find a 10-meg film resistor of the correct diameter and wire of the correct gauge, just count the turns and rewind.

Not knowing where you are, I would suggest you look for vintage radio clubs and/or hamfests in your region. Oftentimes, you can find parts, pieces and all sorts of vintage stuff at such events, and advice through clubs that is far more practical and immediate than much offered here. I make it to Kutztown twice a year, which serves very nearly all of my needs.

Peter Wieck
Melrose Park, PA

 

[Ralph Mowery]

In article <wOidnSPBTuJZCgrAnZ2dnUU7-W2dnZ2d@giganews.com>,
jdangus@att.net says...

I have not been able to find this style of inductor online. Maybe
I'm not using the correct search terms. Can anyone point me in the
correct direction? Maybe I could just wind my own. Anybody know what
the permeability of a carbon comp resistor is?

The permeability is zero. It's "just a coil form"
Unwind the old one, count the number of turns, measure the wire
size. Wind new turns and replace.

--

Would it not be 1 instead of zero ? The same as air.

I do agree that resistors that have over 100 times the resistance
(reactance) of the wire will appear to almost not be there and just a
coil form.

 

[Fox's Mercantile]

On 10/4/19 5:03 PM, Ralph Mowery wrote:

jdangus@att.net says...
I have not been able to find this style of inductor online. Maybe
I'm not using the correct search terms. Can anyone point me in the
correct direction? Maybe I could just wind my own. Anybody know what
the permeability of a carbon comp resistor is?
The permeability is zero. It's "just a coil form"
Unwind the old one, count the number of turns, measure the wire
size. Wind new turns and replace.

--


Would it not be 1 instead of zero ? The same as air.

You're right. It's 1.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

 

On Fri, 4 Oct 2019 14:04:36 -0500, Fox's Mercantile <jdangus@att.net>
wrote:

On 10/4/19 12:53 PM, etpm@whidbey.com wrote:
I have not been able to find this style of inductor online. Maybe
I'm not using the correct search terms. Can anyone point me in the
correct direction? Maybe I could just wind my own. Anybody know what
the permeability of a carbon comp resistor is?

The permeability is zero. It's "just a coil form"
Unwind the old one, count the number of turns, measure the wire
size. Wind new turns and replace.

The schematic just shows the inductor in the circuit. It does not show
the inductor as being in parallel with a resistor. And it is described
as 35 uH "ON 10 M". So I'm thinking I either can just replace the
inductor with an off the shelf 35 uH coil and not worry about the
resistor or connect the coil and a 10 meg resistor in parallel.
Eric

 

[Fox's Mercantile]

On 10/4/19 6:13 PM, etpm@whidbey.com wrote:

On Fri, 4 Oct 2019 14:04:36 -0500, Fox's Mercantile <jdangus@att.net
wrote:

On 10/4/19 12:53 PM, etpm@whidbey.com wrote:
I have not been able to find this style of inductor online. Maybe
I'm not using the correct search terms. Can anyone point me in the
correct direction? Maybe I could just wind my own. Anybody know what
the permeability of a carbon comp resistor is?

The permeability is zero.

Correction, it's 1.
It's "just a coil form"

Unwind the old one, count the number of turns, measure the wire
size. Wind new turns and replace.
The schematic just shows the inductor in the circuit. It does not show
the inductor as being in parallel with a resistor. And it is described
as 35 uH "ON 10 M". So I'm thinking I either can just replace the
inductor with an off the shelf 35 uH coil and not worry about the
resistor or connect the coil and a 10 meg resistor in parallel.
Eric

You don't need the 10 meg ohm resistor.
This will be fine.
<https://www.mouser.com/ProductDetail/API-Delevan/1025-56J?qs=sGAEpiMZZMsg%252By3WlYCkU%2Fuy0w9T3GDQ2AQE7IS6yJE%3D>




--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

 

On Saturday, 5 October 2019 00:07:39 UTC+1, et...@whidbey.com wrote:

On Fri, 4 Oct 2019 14:04:36 -0500, Fox's Mercantile <jdangus@att.net
wrote:

On 10/4/19 12:53 PM, etpm@whidbey.com wrote:
I have not been able to find this style of inductor online. Maybe
I'm not using the correct search terms. Can anyone point me in the
correct direction? Maybe I could just wind my own. Anybody know what
the permeability of a carbon comp resistor is?

The permeability is zero. It's "just a coil form"
Unwind the old one, count the number of turns, measure the wire
size. Wind new turns and replace.
The schematic just shows the inductor in the circuit. It does not show
the inductor as being in parallel with a resistor. And it is described
as 35 uH "ON 10 M". So I'm thinking I either can just replace the
inductor with an off the shelf 35 uH coil and not worry about the
resistor or connect the coil and a 10 meg resistor in parallel.
Eric

As said the resistor is nothing but mechanical support. If you buy inductors they're often cored, but you want air cored. Those kind of wound on a resistor Ls were always a case of wind your own.


NT

 

[legg]

On Fri, 4 Oct 2019 17:29:31 -0500, Fox's Mercantile <jdangus@att.net>
wrote:

On 10/4/19 5:03 PM, Ralph Mowery wrote:
jdangus@att.net says...
I have not been able to find this style of inductor online. Maybe
I'm not using the correct search terms. Can anyone point me in the
correct direction? Maybe I could just wind my own. Anybody know what
the permeability of a carbon comp resistor is?
The permeability is zero. It's "just a coil form"
Unwind the old one, count the number of turns, measure the wire
size. Wind new turns and replace.

--


Would it not be 1 instead of zero ? The same as air.

You're right. It's 1.

Permeability of free space is 4 x pi x 10^-7.

.... but yeah, it's just a coil former.

RL

 

On Fri, 4 Oct 2019 18:31:38 -0500, Fox's Mercantile <jdangus@att.net>
wrote:

On 10/4/19 6:13 PM, etpm@whidbey.com wrote:
On Fri, 4 Oct 2019 14:04:36 -0500, Fox's Mercantile <jdangus@att.net
wrote:

On 10/4/19 12:53 PM, etpm@whidbey.com wrote:
I have not been able to find this style of inductor online. Maybe
I'm not using the correct search terms. Can anyone point me in the
correct direction? Maybe I could just wind my own. Anybody know what
the permeability of a carbon comp resistor is?

The permeability is zero.
Correction, it's 1.
It's "just a coil form"
Unwind the old one, count the number of turns, measure the wire
size. Wind new turns and replace.
The schematic just shows the inductor in the circuit. It does not show
the inductor as being in parallel with a resistor. And it is described
as 35 uH "ON 10 M". So I'm thinking I either can just replace the
inductor with an off the shelf 35 uH coil and not worry about the
resistor or connect the coil and a 10 meg resistor in parallel.
Eric


You don't need the 10 meg ohm resistor.
This will be fine.
https://www.mouser.com/ProductDetail/API-Delevan/1025-56J?qs=sGAEpiMZZMsg%252By3WlYCkU%2Fuy0w9T3GDQ2AQE7IS6yJE%3D

Thanks, I thought so. Today I order caps and an inductor. I'm excited
to see this old scope work.
Eric

 

[three_jeeps]

Given the age of the scope, you might want to consider replacing the electrolytic in the power supply section. Everything starts with solid, clean and correct power
J

 

On Sun, 6 Oct 2019 18:10:58 -0700 (PDT), three_jeeps
<jjhudak@gmail.com> wrote:

Given the age of the scope, you might want to consider replacing the electrolytic in the power supply section. Everything starts with solid, clean and correct power
J

I will be replacing practucally every cap. Besides all the
electrolytics there are some others that, from what I've read about
and seen on YouTube, are also suspect.
Eric

 

[Fox's Mercantile]

On 10/7/19 10:48 AM, etpm@whidbey.com wrote:

I will be replacing practically every cap. Besides all the
electrolytics there are some others that, from what I've read about
and seen on YouTube, are also suspect.
Eric

Caps are cheap. Collateral damages from bad caps are not cheap.
Replace ALL the electrolytics.
Replace ALL the paper caps.

Leave the silver dipped micas, tubular ceramics, and any "postage
stamp" micas alone for the time being.

Replace them one at a time. Take pictures, make notes.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

 

On Mon, 7 Oct 2019 12:03:13 -0500, Fox's Mercantile <jdangus@att.net>
wrote:

On 10/7/19 10:48 AM, etpm@whidbey.com wrote:
I will be replacing practically every cap. Besides all the
electrolytics there are some others that, from what I've read about
and seen on YouTube, are also suspect.
Eric

Caps are cheap. Collateral damages from bad caps are not cheap.
Replace ALL the electrolytics.
Replace ALL the paper caps.

Leave the silver dipped micas, tubular ceramics, and any "postage
stamp" micas alone for the time being.

Replace them one at a time. Take pictures, make notes.

I have tried to identify what types of caps are in this scope but
have been unable to find a site that shows the caps I'm wondering
about. I think some are tubular ceramic caps because they are white
ceramic tubes that are filled with some sort of hard potting compound.
The other type of cap is also tubular but is molded brown hard
plastic. These caps are 5/8" diameter x 1 5/8" long. They are .1 MFD
at 400 WVDC. Anybody know?
Thanks,
Eric

 

[Fox's Mercantile]

On 10/8/19 1:19 PM, etpm@whidbey.com wrote:

I have tried to identify what types of caps are in this scope but
have been unable to find a site that shows the caps I'm wondering
about. I think some are tubular ceramic caps because they are white
ceramic tubes that are filled with some sort of hard potting compound.
The other type of cap is also tubular but is molded brown hard
plastic. These caps are 5/8" diameter x 1 5/8" long. They are .1 MFD
at 400 WVDC. Anybody know?

The wax paper caps come in several varieties.
(Usually) Brown cardboard with a wax coating.
Molded plastic, and ceramic tube.
All of those need to be replaced.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

 

On Tue, 8 Oct 2019 13:56:52 -0500, Fox's Mercantile <jdangus@att.net>
wrote:

On 10/8/19 1:19 PM, etpm@whidbey.com wrote:
I have tried to identify what types of caps are in this scope but
have been unable to find a site that shows the caps I'm wondering
about. I think some are tubular ceramic caps because they are white
ceramic tubes that are filled with some sort of hard potting compound.
The other type of cap is also tubular but is molded brown hard
plastic. These caps are 5/8" diameter x 1 5/8" long. They are .1 MFD
at 400 WVDC. Anybody know?

The wax paper caps come in several varieties.
(Usually) Brown cardboard with a wax coating.
Molded plastic, and ceramic tube.
All of those need to be replaced.

What kind of cap should I replace them with?
Thanks,
Eric

 

[Fox's Mercantile]

On 10/8/19 3:56 PM, etpm@whidbey.com wrote:
> What kind of cap should I replace them with?

These:
<http://www.tuberadios.com/capacitors/>
Yellow mylar film 630 vdc.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

 

On Tue, 8 Oct 2019 16:03:45 -0500, Fox's Mercantile <jdangus@att.net>
wrote:

On 10/8/19 3:56 PM, etpm@whidbey.com wrote:
What kind of cap should I replace them with?

These:
http://www.tuberadios.com/capacitors/
Yellow mylar film 630 vdc.

Thanks. I'm ordering all the caps right now on my tablet. With the
little inductor its way I''l be set to repair the scope. BTW, as I was
looking for all the caps I found a broken wire in the vertical stage.
After figuring out where it was supposed to go and re-soldering it I
tried the scope again and now it works! Still, the waveform is messed
up so the new caps are needed.
Eric

 

On Monday, 7 October 2019 18:03:22 UTC+1, Fox's Mercantile wrote:

On 10/7/19 10:48 AM, etpm@whidbey.com wrote:
I will be replacing practically every cap. Besides all the
electrolytics there are some others that, from what I've read about
and seen on YouTube, are also suspect.
Eric

Caps are cheap. Collateral damages from bad caps are not cheap.
Replace ALL the electrolytics.
Replace ALL the paper caps.

Leave the silver dipped micas, tubular ceramics, and any "postage
stamp" micas alone for the time being.

Replace them one at a time. Take pictures, make notes.

You will of course encounter restorers who don't agree with this approach. Foxy is not known for seeing both sides of this picture.

Ceramic tube caps are often paper. A chinese component tester picks up most bad caps, and is supereasy to use. ÂŁ12 last time I looked.


NT

 

[Fox's Mercantile]

On 10/9/19 10:53 AM, tabbypurr@gmail.com wrote:

On Monday, 7 October 2019 18:03:22 UTC+1, Fox's Mercantile wrote:
On 10/7/19 10:48 AM, etpm@whidbey.com wrote:
I will be replacing practically every cap. Besides all the
electrolytics there are some others that, from what I've read about
and seen on YouTube, are also suspect.
Eric

Caps are cheap. Collateral damages from bad caps are not cheap.
Replace ALL the electrolytics.
Replace ALL the paper caps.

Leave the silver dipped micas, tubular ceramics, and any "postage
stamp" micas alone for the time being.

Replace them one at a time. Take pictures, make notes.

You will of course encounter restorers who don't agree with this approach. Foxy is not known for seeing both sides of this picture.

Ceramic tube caps are often paper. A chinese component tester picks up most bad caps, and is supereasy to use. ÂŁ12 last time I looked.


NT

For fuck's sake, are you not even reading?

Context ya twat.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com