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View Full Version : George, Eddie, Warren, Jerry, Pat ('MHz) et al - inductor question



N8YX
03-02-2014, 12:14 PM
Can any folks who may have been involved with the electronics industry during the '70s help me out with a part?

Below are pictures of a molded choke. It's a 10uH value but I'm not sure of its current rating.

Which manufacturer made these things, and what case type is it?

Bonus Points: If you have a few in various values kicking around your junk box I'll gladly buy them from you.

11792

11793

KJ3N
03-02-2014, 12:52 PM
What did it come out of?

K7SGJ
03-02-2014, 12:55 PM
Those were quite common in TVs of that era. As I recall, they were often used as peaking coils in Chroma and IF circuits as well as sound IF. They were often made by Miller and Millen. I looked in a 1960 Miller catalog I have, but could not find that configuration. I don't have a clue as to max I through them. If you have a bad one, I suppose you could crack it open to see what size the wire is. What did it come out of, and what circuit was it in?

N8YX
03-02-2014, 01:13 PM
What did it come out of?


Those were quite common in TVs of that era. As I recall, they were often used as peaking coils in Chroma and IF circuits as well as sound IF. They were often made by Miller and Millen. I looked in a 1960 Miller catalog I have, but could not find that configuration. I don't have a clue as to max I through them. If you have a bad one, I suppose you could crack it open to see what size the wire is. What did it come out of, and what circuit was it in?

One of the Stoner exciter boards currently on the bench; circa 1978. See the ongoing restoration saga over in the CB section of the site. If one takes a look at the circuit in question, there's no apparent way this thing could source enough power to cook itself unless a collector to base short is occurring (which it isn't) -or- the transistor is oscillating instead of amplifying.

I have a collection of these parts upstairs, sourced from many old Radio Shack "Coil and Inductor Assortments" (remember those?). Of course, I don't have a 10uH...

K7SGJ
03-02-2014, 01:17 PM
I am assuming it is in the collector circuit source supply. What device number is it feeding? You can check specs for the device and get an idea of max I.

Never mind, I just read the other thread post.

N8YX
03-02-2014, 01:26 PM
Take a look at bottom center of the JPG in the link:

http://www.sofafunker.de/stoner/stoner_analog_2.jpg

The inductor in question is L514.

I found some 10uH parts in my junque-box upstairs but they're about 2/3 the size of the original - even though the coil itself appears to be would on a form of the same size.

From the looks of things, I'm the first one to get into the PA area of the rig - it's all original.

K7SGJ
03-02-2014, 01:40 PM
Take a look at bottom center of the JPG in the link:

http://www.sofafunker.de/stoner/stoner_analog_2.jpg

The inductor in question is L514.

I found some 10uH parts in my junque-box upstairs but they're about 2/3 the size of the original - even though the coil itself appears to be would on a form of the same size.

From the looks of things, I'm the first one to get into the PA area of the rig - it's all original.

E-B short is about all I can see, that would cause that, too. Since that didn't happen, about the only other condition would be if the driver were driven into saturation or was biased full tilt. I can see where the choke would open before the device would be damaged. If you can't find a suitable replacement, you could wind one on a 47 ohm 1/2 or 1 watt resistor as a form, and remove the 47 ohm resistor that the choke parallels on the board; at least until you can find another 10uh of that configuration for original aesthetics.

KJ3N
03-02-2014, 01:51 PM
Given the maximum collector current of the MRF-476 is 1A, I would think that one of the following would suffice.

http://www.mouser.com/ProductDetail/Bourns/RLB0608-100KL/?qs=sGAEpiMZZMsg%252by3WlYCkUz6k%252bUjgS74eaWsPXP TjmfQ%3d <- rated for .5A

http://www.mouser.com/ProductDetail/Bourns/RLB0712-100KL/?qs=sGAEpiMZZMsg%252by3WlYCkUz6k%252bUjgS74eALmS2C TE%252bUU%3d <- rated for 1A

N8YX
03-02-2014, 02:00 PM
I'm thinking you may be right, Jim.

After I get done with a few other radio related activities I'm going to revisit this thing...with a scope and a couple more pieces of test equipment. Last night, the problem still manifested itself if the PLL/Counter Board was unplugged from the chassis. All RF and IF signals are generated on that particular board, so something is causing the device in question to behave weirdly. I need to see if an oscillation is present.

X-Rated
03-02-2014, 02:16 PM
I can't see well here on the phone want it is. Probably those 3 hole ferrite sleeves but I can't tell. I am guessing that Q is more important than inductance values. I started in the business in 1980.

kb2vxa
03-02-2014, 04:43 PM
As the director said; cut to the chase, so I will.

"It's a 10uH value but I'm not sure of its current rating."
If you can get your hands on a Kelvin bridge measure its DCR, it's a few milohms, so Ohm's law will give you the current capacity at the intended voltage.

"Which manufacturer made these things..."
Any.

"...and what case type is it?"
A PCB dipped in plastic, you can see the outlines.

The originally a bit longer pins say it was removed from a larger PCB trimmed after soldering, and the bent one says not very gently. (;->) I was in "the business" for a grand total of 50 years, but I've not seen another exactly like it, but similar enough to recognize it. There are just SO many out there like that it's easy to miss one. Even if I still had a junque box I never had a use for one of those things, sorry I can't help you or I'd drop one in the mail yesterday.

K6BSO
03-02-2014, 05:00 PM
I have a few Mylar-dipped (I think it's Mylar, anyhow) PCB chokes, I'll look and see if any of the are the right value. If so, they're yours if you want 'em.

N8YX
03-02-2014, 07:43 PM
...The originally a bit longer pins say it was removed from a larger PCB trimmed after soldering, and the bent one says not very gently. (;->)
It was removed as gently as possible - given the layout of the board, there was no way to get a lever under the device and I don't trust any type of grippers on coated parts. So...I fired up the handy PPS-85A, brought the SX-70 up to temp and removed the solder from both leads. The lead nearest the transistor was lifted out straightaway but getting the other one clear of nearby parts required a slight tilt upward of the freed side.

Trust me, I wasn't jerking this thing out willy-nilly...not with the prospect of it crumbling.

K7SGJ
03-02-2014, 08:05 PM
It was removed as gently as possible - given the layout of the board, there was no way to get a lever under the device and I don't trust any type of grippers on coated parts. So...I fired up the handy PPS-85A, brought the SX-70 up to temp and removed the solder from both leads. The lead nearest the transistor was lifted out straightaway but getting the other one clear of nearby parts required a slight tilt upward of the freed side.

Trust me, I wasn't jerking this thing out willy-nilly...not with the prospect of it crumbling.

That reminds me, I was having a hell of a time pulling a part off a board the other day. It was like the Pace lost suction. After a closer inspection, I noticed I had put an SX-70 tip in the SX-80. You can do it the other way around, but the SX80 has to have that longer tail-piece on the tip that goes further into the disposable filter. I really prefer the SX-70 because I think the suction is better with the glass tube. The seal to the SX80 cardboard filters can't be as tight as the glass.

N8YX
03-02-2014, 08:18 PM
I really prefer the SX-70 because I think the suction is better with the glass tube. The seal to the SX80 cardboard filters can't be as tight as the glass.
Pace makes a glass tube for the SX-80 and later series...and you're right: Those cardboard traps suck. But not very well...

kb2vxa
03-03-2014, 03:16 AM
"It was removed as gently as possible..."
Yeah, I know, that's why my sarcastic winky. I lost count of all the parts I tried to remove gently and ended up breaking something and... well... you get the picture. Anyhoo, good luck with your project and next time use the right tool for the job. (;->)
I'm saying that because I remember well using a solder sucker that gave me cat fits, that is until I rigged up the mother of all vacuum pumps, the compressor from an old air conditioner. You know, one of those Binford Tools doesn't make one that satisfied Tim Taylor, so he made one with MORE POWER! UUUGH UUUUGH UUUGH UUUUGH!!!! (;->)

N4BBQ
03-03-2014, 05:56 AM
When I get more coffee in me, I'll have a look in my junk box. It looks very familiar, plus I have quite a few CBs in a pile that I use for parts.

Ok, I found a few. The one pulled aside measures 10uH. Talk to me!
---
11810

kb2vxa
03-03-2014, 07:37 PM
They look like the ones I found in TVs. (;->)

N8YX
03-03-2014, 08:33 PM
When I get more coffee in me, I'll have a look in my junk box. It looks very familiar, plus I have quite a few CBs in a pile that I use for parts.

Ok, I found a few. The one pulled aside measures 10uH. Talk to me!
---
11810
What do you want for the lot of them? Looks like a few values I can use in these rigs...

N4BBQ
03-04-2014, 06:47 AM
What do you want for the lot of them? Looks like a few values I can use in these rigs...

How's $5 + da shipping? That'll get me a six pack of Fat Tire.

Oh, and I'll ship all that I have. I doubt I'll ever use them. Do you want me to measure and label them?

N8YX
03-04-2014, 07:02 AM
How's $5 + da shipping? That'll get me a six pack of Fat Tire.

Oh, and I'll ship all that I have. I doubt I'll ever use them. Do you want me to measure and label them?

Sold. Measure away if you will. I also have a bunch of surplus components that you're welcome to if you want them.

K7SGJ
03-04-2014, 08:29 AM
I was going to send you an old Silvertone Model 4188 color TV full of those things, but the freight was going to be around $8675.82. Sorry.....

kb2vxa
03-04-2014, 03:41 PM
I looked at the picture again and it jogged my memory, inductors are color coded. It's the same as resistors including the fourth band being tolerance, only the value is in microhenries. You don't have to measure it, the one you're looking for is brown black brown. In case you don't remember try this: http://www.electronics2000.co.uk/calc/inductor-code-calculator.php

N4BBQ
03-04-2014, 03:54 PM
All these things are so old the colors are all smudged together. Red = Brown = Orange. etc. haha

K7SGJ
03-04-2014, 05:12 PM
All these things are so old the colors are all smudged together. Red = Brown = Orange. etc. haha

That's the beauty of it. You only need one of them, and it will be any value you need.

N8YX
03-04-2014, 06:54 PM
I was going to send you an old Silvertone Model 4188 color TV full of those things, but the freight was going to be around $8675.82. Sorry.....

You could always put the SX-70 to work on that TV set. ;)


...the one you're looking for is brown black brown.

For a 10uH?

K7SGJ
03-04-2014, 07:41 PM
You could always put the SX-70 to work on that TV set. ;)



For a 10uH?

Wouldn't that be a 100uH?

X-Rated
03-05-2014, 12:49 PM
Wouldn't that be a 100uH?

You don't want two blacks together. You'd be asking for more trouble. lol.

So the old one burned up? You need to figure out why the old one burned up. They usually don't just burn up. Also, is this in a tuned circuit? If not, (and i can't imagine that thing being in a tuned circuit) something close would probably work if the resistance is small enough. But what do i know? If that thing is in a tuned circuit, AND you can't find the right value, try something really close if you can find that and change the cap as well. It can get you on the air and when you do find the right part as I am sure you will someday, put in the right one and the right cap and away you go, like new.

K7SGJ
03-05-2014, 01:38 PM
You don't want two blacks together. You'd be asking for more trouble. lol.

So the old one burned up? You need to figure out why the old one burned up. They usually don't just burn up. Also, is this in a tuned circuit? If not, (and i can't imagine that thing being in a tuned circuit) something close would probably work if the resistance is small enough. But what do i know? If that thing is in a tuned circuit, AND you can't find the right value, try something really close if you can find that and change the cap as well. It can get you on the air and when you do find the right part as I am sure you will someday, put in the right one and the right cap and away you go, like new.


It looks like it's used as power supply decoupling to keep RF out of the PS.

kom
03-05-2014, 01:54 PM
You don't want two blacks together. You'd be asking for more trouble. lol.

So the old one burned up? You need to figure out why the old one burned up. They usually don't just burn up. Also, is this in a tuned circuit? If not, (and i can't imagine that thing being in a tuned circuit) something close would probably work if the resistance is small enough. But what do i know? If that thing is in a tuned circuit, AND you can't find the right value, try something really close if you can find that and change the cap as well. It can get you on the air and when you do find the right part as I am sure you will someday, put in the right one and the right cap and away you go, like new.

I might be wrong but, that choke seems to be in the base circuit of your driver transistor; tracing the signal back, it is providing bias / control for Q 521. That line also runs down to IC 511 which has some influence on your balanced modulator, by way of Q528 and Q 527 (ALC /AMC control?). What’s the value of the 47 ohm resistor in parallel with the inductor?

.

X-Rated
03-05-2014, 03:06 PM
I might be wrong but, that choke seems to be in the base circuit of your driver transistor; tracing the signal back, it is providing bias / control for Q 521. That line also runs down to IC 511 which has some influence on your balanced modulator, by way of Q528 and Q 527 (ALC /AMC control?). What’s the value of the 47 ohm resistor in parallel with the inductor?

.

I would think it was 47 ohms.

K6BSO
03-05-2014, 03:09 PM
I would think it was 47 ohms.

Unless the bearings are shot.

K7SGJ
03-05-2014, 09:50 PM
Unless the bearings are shot.


Please move that to the gun thread.

K6BSO
03-05-2014, 09:55 PM
Please move that to the gun thread.

I'll just wave it around and de-escalate the situation.

X-Rated
03-05-2014, 10:02 PM
Inductors do it waving wound. Gotta watch for the recoil. Oh Henry, when will you ever learn to discharge your magnetic fields safely?

kb2vxa
03-06-2014, 08:51 PM
Which Henry, Joseph Henry, Benjamin Tyler Henry, or Henry VIII?

X-Rated
03-06-2014, 10:14 PM
Which Henry, Joseph Henry, Benjamin Tyler Henry, or Henry VIII?

Micro Henry Radio.

N8YX
03-07-2014, 05:56 PM
I might be wrong but, that choke seems to be in the base circuit of your driver transistor; tracing the signal back, it is providing bias / control for Q 521. That line also runs down to IC 511 which has some influence on your balanced modulator, by way of Q528 and Q 527 (ALC /AMC control?). Whats the value of the 47 ohm resistor in parallel with the inductor?

It's a quarter watter.

Looking at the circuit, the only way it could fail in the manner observed is if the driver had a collector to base short or if the predriver's coupling capacitor was shorted somehow.

#496 showed up on my doorstep a few days back. It has other...issues...including an S-meter that I did something very stupid with. If I can perform microsurgery I should be able to fix its movement. If not, a handful of LM3914s, 2x 10-segment bar graphs, 2x 8-segment bar graphs and several other discrete LEDs plus some support components are going to make for a very neat digital replacement.