Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1] 2 Next   Go Down
  Print  
Author Topic: restoring tubes  (Read 4014 times)
G4GEN
Member

Posts: 6




Ignore
« on: June 18, 2014, 05:42:18 AM »

hello , has anyone managed to restore continuity in the heater of an 813 ? i have several which are open circuit but seem to be ok visually G4GEN
Logged
K1ZJH
Member

Posts: 1185




Ignore
« Reply #1 on: June 18, 2014, 06:32:32 AM »

How much have they been used? A problem with early thoriated filaments was Miller Larson Effect. If your tubes have been used for some number of years, that may be the reason for the failure.

http://www.w0btu.com/miller-larson_effect.html

RCA recommended keeping the filaments lit, at a 10% reduced filament voltage, during standby to improve their service life. Of course this was during wartime and demand for the tubes often exceeded production or material availability.

If the filament is open, there isn't much you can do to save the tube.  You could try resoldering the filament pins on the off chance that there may be a poor solder connection.

Fortunately, I've been able to locate five good pairs for my homebrew amplifier. At least here Stateside, we can still find NOS RCA graphite plate 813 tubes for about $20 USD with some searching.

Peter
Logged
KI6LZ
Member

Posts: 602




Ignore
« Reply #2 on: June 18, 2014, 06:38:51 AM »

Heard of zapping them with high voltage capacitors in an attempt to get the filaments to reconnect. Never tried it but I guess some did it.
Logged
N6AJR
Member

Posts: 9927




Ignore
« Reply #3 on: June 18, 2014, 07:53:10 AM »

I too have had some older tubes needing the pins reheated. Apparently the tubes get so hot the solder melts in the pins that go in the sockets. gud luck
Logged
K8AXW
Member

Posts: 4002




Ignore
« Reply #4 on: June 18, 2014, 09:44:16 AM »

ZJH:  I built a homebrew 813 amp many years ago (my first amp) and for the life of me can't remember what ever happened to it.

Would you tell me if you built yours from an article....book...or cobbled it together yourself? 

I keep an amplifier file and might be very interested in filing yours.....just in case I get the hots to build one. 

Al
Logged
G4GEN
Member

Posts: 6




Ignore
« Reply #5 on: June 18, 2014, 12:57:04 PM »

hello, i use the 813s in a WW2 transmitter . they last for years. however i have got through a few due to o/c heaters over the years. i have just bought a pair of chinese ones from the states. they are really first class and the tx is giving 15 watts more rf. they must have a harder vacuum than the WW2 ones  alan
Logged
KJ6ZOL
Member

Posts: 415




Ignore
« Reply #6 on: June 18, 2014, 01:10:55 PM »

hello, i use the 813s in a WW2 transmitter . they last for years. however i have got through a few due to o/c heaters over the years. i have just bought a pair of chinese ones from the states. they are really first class and the tx is giving 15 watts more rf. they must have a harder vacuum than the WW2 ones  alan

China has really improved their tubes over the years. I remember, back in the 90s, when Chinese tubes were considered useless. I have a 12AX7 Chinese tube in my tube collection from about 1998, it's obviously very poorly made. As regards vacuum, I believe tubes degrade over time, sometimes there will be vacuum leaks, I would think.
Logged
G3RZP
Member

Posts: 4962




Ignore
« Reply #7 on: June 18, 2014, 11:36:36 PM »

A lot of WW2 tubes had relatively poor seals and weren't pumped that well. In many cases, they weren't expected to have a long life - T1154s in RAF Bomber Command for example - and quantity was more important than long life quality. I very much doubt that one can find a good 826, 829 or 832 these days that was made in WW2.

There was an early  problem at English Electric just after WW2 in making 813s in that the emission and/or filament would die in a few hundred hours. Eventually traced to insufficient thorium in the filament wire.

I doubt you get do much with an o/c filament wire, though.
Logged
KA5PIU
Member

Posts: 446




Ignore
« Reply #8 on: June 19, 2014, 04:48:55 AM »

Hello.

Vacuum tubes suffer from the glass "Gassing" and other problems.
The Russians produce "The cats meow" in vacuum tubes.
The 813 was an OK tube, but was not good enough for SSB service.
But the pesky Soviets did not want to simply get rid of their basics, so they improved that tube with a plate of zirconium plated nickle plated stainless steel.
That tube can dissipate well over  500  watts, and have far better filaments.
But, figure on about 7 amps at 10 volts for the filaments.
They are used in the Soviet era "D" amplifiers, very popular right up to the 80's with CB.
The D amps have a solid state power supply but 2 tubes and put out a whole lot more power than the TV sweep tube models, even the quads, 4 tubes.
And, before anyone gets excited, the FT-101 used TV sweep tubes, and the 813 is a very easy to get Russian tube..
So, plopping one into an FT-101 yields a very cool running tube.
But, the tubes are cheap!
A TV sweep tube may cost upwards of $60!
I can get this tube for so little that shipping is the deciding factor, a box of 8, $100, shipping $20.
The 813 may be a dated tube, but for what I do they really are "The Cats meow"!
Logged
KA5PIU
Member

Posts: 446




Ignore
« Reply #9 on: June 19, 2014, 06:25:38 AM »

Hello.

And, to make this clear, I do not advocate the use of 11 meter amplifiers or the use of tubes being pushed to the limit.
600 to 700 watts on 10 meters is a nice figure for the D amplifiers, and they have a pair of tubes!
The D amplifiers are a module that is used for several Soviet era radios.
The motor generator (dynamotor) was eliminated and this unit was a drop in replacement.
Other modules were likewise upgraded over the years.
The D module has 5 tubes in it, 2 are special "ballast" tubes that do nothing but limit filament voltage of an 813, that is in series with the filament of that one tube.
The odd tube almost always was removed, a tube base thing with a cap in it was plugged in its place.
The connector for power is this Jones plug, easy to get.
The RF connector is the standard UHF.
There is no RF keying, you have to key a line.
No filtering of RF, it was intended only as an RF amplifier, so the RF noise sucks!
But, they show up from time to time, the going rate is about $50 for one with the tubes.
The ballast tube is NLA, or at least I can not find it.
Some have had an adjustable resistor or heater wire added, or even just steel wire rolled up in a loop.
But, this amp will usually yield 2 good tubes.


Logged
G3RZP
Member

Posts: 4962




Ignore
« Reply #10 on: June 19, 2014, 11:50:09 AM »

>And, before anyone gets excited, the FT-101 used TV sweep tubes, and the 813 is a very easy to get Russian tube..
So, plopping one into an FT-101 yields a very cool running tube.<

You just have to find a way to shrink it dimensionally without losing dissipation, as it is far too physically large to fit in a FT101 - or an FT anything. So a totally impracticable suggestion........
Logged
KA5PIU
Member

Posts: 446




Ignore
« Reply #11 on: June 19, 2014, 03:48:29 PM »

>And, before anyone gets excited, the FT-101 used TV sweep tubes, and the 813 is a very easy to get Russian tube..
So, plopping one into an FT-101 yields a very cool running tube.<

You just have to find a way to shrink it dimensionally without losing dissipation, as it is far too physically large to fit in a FT101 - or an FT anything. So a totally impracticable suggestion........
You shrink nothing, you bolt on the Russian amp unit, run 2 wires by way of UHF connectors to the radio, and some make direct DC connections, but I prefer the Jones plugs.
The Pi circuit is not altered.
For tube cooling, a classic muffin fan works wonders.
Dude, CB types came up with this!
Are you going to tell me a CBer is smarter than a ham?!
At Mission open air market they have some guy from Mexico who will convert your radio while you wait!.
http://www.missionopenairmarket.com/
They rewind Microwave oven transformers to your specifications, or you can buy a kit and do it at home.
And even that is not hard!
https://www.youtube.com/watch?v=s6NyTprQCBI
Logged
W9FIB
Member

Posts: 957




Ignore
« Reply #12 on: June 19, 2014, 05:09:47 PM »


Are you going to tell me a CBer is smarter than a ham?!

At Mission open air market they have some guy from Mexico who will convert your radio while you wait!.


No the ham is smarter because a ham builds legal equipment that is used legally on ham bands. Building or converting any CB equipment to anything beyond FCC rules is really dumb. No matter how technologically advanced it is. It is wrong to do, and breaking the law is dumb.
Logged
KA5PIU
Member

Posts: 446




Ignore
« Reply #13 on: June 19, 2014, 06:02:43 PM »

Hello.

I agree, there is no real reason to break the law.
Getting a ham license is easier than ever, and some of the CB shop owners I try to avoid.
In theory, all of the 10 meter radios are operated on 10 meters with a ham license.
And, all of the conversions I have seen  maintain the full coverage of the FT-101.
over half have no desire to operate outside 11 meters.
They do not want SSB or 10 meters.
But, that is the market.
The good news is just that, they do not want any of the ham bands.
This is like watching a rape from the second floor balcony in downtown San Antonio.
Other than call the police, I am going to do nothing.
The FCC has to actually catch a violation of the law, and the market shops are very clear, you will violate the law if you insert this 27 MHz crystal in your FT-101, and if the crystal is in place, it gets removed and put in an envelope with super detailed instructions on how to reinsert it, the guy will pull the covers but not insert the crystal.
Unethical? yes. but totally legal.
The FT-101 is super easy, it has a flip top.
They make a really nice "VFO" that plugs in the back and has a NICE digital display.
And it has a knob that can be set for anything you could want, dual watch, repeater offset, CB channels, Every band the radio can do, etc.
It is real smooth, but most CBers say "It rolls too easy!".
The place is entertainment for me!
If you try and play ham cop you are quickly going to find 2 things out.
First off, the place is private property, and you can go to jail for trespassing.
And, there is a hell of a lot more than illegal CB radios there, and all the parts on your car have value, that is if it does not wind up in Mexico!
Logged
G3RZP
Member

Posts: 4962




Ignore
« Reply #14 on: June 20, 2014, 02:13:33 AM »

>You shrink nothing, you bolt on the Russian amp unit, run 2 wires by way of UHF connectors to the radio, and some make direct DC connections, but I prefer the Jones plugs.<

Much easier to just build an external amplifier....And the miniature Jones plugs aren't rated at 750 volts, although everybody seemed to get away with them at that level. However, in humid conditions, I have seen one that arced and burned up.

The best change to the FT101 PA is to go from sweep tubes to 6146 family tubes, especially now that NOS sweep tubes are getting hard to find at a reasonable price.
Logged
Pages: [1] 2 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!