Tube testing in Lethbridge

[John Bain]

I am a relatively new member and this is my first post. I am also new to this whole field of vintage radio restoration. My wife has an old Sparton radio (Model 98 – big floor model from the 1930s) that she would like to be able to listen to again. I have taken it apart to some extent and replaced the electrolytic capacitors with the help of a local mentor. Our next interest is in seeing how good the tubes are but we don’t have access to a tube tester. Is there anyone out there who knows of someone in the vicinity of Lethbridge that would be able to help us test the nine tubes in this radio. I believe they are all octals, if that makes a difference.

Thanks in advance for any advice.

John Bain

[phil]

some of the spartans used a tube made by sparton that is very similar to a ’45 but has a 5 volt filament rather than the 2.5V or a 45 tube. sometimes people hhave trouble locating the original spartan tube and modify the chassis to accept 45’s instead.

If you have replaced the filter caps and checked for dameaged wiring etc. you might consider just powering it up , using a dim bulb tester. If you know it works the tubes might not be a concern. If you can swap them from other radios often that’s a help.

I have a few tube testers but I can’t say I have one that I trust so I most often just swap tubes at first. If the set does work you are ahead , if not then you have more troubleshooting.

I just say that because often when I speak to other hobbyists who have even less experience than me, they often jump to the connclusion where they need to change tubes. They keep well, it’s mainly the number of hours that wears them and they do last for quite a long time usually.

[Dan Walker]

John. I finished a Sparton Model 98 a while ago and they are a very nice sounding radio.
They also have a nice mirror dial.
I don’t know anyone in Lethbridge, but I do know someone in Medicine Hat that would have a tube tester.
If you want to email me I can give you his email in Medicine Hat.
I live in Calgary.
Dan Walker

[Dan Walker]

Here are a couple of photos of the one I had

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[Dan Walker]

Hello again John,,,I noticed in your post that you changed the electrolytic caps in the radio.
ALL of the caps should be changed for it to work properly. The radio would probably play with just the electrolytic caps changed, but these are very old caps and they will fail at a later date.

[Dan Walker]

John;; All of your tubes in that radio are 6 volt heaters;” EXCEPT” for the rectifier, 5Y4 which is 5 volts
6K7 [2]
6A8 [1]
6C5 [1]
6H6 [1]
6F6 [2]
6E5 [1]
Dan in Calgary

[John Bain]

Thanks to everyone for their suggestions and help. I am about to begin the task of replacing the rest of the caps as I wait for some new tubes that I ordered, so I can swap them in and out to see what works best. I work very slowly but will try and update you when I have made some progress.

John

[John Bain]

A brief update on the Spartan 90 project:

I have now replaced a number of caps in the radio, but as they get more and more difficult to reach I find I am weighing the risk of doing more damage as I try and replace versus leaving well enough alone. I am not the most adept solderer. I have powered up the radio using a dim bulb tester after pretty much every cap that I have replaced and my results appear mixed. Sometimes I think there has been an improvement and other times reception seems a bit worse. It may be more a function of the time of day than anything else. The radio is in the basement attached to a makeshift longwise antenna. Sometimes I can pick up 4 different AM stations, but that is about the best. I never get much volume. During my most recent power-up I touched the metal connector atop the IF 6K7G tube and the radio immediately went quiet and the dim bulb went almost off. There also appeared to be a flickering blue light at the base of either the 6C5G or 6H6G tube. Within a few moments the flickering stopped, the bulb brightened and the static returned to the speaker (i.e. the radio returned to normal). I tried the same thing with the RF 6K7G with the same result. I assume this is a sign that something is not quite right, but I don’t know what it is.

I have also acquired some spare tubes and swapped some in and out. The one that appeared to have the most effect was the IF 6K7G. I also mistakenly purchased a 6A8 tube instead of a 6A8G, forgetting that I needed a tube the same shape as the metal “wrapper” currently covering the tube. I’m not sure if I can adapt the 6A8 in some way and currently have no evidence the original tube is a problem. I still haven’t swapped out the rectifier tube, but again I have no evidence that it is a problem other than it gets quite warm when the radio is powered up.

That is a summary of my “progress” to date. Any advice, insights or suggestions are most welcome.

John

[perry]

Hi John,
I see this is an old thread, but I have recently acquired a tube tester and happen to live in Lethbridge. If you still need assistance I may be able to help.
Regards,
Perry

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