View Single Post
  #9   Report Post  
Posted to rec.audio.tubes
hugeshows hugeshows is offline
external usenet poster
 
Posts: 29
Default Restoring a TV-7/U Tube Tester

Hello All,

Today I received a little package in the mail from Daniel Nelson. If you need to get parts for your TV7 or need an overhaul, he is somewhat of a legend who specializes in this tester. My tester was missing a few things that I wanted, so I contacted him and he gave me a very good deal on some parts.. First off, if you're missing the tube holders like I was, his reproductions are economical and work. I ordered two socket savers, the tube holders, and a socket adapter that my unit was missing. Here's what I got:

https://www.dropbox.com/s/knxqgtha1v...lson_Parts.jpg

I thought that this installing the socket savers and tube holders would only take a couple minutes, but as it turns out I had to do a little fiddling to make it all fit. First, the tube holders. They mount to posts that are threaded through the bracket to which the sockets are mounted. After test fitting the holders, it seemed that my tubes were too tall or the posts not long enough for the holders to fit into place. After a bit of investigating I discovered that if I removed the two screws holding down the resistor board and put it to the side, I had access to the backs of the posts where I could re-adjust perhaps another centimeter of length out of the rods.

https://www.dropbox.com/s/6ehhrzatak...lder_Posts.jpg

As you can see I pretty much took all the play there was. There are nuts on the other side that must be tightened when you adjust these as well. Once I had that done, I was able to fit the new tube holders and here they a

https://www.dropbox.com/s/pa4g1z4vb9...be_Holders.jpg

As you can see, I really did need every last bit of length on those two rods. But once that is done, these work quite nicely. Ten bucks was a good deal since I can't even look at sheet metal without getting a cut.

Now onto the socket savers. Not being a big power triode fan, I typically use octal and noval sockets in my amps. Since those are primarily the tubes I test unless I'm (rarely) working on radios, I bought and octal and noval socket saver. I thought this would be easy as well, but it proved a bit of a pain. First, before I installed them I prepped the old sockets a bit. Working with a dental pick and some de-oxit, I both cleaned and tightened the terminals in the original sockets. After putting in the octal socket saver, I quickly realized that the fit was a bit tight underneath. As it happens, the octal socket is right over the power transformer and leaves little clearance for the mounting hardware.

https://www.dropbox.com/s/1nvmcp0lbo...cket_Saver.jpg

As you can see, it's tight and I had to settle for slightly crooked. It turns out that the only way to even get the white plastic collar and metal washer in place was to loosen the three screws mounting the transformer to the top plate of the tester. Once I was able to move the transformer back a bit, I was JUST able to get the other bits in place. This doesn't have to be perfect, it just need to be tight enough to stop the socket saver from pulling out instead of the tube.

The noval socket provided another challenge - it had some solder or something obstructing the hole through which the center bolt passes. That required some boring out on my part. Once done, the hardware fit fine, but was easiest installed with the power transformer loose.

After that, I put it all back together and am now very happy with the tester. I will get to the shunt portion of the calibration at some point but since it is only used in diodes and rectifiers, I am not terribly worried about it now. Also, something tells me that with the plate voltage and meter bridge correct, the shunt is going to be spot-on unless somebody has messed with it.

Here's a shot of the tester in action, testing some NOS KT-90s I bought back in the glory days of RAT, the late 90's. Notice how well the top plate cleaned up as compared to the first picture. Alcohol for the tough stuff, and windex overall did the trick nicely.

https://www.dropbox.com/s/75zzf7q4ih...ting_KT90s.jpg


Cheers!


-forkinthesocket