Posts: 933
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City: Lansdale
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All, I just acquired this tester.
[Image: http://i292.photobucket.com/albums/mm38/...adi13e.jpg]
It was working as advertised. However I noticed that most if not all the tubes I tested were measuring the same. So I took it out of cabinet . Noticed some repairs were done , new caps a couple of new resistors. ETC.. I decided to measure the filament voltage to see if it was correct.. The manual says to use the line adjust to set the meter at the Line adjust position. When I did that the voltage was low. I was using the 5 volt position. It measured around 4.7 volts. When I put in a 5Y3 tube it could barely be set back to the Line adjust position. It measured around 4.6 volts.. could not get it any higher..
Here is schematic..
[Image: http://i292.photobucket.com/albums/mm38/...b9dhwt.jpg]
More to follow..
Skip...
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Is the 250 Ohm potentiometer still 250 Ohm? And is the voltage select switch clean?
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 933
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Joined: Mar 2015
City: Lansdale
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Funny you should ask that. Here are 2 pictures of the Line adjust Pot..
[Image: http://i292.photobucket.com/albums/mm38/...5evoss.jpg]
[Image: http://i292.photobucket.com/albums/mm38/...pdkpdm.jpg]
Clearly not a 250 ohm 25 Watt RHEOSTAT. It measured 5 K.. But a interesting story.. At first it measured 3 Ohms.. and from center to to end about 1K to 0 ohms.. Same way other direction... I took it apart and cleaned it and now measures 5 K.. the way it should..
Anyway I ordered a replacement. a 250 ohm 25 Watt RHEOSTAT.
So waiting on the pot...
But more to follow...
Skip...
Posts: 933
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Joined: Mar 2015
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Here is a list of all resistors and their values..
Measured
R1 40K 41.7K Replaced
R2 2 Meg 2.05 Meg
R3 27K 27K
R4 15K 17.5 k Replaced
R5 20K pot 20K
R6 10K pot 10K
R7 330 Ohms 3 Watt 330 Ohms
R8 47K 50.2K Replaced
R9 350 ohms Pot 3 Ohms then after cleaning 5K Replacing
The Replaced resistors were chosen to get exactly the Right ohmage..
The 2 Caps were originally replaced Did not change them..
There was a resistor across the R9 pot from center contact to side that goes to the 4 Position switch measuring 464 Ohms.. It was removed as it didn't do anything..
[Image: http://i292.photobucket.com/albums/mm38/...dquezd.jpg]
Skip...
Posts: 933
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Joined: Mar 2015
City: Lansdale
State, Province, Country: PA
09-22-2016, 04:53 PM
Ok, Just received the new Line adjust Rheostat. It cost me almost as much as I paid for the tube tester...
[Image: http://i292.photobucket.com/albums/mm38/...v1ekhi.jpg]
Before I install I want to check the BY1 rectifier. In schematic it say its Drawn backwards. So how would I test it.. I assume its like any other Diode? but really not sure.. I want to make sure its not shorted so I do not burn out the new Rheostat.. Can it be replaced with a modern diode? If so how?
Skip...
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Ok, on schematic.. 8Y1. The side that goes to R5 is marked on part 8Y1 Electron +K RRCO
The other side goes to the Switch..
Measured with meter - side to +k Plus side to switch 5.56 Meg
Measured with meter + side to +K neg side to switch 23.5 Meg
This is with one side disconnected..
Does that look right?
Skip...
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Ok I decided to put in the new Rheostat. Works great. Now on to calibration.. There is a calibration pot R5 I believe but no instructions on how to set.. Anyone know how to do calibration on this tester??
Skip...
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Ok, Did my best at calibration. Now when I set the line adjust to the line adjust line it reads the filament voltage setting correctly. When I put in a tube and compensate for the current draw the voltage is right on after readjusting the control..
Tube tester now works correctly..
It will be a great addition to my equipment for testing the older 4 and 5 pin tubes..
It cost a little more than I wanted but at lease it good now..
Skip...
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Glad to see it worked out for you Skip! I thought it working ok when I had it... but that's what happens when you have a chemist playing with electrons and wires.
I learned something from watching your fix!
Posts: 933
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It did work when I got it. And I got it for a good price..
So I am not unhappy by any means. I need one that would check the older tubes.
Glad I got it.. I just improved it a little.
Skip...
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Well, it is all well that ends well.
Congrats on a good working tester.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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