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Leader LCT 910A CRT Tester : Basic Guide

 
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Leader LCT 910A CRT Tester : Basic Guide

Post by crustytv » Wed Aug 01, 2012 10:58 pm

In light of Neil's recent query about the Leader LCT 910 CRT tester, I thought I would show the device in action and perhaps help others unsure of operation, use theirs. This CRT tester is one of the best and came highly recommended to me by an ex TV engineer.

I liked it so much I bought two as I could not bare the thought of one failing and not having another. The tester comes with the tube base adapters and is capable of testing early CRT's all the way up to the last colour tubes. I have also made up my own loom with various connections.

adaps.jpg


It has on many occasions, brought tubes back from the brink. Cleared a HKS on a PYE V4 (some of you may remember my 32 page journey), a GEC (BT1156) tube revived through the gentle ageing, a Bush TV22 ( MW22-16) and reviving a CRT that had spent 10+ years in a garden. See here viewtopic.php?f=12&t=12

When I get a set I always put the CRT on tester running through the tests to see the condition of the CRT before setting out on the restoration road. Some might say that is like skipping to the end of the book to see how it turned out, I find it saves a lot of wasted time and components.

On With The Test

So here for this example we are going to test a 1963 Perdio Portarama CRT the Mullard AW21-11. This is an 8½" for use in portable transistor receivers. Electrostatic focusing. 90 degree magnetic deflection, A1 400v & final anode of 12kV. The heater is 11.5V. The base is a B8H short spigot.

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As we are testing B&W tubes the colour gun control must be set to "Red" then the B&W/red control should be set to minimum. Ensure heater voltage is at zero and fine control at minimum.

The tester has a number of steps and if you follow these it makes life simple.

With the unit switched off select your CRT base plug and connect it. Ensure the heater control is set to the lowest point. You don't want to switch it on with too high a setting and fry your heater before we start. Get into the practice of always returning it to zero once a test is finished.

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Switch Position 1 (Off). set heater volts, in this case I'm testing a Mullard AW21-11 and the heater volts need to be 11.5v set the heater voltage to the 10-12v setting

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Switch Position 2. In this position power is now on and you will see the heater volts climb on the meter. The meter has number indicators which correspond to the function you are performing, so in this case we read heater voltage on the top scale that has 2 in the left column.The heater volts rise to 10v and with the fine adjust we bring the voltage to the correct 11.5v

Switch Position 3. In this position the tester verifies if there is heater cathode leakage, which can be seen there is not.

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Switch Position 4. This position check for G1 leakage, again nothing untoward.

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Switch Position 5. Here we now have to set the G1 voltage, this is achieved by rotating the G1 control until the meter rises on the scale (5) to the point marked on the scale as indicated by a line which is between 40 & 50.

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Switch Position 6. Now we set the cut-off (G2 voltage), this is achieved by rotating the B&W/red control until the meter rises on the scale (6) to the set cut-off bar.

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Switch Position 7. Now we can read the emission of the tube, as can be seen the AW21-11 is nice and healthy.

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Sometimes a tube will read in the red suggesting low emission but if left in this position the tube revives and the needle will move into the green. If not or any shorts then move onto the functions on the right.

The other function are remove shorts and the 3 levels of rejuvenation, which when selected, are activated by the red button.

Another good way to revive a tube without the need to use the rejuvenate, is as follows :-

1) Connect the tester as normal
2) Then set the heater to be 2 volts higher than it's normal setting.
3) Select reactivate position 2 and let it sit there for 10 mins DO NOT HIT THE RED BUTTON, if you did it could strip the cathode with the heater that high.

This often revives a tired tube without resorting to force.

So there we have it a great tester they often come up on e-bay and I highly recommend it.

Chris

 
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Re: Leader LCT 910A CRT Tester : Basic Guide

Post by neil29 » Thu Aug 02, 2012 5:06 pm

That's excellent, thanks Chris :thumbl: . cheers,neil.

 
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Re: Leader LCT 910A CRT Tester : Basic Guide

Post by freya » Thu Aug 02, 2012 9:04 pm

Also if your tube has been used just prior to connecting the tester, make sure the EHT is discharged completely.

Stephen

 
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Re: Leader LCT 910A CRT Tester : Basic Guide

Post by neil29 » Thu Aug 02, 2012 10:01 pm

8)) :\'( I know all about discharging tubes,or rather i thought i did :shock: . as the things can still give you a tingle even after you think it's safe :wft?: . cheers,neil.

 
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Re: Leader LCT 910A CRT Tester : Basic Guide

Post by Refugee » Fri Aug 03, 2012 1:10 am

I have an old BK tester that has a non working function due to not discharging tubes.
I will have to fix it once we get another TV license and i get the urge again.
It is an emission reading on a green or blue gun or something like that.

 
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Re: Leader LCT 910A CRT Tester : Basic Guide

Post by TVJON74 » Tue Nov 13, 2012 2:00 pm

Hi all,

After reading your excellent guide Chris, I decided to get one.
I now have the tester with setup chart No7 and a few socket adapters (nothing that fits what I need to test).
Can anyone tell me if it can be used to test a triode crt like T9/5 or CRM92 and how to go about doing it?

Best regards
Jon

 
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Re: Leader LCT 910A CRT Tester : Basic Guide

Post by Cathovisor » Sat Nov 15, 2014 8:34 pm

I too now have one of these to accompany my B&K 467, my two generations of Radar testers and my Video Circuits V31A (soon to be disposed of).

I'd like to make a flying lead adaptor, but before I sacrifice one of the adaptors in the kit I have (one is clearly home made, being soldered to a chunk of PCB carrying a tube base!) does anyone know of a source of the free 11-pin plug used for the adaptors? The biggest problem I have with it is that the test chart supplied is solely for Japanese tubes - chart no. 9. I really need something that covers British/European CRTs as otherwise it's pretty useless.

As an aside, B&K still make the setup charts for the 467/490 available for download.
Last edited by Cathovisor on Sat Nov 15, 2014 8:47 pm, edited 1 time in total.

 
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Re: Leader LCT 910A CRT Tester : Basic Guide

Post by cobaltblue » Sat Nov 15, 2014 8:45 pm

Cathovisor wrote:I'd like to make a flying lead adaptor, but before I sacrifice one of the adaptors in the kit I have (one is clearly home made, being soldered to a chunk of PCB carrying a tube base!) does anyone know of a source of the free 11-pin plug used for the adaptors?


Are they same as 11 pin Relay bases ( like octals but with 11 pins) ?

Cheers

Mike T

 
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Re: Leader LCT 910A CRT Tester : Basic Guide

Post by Cathovisor » Sat Nov 15, 2014 8:51 pm

I do believe they are...

 
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Re: Leader LCT 910A CRT Tester : Basic Guide

Post by Katie Bush » Mon Aug 10, 2015 7:11 pm

Even I eventually bought an LCT 910A earlier this year.. At first, it was somewhat rather off the mark when testing "known to be" CRTs, showing extremely optimistic emissions on total duds, and off the scale on good ones.

Luckily, I had a good session one afternoon whilst Marc was here with his B&K.. After a couple of hours of testing, the LCT 910A began to fall more in line with the readings we obtained with the B&K.

My LCT 910A is in "as new" condition, complete with factory tags.. It is virtually unmarked and shows no (and I do mean zero) signs of wear.. Between us, Marc, David and I concluded that it was most likely bought and stowed away unused, or with no more than a handful of uses in its lifetime.. In any event, it is in tip-top condition and working very well.. Like Chris, I'd recommend it, and it's very easy to set up and use.

Marion


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