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Old 7th Feb 2020, 2:05 pm   #1
SEG7RAL3
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Default Transmitter valve tester

Been thinking about making one for years, I have about 100 PA valves of different types.
All threads on many forums seem to end up with the best test is to use it.
But if that is not possible, example I fancy building a small hf amp and have a few STC 3J160e triodes in the junk box, best to test them and if they have gone off in the past 30 years swop to another type and test those.
I have only seen a odd homebrew design on the web most give only partial info.
There was one in a GE Ham news vol 6 no3 did not fancy the RF power test.
Another one is in HAM radio April 78 that looks ok as a start point.
Did find a US gov one the "Hallicrafters Military Electron Tube Test Set S-1487/ALM-23" this tested 4x150,4cx250 and others, no info on this but I may have the images from the original ebay listings.

Think we should follow Bob the Build and say yes we can.

Just looking for thoughts to give me no excuse not to get one built.
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Old 7th Feb 2020, 11:09 pm   #2
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Default Re: Transmitter valve tester

You could only make a tester for a closely related family of bottles, and another family would likely need a different tester. You'd need high power power supplies which would be a major expenditure if you wanted them to be variable.

Low power tests would weed out some seriously bad ones, but would not reliably indicate bottles worth using.

A lot of organisations which could, you would have thought, have afforded such a tester simply sent doubtful bottles back to Eimac for test, where, I believe, they went on individual to type test jigs.

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Old 8th Feb 2020, 5:32 pm   #3
SEG7RAL3
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Default Re: Transmitter valve tester

I can expect you would need different test sets if you were testing at RF, it should be possible to assemble a high power dc/ low frequency 50-1000hz tester and just connect the required valve base.
My AVO valve tester book list the set up for the 805 which is not that small a valve.
Power supplies are not a problem, have to hand or can build 0-3kv at 1a, 0-350v regulated supplies and heater transformers up to 6.3v 30A.
Have valve bases for most pa valves up to and including the 3cx1500 also should be possible to make others up.
I have attached the GE ham news, that lists testing valves up to the 813, also I have found the images of the ALM-23 the circuit diagram is poor be gives a basic idea.
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Old 17th Apr 2020, 11:25 am   #4
SEG7RAL3
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Default Re: Transmitter valve tester

At the moment collecting the bits is going a bit slow, the parts store/garage is not attached to home and not able to spend time there digging about for parts.
I have found the manual for the Hallicrafters Military Electron Tube Test Set, again the circuit diagram is not great, I plan to spend some time re-drawing it, I hope people will find it interesting.
Attached Files
File Type: pdf DTIC_AD0260370.pdf (2.73 MB, 99 views)
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Old 18th Apr 2020, 8:51 am   #5
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Default Re: Transmitter valve tester

The Avo valve tester books included some power valves, but the data was modified to be within the capabilities of their valve characteristic meters. The valves were not run up to their ratings, so a pass on the tester still left you wondering if you were due for a surprise when you ran a transmitter up to full power.

For high power stuff the failures tend to be a bit predictable. Things like 3-500Z tend to go soft due to pin/glass seals, as do the Eimac metal-ceramic jobs. Things in constant-on broadcast or shore station duty lose emission with time, and others left on hot standby can suffer cathode poisoning. So a DC emissions and a gas test ought to find most duds for you.

If you're not going to full RF, then DC testing will be as good as AF.

I've seen 8877s rejected because of dramatic changes in characteristic at full temperature due to mechanical trouble with the grid structure.

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Old 18th Apr 2020, 10:55 am   #6
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Default Re: Transmitter valve tester

Don't forget the interlock switch

Lawrence.
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Old 23rd May 2020, 4:16 pm   #7
claudiomas
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Default Re: Transmitter valve tester

The first thing is to power the heater only for one week to reduce gas and regenerate the cathode. Then you can test between cathode, tied grids and plate with low voltage PSU like a diode, do not go over plate max current.
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Old 24th May 2020, 3:03 pm   #8
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Default Re: Transmitter valve tester

Quote:
Originally Posted by claudiomas View Post
The first thing is to power the heater only for one week to reduce gas and regenerate the cathode.
I thought that would poison the cathode.
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