| Mort Caldwell |
I have a Hickok 539A tube tester which I have used for about 25 years. It recently quit working, with nothing but faint meter jitters when testing transconductance. Meter circuit is working ok, as it tests rectifier and all diode tubes very well.
I've been repairing tube radios, audio amps and test equipment for 50 years but this instrument has me stumped, even though I have the manual with schematic.. The schematic is very hard to follow, as it mostly involves Hickok's great tube pin switch setting design.
Since no oscillator circuit is in this instrument, it seems that it uses a 60 Hz grid input signal to test tube gain. I think that may be what is gone astray, although finding where it comes from and how it is applied to the grid eludes me.. The schematic has no labels of signal flow or notations whatsoever. However, all its lines are drawn very straight and pretty, per the early 1950's style...
Does anyone have a block diagram of signal flow in the 539A? This would greatly help my troubleshooting. Since 1950, I have never failed to repair anything electronic, but am going down in flames this time. Any help will be greatly appreciated!
Many thanks,
Mort Caldwell in Hurricane, West Virginia
Near Charleston |
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| dhaen |
| Thread moved to "Tubes", since there has been no response yet :cop: :) |
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| speaker |
Does the 539A use a lightbulb on the face for shorted tube protection? The 539C (ATT version) that I have does. If you inadvertently knock it loose from it's bayonet socket, the 539C will do exactly what you are describing.
speaker |
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| EC8010 |
| This diagram came from Alan Douglas's "Tube Testers and Classic Electronic Test Gear". |
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| GaryB |
| quote: | | I have a Hickok 539A tube tester which I have used for about 25 years. I've been repairing tube radios, audio amps and test equipment for 50 years but this instrument has me stumped, even though I have the manual with schematic.. The schematic is very hard to follow, as it mostly involves Hickok's great tube pin switch setting design. |
Mort,
I'm not sure if I can help, but there is a very nice site with details on an amazing number of tube testers. Take a look here:
http://www.jogis-roehrenbude.de/Roe-Pruefer.htm
Its in German, but you can find just about every tube tester imagineable with many lovely pictures and often useful documents such as manuals, schematics, and calibration instructions. If you page down to the 539C section, you'll find all the manuals. I know you have these so its not much help, but I thought it worth passing along to others.
---Gary |
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| Mort Caldwell |
Wow - now I believe I can fix my old Hickok 539A tube tester!
speaker - Many thanks for your idea on the #63 car bulb which is used as a fuse. It is ok, and glows brightly when a high-current tube is under test, even though the meter shows no test. Hickok had a great idea in using this bulb as a fuse! Sort of an indicator fuse..
EC8010 - Super thanks for posting Hickok's basic tube test circuit! Wow - this thing, er, wonderful instrument, tests tubes in a grounded-grid circuit. With this info, I think I can get it going. Maybe the 5 volt test input signal is not getting to the tube under test cathode.. That will be my first thing to check..
I've built many ham radio grounded grid, cathode input, linear amplifiers, from 200 to 2000 watts PEP input, but never dreamed that Hickok was doing this in their old 539A tester.. If I get stuck, I'll look up their patent on this circuit and read all about it.. Many thanks for including the patent number.
GaryB - Thanks for sending the link to tube tester site. I'll check it out first thing tomorrow. One nice thing about circuit schematics is that we speak a universal language with them. German, Japanese, English, Chinese, whatever - we can understand each others schematics.. Thanks to the common (almost) symbols we all use.
Gentlemen, many thanks again. I'll keep you posted about my repair of this grand old tube tester!
Mort |
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| odracir |
Hi, I'm living in Argentina I saw that you have the schematics and manual calibration of hickok 539a, can you sell me a copy of them?
thank you very much
Ricardo |
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| lpd |
I would recommend that you look at all solder joints and make sure you have good connections. Secondly did the unit work up until recently? Was there any weird conditions that followed? I would also check the switches. I recently worked on a 533 which wouldn't read on a gm test and it was a faulty connection on the switch itself. Lastly you can try here.....
this forum is designated to restoration of tube testers....
Tester Forum |
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