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 Tube tester Power Supplies

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Cliff Jones
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Join date : 2010-11-22

PostSubject: Re: Tube tester Power Supplies   August 2nd 2018, 8:54 am

This section was from another topic because it became more pertinent to Test equipment.
I will see how I can modify the forum to give notice in the topic when it is moved.

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Rod Clay
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Join date : 2018-08-01

PostSubject: Tube tester Power Supplies   August 1st 2018, 9:16 pm

FrankB

Thanks for the post. I don't think O'Reilly carries [You must be registered and logged in to see this link.] bulbs any more. I just did a search there and couldn't find any. They did have some # 63 bulbs which are similar but at about half the current rating are not suitable. There are some sellers on eBay that have # 81 (new production-not vintage) at reasonable prices in boxes of (10). Yes. I am going to try to get some real 83 tubes. They are a bit expensive though. Not in production anymore. Yes. I did build the SS replacement in an old 4 pin tube base. Actually, I used the base from the bad 83 tube. It had an open filament. I think this 83 tube went bad many years ago. The tester stopped working i.e. would not test any amplifying type tubes (as received it would only test rectifiers) and the original owner probably put the tester away in storage or something like that. It really looks nice-the leather handle is like new. They are usually shabby on these old testers. As you may know, the 83 is a mercury vapor rectifier tube and has a low inherent voltage drop nominally 15 volts but may vary from 12-15 volts. I learned some of this recently from posts by Mike Higgins on a recent AntiqueRadios forum. I had thought for years that these types of tubes had a constant 15V drop as given in the tube manuals but Mike showed they can vary. I knew they could be "noisy" and generate RFI and could be prone to parasitic oscillations. But we had to put up with that in the old days. The parasitics could supposedly be tamed down by inserting small RF chokes in the plate leads of the tubes especially with the 866A. I have seen examples of this in old 866 power supplies. Due to the 83 tube's low voltage drop, I have found that a large dropping resistor is not required (especially in Hickok's special tube tester circuit) although some builders will insert a Zener diode of up to 15V in series with (2) 1000V rectifier diodes for each half of the rectifier (with the required proper polarity) to make up their (4) pin SS replacement. These builders are concerned about getting their SS replacement to have a similar voltage drop to an 83. Of course (2) silicon diodes in series will have a drop of about 1.5V to start with. There is some controversy about this and there have been many posts back and forth I understand although I just joined AntiqueRadios. Some employ a center tapped resister circuit for the internal filament connections in these replacements or conversions as we used to call it. I don't think this resistor network is necessary and have not employed it. So my SS replacement is very simple. As for the internal line voltage, it is set by a rheostat to the usual recommended setting (line test in most testers) so the tester's power transformer does not see modern high line voltage. The Navy war time Hickok tube testers employed a separate AC voltmeter mounted in the upper left corner. The proper setting for test on these testers is to adjust the internal line voltage to 93V (with the tube under test plugged in) on the external meter.  I like the setup and mostly have worked with older tubes in the past but I am thinking about getting another tester for 7 and 9 pin miniature tubes. I used to have a Navy TV-7D which was very good for this purpose. I also had a TV-10 that I liked. Well, I'd say the Hickok 540 tester is now working very well with the SS 83 substitute. Years ago I had another WWII vintage tester the Hickok 550X which is similar to the 540 except it has a multimeter feature. This 550X was prone to overheating of the power transformer if left on for any length of time. I tried to improve the ventilation and finally came on the idea of eliminating the 83 tube and its 15W filament load on the power transformer by SS the 83 rectifier. I did this by building the rectifier in an old tube base back then as I did just recently for the Hickok 540. Well, the SS 83 in the old 550X did help to cool it down and I used it for years that way. I saw no effect on tube test results. I made tests with various types of tubes to confirm this. Well, luckily the Hickok 540 that I have now does not run hot. I ran it for several days-perhaps a couple of weeks in fact to dry it out. As received it had a strong musty odor-something the seller didn't mention. Now it is much less noticeable and acceptable to be around and use. Well, that may be more than you wanted to hear-when I get going I can really crank it out. Edit it down if necessary. 
73, Rod (DeWitt) N4QNX
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FrankB
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PostSubject: Re: Tube tester Power Supplies   August 1st 2018, 7:41 pm

Rod,

Thanks for joining our little group.

If you have anything of interest to post, please do. We all can benefit.
 I for one, was unaware that supplier had merged with the "big guys".

 You will need to add a series resistor to the diodes, as the B+ will go up a lot, and don't forget to take into account the higher line voltages we have now days too.
 I would  suggest you mount the diodes (Please read my blurb in the forum about diode lead length) and resistor to a 4 pin tube socket for ease of changing back. You will need to likely recalibrate the tester after the mod too.

 The [You must be registered and logged in to see this link.] lamp is available from O'reillys auto parts, at least that is where I got mine. Buy them by the box, as they are really cheaper that way. IIRC, I got a box for less than the cost of 2 in the bubble packaging. This was about 10 yrs back though.

 Personally, I would really try to find an 83 tube. The tester I had that had been previously modified by the other owner, really didn't like the diode mod. It didn't really want to work very well. I might have an 83 around, but no idea where in the tube trailer I put it. (Ask Cliff- he has seen it!) Shocked >If I run across it in the near future, I will let you know.<
But who knows what else the guy screwed up.
73'
Frank
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Rod Clay
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PostSubject: Re: Tube tester Power Supplies   August 1st 2018, 12:09 pm

All very interesting. I never worked at a parts house but I used to frequent them looking for various items. That and surplus radio stores and hamfests. We had an in-house supply setup for getting parts and supplies for projects somewhat similar to what was described elsewhere when I worked at Raytheon Semiconductor-Mountain View, CA years ago while I was an R&D technician there and later as an engineer. Local parts Houses seem to have gone away in a lot of areas. I used to get parts and Stuff at bargain prices from MCM Electronics first by phone and later by online shopping but they went away recently when they folded into Newark Electronics (as Newark14). I have a box of bargain electrolytic caps I got from them here about a year before the change. Now I don't know what they have if anything anymore. I miss them though. There was another place in Brooklyn, NYC that I used to get TV repair parts from when I was doing tv repair-bet they're gone now too. I recently had my own parts "what is it" moment when I went to our local Williams TV Repair shop here in my small city of Oroville, CA hoping to try and get a few parts to get a WWII vintage Hickok 540 tube tester going that I recently picked up. It came with a bad 83 rectifier tube in it. I didn't have a spare 83 and was anxious to get it going as the substitute 80 tube I put in wasn't an ideal replacement. Well, I went inside to the tv shop owner and tried to explain to him what I needed to fix up an old tube tester. It was a little comical as I explained that I needed some rectifier diodes to make a SS replacement for the 83 and also I could use a number 81 miniature lamp (bulb) that Hickok used for a panel fuse as you may well know. Well, after a bit I introduced myself and had a good time there talking with the owner about servicing and the parts business. The visit ended with the 2nd generation owner (now 70) telling me to come back with a wheel barrow for a load of stuff when the place finally closes down. 73, Rod ex-N4QNX hope to be reactivated soon.
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