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#1
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Knight Tube Tester Mystery ????
Hi Folks,
I posted this on the Knight Bulletin Board 10 days ago but got no response. I'm hoping some of the tube tester experts here can help out. I picked up a Knight tube tester recently that has no model number. It appears to be almost identical to the "600" series with one exception: there are only 14 filament voltages instead of the usual 16 that are present on the 600. The "missing" filament voltages are 3.0 and 4.2 volts. The filament voltage selector goes from 2.5 to 5.0 volts. The roll chart has been updated but it's for a 600A, so I don't believe it's quite right, though it may be the only replacement available. Of course, any settings for 3 and 4.2 volt tubes are irrelevant for this tester. Otherwise, it is in excellent condition and works great. It appears to be modeled on the Heathkit TC-2 emission tester. The front panel is a light olive/gray with white text. The knobs and dials are dark brown. The case is a very dark green color. Is anyone familiar with this model? Could you identify what the model number is so that I can search for a manual and/or verify if the roll chart has the proper tube data? I want to sell this tester but I want to be sure that I represent it accurately when I list it on ebay. I would sincerely appreciate any help. Thanks. Regards, Tim |
#2
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Hi,
The early Knight testers were identified by their catalog number. As far as I know, they all use the same data, pretty close if not identical to the Heath TC data. There's hardly any point looking for a manual, unless you can download one free, and likewise the charts, because you'll never make your expenses back on the sales price. 73, Alan |
#3
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Alan,
Thanks for the response. I have downloaded a Model 600 manual from BAMA and the functions and schematic appear to be correct (with the exception of the 3 and 4.2 volt taps on the filament transformer). The updated 600A tube chart in the tester is dated 1965 so it has settings for later tubes like 7868, 7591, 6DJ8, etc. What I find so unusual is the missing filament voltages. I've seen numerous pictures of the "600" style tester on ebay and in other places but I have yet to see one with only 14 filament voltage settings. In every other way, it looks identical to the 50's style Knight kit tester (which is essentially identical to the 50's Heathkit TC-2). My best guess, based on your feedback and some additional web surfing, is that it may be a Model # 83YX142 or 83YX143. But I'm unable to find any pictures or literature to confirm this assumption. As always Alan, I sincerely appreciate your wealth of knowledge and your willingness to share it. Thanks again. Regards, Tim Alan Douglas adouglasatgis.net wrote in message . .. Hi, The early Knight testers were identified by their catalog number. As far as I know, they all use the same data, pretty close if not identical to the Heath TC data. There's hardly any point looking for a manual, unless you can download one free, and likewise the charts, because you'll never make your expenses back on the sales price. 73, Alan |
#4
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Hi,
Tim wrote: My best guess, based on your feedback and some additional web surfing, is that it may be a Model # 83YX142 or 83YX143. But I'm unable to find any pictures or literature to confirm this assumption. The 142 was portable; the 143 was a counter-top model without a lid. They were renamed to "600" in the 1960 catalog. This 142/143 first appeared in 1955 and I expect you have an early one. 73, Alan |
#5
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Alan Douglas adouglasatgis.net wrote in message . ..
Hi, Tim wrote: My best guess, based on your feedback and some additional web surfing, is that it may be a Model # 83YX142 or 83YX143. But I'm unable to find any pictures or literature to confirm this assumption. The 142 was portable; the 143 was a counter-top model without a lid. They were renamed to "600" in the 1960 catalog. This 142/143 first appeared in 1955 and I expect you have an early one. 73, Alan As a point of reference on the Knight 600 series, I was told by a Triplett engineer (Bluffton, OH) in the early 1960's that the three major kit companies Heath, Knight, and EICO received permission approx. late 1953 or early 1954 (not sure of the date) to use the circuit design from their early 3413, as Triplett was about ready to release their model 3413A by then. The early 3413 was similar to their previous (late) 2413 but with the U and C busses reversed, and with an improved 626 panel meter, and other small improvements. As far as I know, the early Triplett model 3413 predated any of the kit models. The nice thing for us is that the Knight 600, Eico 625/628, Heath TC/IT, and Triplett 3413/3413A/3413B data charts are interchangeable, as long as one converts Heath letters to numbers and be aware that some models have ten toggles, and some have twelve or thirteen toggle switches on the three busses(be careful of the "cap" switch assignment), and Heath eliminated the letter "I". Triplett models 3413A&B had a redesigned circuit, but their charts were still interchangeable with the 3413, by design. (3414 charts are different.) Very late Knight 600 chart formats eliminated listing the plate, suppressor, and screens as "Up", but retained the most significant one, the control grid for the Up toggle; which also simplified their Gas test, as one didn't have to look up the control grid in a tube manual any more. These late Knight 600 charts also work on all of these testers. For those who own only a Triplett model 2413/3212; a simple modification can be made so it can use all of these data charts, so you don't have to buy another emission tester, just to test your tubes. Install a miniature (~$4.50 at Radio Shack) DPDT toggle switch as a buss reversal for the "U" and "C" busses, so it will function either as a model 2413 or 3413. It's also a good idea to go through the entire circuit to calibrate the (neon) short, Line Adjust, and the four "A" ckt. (Eico "Selector") ranges, as the old carbon comp. resistors, panel meter magnets, and solid (CuO, Se, Ge, etc.) rectifiers often aged or failed, and some of the kits weren't calibrated from the start. Fred Scoles, |
#6
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Fred,
As a point of reference on the Knight 600 series, I was told by a Triplett engineer (Bluffton, OH) in the early 1960's that the three major kit companies Heath, Knight, and EICO received permission approx. late 1953 or early 1954 (not sure of the date) to use the circuit design from their early 3413, as Triplett was about ready to release their model 3413A by then. Eureka! I found some pics of the Triplett 3413 and lo and behold, it had 14 filament voltages (no 3v or 4.2v) like my rather unique Knight tester. I think I can deduct from your message and Alan's last message that this is the earliest model 142, based on the Triplett design. I'm wondering if the first Heathkit TC-1 models also had 14 filament voltages like the 3413. Apparently, both Knight and Heath began to use different filament transformers shortly thereafter, adding the additional 3 and 4.2 volt taps to the design. Many thanks to you both. Mystery solved! Regards, Tim Gregoire |
#7
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Hi,
Fred wrote: As a point of reference on the Knight 600 series, I was told by a Triplett engineer (Bluffton, OH) in the early 1960's that the three major kit companies Heath, Knight, and EICO received permission approx. late 1953 or early 1954 (not sure of the date) to use the circuit design from their early 3413, as Triplett was about ready to release their model 3413A by then. That's very useful information. Do you mind if I repost that to the radio-collecting newsgroup, rec.antiques.radio+phono? I expect that what the kit outfits really wanted, was the test information, as none of them could possibly have afforded to buy a half-dozen samples of all tubes being produced and assign an employee to go through all of them and come up with test data. This also explains why all the kits used the same circuit. 73, Alan |
#8
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Yes, it's OK to repost the information. Thanks, Fred
Alan Douglas adouglasatgis.net wrote in message . .. Hi, Fred wrote: As a point of reference on the Knight 600 series, I was told by a Triplett engineer (Bluffton, OH) in the early 1960's that the three major kit companies Heath, Knight, and EICO received permission approx. late 1953 or early 1954 (not sure of the date) to use the circuit design from their early 3413, as Triplett was about ready to release their model 3413A by then. That's very useful information. Do you mind if I repost that to the radio-collecting newsgroup, rec.antiques.radio+phono? I expect that what the kit outfits really wanted, was the test information, as none of them could possibly have afforded to buy a half-dozen samples of all tubes being produced and assign an employee to go through all of them and come up with test data. This also explains why all the kits used the same circuit. 73, Alan |
#9
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#10
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Some folks are concerned that their older testers (Knight, etc.) don't
have as many filament voltage taps, and they cannot quite reach a listed filament/heater voltage. This procedure might help; and you won't have to buy or change any parts. There is usually a way to obtain the desired filament voltage when your particular model tester does not have a tap/switch position for the exact voltage that is listed on the data chart. First,set the Line Adj. Pot. at its lowest setting (counterclockwise, so the tube's filament/cathode won't get damaged); then set the fil. v. sw. to the closest setting available, with the tube under test installed, and all the other tester controls set properly. Install your good AC Voltmeter (DMM, etc.) probes to any D (down buss), and C (center buss) vacant tube socket connectors to read the actual filament voltage being applied. Then, slowly increase the Line Adj. Pot. until your Voltmeter reads the proper filament voltage. Since you are selecting a fil. voltage that isn't listed on the switch taps, a Line Check probably won't place the tester's meter at the mid-scale point; that doesn't matter as long as you've applied the correct voltage to the filament. If you can't reach the desired fil. v. in this way, then you might try by starting with a different fil. tap. switch setting to achieve the correct final voltage. One doesn't need to install a different transformer, or put up with taking readings at the wrong fil. voltage by doing this. Remember that most tubes will operate fine at a filament voltage as low as about 85 percent below nominal, but fil. v. shouldn't be greater than around 5 percent above nominal (listed), otherwise filament/cathode/or grid damage might result. Fred |
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