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 Post subject: Re: Hickok 752 Calibration
PostPosted: Sep Mon 06, 2021 6:31 pm 
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Joined: Aug Wed 31, 2011 11:23 pm
Posts: 545
Location: Tucson, AZ
I would check the voltages with the 83 tube and then the SS 83 design of your flavor. The zener reverse bias dropping voltage is selected to give the proper plate voltage when all other voltages are correct. Line voltage should not be set based on the plate voltage, depending on the Hickok tube tester model I set the line voltage to 100VAC (I use an external variac and have the rheostat set to full on). Then check all your other voltages and do the calibration.


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SS 83 Replacement Rectifier Fused no zeners.jpg
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 Post subject: Re: Hickok 752 Calibration
PostPosted: Sep Mon 06, 2021 8:40 pm 
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Joined: Oct Fri 19, 2018 8:30 pm
Posts: 110
My current setup is like the second diagram where zener and 1n4007 silver bands are facing away from each other. Except the zener is going to filament pins and 1n4007 are going to 2 and 3. My setup looks exactly like those 2 1n4007 in series. My tester calibration instructions are based on line being set with 150v then adjust R5 till line is on line test mark


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 Post subject: Re: Hickok 752 Calibration
PostPosted: Sep Mon 06, 2021 8:58 pm 
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Joined: Oct Fri 19, 2018 8:30 pm
Posts: 110
Filament voltage of 83 is 4.78v. When measuring 1 side it's 1.7v and other side is 2.9v. 5Y3 voltage is 4.27v. SS83 I get 5.37v. Unless your talking about plate voltage of 83 tube where the plate voltage with 83 is 150v cause calibrated it at 150v and all other voltages are within spec. when swapped with the modified SS83 its 149v and all other voltages havnt changed which tells me its like an actual 83 tube since dont have to re calibrate. If i was to switch zener diode back to how its suppose to be in the diagram plate voltage is 144v, low plate is way to low to use S4 button, other voltages are still same but if brought line test back up to 150v then other voltages are way to high and out of spec.


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 Post subject: Re: Hickok 752 Calibration
PostPosted: Sep Tue 07, 2021 3:00 am 
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Joined: Oct Fri 19, 2018 8:30 pm
Posts: 110
If i put SS83 on a variac set at same voltage in AC with one side of meter on one of the filament pins and other on 2 or 3 i get 1v DC. With 83 Tube doing same test get about 2v on one side and 2.7v on other. Im not really that worried the point of SS83 is to simulate a real 83 tube and also to not have to re calibrate tester so even though diode might be backwards the voltages tells me its working correctly. I could also put it back to way its suppose to be and leave line adjust alone and not worry about the Low plate being out of spec for being to low at 61v and plate voltage being 144v


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 Post subject: Re: Hickok 752 Calibration
PostPosted: Sep Tue 07, 2021 3:27 pm 
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Joined: Aug Wed 31, 2011 11:23 pm
Posts: 545
Location: Tucson, AZ
Line adjust is not determined by the plate voltage, it is based on 100VAC going to the transformers. Different Zener's have different reverse bias voltages, so one can use a value that works for the particular tube tester or a series diodes and resistors to get the plate voltage withing the 150V range. Whatever works as long as one understands that the other voltages must also measure in spec.


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 Post subject: Re: Hickok 752 Calibration
PostPosted: Sep Tue 07, 2021 4:08 pm 
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Joined: Oct Fri 19, 2018 8:30 pm
Posts: 110
Ok i understand, its not just plate voltage to calibrate line its the screen voltage also. instructions say if voltages are out of spec to adjust line adjust till voltages fall within the 150v +- 5v and 130v +- 3v then the adjustment of control R5 to bring line on line test mark.


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 Post subject: Re: Hickok 752 Calibration
PostPosted: Sep Tue 07, 2021 7:00 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 11097
Location: Sunbury, Ohio 43074
I think by now you could have bought a dozen 83 tubes ....... :mrgreen:

_________________
Preserving the hist. of electronics, one boat anchor at a time! :)
https://www.bbtvtestequipment.com


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 Post subject: Re: Hickok 752 Calibration
PostPosted: Sep Tue 07, 2021 8:07 pm 
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Joined: Oct Fri 19, 2018 8:30 pm
Posts: 110
Lol yah probably but not much available I'm going to use this ss83 after my 83 tube quits working. Which it will since it's not reading like a new 83. Rather go with something more stable and won't drift with age also with less load on transformer the 5Y3 gets more filament voltage which is good also. I'm not that worried using the zener backwards since fuse will protect it just not sure why in my application have to, I have some 5.1v zener diodes coming will see if .5v less will help be able to use the zener the proper direction


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 Post subject: Re: Hickok 752 Calibration
PostPosted: Sep Wed 08, 2021 1:32 am 
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Joined: Oct Fri 19, 2018 8:30 pm
Posts: 110
How would i measure the voltage drop?


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 Post subject: Re: Hickok 752 Calibration
PostPosted: Sep Fri 10, 2021 2:19 am 
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Joined: Oct Fri 19, 2018 8:30 pm
Posts: 110
installed new 5.1v zener diodes in proper way. Got simular results in voltage. But i did notice if i was to adjust the slider for R27 to bring low screen voltage down it also brought plate voltage down for ss83. So if i was to put original 83 back in and adjust R27 so low screen voltage is almost at upper edge of its spec. I could use the ss83 without adjusting anything. Also noticed that even though low plate and normal plate voltages are way to low the test results for 6V tubes and a 1R5 are same as with 83 tube except for output tubes they read to low. Easiest of course is to just have zener in backwards and dont have to adjust anything cause all voltages are perfect


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 Post subject: Re: Hickok 752 Calibration
PostPosted: Sep Fri 10, 2021 4:10 am 
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Joined: Aug Wed 31, 2011 11:23 pm
Posts: 545
Location: Tucson, AZ
The idea is to have a range of zeners, so you get the appropriate plate voltage. If you consider that an 83 tube is suppose to drop the plate voltage ~12V, then if you did not compensate for this using single diodes that the voltage would be high. If you start adding lower value resistors to the filaments and also in line with the diodes, then the value (voltage drop) of the zener needed is less. In my case with the first design noted, my plate voltage was 150 +/-1V with my variac set to exactly 100V. Also all my other voltages where within spec. So use whatever works.


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 Post subject: Re: Hickok 752 Calibration
PostPosted: Sep Fri 10, 2021 4:14 am 
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Joined: Oct Fri 19, 2018 8:30 pm
Posts: 110
Ah ok so basically not all testers will work with exact setup it's more of a baseline then if adjustments have to be made can change parts till it works properly. That makes sense so will use zener backwards idea since everything is perfect. Appreciate the help


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 Post subject: Re: Hickok 752 Calibration
PostPosted: Sep Fri 10, 2021 10:17 am 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 11097
Location: Sunbury, Ohio 43074
Quote:
then if adjustments have to be made can change parts till it works properly

You may never really know if it "works properly". Just put an 83 in and start using your tester :)

IMHO the entire SS replacement "solution" fixed a problem that was never there in the first place. There are plenty of NOS 83 tubes out there, and they are not expensive. Can you "make a tube tester better" ? Perhaps, but how much better, and to what end? It's still never going to be a precision instrument, just as tubes are not precision devices.

Ok, I"ve said it enuff times lol ... I suppose it's one of those personal decisions, but I've got enough to do without redesigning an instrument to do .. what exactly ... weed out bad tubes better than it could before ?

_________________
Preserving the hist. of electronics, one boat anchor at a time! :)
https://www.bbtvtestequipment.com


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