Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently May Fri 29, 2020 5:56 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 16 posts ] 
Author Message
 Post subject: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Sat 04, 2020 8:31 am 
Member

Joined: Feb Wed 07, 2018 6:52 pm
Posts: 724
Location: Stone Mountain, GA
Picked up a TV-10 off ebay. Had a bad pot that has been replaced

It seems to work ok.

However, looking at the setup charts the "P" switch seems to always be connected to G1. Have checked 4 different tubes, all have G1 as the plate in the setup. Plate is grounded to K.

If I swap the P pin for the real plate, I get a very low reading, like 5%.

Can't find docs on the TV-10, just the TV-11. There are differences in values. TV11 says meter is 5ma/10 ohms and I measure 6.4ma/20 ohms full scale. There is some thin wire bundled in heat shrink as a shunt on the meter. The meter itself is 500ua.

I may redo the resistor values for the TV-11 and add the extra cap. Then calibrate the meter for 5ma.

I don't like the idea of running several ma through the grid of the tube when the max plate current is near the same value.

Yes it will test tubes but I would expect it to test the plate. I guess this is a hack as the voltage is too low to get enough plate current.

_________________
Scott.
Powered by infinite improbability drive.


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Sat 04, 2020 5:01 pm 
Member

Joined: Jun Sat 09, 2007 8:14 am
Posts: 4137
Location: Florida
Most emission testers tie all the elements together and run tubes as diodes. Since the grid is closest to the cathode it takes most of the current. The tester is supposed to limit the current so as not to destroy the tube.

RRM


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Sat 04, 2020 5:09 pm 
Member

Joined: Feb Wed 07, 2018 6:52 pm
Posts: 724
Location: Stone Mountain, GA
My PACO 660 ties the grids to the plate like most testers.

Just find it odd the plate is tied to the cathode in this tester.

_________________
Scott.
Powered by infinite improbability drive.


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Sun 05, 2020 7:03 pm 
Member

Joined: Feb Wed 07, 2018 6:52 pm
Posts: 724
Location: Stone Mountain, GA
Well, I wired it up as the TV-11 schematic.

Needed to turn up the line adjust cal pot and rheostat all the way up to get to the line center. The needle vibrates some.

I think there are errors on the schematic. The added 0.5uf cap does not seem right. I also think the condenser test jack needs to be on the other side of the rectifier. as the Neon bulb would have to have DC to test capacitors.

_________________
Scott.
Powered by infinite improbability drive.


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Sun 05, 2020 7:44 pm 
Member

Joined: Jun Sat 15, 2019 7:43 pm
Posts: 657
I really don't understand what you are trying to achieve, you had a working tester and now you want to modify it because you feel it was not designed properly. Thousands of testers were made with this design and they all worked fine for what they were designed. They were designed to measure cathode emission by applying a limited current between the cathode and any other element or elements.
The rectifier is only for the line adjust function, it does not supply any voltage for the shorts or condenser test. If you study and understand the schematic you will see this. There are no errors in the schematic.

DM


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Sun 05, 2020 8:16 pm 
Member

Joined: Feb Wed 07, 2018 6:52 pm
Posts: 724
Location: Stone Mountain, GA
The results did not seem right, I get a reading of just into good on almost any tube.

There is no data on the TV-10. The shorts test seemed way too sensitive. Since there is a schematic for the TV-11 and a way to calibrate the voltage, I decided the change the resistors to match the TV-11.

It was minor changes to the resistors and recalibrating the meter to 5ma. Now test results seem to match my PACO tester. Just the line adjust seems off.

Well: put a scope on the meter:
Attachment:
paco1.jpg
paco1.jpg [ 209.79 KiB | Viewed 290 times ]


Seems the selenium is breaking down, no wonder meter vibrated.

Replaced with 1N4004:
Attachment:
paco2.jpg
paco2.jpg [ 191.01 KiB | Viewed 290 times ]


That is a rectified signal. Now can calibrate the line voltage. Still the 0.5 cap gives an odd waveform and I don't see how the condenser test could work as shown on the schematic.

_________________
Scott.
Powered by infinite improbability drive.


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Sun 05, 2020 8:21 pm 
Member

Joined: Feb Wed 07, 2018 6:52 pm
Posts: 724
Location: Stone Mountain, GA
I guess I thought the condenser test would test using DC. The manual says the bulb will flash once, as if charging up. As drawn, it feeds AC to the condenser then through the neon bulb. It would light except for very small caps.

Routing the rectifier to the COND terminal will feed DC. Any leakage would cause the bulb to turn on or flash. This makes sens the need to add the 0.5uf cap to have a constant DC for condenser testing (TV10 does not have feature.).

_________________
Scott.
Powered by infinite improbability drive.


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Sun 05, 2020 8:58 pm 
Member

Joined: Jun Sat 09, 2007 8:14 am
Posts: 4137
Location: Florida
SHenion wrote:
....... Just the line adjust seems off........


The way to fix this is to rework the rectifier circuit until the filament voltages are about right when the line adjust is set with a tube inserted, say 6.5 or so with a 6L6 or some other tube that pulls about the same filament current. You won't be able to get all the other voltages to track exactly but this should get things in the right ball park.

The way I do this is to set the line adjust pot to the mid point and then tweak things until I get the desired filament voltage.

Remember that the tube charts were made with bogey tubes.

RRM


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Sun 05, 2020 9:25 pm 
Member

Joined: Feb Wed 07, 2018 6:52 pm
Posts: 724
Location: Stone Mountain, GA
Retired Radio Man wrote:
The way I do this is to set the line adjust pot to the mid point and then tweak things until I get the desired filament voltage.

Remember that the tube charts were made with bogey tubes.

RRM


Thats how I adjusted my PACO 660 that there is little calibration info. Just did the same on the TV-10. As it was, the line adjust barely moved the meter; as voltage went up. meter went down. Fix the bad rectifier an now have normal operation.

_________________
Scott.
Powered by infinite improbability drive.


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Sun 05, 2020 10:22 pm 
Member

Joined: Jun Sat 09, 2007 8:14 am
Posts: 4137
Location: Florida
I looked at the TV-11 manual on the web. It looks as if they decided to make tests as simple and quick as possible by requiring only the minimum of switch settings. This checks emission by only using the cathode and the grid.

If you are skeptical of this method, here's something to try. Set up your PACO normally and read a tube. Then set it up with the plate out of the circuit and compare the readings. On my EICO 625 the readings are almost exactly the same.

Another check would be to compare TV-10 readings with and without the plate. All this requires is one more switch thrown.

RRM


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Sun 05, 2020 10:44 pm 
Member

Joined: Feb Wed 07, 2018 6:52 pm
Posts: 724
Location: Stone Mountain, GA
6SA7

with P on G1 - reads 76
with P on plate - reads 0
with P on G2 - reads 57
with P on G1+G2+P = 78

_________________
Scott.
Powered by infinite improbability drive.


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Mon 06, 2020 1:23 am 
Member

Joined: Jun Sat 09, 2007 8:14 am
Posts: 4137
Location: Florida
SHenion wrote:
6SA7

with P on G1 - reads 76
with P on plate - reads 0
with P on G2 - reads 57
with P on G1+G2+P = 78


Yep, that all makes sense. Using only G1 is almost the same as all elements. That's to be expected since G1 is closest to the cathode.

RRM


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Mon 06, 2020 4:28 pm 
Member

Joined: Jun Fri 19, 2009 6:34 pm
Posts: 9492
Location: Long Island NY
The grids have to be connected to something. If they are left open circuit, they accumulate a negative charge due to the electron stream which then cuts off the tube and gives a lower or zero meter reading. This effect is most noticeable when the first grid is open, since it has the most influence on the electron stream. The subsequent grids have less influence but it can still be noticed if they are opened.

In most emission tube testers the grids are tied to the plate, but back in the early 1940s a company called Radiotechnic Labs (RTL) made a series of tube testers which tied the grids to the cathode. They claimed this was a big innovation. It gives the same results as connecting the grids to the plate for emission testing. However, applying high voltages to the grids of tubes, as happens when they are connected to the plates in conventional testers, can cause debris in tubes to break down and form shorts or low resistance leakage paths between the elements. Such tubes might have lasted a while longer if they were not tested that way. By connecting the grids to the cathode, the voltages are the same and such breakdowns are avoided.

So it sounds like Superior was trying to do something similar in the TV-10, following the method used by RTL to apply voltages in a manner that was safer for old tubes with high hours on them which can be expected to have lots of cathode debris in them.

_________________
"Hell, there are no rules here--we're trying to accomplish something!"

Thomas A. Edison


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Mon 06, 2020 7:48 pm 
Member

Joined: Jun Sat 09, 2007 8:14 am
Posts: 4137
Location: Florida
Chris108 wrote:
......

So it sounds like Superior was trying to do something similar in the TV-10, following the method used by RTL to apply voltages in a manner that was safer for old tubes with high hours on them which can be expected to have lots of cathode debris in them.


I'm not sure what you mean here. The TV-10 test connects all the elements to the cathode except the control grid, which takes all the current.

RRM


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Mon 06, 2020 8:39 pm 
Member

Joined: Jun Fri 19, 2009 6:34 pm
Posts: 9492
Location: Long Island NY
If all the current is between the cathode and the grid, then grounding the plate would repel electrons and no current would flow to it. But if they were following the RTL "school" (to use the term loosely), they might have thought that it would prevent leakage paths from forming between grid to plate. Otherwise it wouldn't seem to serve much purpose.

_________________
"Hell, there are no rules here--we're trying to accomplish something!"

Thomas A. Edison


Top
 Profile  
 
 Post subject: Re: Superior Inst. Co. TV-10/11 oddness.
PostPosted: Apr Mon 06, 2020 9:13 pm 
Member

Joined: Jun Sat 09, 2007 8:14 am
Posts: 4137
Location: Florida
With the setup the TV-10 uses there isn't any current to the plate and if the plate is also connected there is very little added (see the chart the OP posted a few posts earlier). I noticed this same characteristic on my EICO 625 one time when I goofed and left the plate grounded.

Why superior decided to set things up this way we'll probably never know. My guess is that they wanted to make tests quick by only requiring the minimum of switch settings, thinking this could be a big help if the service guy needed to check several tubes at a time, especially while on a call.

I vaguely remember picking up a tiny Radio Shack tester at a garage sale that did something similar but I don't remember exactly what and it was soon junked.

RRM


Top
 Profile  
 
Post New Topic Post Reply  [ 16 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: Findm-Keepm, paronaram and 11 guests



Search for:
Jump to:  


































-->


Privacy Policy :: Powered by phpBB