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Old 2nd Apr 2024, 3:39 pm   #1
Malloy1
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Default Looking for information on the Weston TV-4A/U

I just purchased a AN/USM-3A with a TV-4A/U tube tester and I'm looking for information on it. Seems to work (missing the short indicator bulb-on order and waiting for it-Hopefully I got the right bulb ordered-> GE NE-51).

Came across this post here:

https://www.vintage-radio.net/forum/...ad.php?t=27731

I did find a manual for a AN/USM-3 with a TV-4/U tube tester, and two different tube index (one original photo copy [looks like the correct one for a TV-4*] and one created by a gentleman name Nolan Lee [looks about the same but some differences]).

This manual looks close to the TV-4A/U - faceplace controls look the same but the tube sockets look different (the TV-4/U looks like 13 sockets and the TV-4A/U has 14 sockets). The manual also has a schematic, but since the tube sockets are slightly different, the schematic don't align up with the TV-4A/U.

Also, the TV-4A/U looks like there is nothing to adjust/calibrate.

I do have the Weston 777 downloaded. The tube index in the 777 manual looks like the photo copy of original I have.

Any insight on this unit would be appreciated, especially on how to check if the unit is functioning properly.

Paul
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Old 2nd Apr 2024, 5:26 pm   #2
Phil G4SPZ
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Default Re: Looking for information on the Weston TV-4A/U

Hi Paul, PM received.

The TV-4A/U tube emission checker is fundamentally very simple, as you will have seen from my equivalent circuit. To do your initial tests, you’ll need a 110 volt AC mains supply, a suitable connector to fit the mains input socket, and one or more known good valves. Plus the data book, which it sounds like you already have.

When first applying 110 volt mains, ensure that you can set the meter pointer to the mark.

Come back here when you’ve got that far!
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Old 3rd Apr 2024, 1:39 pm   #3
Malloy1
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Default Re: Looking for information on the Weston TV-4A/U

Thanks Phil-

It does power up and the line voltage can be adjusted to centering the needle to the middle (barely-the pot needs to be turned all the counter clockwise to center the needle). I used a 6AL5 valve for the line voltage check (valve lit up).

Going to wait until I get the short indicator bulbs before moving on. I do have a few known good valves I can test (6AL5, 12AU7, 12AX7) and some unknown condition valves from some old radios I have.

Been cleaning her up (she was a really dirty girl). Attached a couple of photos when I got her.

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A couple of the inside, which was very clean (looks like it was sprayed with Cosmoline).

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Old 5th Apr 2024, 2:46 pm   #4
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Default Re: Looking for information on the Weston TV-4A/U

Found somebody who had the manual with the schematics for the TV-4A/U. Some minor differences (values and number of valve sockets) between the TV-4/U and the TV-4A/U. Happy to share any of the stuff I dug up on these two units.

Still waiting on the short indicator bulbs. But it cleaned up pretty nice.

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Old 5th Apr 2024, 11:27 pm   #5
Malloy1
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Default Re: Looking for information on the Weston TV-4A/U

OK- Got the new short indicator bulbs.

Initial test with the bulb in place.

"Circuit Selector" set to "Line Short Check".

When toggle "E" set to "In", all other toggles are set to "Out", the short indicator bulb illuminates.

When toggle "H" set to "In", all other toggles are set to "Out", the short indicator bulb illuminates.

When toggle "E" and "H" set to "In", all other toggles are set to "Out", the short indicator bulb goes off.

When toggle "E" set to "In", all other toggles are set to "In" except "H", the short indicator bulb illuminates.

When toggle "H" set to "In", all other toggles are set to "In" except "E", the short indicator bulb illuminates.

When toggle "E" and "H" set to "In", all other toggles are set to "In", the short indicator bulb goes off.

Is this correct?

I'm going to start by going through all the checks in the TV-4A/U manual in the maintenance section 5 to see if anything is off.

Paul
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Old 8th Apr 2024, 2:47 pm   #6
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Default Re: Looking for information on the Weston TV-4A/U

So looking at the manual, this is not right. Appears to be a short somewhere.

This is supposedly some of the causes:

-Short in the Socket Panel Wiring
-Short at the Terminal Strip
-Short in the Wiring of the Circuit Selector Switch (S-101)
-Short at the Terminals on the Transformer (T-101)

I did start looking around inside and checked some of the resistors. Then closed up the unit and the neon lights at "E" and "H" didn't come on as it did as above post.

Since it appeared to be working correctly, I tested a couple of known valves (6AL5, 12AU7 and 12AX7), and they tested "Good", then I checked a couple of unknown valves (6BA6,6SC7, and 6T8). The 6BA6 tested "Bad", the 6SC7 tested "Good".

The 6T8 first tested in "Line Short Indicator" mode as "Shorted"(neon light came on), then I rechecked it in the "Short Indicator" mode, it show it was shorted. I moved on to the "Normal and Diode" mode. When I tested it in these modes, it showed the valve as "BAD", but when I checked again in the "Line Short Indicator" mode (no valves in the sockets), it showed again as "Shorted"(neon light came on).

I messed around again inside checking stuff and the unit again didn't show the short in the "E" and "H" check. But ever time after testing some tubes, it came back.

So, I got myself a copy of the test instructions (attached) for this fault and will check it out. Hopefully, it's not the transformer.

Side note: When I first opened up the unit, the plate lead wire (one of the two wires that come out the front panel) was rock hard and had several exposed sections of wire that looked like they were touching some of the socket leads. I removed both of the two wires, and replaced them with some nice 5000V lead wires.

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Old 8th Apr 2024, 6:58 pm   #7
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Default Re: Looking for information on the Weston TV-4A/U

It sounds like you are making considerable progress! Well done.

Mine had an (intermittent) dry joint on one of the switches, which only showed itself when testing a single particular type of valve, I forget which type. Those valves tested completely dead. After three or four examples of the same valve also tested ‘dead’, I started to suspect the tester. I think that particular valve had its cathode brought out to a different pin from most.

The soldered joint on the switch looked gleaming and perfect, but re-flowing the joint cured the fault.
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Old 9th Apr 2024, 2:12 pm   #8
Malloy1
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Default Re: Looking for information on the Weston TV-4A/U

Phil-

So, I went into the unit again last night and did a physical inspections of the connectors from the terminal strip to sockets. I lifted up some wires and straightened out some socket connectors. Nothing was obvious causing the short. After I did that, the "E/H" short disappeared. I tested all the valves again that I had done before. The "E/H" short problem didn't come back like before.

I'll see if the problem comes back. If it comes back, I'll start with reflowing all the joints from the terminal switch to the sockets. I would have done that anyway, but with all the sealant (Cosmoline/varnish-whatever is sprayed all over the inside) that is on all the solder joints and wires, it seems that it would take awhile to remove. I assume alcohol will dissolve the sealant.

It seems to work well. Not sure there is anything to set/calibrate on this thing. Do you have any suggestions?

Paul

BTW-The original Tube Index I found online seems to be for the TV-4/U, not the TV-4A/U, but the spreadsheet I found from Nolan Lee seems to be the right one for the TV-4A/U (not sure why they would be different?). I uploaded both of those files and the full Section 5 for the TV4A/U maintenance.

Weston TV4_U Tube Index_Optimized.pdf

tv-4A_U Tube Index.pdf

TV-4A Maintenance Sec5_Optimized.pdf
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Old 9th Apr 2024, 2:51 pm   #9
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Default Re: Looking for information on the Weston TV-4A/U

Hi Paul. Thanks for those scans, they’re excellent!

If the ‘known good’ valves test ‘good’ on the tester, it’s probably working properly. As you say, there is little to adjust or calibrate. Each time you close a switch (“IN”) you connect an electrode to an AC supply of around 30 volts. The grid, being closest to the cathode, gives the greatest amount of deflection on the meter, and this tends to swamp the effect created by the outer electrodes. Somewhere in the instructions it suggests backing-off the ‘tube selector’ control, which is basically a calibrated variable shunt, and throw IN just the switches corresponding to the outer electrodes, to enable you to see the meter deflection more easily.

These testers are quite versatile. I extended the number of sockets by making a pair of extension boxes carrying a wide variety of sockets, all wired pin-for-pin back to a B9A plug.

If the valve you want to test (or its US equivalent) is not in the valve data, as long as you know the pin-out and you can find a known good example of the valve, you can make a note of the setting on the tube selector that gives a ‘mid-green’ reading, and use that against which to judge the emission of other valves of the same type.

Note that of course the ‘capacity’ range is calibrated at 60Hz not 50Hz, but still usable if you allow for that.
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Old 9th Apr 2024, 3:54 pm   #10
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Default Re: Looking for information on the Weston TV-4A/U

I'll keep this in mind.

I'm in the US, so my power is in 50Hz. My voltage in my house is 128VAC, which is probably why my Line Voltage needs to be adjusted so much to CCW rotation. I found that checking the voltage at the valve socket, I can pinpoint the voltage better.

Here's the rest of the scans I got for the AN/USM-3A:

ANUSM-3A_Section_1_Optimized.pdf

USM-3A Injector.pdf

Best Regards,

Paul
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Old 9th Apr 2024, 10:10 pm   #11
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Default Re: Looking for information on the Weston TV-4A/U

Sorry, Paul. I glanced at your location, saw ‘Brighton’ and never read any further!

Your mains supply will be 60Hz of course. I run my TV-4A/U from a 120-volt step-down transformer and the line voltage control is pretty-well midships.
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