Wire wound Resistor??HELP

[dumbassbob]

I have a real old tube tester,one of the small in a wood box,There is a red thing in side it started to fall apart... the leads came off going to the push button...Can I use a regular resistor insted I cant solder the leads back on, I put a VOM accross it and got a reading of 819 Ohms,all the red "Sand" has come off and I see wire wraped around metal... so I put the VOM leads at each end and got that number...

[Enzo]

Well, it WAS a regular resistor, just back then they looked different. This is a wire wound resistor. These days those come in the rectangular cement shape. They also come in the ceramic cylinder form, but we don;t see those much in amps these days. This isn't high tech, so yes, a regular resistor works. But it is a power resistor. depending on size, 10-15-20-25 watts. SO don;t just stick a half watt one in there.

[mozz]

Make and model of the tube tester? Most schematics are out there.

[J M Fahey]

Or at least a picture or two.

Iīm constantly amazed about how high do people consider our divinatory skills.

[dumbassbob]

I was able to fix it..I broke the coil wire and I found the two leads and soldered it... Then I cleaned off the two leads that broke only had about 10th of a inch to grab on to,I used some leads from a resistor and was able to resolder them on....I was getting different measurement with my VOM 29.5Mohm ...6.5Mohn...But when I put it in it worked...The Tube Tester is called a EMC model 301 Electronic Measurement Corp NYC ..The "sand" covered wire wound resister goes from the Control 0-100 to the press for test 30 for 12ax7 and 35 for 6l6gc el34 I have never found a schematic for it..All it is good for is to see if a tube is close to those numbers...or how much I have worn a tube down....If I didnt
fix it I would never have found the right resistor...Mr Tube Tester starts at $150..Just to send it to him..I only paid $25.00 for this....Thanks Enzo

[Jazz P Bass]

Is the sand still surrounding the resistor element?

Here are a few EMC schematics:

200 Schematic.pdf

205 Schematic.pdf

213 Schematic.pdf

215 Schematic.pdf

[J M Fahey]

I broke the coil wire and I found the two leads and soldered it... ....I was getting different measurement with my VOM 29.5Mohm ...6.5Mohn...But when I put it in it worked...

You havenīt actually *soldered* those twisted wires, even less through 60 years of surface oxide, nichrome wire simply canīt be soldered with tin-lead solder anyway .
You just twisted the (oxidized) surfaces together and a ball of solder cooled around them, without actually touching the surface,
Thatīs why your multimeter reads Megohms around that poor connection.
Now if you apply 120 or more volts across that gap, sometimes a spark will jump and make contact ... it simply canīt be trusted.
Get a new resistor, same specs, and replace it.

Check page 41 https://books.google.com.ar/books?id...%20NYC&f=false

[dumbassbob]

The sand came off on one side I got some deoxit on it I think that might of helped to messed it up Also I live at the beach,and the salt water and afternoon winds get into everything..

[Chuck H]

Juan has it right. The erroneous reading of the resistor value after "fixing" it are something to be concerned about for certain. Especially since it read consistently in a reasonable value BEFORE the "repair". Just because the tester "works" doesn't mean it's working correctly. Just that it's offering test results. I'd bet there are a dozen parts you could straight up REMOVE from it and it would still give a reading of some kind. The resistor is badly compromised, why would you trust it when replacing it WAS easier than fixing it.?. Please DO attempt to look at available schems of similar circuits, determine a likely value and rating based on circuit use, your original reading and schematic reference and REPLACE THE DAMNED THING.

[J M Fahey]

The sand came off on one side I got some deoxit on it I think that might of helped to messed it up Also I live at the beach,and the salt water and afternoon winds get into everything..

True,salty wind definitely does not help, but anyway solder flux does not work on Nichrome wire, itīs a Chemistry problem.
That wire is either crimped (I make custom resistors by winding its ends around eyelets which then are crimped to a piece of insulating material) or industrially resistance soldered so best option is to plain replace it.

IF sand covered it might be a "fusistor", power resistors which were *designed* to blow under overload.
Once very popular on TVs.

Antique Radio Forums ? View topic - TV fuse resistors?

Primarily used as current-limiters in TVs that had selenium rectifiers.

[dumbassbob]

It is made with that type of red sand Each end goes to a pot lug...I wish I had the schematic for the EMC 301.... I tried a few resistors I have none of them worked,The only thing that moved the meater was a plain wire,but it "Pegged" it...

[J M Fahey]

Ok, then that means itīs a low value resistor.
Whatīs the pot value?
What does the pot adjust: filament voltage?
Is it a variable cathode resistor for power tubes?
Short ago somebody was asking at DIY Audio about a 60`s variable power supply.
It was *very*crude, it had a 24V secondary feeding a power rheostat which fed a half wave selenium rectifier and an inadequate value electrolytic, OP worried about its poor regulation under load ... no kidding.
You might have something similar.

[Chuck H]

I tried a few resistors I have none of them worked,..

Can you be specific about what values you tried?

The only thing that moved the meater was a plain wire,but it "Pegged" it...

Well 819 ohms isn't many ohms. And as Juan speculated it may be appropriate for a variable cathode circuit. If that is the case a straight wire may have "pegged" the meter (though we don't know the context) because of excessive current in the tube under test. Resistor values in k ranges may not allow enough current to register. If you haven't tried something as low as 820 ohms then you haven't actually made a reasonable replacement attempt.

You mentioned that you couldn't get a good reading on the resistor after the repair. But if it's "working" in the circuit then you should be able to test it's value in circuit and get a steady reading. This may require some figuring to determine it's value in circuit context.

[Chuck H]

Here are some pics. Bob, is this your tester?





I pulled these from a thread where the poster thought he could make out 90 on that sand resistor. Seems unlikely a 90 ohm resistor would drift to 819 ohms and still work in the unit so I'll speculate it could be a 900 ohm resistor.

[g1]

820 is a common stock value resistor.
What is the function (and value) of the pot that it is in series with? What is the function of the switch at the other end of it?