2W 4M resistors....

[TaDa]

I was lucky enough to get a retired TV repair man's unused stock - mostly resistors.

I've been trying to whittle the selection down to a useful set but I've been surprised at the large quantity of high power (>2W - 20mm long 9mm diameter) high resistance resistors.

What use could anyone really have for a 2W 4M resistor?

Alright, I know old CRTs had high voltages - but I'd need to be dropping nearly 3000V across one of these resistors to make it work - Maybe 1500v in a useable part of the resistor's capability. Did old CRT's do this sort of thing?

I can't really imagine trying to light an LED from the rectified output of a microwave transformer

So am I likely to need any of these higher power resistors?

Ha ha ha - I just found an 8M one!!!

Wow! I just found one that looks like 82M! Really? Grey Red Blue Gold - my Fluke ohm meter says its 1.9M - I think it maxes out

 

[kubeek]

Not unless you happen to need a 4M resistor. Maybe in a divider to measure high voltage that power rating could come handy.

 

[TaDa]

Cheers!

True - if I need a 4M 2W resistor - I would definitely want one

I don't see myself wanting to measure high voltages either - they kinda scare me - I scared myself somewhat when I made my multi capacitor ladder and that barely made it over 2kv

I reckon I'll keep the low wattage ones and bin the rest (or sell them on ebay maybe!)

Or can anyone think of another scenario where I'd need them?

 

[RichTheDude]

Put them on ebay, high value resistors are more commonly used in Valve gear.

 

[TaDa]

Do you reckon it'd be worth it?

I have about 400 resistors in the range 1m2 through 10m0

 

[dr pepper]

Old valve sets as mentioned did have high value resistors in them, for some reason esp the higher values have a tendancy to go even higher over time, maybe thats why the old guy had a stock.

I dont know for a fact however I suspect they were high wattage just because it was easier to make them in that physical size, and you wouldnt want to wire a 1/8w resistor point to point in a chassis.

Sometimes you see such resistors around the eht rectifier in old sets.

Ebay them, they've not made stuff like that for a long time, those restoring valuable old sets as original will want them, or do a google and mail your nearest vinatge radio club and see if they have anything for swaps.

 

[audioguru]

I use a 22M 5% 1/4W resistor in my 6V Ultra-Brite Chaser project. It sets the Cmos timer to allow the chase to go around for about 5 seconds then a pause.
It does not use UK VALVES. It also does not use American vacuum TOOBS.

 

[crutschow]

Those high power, high value resistors were typically used as voltage dividers from the picture tube anode voltage to generate the voltages required to bias some the the tube's control grids. Thus, even though the resistors were a high value, they still dissipated significant power because of how high the picture tube anode voltage was (perhaps 15kV-20KV).

 

[KeepItSimpleStupid]

Yep. I once had to replace a 1 Meg, 200 Watt resistor. A bleeder on a 15 KV power supply.

I once bought a 0-0.5 ohm 2000 Watt resistor too.

And a few in the GigOhm range.

 

[dr pepper]

I have an american 5 table top vintage valve radio, it doesnt work, maybe its cause I've been putting valves in it instead of toobs.

 

[KeepItSimpleStupid]

Probably uses American Tubes from RCA instead of Russian Valves. No wonder why it doesn't work.

 

[dr pepper]

They still make valves in slovenia.

They dont make toobs anymore.

 

[Mr RB]

They sound like Philips high voltage rated resistors, used in the focus circuit voltage dividers. I have a heap here, generally a blue colour.

They are also fairly expensive resistors too, although I doubt you will get any money for them.

Re tubes, the "toob" market is going strong with many suppliers offering not just the standard tubes but different bias versions, "hot" and "cold" etc, new tube varieties coming out all the time. There is a big market with sane musicians for their guitar amps etc and some mentally ill Audiophiles that use them for their "HiFi" amps.

 

[canadaelk]

Mr RB: play nice , the audiophools are not mentally ill, just financially solvent! E

 

[alec_t]

And a few in the GigOhm range.

What on earth were those for? And how would you check their value (horrible vision of arcs leaping across test bench....) ?

 

[tvtech]

Hello all

The resistors spoken about above were VERY COMMON with older TV's with a seperate LOPtX and Tripler combination.

....LOPTX = Line Output Transformer.
....Tripler = Triples Line Output Transformer Voltage.

Follow closely here....

A TV Cathode Ray tube needs around 30 KV to operate with a 68 CM tube. Years back, the Standard here anyway was a separate LOPTX and Tripler combination. So you need both the LOPTX and Tripler to see a picture....

Back to the high value Resistors. These were used to used to Focus the TV from the Tripler.... a special third pin on the Tripler.

These high value and high voltage resistors started @ 5.1M for a Philips K9 chassis all the way to a 47M on a Telefunken 711 Chassis.

Depending on what you needed to do to bring the Focus in.

Nowdays, it is way too easy. All is built into Minute packages that you adjust with a simple twist of a POT for Focus or G2. No Triplers anymore and it's become a free for all.

That is why every Tom, Dick and Harry think they are capable of repairing a TV.....until it belts them.

Seen it all. That 30 KV stays the same. No matter what.

Fun and games. I was taught the safe way. I rarely shock . And if I do, I have been lax. Wake up call and all.

I respect HV big time. It is really sore to get belted.

Regards,
tvtech

 

[TaDa]

Well I've sorted them all out, bagged them up and annotated the bags.
For each resistance value I split out the 'big ones' from the 'small ones'
I'll leave the big ones in the loft for emergency use and the small ones in the garage for easy access

Thanks everyone!

 

[dr pepper]

I'm with you on that one RB

 

[audioguru]

Where can you buy valves or toobs anymore today? When I was young they were sold at the corner convenience store.
There are (were) many different ones that all looked the same. The part number printed on the glass always quickly disappeared.
If you plug in the wrong one then the antique radio will not play.

 

[dr pepper]

Ebay where else.
New ones are still made in slovenia and china, esp audio ones.
And you can still pick up new soviet tubes from those who have bought up scrap military stock.
Theres also at least in the uk a few specialist valve supplier houses, some will even supply tubes in different hardnessess's