The parts list for my B&K 650 calls the bridge resistors glass resistors. They don't look any different than the other resistors. What is a glass resistor<P>------------------<BR>

Is a glass resistor a person who will only drink the beer from a can?<P>------------------<BR>Larry

Hi Ed,<BR> Atwater Kent used glass resistors on a lot of his sets. Most often he used them for grid leak. Most all the one's I've seen were either open or way out of specs.<BR>Take care<BR>Bud<BR><P>------------------<BR>

Hi Ed<P> All of the above is correct. <P> There are also glass precision resistors. Being a bridge this might be what they are calling out?<P>------------------<BR>Norm

Hi Ed, My guess would be either a precision wire wound resistor on a glass former or some kind of vitreous track resistor, perhaps metal oxide. If you're needing to replace them I think a modern precision metal film resistor should fill the bill. You'll have to check the circuit but I don't think there would be much power dissipation in a bridge circuit and the little 1/4 watt variety should do. You should be able to find a greater range of values than the common range but it's probably easier to add two or more in series / parallel to make up the exact value. If they're similar values they will share the load beween them.<BR>Don Black.<P>------------------<BR>

Glass resistors are precision resistors mounted inside a glass tube to minimize leakage. Normal resistors have relatively low insulation resistance as compared with glass. In a glass resistor there is no coating on the element itself, so no leakage path in contact with it.<P>It also provides an environmental seal to keep humidity from changing the resistance.<P>This only matters for high-value resistors, obviously. These are very high quality parts.<P><P>------------------<BR>73 de Leigh W3NLB

Thanks Leigh, that makes a lot of sense. I wonder what values we're talking about here? Certainly the average modern resistor is far better than 30 years ago.<BR>Don Black.<P>------------------<BR>

Hi Don,<BR>Don't know. I couldn't find a manual on the net. What literature do you have? Any notations on the schematic or parts list?<P>I'm wondering what this bridge is for. Most likely for the leakage test, which means they would probably be very high values.<P>Maybe you could shoot me a copy of the schematic (a partial of the bridge circuit would be best). <P>If all else fails, we can always re-design the bridge. Then (presumably) we would know the values <BR><P>------------------<BR>73 de Leigh W3NLB

I miss spoke when I said the resistors were part of the bridge ciccuit. They are part of a bleeder for the output of the rectifier. The values are 1200/620 and 240 ohms 7 watts 5%. I think the ones in my tube tester are carbon they don't appear any different than all the other resistors. I had never heard of glass resistors before and just wondered what they were. My tube tester has had work done on it in the past and may be the glass resistors were replaced and maybe they were never installed in the first place<P>------------------<BR>

Hi, ED... The resistors that you're talking about are probably the deposited-carbon type that used a glass form; they were popular in TV sets in the late 50s on. I think Corning made some of them. Carbon or wirewound resistors of the proper value and wattage would replace them OK.<P>Tim<P><P>------------------<BR>

Corning made tin oxide power resistors that as far as I recall were high quality but probably too expensive to find much use in cheap test gear. As I recall they were dull gray and I suppose may have used a glass form. But I never heard of them being called glass resistors. 7 watts does sound like a reasonable size for those.<P>------------------<BR>

Time to restart this ancient thread. I have what were supposed to be 12500 ohm and 65000 ohm glass resistors that came out of my 1928 Atwater Kent Model 40 AM radio. Both of these resistors are out of tolerance. Is there some shop that specializes in manufacturing reproduction glass resistors for something like this? Thanks.

I just thought that I would ask before searching for carbon replacements.

Here is an example of a glass resistor, being used in a 50KV probe.

From an engineering perspective alone, the closest modern replacement that I can think of are high voltage thick film resistors such as those made by Vishay. However, they bear absolutely no mechanical resemblance.

Some power resistors have a glassy shiny ceramic coating... or maybe they meant that they were supposed to be "flameproof" power resistors.... when a bunch of TV's were cathcing on fire in the late 60s some laws were passed and TV's had to have "flameproof" power resistors. Basically not your cheap phenolic-cased 2-Watters, but instead glass or ceramic cased resistors. Maybe B&K were following the same rules?