5u4gb long body vs short body

I know this is an old post but I think it is a good example of what you might find in an old radio with an unknown history. I agree with Frank that that round carbon composition resistor was an add on at some point in the radio's history. I make it out as a 25K Ohm 2W resistor (red-green-orange) rather than a 15K 2W (brown-green-orange). In either case, it was probably unneeded in the circuit and could have been safely cut out and not replaced with no harm done to the radio.

73, Rod  WB6FBF

That round resistor looks like someone added it to the circuit at a later date.
That style resistor is typically rated at about 2 Watts for that style & vintage.

You also said you did hear a FM station so that means the FM is working Look at the schematic and you will see 3 tubes V1,V2,V3 these are the ones for the FM path so you may have a weak tube or faulty circuit component(s)
Do you have an FM antenna hooked up? If not then thats your problem with FM.

sorry for the delay Wow!
That 10 watter would be the best bet.

I did find a Link for the Schematic:
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I did find an R13 and it is rated as 120ohms 1 watt and its connected to V3 (6BQ5) Output tube Pin #3 on oneside and ground on the other with a 25MFD cap in parallel to that resistor. (the one you said was burned.) This is used as the bass output tube.

Hi Cliff, the other amp does have a 7watt resistor also but has a different ohms value its 820 ohms but it has no additional round resistor attached to it in parallel. I measured the 3300 ohm 7watter and i got a reading of 3399 to 3400 ohms . I measured the round cracked resistor and i get a reading of 8.5k and if im reading the colours right its supposed to be 15k. These readings are with them removed from the amp. Last measurement i took was with the 2 resistors together as a unit (picture) and reading i got was 2.4k and the schematic says its supposed to be 2.7k. I could easily get a 2.7k replacement but what wattage? My supplier has 5 and 10 watt sizes available for 2.7k.[img][You must be registered and logged in to see this link.][/img] I cannot find the cracked resistor in my parts list. I checked all the tubes and they are all in the correct spots. The am radio works and the phonograph all work beautifully just fm not working.

you ask Are they power resistors?
Answer:Only if there in the power supply circuitry. (They could be used in the filament circuit but I doubt it as most big tube radios use transformers and most tube filaments are in parallel.)

However If they (the tubes) are in a series string then that's a different story.

Did you find the cracked resistor in your parts list? if so what is the listed wattage?

Did you have the same two resistors on the other Amp channel?

Note: you have to use at a minimum the total wattage combined.
(another note) the resistance is critical because the resistance determines two things, the voltage drop and the current limit.
Those determine the operation of each tube, if they are not correct then the radio will not work right.

Also RCA and GE used a lot of the same chassis.

They are power resistors correct? ( the cracked one and the square one)

Cliff, my supplier has exactly the right size 2.7k at 10 watts i may go that route!

Definately RCA it says victrola on the unit and has the nipper dog picture too.

You cannot replace resistors that are not close to the original value, they could have a tolerance of 5 to 20 % which would allow to use a close value and you could get a 2.7K ohm 10 watt and replace both resistors for one.
So if that combined value is 2.7Kohms the tolerance could be as low as 2.7K-270 ohms = 2.43 Kohms or 2.7K + 270 ohms = 2.970 Kohms. so any resistor measured need to be no less than 2.43Kohms and no more than 2.97Kohms



The only type I see is a wire-wound type from Newark but if not available stick with exact replacements. That's a good idea as far as finding the equal resistors in the other channel amp. rather than remove them you may be headed for grief as when you solder and desolder them they may change value from heat.

Leave them be and just get the values and replace with new ones for the burnt ones.
Does the other amp have the same two big wattage resistors?
If not then start testing voltages in that particular area of the circuit and note each voltage to compare with, to amp not working. and check each tube and note location on both amps. if they are not the same, someone may have put the wrong tube in the wrong socket and caused the non-working condition. And then forgot about the replacement error and decided to troubleshoot and correct circuit to make operate. I have my suspicions that, that's whats happened.

PS just a note that you said RCA are you sure? It may be a GE as thats the models they use.

Hi Cliff the 7 watter is R13 on the shorter list of resistors, i also located the 7 watter on the schematic. The first schematic i posted i put a black arrow showing its location. There are other schematics, but they are for the other amplifier in my stereo, it has dual amps. One funny thing i noticed after i replaced all the caps in the amp with the two burnt resistors, i plugged it in an i faintly heard the fm tuner picking up a station, but you would have to put your ear right up to the speaker to hear it.Before i changed the caps i wouldnt even get a sound when fm was selected!. My supplier has 5watt 15k resistors to replace the cracked resistor, but i wanted to up the wattage to 10 but he only has 20k 10watt could i use the 10watter 20k resistor? or does it have to be 15k. As far as the tubes go Cliff, i have a shelbern stereo which has the same number tubes and when i change the burnt resistors i was going to swap them and see what happens. I still dont have enough experience to know what im doing when testing tubes ........yet!

normally you would lift one lead. but since both are hooked together you need to separate both leads from each other on one end and measure to find out each resistance. Measuring them together will not tell you which one has changed value. I think when you remove the connection of both you may find if you tug on the cracked one it may fall apart. I would be surprised if it doesn't.

I can make out the connections on the schematic but when I use my graphics program to enlarge it it gets too blurry.

follow the parts list of resistors and mark each off each as you find it on your list and in the schematic. (I would just put a very light pencil mark next to them as you find each one)I know it will be tedious but that may be the only option you have. you can start looking where the resistors are and deduce from surrounding tubes and other parts where in the schematic it may be.

Make a landmark such as a close resistor of know value, search for it on the list then look for the designation on the schematic. Put a tick mark along side each component as you find it and that may guide you to what the burnt resistors are. Have you tested the tubes? if not you may have to as if one is shorted you may be back in the same boat again.

PS edit here I just noticed that you do have them marked on the parts list already.
I see 81 resistors but not the the 7 watter
Is there more than one schematic, and parts list?

Hi Cliff, when i measured the resistor i only disconnected one end of it , can i measure them both together by disconnecting only one end , or would you recommend that i remove them totally? (its easy enough ). There is an electrolytic wired to these resistors, i have just replaced all caps last week, i just wanted to wait and see what input i received on the cracked resistor before putting in my resistor order. I managed to locate the two burnt resistors in my schematic as they were badly discoloured i couldnt read the colour codes. I scanned my schematic to see if it turned out any better, here it is:[img][You must be registered and logged in to see this link.][/img]

Those two resistors in parallel should read 2.7K ohms in total. As measured now though it would be 2.35Kohms It looks like the round one should be a 5 watter. Hard to tell though. That might have been a modification because of circuit changes. Since it is a higher resistance in the round one less current would flow through it and no need to be as big a wattage. The crack and what you measured as far as its resistance would be a sign that it does need to be replaced. it might be that since it was cracked it was soldered without a stress loop in the lead, as both of them heated up it caused the round one to crack as it had no room to expand, and they shouldn't be that close together, get another resistor and replace, but put some space between the two. I would say at least 1/4 inch.

Measure the big 7 watter just to make sure it hasn't changed value. See if it is in line with any capacitors, paper or electrolytics. If so replace adjacent caps as a precaution. The small disk capacitors should be no problem though. Yes the pictures are too small to even see clearly. What you could do is scan them if you have a scanner. That would help rather than a camera shot, unless you can photo them with a macro or closeup lens.

What do you other guys say???

Hi Cliff got schematic posted but is very difficult to see.

Go to this link on our forum:

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also reduce the size of your picture it may be too big.

[url=JPEG image (.JPG]JPEG image (.JPG[/url]

Hi Cliff i have tried to post the picture but i had no luck.

The schematic would help if you posted it as I have looked at the indexes for Beitmans, Riders and Sams with no luck.
Can you get a picture of the resistor in question and post . Without some reference, it would be difficult to give help.

Hi guys im still working on my no fm problem, i got a schematic for my unit and i figured out what resistors i need, but im stumped on finding the wattage rating on this one resistor. This resistor does not appear to be in my schematic. The resistor is fairly large (about an inch and a half long) round in shape made out of a ceramic type substance. This resistor is not burnt, it just has a crack down the middle so i wanted to replace it. I removed it to measure it and it is still intact (not cracked all the way in half. This resistor is wired in parallel to a square shaped resistor that is rated at 7watts 3300 ohms. So would the round resistor be around 7-10 watts?.The square shaped resistor is in my schematic but i dont see the round one. Both resistors are actually touching side by side. The colours on the round resistor indicate that it is 15k ohms and when measured i get 8.2 k ohms.[img][You must be registered and logged in to see this link.][/img][img][You must be registered and logged in to see this link.][/img][img][You must be registered and logged in to see this link.][/img][img][You must be registered and logged in to see this link.][/img] Thanks Cliff got pics up. R13 is the 3300 ohm 7watt square resistor, just cant seem to find the round resistor that is against it in the schematic. [img][You must be registered and logged in to see this link.][/img]

Good news i found a schematic My capacitor supplier has one. That will help me alot!

Everything works except fm all the tubes light up also. i believe my stereo was made in 1960. I tried sams but i didnt come up with anything.

First thing you need to do is find out why the resistors are bad, until that is done, you will have the same problem recur.
check the tubes first, for shorts. Filament to cathode. You may have a dead tube if the filaments are in parallel.

In fact always test tubes for shorts before using the tube tester for anything else or you could damage the tube tester.Capacitors are almost always the same culprit, causing shorts. Power supplies first problem area to look at, if its not the problem then start measuring B+ .

I think once you get the resistors and tubes checked out you may have solved the problem.

By the way you were given the wrong information concerning the multiplex plug-in, it isn't needed to play FM. That's why its an option. Your radio must have been made after 1959-63 because that's when Stereo (Multiplexing) Started. You would have to make modifications to the audio section also, or add another audio amp and speaker(s).

I don't recall if you stated the AM section or phono works?

The FM would work without them. I cannot find a schematic in Riders or Beitmans, you might find one in Sam's photofacts.

Hi guys did some further inspection on my no fm problem and i found two burnt resistors that are part of the fm. rf. amp which houses a tube. Not 100 percent sure this is the problem, but i will order the resistors, replace them and let you all know what happens. My only problem is that the resistors are so badly burnt that i cant read the colors, so i would have to try and find a schematic. Also found a rather large body resistor with a crack down the center. It looks to be made out of ceramic material but colors are visible.

On my Rca cabinet radio/phonograph it has am and fm radio in it, but when i select fm all is silent. I did some reasearch and was told that fm was an option back then and that an optional multiplex unit would have to be installed to receive fm. On the amp there looks like theres an empty spot for an optional piece of circuitry and there is a socket on the amp that says multiplex above it. Inside the unit the fm tuner and dial cord is all there but no life when fm is selected. Any help would be greatly appreciated. Model shc 662 .

Thanks again Cliff good to know.

It doesn't matter. A lot of tubes started out big, but in decreasing the size of the envelope, they saved on the glass. The important thing is the tubes electrical characteristics, not the size, if and as long as it fits anyway!

Also manufactures of tubes may have there own design to make it appear that it looks different, so the customer would remain loyal to that brand.

Hi guys i have an Rca cabinet style radio phonograph, The Carmen model shc 662. I recently replaced the rectifier tube 5u4gb in it because the glass was loose where it attaches to the base and i would have to wiggle it to get it to work. I found a NOS tube and when i received it, i noticed the body was shorter than the original. I did not realize they came in two different sizes, but i put it in and it is working fine. Is it okay to use the shorter body tube or would the proper one be better?