Once the L49B is numbered right according to the L49B actual data (I gave you the link), look at the diagram.
What L49B is is a ballast tube: it drops some voltage at a given current (in short it is simply a glorified resistor) so the rest could be applied to the serialized filaments of the other tubes, and at the same time uses a tap in that resistor to derive the voltage to power the dial lamp(s).
Now I believe it has just 3 pins that are functional - the beginning, the tap and the end of that resistor. The rest of the pins is typically a dummy - the pins do not go anywhere or even missing.
Now once you have mapped your socket with correct pins and look at the tube's data, look how the MAINs wires actually connect. One, very similar to the Stromberg radio diagram I listed, will go directly to the beginning pin of the ballast.
The other then should go to a pin that is dummy or not used, they usually do that to use a spare pin as a solder post, for convenience. If it is the case (and I think it is) you are OK.
PS. A diode is not a resistor, cap or whatever, It is a semiconductor with a P-N junction which by its nature works as a one-way conductor for DC. Consider it two pieces of separate metals (or rather semiconductor materials) touching each other. The rest is physics and it is complex - you would have to learn about bandgaps, Fermi levels and all the good stuff which you do not really need.
Important is: a Si diode (silicon) will conduct current one way, not conduct the other and when conducting will drop about 0.7V across itself. This is it.
This is the proper numbering of the L49B. The mains connect to terminal 3 and terminal 5 (being the 2nd and third pins), both are occupied by pins. I would assume that since I did plug it in and turn it on when I first bought it and nothing exploded that it was wired correctly unless it blew up in the past. there was no response when i turned it on. nothing lit up, nothing hummed, it was dead One thing is the main is not connected to the #1 pin. I cant tell from the ballast tube diagram you sent me which are active and which are dummy pins.
You will see that the pin 5 is a dummy pin.
They use it as a solder post, just to hold a wire. It is a popular practice.
Pin 3 is one end of the resistor which is consistent with how it should be. Now the pin 7 then (another end) should go to the strung up filaments, and also to the dial lamp.
Pin 8 should also then go to the dial lamp.
Yes, pin 8 goes directly to the dial lamp and pin 7 runs through pin 5 of 25z5 to the dial lamp. Main runs to pin 3 (active) and pin 5 (dummy)
Did we ever figure out what the 2 ecap values should be? you said 40 and 20 at 150V right? but that was before you know they were 3 lead double caps.
Do I just get 2 20's and 2 10's and combine the negatives to ground and run the 2 positive leads to their respective terminals?
1. The pins 3 and 4 of this tube (Cathodes) are likely connected together (or it can be just pin 4 alone) and then they will go to the first electrolytic cap's positive (the negative which is the common for both caps inside the single body as we established probably goes to the Chassis).
Find that cap's wire that goes to the pin 4 (or 3&4) of the 25Z5.
We will consider this the first cap and it needs to be about 40uF 150V (could be 200V or more, but 150V is sufficient).
Again, its positive goes to this point and the negative - to the Chassis.
2. From that point the following is likely to happen: this first cap's positive and 25Z5 Cathodes will have another wire coming to them and it will likely go to either:
a)some choke (the filter choke, something that looks like a transformer) or
b)The field coil of your speaker that doubles up as the filter choke.
The second wire of that same choke or the field coil will likely goo to the second cap (which can be the other wire in your electrolytic cap).
Trace it, mark it.
That capacitor has to be about 20uF 150V.
Again, this wire is its positive and the negative will go to the Chassis.
We will call it the second cap.
1. The pins 3 and 4 of this tube (Cathodes) are likely connected together: yes they are...
and then they will go to the first electrolytic cap's positive: Yes they do...
Find that cap's wire that goes to the pins 3&4 of the 25Z5. Found it...
We will consider this the first cap and it needs to be about 40uF 150V (could be 200V or more, but 150V is sufficient).
Again, its positive goes to this point and the negative - to the Chassis. Ok so the positive of the 40uF ecap goes to either pin 3 or 4 of 25z5 and the negative goes to the chassis
2. From that point the following is likely to happen: this first cap's positive and 25Z5 Cathodes will have another wire coming to them and it will likely go to either:
a)some choke (the filter choke, something that looks like a transformer) or
b)The field coil of your speaker that doubles up as the filter choke. I believe that wire goes to the speaker field coil.
The second wire of that same choke or the field coil will likely goo to the second cap (which can be the other wire in your electrolytic cap). So I put a 20uF ecap from the field coil to the chassis...
Trace it, mark it.
That capacitor has to be about 20uF 150V.
Again, this wire is its positive and the negative will go to the Chassis.
We will call it the second cap.
b)The field coil of your speaker that doubles up as the filter choke. I believe that wire goes to the speaker field coil.
The second wire of that same choke or the field coil will likely goo to the second cap (which can be the other wire in your electrolytic cap). So I put a 20uF ec
You did not say if the capacitor connects there. If it does - yes.
Careful. In all of these type sets I've seen, the field coil isn't used as part of the filtering circuit. On the Halson chassis I recently worked on, the 25Z5 was split up, one half doing the half wave rectification for the radio, the other half going directly to the field coil, with the other field coil connection going to B-. You can do a simple test to determine whether this would be the case with your radio. Measure the field coil with an ohmmeter. If it reads 7kOhm or greater, it should be wired as noted above. If it reads 2kOhm or under, then it's in the filtering circuit.
Well in the Carlson sch which I listed the field coil is not filter, it is going from the rectifier to the chassis, that is being a load. However there is a choke there for a filter, this is why I said it is either choke or field coil. It is possible there is none but I would be surprised as filtering would degrade unless a large cap is used.
(This post was last modified: 01-24-2014, 09:28 AM by morzh.)
Maybe that's why they have those large caps in there.. the power supply set up more like a modern AA5? I don't remember a choke in my Halson, just the resistor between the first and second filters. One of those filters, BTW, would be just for the speaker field coil.
As for checking the field coil, just follow the wires down to where they connect to the chassis. One would go to chassis ground (or ground buss), the other would go to one of the cathodes of the 25Z5.
These are 3 lead caps. You said to get a 40 and a 20 to replace them.
1. Is 40 big enough? It is a really large cap, almost 4" long.
2. It is a 3 lead cap so would I need (2) caps to replace it?
3. If I do need 2, what uf do I need. (2) 20's? or (2) 40's
4. The second ecap you said is 20uf but it is also 3 lead so same questions as above.
Brenda, thanks for explaining. I Pm'd you since you have done Halsons.
So far we only went through the 1st physical dual cap.
Again, I am not sure which scenario played out with the second half of the cap, the one I described (analogous to my Emerson/Stromberg) or Brenda's. So I am still not sure about the second half. We did establih the plus of the 1st cap goes to the Field coil, but then we never affirmed where the other wire of the field coil goes.
We never started with the second dual cap. You need to map the wires to the tubes.
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