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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sat 16, 2019 6:48 pm 
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Got the coil rewound and still have low volume but both if screws are working.But I noticed that the filament is coming and going on one of the tube 45 and the only way I get any signal is with antenna wire attached to tube 235. I also noticed that the center tap resistor that connects to filament of both tube has only 15.8 ohms on either side instead of 60 ohms. But how would one make a center tap resistor out of two separate ones and what wattage is the original?


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sat 16, 2019 8:04 pm 
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A center-tapped resistor is just 2 resistors in series.
You can't measure that resistor in circuit.....the only way to get the right reading is when nothing is connected to it.

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"Measure voltage, but THINK current." --anon.


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sat 16, 2019 8:06 pm 
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So what would cause the filament to come and go? I will check the resistors later . So does the resistor have to be completely disconnected or can the center connection be disconnected?


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sat 16, 2019 11:28 pm 
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spsquires wrote:
So what would cause the filament to come and go?

--bad tube
--bad socket
--bad solder joint
--If anything else is changing--then a bad connection at the input of the power transformer
The big question is whether it only happens with one tube--in either socket

Quote:
I will check the resistors later . So does the resistor have to be completely disconnected or can the center connection be disconnected?

The resistor shunts the filament line through the end connections---the only reason to ground the center-tap is to minimize hum. The main path through the filaments is from transformer to one side of the filaments--to the other side and back to the transformer. the resistor is in parallel with the filaments. (with or without the ground connection)

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"Measure voltage, but THINK current." --anon.


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 12:05 am 
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So this resistor will not cause this tube problem? But to answer my other question about measuring it does it have to be completely out of circuit or will center tab disconnected work?


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 4:12 am 
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spsquires wrote:
So this resistor will not cause this tube problem? But to answer my other question about measuring it does it have to be completely out of circuit or will center tab disconnected work?

I answered that...

"The resistor shunts the filament line through the end connections---the only reason to ground the center-tap is to minimize hum. The main path through the filaments is from transformer to one side of the filaments--to the other side and back to the transformer. the resistor is in parallel with the filaments. (with or without the ground connection)"

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"Measure voltage, but THINK current." --anon.


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 12:05 pm 
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So could I take out that resistor and put a 68 ohm 1/2 watt resistor at the two filament connections to try without a ground ?


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 12:16 pm 
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spsquires wrote:
So could I take out that resistor and put a 68 ohm 1/2 watt resistor at the two filament connections to try without a ground ?

I don't understand......The only reason for the resistors across the filament line is to establish a ground reference for the tubes. The ones's with separate cathodes don't care, but the 45s need a path to ground for the DC tube current.

To avoid introducing an AC signal at the cathode, each side of the AC line to the filaments needs the same resistance to ground. That's what the center-tapped resistor does.

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"Measure voltage, but THINK current." --anon.


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 12:43 pm 
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I disconnected the resistor and it measured 61 ohms.


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 1:20 pm 
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The radio receives a station better with just the tube 45 next to tube 80 in then with both.


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 1:29 pm 
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I think you mean:
The radio performs better with one 45 than with two.

To me, that means that one of the 45s is bad----OR:
bad output transformer
bad interstage transformer
one of the 45s not getting filament power (your previous comments)

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"Measure voltage, but THINK current." --anon.


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 1:43 pm 
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I cleaned all tube contacts and now have 2.0acv across one tube and 1.8 acv across the other tube. I also checked tube 27 and it has 2.1acv .


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 7:18 pm 
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Since the voltage on the filaments should be 2.5VAC, I'd be looking for why everything is so low. 1.8 / 2.5 is 72% meaning that the filament power is about 1/2 of nominal. I'm not sure I'd expect a 45 to work at all with the power that low.
add to to my previous checklist:
--power transformer OK?---eg are the other windings producing the right voltage
--input voltage too low?

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-Mark
"Measure voltage, but THINK current." --anon.


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 7:22 pm 
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Will have a look over the next few days. Thanks. What voltage should be across the filament windings?


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 8:04 pm 
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spsquires wrote:
Will have a look over the next few days. Thanks. What voltage should be across the filament windings?

??
The tube filaments are speced at 2.5 volts. With no load the voltage from the transformer will be higher.

_________________
-Mark
"Measure voltage, but THINK current." --anon.


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 8:55 pm 
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Checked acv across tube 80 and it was 5.1acv. Cleaned all contacts on all tubes and now have 2.0 acv across all tubes but still no better reception or volume. Also I think the acv should be higher but not sure why when we have good on rectifier tube.


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 10:27 pm 
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spsquires wrote:
Checked acv across tube 80 and it was 5.1acv. Cleaned all contacts on all tubes and now have 2.0 acv across all tubes but still no better reception or volume. Also I think the acv should be higher but not sure why when we have good on rectifier tube.

The rectifier tube uses a different winding on the transformer....right?

Consider this: If a voltage is too low, it often means that a resistance is too HIGH. Resistance can be too high for MANY reasons......and in this case, your meter will likely not measure accurately enough

What is the no-load voltage for each filament winding? (Just remove all the tubes, but you can leave in the dual resistor across the 2.5)

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-Mark
"Measure voltage, but THINK current." --anon.


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 10:38 pm 
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When you say each filament winding , do you mean each tube? Also when you say dual resistor , do you mean the 60 ohm center tap across filament of the two 45 tubes?


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 Post subject: Re: Westinghouse model 801 grandfather clock radio.
PostPosted: Nov Sun 17, 2019 10:46 pm 
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Am I correct that the transformer has 2 filament windings? This is where the power comes from. Knowing the no-load voltage helps rule out some problems.

Quote:
do you mean the 60 ohm center tap across filament of the two 45 tubes?
that's the only resistor that we have discussed in this discussion......

Quote:
across filament of the two 45 tubes?
Is it not across ALL of the 2.5-volt filaments??

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"Measure voltage, but THINK current." --anon.


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