Newbie from Tennessee

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Newbie from Tennessee

Post by snowscad on Sat Apr 29, 2017 11:08 pm

Hello everyone my name is Dwain I am somewhat new to this I have been working on these tube radios
For about 5years now on my spare time i have learned alot and there is alot I don't know so all the help
Is appreciateit. I have somewhat restored about 7 radios some was not working and some was, i
Have in my collection now 7 working and 3 not working and the 3 I'm working on now.

The 7 working ones are zenith 4724, 8h034, z733,7h820-0.
Philco b956,41-296,38-45
Here recently I pick up a Zenith 6D525 that I recapped replace some wires and it works but it
Only picks up a local station with the voices sounding if I can explain this gerbering, far as I can tell the antenna looks like
It wired right I'm at a deadend on this one.

And also just pickup a Zenith 5-S29 which as not been in use for a long time I clean it up and got the
Switches working and replace all caps and the rectifier tube,it's got three bands on the radio
A B C I don't know now which is the broadcast I think it is the A but not sure and now I can pick up
Stations good on C band which it sounds like shortwave but not getting nothing on the other bands but I think the band A is broadcast but not sure. I cleaned the band switch two or three times.
I also pickup a Philco 38 that I have not started on.

Like I said am somewhat new to this hobby so I need all the help I can get.
So thanks in advance
My grandchildren call me D

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Re: Newbie from Tennessee

Post by jukeboxman on Sun Apr 30, 2017 12:10 am

Hello and welcome to TRF -i know there are a lot of very knowledgeable people here -we are a slower site than some but feel free to enjoy

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Re: Newbie from Tennessee

Post by Bill Cahill on Sun Apr 30, 2017 7:02 pm

Welcome to TRF. Generally speaking A is the AM band.
Welcome here.
Bill Cahill

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Re: Newbie from Tennessee

Post by Chas on Sun Apr 30, 2017 7:54 pm

Dwain,

Sounds like the poor audio is from a bad speaker. Be sure voice coil is not rubbing. Minor rubbing can be fixed with a loose wad of cotton on the side of the frame. More severe rubbing the cone has to be replaced. Crashing or static noises are another problem. Let us know and that problem will be a walk in the park Very Happy Do try to preserve electro-dynamic speakers. Often a PM replacement is at best awkward.

Poor reception on a multi-band receiver on a particular band or broadcast band is usually a fault either in the band switch, wiring to that circuit, the antenna input coil gone open or the oscillator coil on that band open. Severe mis-alignment is possible too.

If you have not heard or maybe soon will. Electrolytic and paper capacitors must be replaced to provide safe and peak operation of the radio. When doing this to a radio that manages to work do the repair two caps at a time then operate the radio. Any failure to operate can be traced to just four connections. Mark replaced caps with a tiny dot when the set works...

Some sort of tube tester is required and some sort of RF generator to align the sets. Alignment will most always perk-up a set that has been sleeping for 60 years...

Three other bits of antique radio wisdom:

- 1 - Chassis rivets used for ground connections can fail from oxidation even though an ohmmeter says the resistance is zero. Solder to chassis or replace with hardware and serrated washer. How will one know if there is a problem? When all other avenues of repair have been done an radio still works poorly.

- 2 - Keep an analog VOM on the bench even though the $10 DVM digital meter (seems) to work. Digital meters tell resistance lies when attempting to measure inductors and leaky caps.

- 3 - Use an isolation transformer when working with live AC-DC hot chassis radios. OR have a full understanding that a shock is possible.

GL

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Re: Newbie from Tennessee

Post by willy3486 on Sun Apr 30, 2017 8:18 pm

Welcome from another Tennesseean. Where are you located here in Tennessee? I am just outside of McMinnville/Smithville Area. There are a few clubs around, One in Nashville.

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Re: Newbie from Tennessee

Post by Tony V on Sun Apr 30, 2017 9:33 pm

Welcome to TRF Dwain! Glad to have you here!
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Re: Newbie from Tennessee

Post by snowscad on Sun Apr 30, 2017 10:17 pm

Thanks Chad for your advice on the speaker and coil on the 6d525 and the 5-S39
I will take your advice when I get back to the radios and I will let y'all know what I come up with .

It a small world Willy3486 I'm right here in the city of Smithville.

Thanks,
D

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Re: Newbie from Tennessee

Post by willy3486 on Mon May 01, 2017 8:08 am

snowscad wrote:Thanks Chad for your advice on the speaker and coil on the 6d525 and the 5-S39
I will take your advice when I get back to the radios and I will let y'all know what I come up with .

It a small world Willy3486 I'm right here in the city of Smithville.

Thanks,
D

Now thats funny, We probably have met or passed by at times. I will PM you. One question is snowscad from Snows Hill?

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Re: Newbie from Tennessee

Post by snowscad on Mon May 01, 2017 8:45 am

I had a uncle to own the property back before the state took over the highways he would charge a toll at the bottom of the hill and told at the top of the hill that is why it's called snowshill today

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Re: Newbie from Tennessee

Post by snowscad on Sun May 07, 2017 10:39 am

Chas
Apparently the B band switch is AM broadcast I'm like you I though the A band switch was Am and
I have been trying to tune in stations on it then today I done a little cleaning on the band switch and when
To try to tune in a station and all of a sudden my local radio station tuned in loud and clear on 1480 but I was not able
To pick up any other stations and I look down at the band switch it was on B and I didn't know it.
And also I fell to mention that there was a low hum on the radio when turned on with no effect with the volume control
Can you tell me how to eliminate this hum I changed the Electrolytics

Dwain

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Re: Newbie from Tennessee

Post by Chas on Sun May 07, 2017 11:28 am

Reference the schematic: [You must be registered and logged in to see this link.]

The speaker field is in the return of the High voltage. By doing so the voltage drop is used to develop bias along with a portion of the Candohm resistor (250 ohms).
What often happens is the negative of C13, the one connected right after the rectifier, (8 mf/450) will get connected to the chassis instead of the center tap of the power transformer.

The capacitor "C13" is a dual section with a common positive. It can be replaced with two single capacitors. Use a value of 10mf as 8mf will be harder to find. Be aware where the negatives get connected. One negative to the center-tap, the other to the chassis...

A heater to cathode leak in the 6F6 output tube can cause hum. If hum is still present there are other things to check, like leaking sections of the Candohm resistor, leaking field coil, leaking output transformer. Resistors and capacitors in the audio section.

Be sure the bias voltage on the 6F6 is correct.

BTW: The schematic uses the term "M" to denote thousands NOT megohms.

GL

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Re: Newbie from Tennessee

Post by snowscad on Mon May 29, 2017 11:20 pm

When replacing Dog-bone resistors and you can't find the exact ohm should you go up or down in ohm?
What kind of resistors should I replace the R4 with?

D

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Re: Newbie from Tennessee

Post by willy3486 on Tue May 30, 2017 8:04 am

snowscad wrote:When replacing Dog-bone resistors and you can't find the exact ohm should you go up or down in ohm?
What kind of resistors should I replace the R4 with?

 D

One thing I do if I want to get exact is to put two in parallel. For example if you need a 37 ohm resistor but have a 52. You can go to
[You must be registered and logged in to see this link.]

On the calculator they set up put 52 in for r1 and then put in 37 for R total. It calculates to 128.26666. So in that case if I had a 130 I would use it.

If I read the schematic right you need a 990k ohm resistor. If I did the math right you could use a 1 meg and 100 meg resistor to get it almost right.


Keep in mind the parts were many times off, someone help me on this, maybe 5%.10% or more IIRC. I am more particular with the wattage than the value. As far as wattage if a resistor is say 5 watts I replace it with 5 watts or higher.

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Re: Newbie from Tennessee

Post by snowscad on Tue Jul 04, 2017 10:32 am

How do I check for leaks in the candohm resistor,field coil,output transformer and resistors and capacitors.
Like I said I'm new at this.
Thanks

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