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 Post subject: Sylvania Model 4P19W
PostPosted: Mar Tue 31, 2020 12:28 am 
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Posts: 31
I recently bought a Sylvania 4P19W AM transistor radio. Probably from about 1960.

It is in good shape, but the reception is poor, and the volume low.

When I got it, I could hardly get the strongest local AM station. Very low volume. Turning the volume up did not help. And after a while the station faded away, and there was only static.

I replaced the two electrolytic capacitor inside. Hardly any improvement. Then I cleaned the volume pot, and cleaned up the connectors on the 9V battery connector. Now the volume is higher, but after a while it fades again.

I tested some of the resistors, and they all seem higher then spec. Some more than 20%. I was thinking about changing them next,

What do you think?

There is a 2kOhm "sensitivity resistor". Will adjusting that one make any difference,


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Mar Tue 31, 2020 1:36 am 
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Location: Mountains of Mourne. Ireland.
Schematic...
http://americanradiohistory.com/hd2/IDX ... e-0125.pdf

Greg.


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Mar Tue 31, 2020 1:40 am 
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Location: SF Bay Area, CA
I think this is a link to your radio with detailed steps and pictures:

https://trybotics.com/project/how-to-re ... stor-49472

JC


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Mar Tue 31, 2020 1:54 am 
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Location: SF Bay Area, CA
Thanks to the Schematic posted by Egg, I think this is what you can do:


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Mar Tue 31, 2020 2:22 am 
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Thank for all the tips!! Incredibly fast! I will study this, try it, and report back!


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Mar Tue 31, 2020 5:42 am 
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Location: SoCal, 91387
I have one.
Just tested it again, and it gets stations all over the dial, with the locals at room filling volume.

You might go ahead and replace the resistors to get within spec, and it should help a bit, but in addition I would adjust not only the sensitivity control, but the two IF's as well. Tune the radio to a weak but non fading station for their adjustments, and use a non metallic blade to peak the audio.

If the above doesn't cure the problem, the volume declining situation might indicate a Transistor failing. Take voltage measurements on the elements of each immediately upon turning the set on, and take them again once the volume has faded completely.

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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Mar Tue 31, 2020 6:18 pm 
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Joined: Nov Tue 12, 2019 3:24 am
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I cleaned out the volume pot. It worked for a while. But now I am only getting static across the frequencies.

My gut feel is that some component worked immediately when turning on, but then faded and died when the radio "warmed up", and now is dead.

I will replace all the resistors, as a start.

Not sure how to test the transistors. Maybe I should just replace them? Maybe replace the volume pot as well? Any suggestions for a source to buy new ones?


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Mar Tue 31, 2020 8:05 pm 
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Location: Mountains of Mourne. Ireland.
If you replace all, or most of the components in your radio, there is every likelihood that it will never work again.

Expected (ballpark) Resistance and Voltages are shown on the Beitman schematic above.

Take some readings.


Testing a transistor using the diode function on a multimeter.
viewtopic.php?p=3096126#p3096126

Greg.


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Mar Tue 31, 2020 8:16 pm 
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Location: Mountains of Mourne. Ireland.
Sams Photofact (pretty pictures) service manual (four-pages) Set-573 Folder-16 can be downloaded from radiomuseum.org for free.
https://www.radiomuseum.org/r/sylvania_4p19w4_p_19.html
(in the scrolling window) the bottom four pages are Sams 573-16


Downloading from radiomuseum.org (non members).
Click a schematic page from the right-hand scrolling window, then again in the main center window.
Each page will be emailed to you immediately.
You can only download three pages a day + up to a maximum of ten every 30 days.

If you experience any downloading difficulties... see this→ viewtopic.php?p=2571007#p2570117
pdf attachments are not visible in junk email folders.

------------

Edit: Here is the cover page from Sams 573-16, download the other three pages (as shown in the thumbnail images at the bottom of this post) from radiomuseum.org

Image
Large image: https://i.ebayimg.com/images/g/SqoAAOSw ... -l1600.jpg

:) Greg.

Image

Image

Image


Last edited by egg on Apr Wed 01, 2020 3:28 pm, edited 1 time in total.

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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Mar Tue 31, 2020 8:41 pm 
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Location: Mountains of Mourne. Ireland.
Resistors can fail open or short, alongside their value changing.
Do a good close visual inspection, and look for burned or near-burned,
(Mostly with mains voltage equipment)
.


Test them quickly in-circuit... If you see something "funny", lift a leg and re-measure.

For suspect dry joints, touch them up (reflow) with your soldering iron.


Greg.
fyi... resistors failing in short circuit are not very common, but it can happen.


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Mar Tue 31, 2020 8:47 pm 
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egg wrote:
If you replace all, or most of the components in your radio, there is every likelihood that it will never work again.

Boy ain't that the truth!

Raspberry wrote:

Not sure how to test the transistors. Maybe I should just replace them? Maybe replace the volume pot as well? Any suggestions for a source to buy new ones?

Understand that there are active components, the Transistors, and passive components (everything else). The primary suspects in the second group, Electrolytic capacitors, you said you replaced.

Each Transistor has three leads coming out of it, Base, Emitter, and Collector. The normal voltage difference between the first two is two tenths of a volt. The Collector's voltage is usually around what the supply is.

You would connect one meter lead to circuit ground, usually the widest trace on the PCB, and the other to each of the three leads of each Transistor, and write down what the voltages are, again, on startup, and then once the audio dies. Most Transistor sets have a positive ground, so that's where your positive meter lead would most likely connect.

Since you are now posting that all you get is static, compare your voltage findings to the values in the schematic that Greg supplied, and post any differences here.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins/////////////////////////


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Mar Tue 31, 2020 11:01 pm 
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OK. I measure the resistance of all the resistors, in circuit. Below are the results.

The radio once in a while comes on at the strongest local station, before it fades off and only delivers white noise, with a faint crackle where I know the stations are.

I will test the voltages next


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Apr Wed 01, 2020 1:22 am 
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Here are my measurements the transistors. Some of the measurements were fluctuating a +- 0.3V around the number indicated


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Apr Wed 01, 2020 4:17 am 
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I have the service information on this model.

R1, the volume control, & R2, the sensitivity control, should certainly show a resistance across them. Don't measure from the center lug, but rather across each end.

I'm not sure how you are measuring the fixed resistors, but your best bet would be to unsolder one end from the PCB, and then measure across it. These resistors have a tendency to increase in value over the years, sometimes into the 20-25% range above spec.

Your measurements in-circuit simply don't display that. R3 going from the base of the Converter Transistor to the supply, and R4, R5, going from the base and emitter to ground from the same Transistor would have no reason to display such decreases in value as you have posted.

Notice that the X2 emitter and X4 base -connected together through R9- should each be at 1.8 volts, and instead are at 3.5 - 3.9. R8 and C7 might be responsible.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins/////////////////////////


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Apr Fri 03, 2020 6:47 am 
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I posted this thread that might help with your troubleshooting. The linked article covers most all the basics.
-Ed

viewtopic.php?f=4&t=375254

_________________
My life is loosely based on a true story.


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Apr Fri 03, 2020 12:25 pm 
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Downloadhttps://www.americanradiohistory.com/Ar ... Lemons.pdf

Image

Greg.


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Apr Fri 03, 2020 12:34 pm 
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Joined: Jan Tue 31, 2012 1:55 am
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Downloadhttp://americanradiohistory.com/Archive ... e-1959.pdf

Image

Greg.
viewtopic.php?p=2993108#p2993108


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Apr Tue 07, 2020 4:33 am 
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Joined: Nov Tue 12, 2019 3:24 am
Posts: 31
Thanks for all the reading material.

I sat down and replaced the resistors R3-R13 this afternoon. They where all 5-20% higher than spec (my understanding is that this was expected?).

I tested R2, and I think that works. I can get a variable resistance between 0-2k from that one.

R1, I can still not measure any resistance from. The volume also does not change when you turn the knob.

There is still just constant white noise. Once in a while, just when you turn the radio on, you get a split second of reception.

I remeasured the transistor voltages. They changed some, after the resistor change. The readings on X2 and X4 are still fluctuating.

Will accept any additional ideas. Do you think X2 and X4 are broken? Or can R1 be the culprit? After all, I had faint reception before I cleaned it. Or was that just a coincidence?


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Apr Tue 07, 2020 4:51 am 
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Raspberry wrote:

R1, I can still not measure any resistance from. The volume also does not change when you turn the knob.


Disconnect the leads from T1 and C2 from the high side of R1, connect them together and try the radio.

Also, while they are disconnected from it, measure R1 again. T1 connected across it would have affected the reading.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins/////////////////////////


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 Post subject: Re: Sylvania Model 4P19W
PostPosted: Apr Tue 07, 2020 5:54 am 
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Joined: Nov Tue 12, 2019 3:24 am
Posts: 31
You mean like this?


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