My new project

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Re: My new project

Post by frank1956 on Mon Jan 05, 2015 2:21 pm

DR. Radio,
Just a small progress report.

(1) Radio fires up after swapping the 12AT6 tube out.. All tubes light up. Radio is on all the time via the jumper you recommended I install.
(2) Used test rig and with radio UNPLUGGED my music was heard through the speaker.

Have not proceeding with any other test at this point.

Frank
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Re: My new project

Post by frank1956 on Tue Jan 06, 2015 2:18 pm

Dr Radio,
Proceed with the second part of the test rig test.

(1) Disconnected pins #1 & #7 from the 50B5 tube.
(2) Connected the .1 cap via the test rig to pin #7 50B5 tube and the other end of the test rig to the B-. Turned radio on and my music was heard loud and clear through the radio speaker. Test was a success!!! cheers

Both test were repeated per your request to ensure I did not damage the radio after my accident!!!  Sad


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Re: My new project

Post by Dr. Radio on Sun Jan 11, 2015 9:29 pm

Hi Frank,

I certainly hope you've been powering up your radio thru your isolation transformer?!

Please continue to do so (using it!)

Repeat the test found towards the end of page 8 of this thread. You don't have to break the circuitry (pull wiring apart), this time. It's the test where you feed audio with your tester into the "hot" side of the volume control to see if the radio works like a radio, you can control the audio output with the radio's volume control.

Audio test rig's "probe" capacitor leg connected to the hot side of the volume pot (where the 3.3 meg resistor connects to it) and the other side of the test rig to B-.

Does this function a-ok?

If it does, the next step will be getting out your RF generator and feeding modulated signals into the radio stages further back stream towards the antenna (more on this later).


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Re: My new project

Post by frank1956 on Mon Jan 12, 2015 11:21 am

Dr. Radio,
To answer your question I learned my lesson the first time and the Isolation Transformer is part of my safety feature now!!!

I preformed all the test  that were suggested on this thread in regards to the test rig and all pass with flying colors cheers

I then moved on to the signal generator test, using my Eico 324 I connected the HOT lead via a .1 cap @ 630 V to pin #1 of the 12BA6 tube and the ground lead to the B- of the radio. The signal generator was set at 455 kHz with the signal selector switch set to internal mod AF out.

When the radio was turned on a beeeeeeeeeeeeeeeeep was heard through the speaker (not very loud), and the volume of the tone could be controlled using the AF Mod/Output switch.

The question I have, is when the tone was heard and the band selector switch was moved from 455 kHz the same tone was heard at 500 kHz. I would think the tone would either change or go away when the band selector switch was moved???? Not sure if this test was a success or not???


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Re: My new project

Post by jerryhawthorne on Mon Jan 12, 2015 1:27 pm

Frank, you could be "overdriving" the radio with the sig. gen. Generally you want to turn the radio volume to max and the generator output as low as you can and still hear the beeeeeep at 455. Then try moving away from the 455 as see it the volume of the tone changes.
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Re: My new project

Post by Wildcat445 on Mon Jan 12, 2015 1:43 pm

Would someone be good enough to synopsize this project so that everybody could be brought up to speed with what is going on? Thanks.

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Re: My new project

Post by jerryhawthorne on Mon Jan 12, 2015 2:32 pm

It's gone way to far for that WC. Shocked
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Re: My new project

Post by Wildcat445 on Mon Jan 12, 2015 2:41 pm

I gather, by reading the last three pages or so, that Frank was having a problem with no filaments lighting. That has been remedied and he is now trying to find out why he still has no working radio. He is being instructed to inject an IF frequency in the various stages with his signal generator. He apparently had the generator turned up too high and the volume control on the radio not at full volume and is suffering the problems associated with that.

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Re: My new project

Post by frank1956 on Mon Jan 12, 2015 3:40 pm

jerryhawthorne wrote:Frank, you could be "overdriving" the radio with the sig. gen.  Generally you want to turn the radio volume to max and the generator output as low as you can and still hear the beeeeeep at 455.  Then try moving away from the 455 as see it the volume of the tone changes.
Jerry


Jerry,
Thanks for the advice, but I have the same results. Turned radio volume all the way up, got signal generator volume as low as I could get it, but still be able to hear the tone. Turn band selector switch from 455 kHz, but the tone did not change??? i.e. go away, change in tone etc.


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Re: My new project

Post by Wildcat445 on Mon Jan 12, 2015 8:16 pm

You may be tuning to a harmonic of the IF frequency, rather than 455 kc. Set the signal generator to 455kc, then move the tuning capacitor on the radio thru its range, from the low end to the high end. If you can hear the modulated 455kc note all thru the tuning range of the cap, you are tuned to the true IF frequency. If the note comes and goes, you are tuned to a harmonic. Always run the radio volume full on and the generator input just loud enough to hear. Have an AC volt meter connected across the voice coil of the speaker to measure output. You have done an alignment before. Good luck.

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Re: My new project

Post by frank1956 on Tue Jan 13, 2015 12:46 pm

WC,
I set the signal generator to 455 kHz and moved the tuning dial from the low end to the high end, the tone was heard all the way through with no interruptions in the tone. Radio volume was full and signal generator was set so that I could barely hear the tone.

Just an FYI this radio has and has had a bad hum in it from the beginning so the tone is very hard to hear at time without cranking the signal generator volume up, probably more then it should, but without it I would not hear the tone over the hum!!!! Before anyone says change out the electrolytic capacitors I did twice with same results!!!


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Re: My new project

Post by Wildcat445 on Tue Jan 13, 2015 5:00 pm

Before you try to go any farther, perhaps it would be well to step back a bit and review where we are.

You can get the 455kc IF note all the way thru the radio, and at all areas of the dial. That shows that the alignment is at least reasonably close enough that misalignment can be ruled out as a cause. If you have a bad hum, bad enough that you cannot tell the difference between hum and generator tone, we should probably eliminate the hum first. You say you have replaced electrolytic filter caps. Have you confirmed that they are wired properly? Posting a schematic of this radio would be good, but normally the negatives of the filter cap(s) are connected to common negative, or B-, of the set. This is normally one side of the power switch. Check the solder joints on these as well for cold solder joints. Do I remember some talk of a boo-boo of some kind? The reason you got an isolation transformer? Could something related to that incident have damaged one or both of the filter caps? Do you have two more that you could sub in to note any difference in operation? You are working on an AA5, not a color TV, so the answer has to be a simple one. Please check the basics and we will go from there. You really do need to get rid of that hum in order to hear your signal generator accurately. Good luck.

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Re: My new project

Post by Wildcat445 on Tue Jan 13, 2015 5:03 pm

Frank, could you post a schematic of this radio, and a good picture of the bottom of the chassis? That would help, and I thank you.

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Re: My new project

Post by Bill Cahill on Tue Jan 13, 2015 8:09 pm

Frank, it would really help if you could post good photos of the bottom of the radio, and, at least tell us the model number of the set so we can see if it's on Nostalgia Air. We really want to help you, but, the first thing to do is repair your power supply problem, which is likely causing the loud hum.........

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Re: My new project

Post by Dr. Radio on Tue Jan 13, 2015 11:41 pm

Guys, the model and schematic were listed in the first page on the very first post.

This is an AC/DC Crosley model 58TK

http://www.nostalgiaair.org/PagesByModel/494/M0003494.pdf

We've since discovered this is a poor schematic with errors though, ie ground (B-) not shown in the power switch leg/heater return, 100 ohm cathode resistor in the 50B5 etc.


Frank,

Let's back up here a minute. I remember you saying there was hum in the background, but the way you make it sound now, it's pretty much over-powering the audio?!

When you used the "audio test rig", how was your music? Just slight hum in the background, or annoying "can-just-hear-my-audio-above-the-hum"?

The gang is right, we need to address that if it's more then just slight hum.

Lead-dress comes to mind. This little radio was a hack job when you got it, so it's pretty easy to have wiring where it shouldn't be. Things like wires to the volume pot need to be kept short and not routed around sources of "noise". The heater wiring should be kept only long enough to make proper connections and away from signal and audio wiring, in fact, heater wiring should be kept pretty darn near "flat" against the chassis.

Another thing that can happen is cathode to heater "leakage" in the output tube. This requires subbing a different tube.
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Re: My new project

Post by Wildcat445 on Tue Jan 13, 2015 11:52 pm

If we are going after the hum, perhaps a good question would be is the hum affected by the volume control? If so, we need to suspect a possible heater/cathode short in the output tube. If not, something in the power supply is suspect. I think I remember this set now. They only drew one side of the filament circuit, IIRC. Good old Crosley schematics.

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Re: My new project

Post by frank1956 on Wed Jan 14, 2015 1:49 pm

Dr. Radio wrote:Guys, the model and schematic were listed in the first page on the very first post.

This is an AC/DC Crosley model 58TK

http://www.nostalgiaair.org/PagesByModel/494/M0003494.pdf

We've since discovered this is a poor schematic with errors though, ie ground (B-) not shown in the power switch leg/heater return, 100 ohm cathode resistor in the 50B5 etc.


Frank,

Let's back up here a minute. I remember you saying there was hum in the background, but the way you make it sound now, it's pretty much over-powering the audio?!

When you used the "audio test rig", how was your music? Just slight hum in the background, or annoying "can-just-hear-my-audio-above-the-hum"?

The gang is right, we need to address that if it's more then just slight hum.

Lead-dress comes to mind. This little radio was a hack job when you got it, so it's pretty easy to have wiring where it shouldn't be. Things like wires to the volume pot need to be kept short and not routed around sources of "noise". The heater wiring should be kept only long enough to make proper connections and away from signal and audio wiring, in fact, heater wiring should be kept pretty darn near "flat" against the chassis.

Another thing that can happen is cathode to heater "leakage" in the output tube. This requires subbing a different tube.

Dr. Radio,
The test rig worked great, music was heard very clearly on both test. Especial when I removed the connection from pin's #1 and #7 the 50B5 tube and connected the test rig to either one of the pin's the music was fairly loud with slight hum and the volume control worked like it is supposed to.  With the signal generator test there is not a loud tone being produced through the generator, that is why I am having a hard time hearing it, not because of the hum. Though I do have to crank the volume up on the generator in order for it to produce a audible tone for these ears to hear it.


Attached are two video's one without the signal generator attached and the other one with the signal generator attached


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Re: My new project

Post by frank1956 on Thu Jan 29, 2015 8:12 am

confused


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Re: My new project

Post by Bill Cahill on Thu Jan 29, 2015 8:18 pm

That doesn't even sound like your signal generator. That shouldn't be a hum. It should be a high pitched tone. Sounds like you have radio audio problems. Where are you connecting your signal generator??

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Re: My new project

Post by frank1956 on Fri Jan 30, 2015 11:07 am

frank1956 wrote:Dr. Radio,
To answer your question I learned my lesson the first time and the Isolation Transformer is part of my safety feature now!!!

I preformed all the test  that were suggested on this thread in regards to the test rig and all pass with flying colors cheers

I then moved on to the signal generator test, using my Eico 324 I connected the HOT lead via a .1 cap @ 630 V to pin #1 of the 12BA6 tube and the ground lead to the B- of the radio. The signal generator was set at 455 kHz with the signal selector switch set to internal mod AF out.

When the radio was turned on a beeeeeeeeeeeeeeeeep was heard through the speaker (not very loud), and the volume of the tone could be controlled using the AF Mod/Output switch.

The question I have, is when the tone was heard and the band selector switch was moved from 455 kHz the same tone was heard at 500 kHz. I would think the tone would either change or go away when the band selector switch was moved???? Not sure if this test was a success or not???


Frank



As stated above Bill.

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Re: My new project

Post by frank1956 on Sun Feb 15, 2015 12:30 pm

Has all my help run out on me??  lol!  Just checking to see if this was a dead project or do I need to be a little bit more vigilance?

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Re: My new project

Post by Wildcat445 on Sun Feb 15, 2015 10:21 pm

I'm confused. I'm still here.

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Re: My new project

Post by frank1956 on Tue Feb 24, 2015 4:56 pm

WC,
Thanks. I am still here to.
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Re: My new project

Post by jerryhawthorne on Tue Feb 24, 2015 5:11 pm

Frank, I'm still here as well. This thread has gone on so long it would be nice for you to do a summery of exactly where your at. What works and what does not. Dr. Radio is your best adviser but we can all chip in to confuse things. Laughing
This radio will work.
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Re: My new project

Post by Wildcat445 on Tue Feb 24, 2015 10:31 pm

What Jerry just said goes for me too.  What's the next step?

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Re: My new project

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