Help!!!

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Re: Help!!!

Post by frank1956 on Tue Aug 05, 2014 4:49 pm

Just two more days and hopefully I will have a signal generator, so I can get back to my Silvertone 3004!!!!!
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Re: Help!!!

Post by Wildcat445 on Tue Aug 05, 2014 7:37 pm

We are still here. I'm glad to see you are as well.

WC

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Re: Help!!!

Post by frank1956 on Wed Aug 06, 2014 5:30 pm

Signal Generator arrived today. Pic attached. Now I need to learn how to use it. Checked it over inside and out. The two tubes inside checked out ok, everything else looks good.  cheers 





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Re: Help!!!

Post by frank1956 on Wed Aug 06, 2014 11:47 pm

I kinda messed around a little bit with the signal generator on a working radio I have, just to get some what familiar with it. Seems to work ok on that radio, got the tone per the instruction manual. Tried it on the radio I am working on but not the same results. No harmonic tone, pitch or signal of any kind was generated.


Again just messing around, so if any one has any suggestions or something I may or may not have done please let me know. Thanks
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Re: Help!!!

Post by Wildcat445 on Thu Aug 07, 2014 12:34 am

Since you know how to operate your signal generator somewhat, what you need to do is to inject a signal into your Silvertone radio in specific locations and see what effect it has.  How are you using your generator?  When you were "messing around", where did you inject the signal into the good radio?  You need to be sure and use an isolating capacitor in the hot lead of your signal generator.  This will protect your signal generator from high voltage DC, which could be harmful to the generator, and possibly you.  Since you do not have an isolation transformer, extra caution is necessary since you are working on a potentially hot chassis.  I use an .01uf @630 volt cap on mine.  

WC

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Re: Help!!!

Post by frank1956 on Thu Aug 07, 2014 6:57 am

WC,
As the term implies messing around. I watch a you tube video and read a little bit of the manual I downloaded. I just laid the RF out cord next to the radio as the video suggested,did not hook it to anything on either radio. Tune the working radio to a spot half why between a station (basically to a null spot on the radio) Turn the band selector to the B band and turn the frequency selector on the generator until I had a pitch sound on the radio and tune the generator in between the pitch sound (zero beat) and no sound. The generator was on the same frequency as the radio. That is the extented of my training on the use of a generator. Try the same principle on the non working radio but as I stated without the same results. After reading your replay above it does not sound like the correct procedure?????


After re-looking at the Eico 324 generator it will need to re-capped and probably re-calibrated
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Re: Help!!!

Post by 75X11 on Thu Aug 07, 2014 8:59 am

That is a good plan to make certain that your test equipment is up to snuff. They are the indicators that should be doing right when everything else is going wrong. You might look on Ebay for the period troubleshooting guides for tube radios they offer, usually on disc. They can make a good reference for when you want to do a session on your own.
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Re: Help!!!

Post by frank1956 on Thu Aug 07, 2014 12:01 pm

Here is a video I did of the signal generator and a working radio. Please tell me what you think. Does the generator seem to working correctly? In the video I said my new Eico generator, it's my used Eico generator.


http://s1259.photobucket.com/user/relichtr/media/WP_20140807_001_zpsdadfa578.mp4.html?sort=3&o=0
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Re: Help!!!

Post by frank1956 on Sat Aug 09, 2014 10:13 pm

I have started my first step in signal generator use. I injected a signal into the radio (UNPLUGGED) starting at the speaker. I worked off tube 50L6 pin 3 (Power Amplifier) and off R9 1.5 K resistor. Success sound was produced out of speaker
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Re: Help!!!

Post by Wildcat445 on Sun Aug 10, 2014 1:16 am

Frank, I am not ignoring you. I have had guests this weekend, and have had little time to be on here. Everyone is in the rack, so I thought I would check in on you. They will leave tomorrow, and I will have more time to spend on this after Monday. I will get back with you then, if that is okay. Sorry for any inconvenience on your end.

WC

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Re: Help!!!

Post by frank1956 on Sun Aug 10, 2014 9:04 am

WC,
Never though that for a minute  Smile. I will check back in after Monday to see what going on. Thanks again.

Frank
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Re: Help!!!

Post by Bill Cahill on Sun Aug 10, 2014 7:22 pm

Pin three is the plate. That proves nothing, but, that the speaker is working.
Further, I'll say it one last time. I believe your problem to be one, or, more bad I F transformers. Silver mica disease is more common than you think.

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Re: Help!!!

Post by Wildcat445 on Sun Aug 10, 2014 8:58 pm

The IF's were checked earlier, and silver mica migration was tentatively ruled out as a possibility.  There was no positive voltage on the grids following the IF transformers.  There is still a possibility of problems in the IF stage, of course, but at this stage at least, SMD is not a sure thing.  I wonder if someone before Frank got the radio,  has not been turning screws, if you know what I mean.   Rolling Eyes 

What you need to do now, Frank, is to inject a modulated signal, at the Intermediate Frequency, (probably 455 kc)  to pin 5, the plate, of the 12BA6.  The radio needs to be turned on and warmed up for 10 minutes or so for this test. Be sure that your signal generator has been on for 30 minutes or so, to give it a chance to stabilize.  You will put the postive (hot) lead of the signal generator, in series with a .01 @630 volt capacitor, on Pin 5.  You can try just connecting the ground lead of the generator to the chassis.  Your service literature will tell you where exactly, so follow those instructions.  If you hear the signal, we know the second IF transformer is okay.  If not, we need to find out why not.  Try this and let me know what happens.  If you have questions on how to proceed, we are here to help.  Good luck

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Re: Help!!!

Post by Resistance is Futile on Mon Aug 11, 2014 4:23 am

I have followed this discussion and am Keeping a copy in Notepad.
I must say there is a lot of good tutoring going on, and the principles are well explained. I will enjoy this to the end.

One thing that I did note, and there was some mention of it. However---- The original pictures had a lot of sloppy soldering and I even noticed some cold solder joints. I even thought I saw some wires touching a tube rivet, (it could be the angle though that it was shot at) I did see a few strands of wire, that were right next to tube soldered pins. This is a definite NO-NO.

Just to digress the point, make an inspection of every and I mean every connection. Remove any flux, as it may cover up a cracked or cold solder joint.

I cringed when I saw that first picture. (Excellent pictures by the way and well focused, which helps tremendously, good Job)

And to re-emphasize, every resistor and capacitor should be listed in your notes, and even the part number if on the schematic. An your tested value for comparison to the schematic. That way as you go through your trouble shooting and write down your findings and steps you took, will benefit you and yes you will learn easier when you take notes. It is to your advantage to do this believe Me, experience is the best teacher.

Keep up the good discussion!
This will benefit both us Old-Timers and Newbies!!!!! Cool  Cool
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Re: Help!!!

Post by Wildcat445 on Mon Aug 11, 2014 11:32 am

This is one of those RARE cases where we get the opportunity to go completely thru a radio, from start to finish.  Frank has to be given a lot of credit here as well.  99% of the people just starting out would have given up by now.  Not Frank!  He has stuck this thing out, has followed our suggestions to the letter, and is learning as he goes.  In return, he is getting an education that money cannot buy.   Your suggestions, Cliff, are certainly well-taken.  Frank posted a pic of the chassis and we all offered our critique.  And thank you for your input and your kind words.

WC

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Re: Help!!!

Post by frank1956 on Tue Aug 12, 2014 9:19 am

Gentleman,
I appreciate everyone input/advice here on this forum. I must say the experience that I am receiving is very helpful and informative. I just got back home last night, went to West Virginia to watch the New Orleans Saints at their training camp. "WHO DAT".

WC I will at some point today processed with the the next test stage of injecting a modulated signal to pin 5, tube 12BA6. Will post results. Hopefully good news!!!!
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Re: Help!!!

Post by frank1956 on Tue Aug 12, 2014 9:49 am

Wildcat445 wrote:The IF's were checked earlier, and silver mica migration was tentatively ruled out as a possibility.  There was no positive voltage on the grids following the IF transformers.  There is still a possibility of problems in the IF stage, of course, but at this stage at least, SMD is not a sure thing.  I wonder if someone before Frank got the radio,  has not been turning screws, if you know what I mean.   Rolling Eyes 

What you need to do now, Frank, is to inject a modulated signal, at the Intermediate Frequency, (probably 455 kc)  to pin 5, the plate, of the 12BA6.  The radio needs to be turned on and warmed up for 10 minutes or so for this test.  Be sure that your signal generator has been on for 30 minutes or so, to give it a chance to stabilize.  You will put the positive (hot) lead of the signal generator, in series with a .01 @630 volt capacitor, on Pin 5.  You can try just connecting the ground lead of the generator to the chassis.  Your service literature will tell you where exactly, so follow those instructions.  If you hear the signal, we know the second IF transformer is okay.  If not, we need to find out why not.  Try this and let me know what happens.  If you have questions on how to proceed, we are here to help.  Good luck

WC I am a little confused. If I am working from the speaker back to the antenna would not my next step be to proceed to tube 12AV6 vice 12BA6? I do not see a .01 @630 volt capacitor on pin 5 tube 12BA6. Thanks
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Re: Help!!!

Post by Bill Cahill on Tue Aug 12, 2014 10:49 am

Yes it would. But, instead of that, why not check the low voltage pins on secondary or the I F transformers just to confirm there is no positive voltage there. If there is, the transformer is the culprit.

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Re: Help!!!

Post by Wildcat445 on Tue Aug 12, 2014 11:55 am

Frank, you need to use a .01 @ 630 volt capacitor from your stock. This is called an isolation capacitor. Its purpose is to protect the signal generator from the high DC potential (voltage) found on the plate of the 12BA6. You connect the isolation capacitor to the hot lead of the generator, then a test lead from the capacitor to the plate of the 12BA6. The signal from the generator will be modulated at 400 hz (nominal) at the Intermediate Frequency (IF) of the radio. The reason you inject a signal to the plate of the 12BA6 is to see if the IF signal will pass thru the IF transformer, which is supposed to be tuned to that frequency (455kc). The 12AV6 is the second detector, and its job is to detect the audio signal and seperate if from the IF signal. So injecting IF into the detector is like trying to pour gasoline in the tail pipe of your car to make the engine run.

We have previously determined that the power supply and audio sections of the receiver from the volume control to the speaker are operating as they should. For purposes of further troubleshooting, let's focus our attention on the section of the receiver from the volume control back to the antenna, basically the grid of the 12AV6 to the antenna. We have previously determined that there is NO POSITIVE VOLTAGE on the grid of the 12AV6. The next step, then, would be to inject our IF signal into the plate of the 12BA6 to see if it passes. If so, we move toward the antenna one more step, and if not, we find out what ails it. Do this and let us know how you come out. Any questions, just ask. I hope this made sense. I got interrupted by a phone call, and lost my train of thought.

WC

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Re: Help!!!

Post by Wildcat445 on Wed Aug 13, 2014 1:10 am

Bill, we are now working our way back from the second detector to the antenna. In our previous testing, according to my notes and memory, we did not find positive grid voltage on either tube grid following an IF transformer. Following our disciplined troubleshooting approach, and so that Frank not only finds the fault, but learns something in the process, we will start with the plate, pin 5, of the 12BA6 and see if it will pass a signal, at the IF frequency, thru the second IF transformer. Then to the grid of the 12BA6, then to the plate, pin 5 of the 12BE6 and so on. There may still be a fault in the IF transformer (s). We are going to avoid a shotgun diagnostic approach, since it could well be wrong, and Frank wants to learn the correct diagnostic procedure. So please bear with us and we will get to the first If in due course. Thank you.

WC

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Re: Help!!!

Post by frank1956 on Wed Aug 13, 2014 2:40 pm

I had to place an order for the .01 @630v Cap. My local Radio Shack did not carry it. Hopefully the next 2-3 days it should be here. Though I had one on hand.
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Re: Help!!!

Post by 75X11 on Wed Aug 13, 2014 4:55 pm

I think 50v is the speed limit at most Radio Shacks.  Very Happy 
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Re: Help!!!

Post by Resistance is Futile on Wed Aug 13, 2014 5:08 pm

75X11 wrote:I think 50v is the speed limit at most Radio Shacks.   Very Happy 
And it gets lower, And it gets lower, And it gets lower, And it gets lower, no wonder their closing all over the country. Sleep Crying or Very sad
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Re: Help!!!

Post by Wildcat445 on Wed Aug 13, 2014 9:09 pm

Frank, you would be better equipped for little surprises like this if you would buy at least a small stock of the most needed capacitors and keep them on hand.  Radio Daze has an assortment of the most needed sizes, something like 10 each, that will set you up in good enough shape that you will have a decent supply to start.  As you gain experience and figure out what you will need, you can stock up.  I buy hundreds at a time.  They are considerably cheaper in quantity.  Many times there is free shipping if you buy a quantity.  Your project will then not be held up waiting for a 30 cent part.  Good luck.

http://www.radiodaze.com/

WC


Last edited by Wildcat445 on Wed Aug 13, 2014 9:19 pm; edited 2 times in total

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Re: Help!!!

Post by Wildcat445 on Wed Aug 13, 2014 9:14 pm

Bill Cahill wrote:My "Shotgun" diagnostic approach has helped me a lot over the years...........

With all due respect, a shotgun diagnosis is one thing when you have 40 years experience. It is quite another when you are just learning the ropes. Frank will learn much more, and his project will have a greater chance of success if he adopts a systematic troubleshooting procedure. His final diagnosis may be the same as your shotgun diagnosis, but he will better understand how he arrived at that diagnosis.

WC

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Re: Help!!!

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