EMERSON 547A WON'T WORK

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EMERSON 547A WON'T WORK

Post by RJP0614 on Sun Jan 24, 2016 3:57 pm

I'm somewhat of a newbie.
I bought an Emerson 547A a while ago that I replaced all the caps and filter caps, I replaced all the bad resistors. I checked all the tubes and found them good......I forgot to mention that the radio did work but only hummed.

Ws told it might be the IF or RF transformers. I removed the first (I believe to be the IF) can. Following a site that shows how to do this trick I drilled out the rivet that held the mica cap inside. The mica cap showed a lot of black indicating SMD (silver mica disease), I cut out the tabs that acts like a cap.
I did it gently.
The video showed how to remove the flat piece of mica and put all the stuff back together, sealed it up, place it back in the chassis, find a couple pf caps and bridged them in their respectful place on the IF coil tabs. They take over the place where the original mica caps used to be. Instead of being in the can they are connected under the chassis.
The radio still hums and no other sounds.
I understand that crackling would be warning signs of a bad IF can. I now don't know If I did the right thing replacing the caps. The mica in the cans had a good amount of black to begin with.
For the heck of it, is there anywhere I can find some IF and RF cans? I have two other radios with similar problems.
HELP!!!

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Re: EMERSON 547A WON'T WORK

Post by Wildcat445 on Sun Jan 24, 2016 7:44 pm

First off, if I haven't said this previously, welcome to TRF!

Do you have the schematic for your radio? If not, it would surely help you to have one. The schematic is the road map for the electrical circuits in your radio. Posting the schematic on here will help members follow along with your project and will enable them to make constructive comments as necessary.

I have a couple hundred radios in my collection and have worked on many hundreds more. In nearly 40 years in the hobby, I have run across exactly three confirmed cases of silver mica migration, aka SMD. I have found this condition to be massively over-diagnosed. There are causes for noise in the output of a radio other than SMD. SMD is best diagnosed by checking for positive voltage on the grid of the stage following the IF transformer in question. Voltage leaking between the mica sheets in the transformer causes the crashing sound. This leakage drives the grid positive. Without more information on how the condition was diagnosed and the troubleshooting methods employed, it is impossible for me to tell if you did the right thing or not.

More information will be necessary to help you further. I would suggest developing a directed series of tests, first to eliminate the hum, then to "divide the radio" at the volume control to determine where the fault lies. Why the radio is dead.

Is the hum affected by the volume control? If not, you should look to the filter caps, whether they are good and installed correctly. A heater-to-cathode short in an audio tube will cause a hum. Substituting the audio tube(s) with those known good are the best test for this condition. A tube tester may or may not reveal such a fault. If the hum is affected by the volume control, it originates ahead of the volume control. It might also be helpful to take a picture of the bottom of the chassis and post it. We will be happy to help you any way we can to figure out what is going on with your set. Directed tests will determine whether or not you need replacement IF transformers. Good luck.

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EMERSON 547A WON'T WORK

Post by RJP0614 on Mon Jan 25, 2016 12:05 am

I got this radio quite a while ago.
I was on another forum and found some of the help getting a bit uptight with me. I thought I had a grip on reading schematics but I was wrong. I ended up after eight pages long with one good member and another radio using the radio as parts, no matter what I did to the radio, it wouldn't work. I pretty much rebuilt it from scratch.
Now I have this Emerson 547A to work on and it seems to start doing the same as the other radio. I only have a tube tester and a multimeter to go by.

I was told by the other forum that this Emerson needed a new IF transformer. I gently removed it, took it apart to find the mica cap was almost totally black. I found a website that tells you how to rebuild the transformer. I found it a lot more difficult than what the say. The IF transformer was very fragile and ended up as scrap. I am hoping to get another one somewhere and hoping I can find someone who can rebuild it for me, unless the IF trans former really needs it. I have two other radios with the same problem both of which showed the same problem with the same results all are broken because being fragile. I am now afraid that if I get another IF transformer I'll get stuck with the same problem.

The radio, when turned on, starts humming. The hum is not affected by the volume. I was told it might be heater to cathode problem. I switched all the tubes for known good ones so I think that rules out that problem.
The filter caps and non polar caps are new...I installed them one end at a time so I wouldn't forget where they went. I did the same thing to the bad resistors as well.
Where to go next when I get a new IF transformer.
I was also told to learn by reading he schematic not by pics.
I tried to upload a schematic but the forum file notification won't let me...it says it's to big......

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Re: EMERSON 547A WON'T WORK

Post by Wildcat445 on Mon Jan 25, 2016 12:58 am

We'll try to not give the impression of becoming impatient. Sometimes, it is difficult to "see" what someone else is trying to do, and how he is doing it, via electronic media. Talking someone thru a procedure is at least as equally difficult as it is for the person being guided. We hope we will be more successful than what has taken place in the past.

I sincerely feel that having a look at the schematic is the next step. My Riders library is not available to me at the moment. Then we need to make certain that the filter caps are wired correctly. You have subbed the tubes, so we'll move on from this point. Filter caps have been known to be wired incorrectly with the negatives to chassis, rather than B-. That could account for the hum.

I have not had a lot of luck repairing IF cans with SMD myself. It is a skill not possessed by everybody. Don't kick yourself for not getting it right. Perhaps we can find a replacement IF transformer if you feel that is what you need.

Reading a schematic is certainly a necessary skill. Most experienced restorers, myself included, take detailed pictures while proceeding to eliminate any failure of memory. This gives another point of reference in the case questions should arise. This is why I asked for a picture of the bottom of the chassis. We can look at what you have done, and perhaps make suggestions or even see something that could be done differently. Or we could also eliminate a misstep as a problem.

Posting pictures takes some practice and patience on this forum. It is really easy after you have done it once. Doing it once is sometimes the challenge.

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Re: EMERSON 547A WON'T WORK

Post by Wildcat445 on Mon Jan 25, 2016 1:12 am

I got on radiomuseum.com to try to find the schematic for this radio. I really hate that site, and my feeling has not changed. The best I could see it that the negatives of the filter caps should be connected to B-, which looks to be one side of the power switch. I could not print the schematic. I will try again tomorrow. You might just double-check the wiring on the filter caps to make sure they are wired correctly. Good luck.

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Re: EMERSON 547A WON'T WORK

Post by jerryhawthorne on Mon Jan 25, 2016 2:27 am

Here is a link to the schematic.
Jerry

http://www.nostalgiaair.org/pagesbymodel/651/M0004651.pdf

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Re: EMERSON 547A WON'T WORK

Post by willy3486 on Mon Jan 25, 2016 9:08 am

A few thoughts I have. First a suggestion, anyone new to the hobby I tell folks a few things to look for that will help tremendously. Some sort of isolation transformer and dim bulb tester. You can do a search for dim bulb maker and they are easy to make. Isolation transformer are to keep you safer. The next thing I suggest is a signal tracer. There are also designs on the web, I have used the same one for over 30 years that I made from a transistor radio. This is one of my most used troubleshooting tools. Next in line is a signal generator that can generate am signals and the signal in transformers. Don't worry about not having them right now but don't let these items pass you by if reasonable.

Next on to the radio. I agree with wildcat to the SMD. I have rarely seen it so bad I feel like I need to fix it. I have seen it a few times. If I have one of my own and it does the SMD pop from time to time I usually leave it. But if it sounds like a constant lightning discharge I will do something. I have been doing radio repairs since the 70s and I have only seen this recently since getting back into them. I think I have fixed two or three with it. As far as fixing this I suggest leaving it until you have better experience.  One of the reasons I leave them and do not fix the cap on every one it is a pain. I have fixed many hundreds if not into the thousands of tube radios. Here are my steps I do before I even turn one on. I will disassemble the chassis from the case. I then will clean it good, dusting off type stuff. I then will use a  electronics cleaner that evaporates, last I got was from lowes at a decent price. I spray this on the tube sockets with the tubes out and the tuning coil. I do this to remove dust and hopefully corrosion. Next I spray a good tuner or lubricating cleaner on the sockets lightly,the tuner, and the volume controls. This helps to smooth out popping in volume controls,helps the tuner move smother and on the sockets helps prevent and remove corrosion. I will wiggle the tube in the socket to help get a better connection. I have heard of folks using WD40 but I personally don't think I would as it is flamable. One thing I do use for rusted items is brake fluid. If the volume control is rusted or the tuning cap I will place a drop or two on the area once a day. I have been able to get volume controls and tuners going again doing this. After a while of this and wiggling the shaft it will loosen up.   I then use cleaner to clean the fluid off.


My next step it to do a visual on the circuitry. Sometimes you might see a resistor or some other part burned out. For example if a cap shorts it can burn up a resistor. If no parts can be seen as bad I will then replace the caps in cans and also the wax caps. With the cans, many times they are in mf. For example  I replaced a can this weekend that was 20 mf,20mf, and 10mf in one can. What I will do is to put one of the terminal strips that can be mounted. I usually look for a hole in the chassis then bolt the strip to it. I then clip the leads off the cap one at a time then run the wires to the new terminal strip. These cans most of the time are grounded so I just make sure I have one ground on the strip. I then put one can at a time on the strip. Most replacement caps can go under the chassis and I just leave the old cap on top disconnected for looks. As far as the wax caps I usually replace with some type of epoxy dipped caps. Sprague is one brand and many are orange. Most of the time I also replace the power cord. I then do a visual inspection and after that I will then and only then bring it up to 120 volts with my variable isolation transformer.

Most of the time then and only then will I think about looking for issues such as SMD.Many times,probably 70% to 90% of the time the radio will play. Usually if I have to dig and troubleshoot it is because someone else had been in it trying to fix it. If this process at this point does not fix it I then go to my signal tracer and generator and follow the path. One rule that works great I learned in tech school. they called it something like half rule or split it in half rule. What that means I would inject a signal into the transformer on your diagram between the 12ba6 and 12at6 tubes. If I heard sound come out of the speaker I knew that the last half was not the issue. Then I would go back to the first part and inject a signal in the middle of that section, like the input of the 1st if transformer.  As far as yours go back and look at the diagram to see if you have any parts you replaced in wrong or wrong location. We all have done that from time to time. Usually most of the time I see hum from caps, I would eliminate this as causing the issue first.


As far as other sites on radios take what you hear with a grain of salt many times unless it is about safety. One site I use to go to before this had a lot of arm chair experts that would drown out the folks who had worked in this field. One time for example there was a question on soldering and replacing a part. One fellow posted about it and how to do it. He posted how I was taught, I have been a electronics tech making my living since the 80s and working on stuff since the 70s. His explanation was also the same as in many books and manuals I had from the radio companies themselves. Well this armchair expert chimed in and said that fellow had no idea what he was talking about. He said it was all wrong and to do it a totally different way. This way I learned was wrong in both my training and manuals. I got curious and looked up these fellows profiles. The first fellow who did it like I did was a Radio/TV repairman and shop owner for decades who was retired. The self proclaimed expert was nothing more than a newbie who had only got into radios in the last two years.

This is a great hobby and compared to say cars a relatively cheap one for the rewards you get out of it. The folks here at this site are more laid back and easy going than other sites. Many of us here have made living doing repairs of some type and don't mind helping out newcomers to the hobby.

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Re: EMERSON 547A WON'T WORK

Post by RJP0614 on Mon Jan 25, 2016 11:11 am

I just typed a whole lot of replies and the forum kicked me out. arg!
I'll try to remember what I already did.
As far as the veterans go..... What they should be doing to help out is help...but what they actually are doing is trying to puffer up and act as though they are greater than thou attitude. Try giving the knowledge as a tool and not act as a "TOOL".
Everyone wants to learn here. just about everyone learned how to drive a car by being shown how to do it. I understand electricity kills if mishandled" so can a car"!
With that out of the way...........................
When I get a tube radio I take the chassis out. I clean both the chassis and the case. The case, depending on how bad a shape glue back together, prep it waiting for the chassis.
The chassis cleaned from rust, dust and all that is built up foul, lube the movable parts with electronics cleaner or as said brake cleaner, all evaporate quickly, clean off the tubes then I replace all the caps, one end at a time, I don't snip both ends and hope to remember where it went.......I snip one end of the old cap then solder in the new one of same value, snip off the other end and solder the new one. I do the same with the filter caps making sure of the polarized ends. I learned that one the hard way. Soldered in the new one the wrong way and " POP" LIKE A CHERRY BOMB...... The filter cap was destroyed and left bits and pieces under the chassis. Quite the mess!
I built a dim watt or bulb tester via the web, easy to build.
A thought I had! I was told the IF coil was bad hence the need for a new one, or actually three new or used ones...different radios waiting for parts. I removed the rivet out of the coil via melting it out...drilling is not recommended.....

removed the cap where the mica is, carefully bend up the tiny metal tab, remove the mica "the one I removed was more black than white.........

here's an idea.....and no I didn't do the following..............

" replace with a new piece of mica? "I feel the mica needs to have a little silver on it" hence SMD!
or squirt on a little bit of silicon rubber to prevent contact of the two metal tabs. When the silicon is dry replace the coil under the chassis and place a silver mica cap between the tabs of the coil?

When, each time I worked on any of the coils, those metal tabs that hold the mica in place break off and can't hold themselves in place while being soldered. The little tabs that need to be soldered actually melt the plastic holding the coil together.
I've tried to finish off the soldering parts but when they are finished there's no change in the performance of the radio.
I read on the internet that SMD is usually detected by a crashing or loud scratching sound, which wasn't the case with these radios.
Either way I now have to get hopefully used coils.
This Emerson I only tried to repair the IF coil. I left the other one alone.
I trying to contact a vender for the used coils. When that happens I will contact people here.
Sorry for the long winded approach.
Thanks for the understanding.


Last edited by RJP0614 on Mon Jan 25, 2016 11:16 am; edited 1 time in total

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Re: EMERSON 547A WON'T WORK

Post by RJP0614 on Mon Jan 25, 2016 11:14 am

By the way! I've been playing with tube radios for about two to three years. I find that these radios are hitting me with harder and harder fixes....I think they are testing me with harder and harder problems to see if I can figure them out! Just a thought

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Re: EMERSON 547A WON'T WORK

Post by willy3486 on Mon Jan 25, 2016 11:41 am

Keep in mind this is the internet and chance are none of us have met or even know experience each one has. Because of that I usually explain the basics like what is good to have in the way of tools and how to do stuff. Keep in mind with many of us its not a puffing up attitude with a greater than thou attitude to someone, We just try to help. Like I said I have been tinkering with them since the 70s but we still find the tough dogs. I learned to set aside the ones I got stuck on and come back to them. I got out of fixing them around 92 and got back into them about 2012. I had all my original stuff. I fixed one I had set back 30 years ago . None of us get paid here to do this we just help out as we are "neighbors" working on radios.


One way I test coils is just use a ohm meter. On many IF transformers there are two coils one in and one out. I usually check for continuity. As far as the mica/if transformer stuff I keep it simple. I take it apart. I clip out the mica connections then I replace the mica stuff with a simple disk cap I think 120 to 150 pf range if I remember. Mainly you are replacing the caps across the IF coils.

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Re: EMERSON 547A WON'T WORK

Post by Wildcat445 on Mon Jan 25, 2016 2:52 pm

There are some really fine folks on this forum.  Everybody is more than willing to help anyway they can.  We work together here and that's the way our hosts want things to go.

With all due respect, my suggestion to the OP would be to try some of the suggestions he is soliciting from us and try not to argue or criticize those who are only trying to help.  I made specific suggestions for him to check trying to find the source of the hum.  As far as I know, this has not been done.  Jerry was good enough to post a schematic so we would have documentation to work with.  His efforts should have been recognized and appreciated.  Willy was good enough to provide a refresher course in the basics, something that is always good to read occasionally, even by more experienced radio servicers.  This effort as well should have been recognized.

Finally, nobody is trying to make themselves look good at the expense of the OP.  Veterans teaching are only as effective as the newbies listening.  The OP appears either unwilling or unable to follow our directions.  We are trying to "see" his project in our minds' eye and are attempting to help based solely on our experience.  It seems to me that the OP would make more progress fixing his radio by trying the suggestions offered in good faith.  And to not criticize those trying to help.

Thank you, Jerry and Willy, for your input.  And good luck, RJP0614, with your radio.  I will be watching this hunt from the porch.

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Re: EMERSON 547A WON'T WORK

Post by RJP0614 on Mon Jan 25, 2016 4:38 pm

I just read the posts
Willy I am very sorry. I didn't mean to come across as being rude and not appreciating the info you gave. I only meant that I already tried those steps.

Jerry: I also apologize to you, and thanks for finding the schematics. I didn't mean to ignore you or anyone that gave me help with my radio.
All the info was a bit overwhelming and I forgot to give the people that helped me a proper thank you.
Wild cat: I never indicated that anyone in hear gave me a hard time. Everyone in hear has been very helpful and pouring their help on me. I sometimes forget to thank the rightful people. I never criticized anyone here.
Have a wonderful evening.
.

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Re: EMERSON 547A WON'T WORK

Post by 75X11 on Mon Jan 25, 2016 4:44 pm

Another welcome. WC just meant he was stepping aside to let Willy help.
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Re: EMERSON 547A WON'T WORK

Post by willy3486 on Mon Jan 25, 2016 9:11 pm

75X11 wrote:Another welcome.  WC just meant he was stepping aside to let Willy help.

So much pressure! Seriously though my comments were suggestions. As far as rjp0614 no offence taken at all . I was trying to get across that all of us here don't have that attitude you saw on the other site. We are few in numbers compared to some but as far as groups go this has been the one I have joined at that has the least bit of rudeness and know it alls of any site I have been at. I bet I know where you were talking about and many of us are misfits from there and left due to rudeness. On back to the repair.

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Re: EMERSON 547A WON'T WORK

Post by willy3486 on Mon Jan 25, 2016 9:22 pm

I reread what WC wrote. I would check what he says on the voltage of the tubes. It was early and it didn't click then.I don't know if everyone will agree with this but here is how I replaced a bad IF transformer a while back. I had the diagram for a radio the IF coil was shot on one side. I have resoldered broke wires to the coils at times but there was no reading on the ohms side. So I looked around in my junk box and found one similar that had close to the same ohms reading of the side was good, for example the schematic said 70 ohms but this one was like 80. I tried it by using jumper wires and it came on and I could tune it in. I installed it and got the radio to going. Save junk parts for such an occasion.

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Re: EMERSON 547A WON'T WORK

Post by Wildcat445 on Fri Jan 29, 2016 5:24 pm

Finding and using spare parts is about the only thing that can be done if a replacement IF can is needed. My problem is that I get my parts radios going then don't want to take them apart for fixing another radio. I do have a few radios that are too far gone to try and save. I get those running to see what parts are good. That procedure can be a double-edged sword.

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