Videokarma.org

Go Back   Videokarma.org TV - Video - Vintage Television & Radio Forums > Antique Radio

We appreciate your help

in keeping this site going.
Reply
 
Thread Tools Display Modes
  #16  
Old 09-26-2009, 05:33 PM
rollei35guy rollei35guy is offline
...
 
Join Date: May 2008
Posts: 86
Quote:
Originally Posted by radio nut View Post
Yes to the variac. yes again to the 125 line voltage.I will start where you stated. I did notice That at least one of the heater lines did junction to a couple of caps parallel to a IF trans. I wonder if those mica or ceramic caps are bad.I will keep you posted.
Mica and ceramic caps are usually pretty stable. So I would not think that would be a problem.

You know I just realized those 1Lxx tubes all have a directly heated cathode. That might affect the voltage readings you are getting.
Reply With Quote
  #17  
Old 09-26-2009, 05:37 PM
rollei35guy rollei35guy is offline
...
 
Join Date: May 2008
Posts: 86
Quote:
Originally Posted by radio nut View Post
Yes to the variac. yes again to the 125 line voltage.I will start where you stated. I did notice That at least one of the heater lines did junction to a couple of caps parallel to a IF trans. I wonder if those mica or ceramic caps are bad.I will keep you posted. The 82 volts was across the "hot" cap. If I go from pos of the hot cap to chassis ground I had 5 volts " if " I remember. My printer is dead. I usually print the diagram and then right all over it. Now I keep running to the computer and then back to the set.Right now I am more worried about my radio.
Which one is the hot cap?

And remember this circuit does not have a chassis ground.

Sure wish that schematic had some voltage readings.
Reply With Quote
  #18  
Old 09-26-2009, 05:50 PM
rollei35guy rollei35guy is offline
...
 
Join Date: May 2008
Posts: 86
Quote:
Originally Posted by rollei35guy View Post
You know I just realized those 1Lxx tubes all have a directly heated cathode. That might affect the voltage readings you are getting.
Ok the deal with a directly heated cathode is the filament voltage is DC, and the signal voltage AC.

That would change the readings you get based on your meter settings and points you used as reference.

Sorry I missed that.
Reply With Quote
  #19  
Old 09-26-2009, 07:58 PM
radio nut's Avatar
radio nut radio nut is offline
Born in the wrong decade
 
Join Date: Dec 2007
Location: Lima, Ohio
Posts: 817
Quote:
Originally Posted by rollei35guy View Post
Which one is the hot cap?

And remember this circuit does not have a chassis ground.

Sure wish that schematic had some voltage readings.
The cap that is getting hot is the 100mf @25 volts on the diagram. My set had a 200mf@25 in what looked to be an original sectional electrolytic.I went ahead and put in a 200mf cap.
Reply With Quote
  #20  
Old 09-26-2009, 09:17 PM
radio nut's Avatar
radio nut radio nut is offline
Born in the wrong decade
 
Join Date: Dec 2007
Location: Lima, Ohio
Posts: 817
I did replace the 100pf cap in the last tube in the series- heater line. I just did this because I had one. I put the tubes back in and tried the variac slowly keeping an eye on the voltage across the whole tube heater line. I reached 9 volts at about 90 volts on the power cord. This time I heard static out of the speaker. I also noticed if I tapped the chassis with a screwdriver the static stayed the same, but if I tapp any of the tubes besides the rect. the volume changed or the static changed. Looks like I need to clean some pins and sockets and try this again. Also in my area I can't pick up anything pretty much below 600kc. due to interference . This set also had the appropriate noise at this spot on the dial. no real stations came in though.
Reply With Quote
Audiokarma
  #21  
Old 09-26-2009, 10:48 PM
radio nut's Avatar
radio nut radio nut is offline
Born in the wrong decade
 
Join Date: Dec 2007
Location: Lima, Ohio
Posts: 817
I feel the need to qualify an earlier statement of mine. I replaced a 100 pf. cap because it has full line voltage on it and it junctioned with the heater line(number 10 on the diagram by the junction were I was told to check voltage). it seemed the most logical to cause a back door problem being that the begining of the heater line is per the diagram. As I ran the set for a while I was able to turn up my variac and still maintain 1.5 volts across individual tube heaters. so, i am thinking that either the elctrolytics were still forming or I have a resistor changing value on me.I did not form the electros. because they are relatively lower voltages as compared to other AC sets.I did check B+ at 117v. so I now also need to make sure the voltage dial on my variac is accurate. I am thinking that the 117z6 should be putting out 117v. at the same line power.
Reply With Quote
  #22  
Old 09-27-2009, 06:01 AM
rollei35guy rollei35guy is offline
...
 
Join Date: May 2008
Posts: 86
Excellent progress! You have something coming out of the speakers and the filaments are not burning out. So you know you have B+, proper filament voltages and a working output stage.

That 100pf cap might well have been shorted. You can check them with an ohm meter by applying and reversing the leads. When you reverse the meter will deflect from the discharge. It's not a great test since it does not test the cap at working voltages Here is a link discussing capacitor testing

Your earlier problems might have been from the caps forming and resistors can change values. You can check them. It might be also that 125 volts just stresses the set too much.

On really old sets I just replace the electrolytics and the wax covered caps. Makes life easier.

As far as reception, if someone had been fiddling with the set all the transformer cores and trimmers in the IF and tuning might have been changed.

After dark you should be able to pickup stations across the country. But there could be alignment problems or some other cleaning issues in the tuning section. Typically alignment does not need more than a tweak if anything. But if someone was messing with the set who knows?

So the next question is do you have a signal generator?

Here is a link to an alignment guide for AA5 radios Yours is not an AA5 but and you have the procedure on the schematic (assuming you have rf generator). But he describes how to use a 2nd AM radio for alignment.

BTW WA2ISE posts here as well and has written some very interesting and informative articles online.
Reply With Quote
  #23  
Old 09-27-2009, 09:45 AM
radio nut's Avatar
radio nut radio nut is offline
Born in the wrong decade
 
Join Date: Dec 2007
Location: Lima, Ohio
Posts: 817
I have a cap checker(heathkit). I just have not used it . My signal gen. burned up but I have access to another so alignment will be easy enough. This radio came from Fair Radio in Lima, OH.They bought the stock from a tv/radio repair shop that closed in the 70's. I have purchased all sorts of radios and a couple tv's from them. What is unusual about the ones I have worked on is there are alot of mica/ceramic caps that are bad in these sets. The owner at Fair stated that he felt is was the fact that these sets were stored in an unkept building for 30 odd years. The temperature changes he felt ruined more caps then you would normally see. I did go ahead and spray this set with electronics cleaner last night but it is still kind of wet so I will try again later tonight.

Last edited by radio nut; 09-27-2009 at 09:50 AM. Reason: hit the wrong key
Reply With Quote
  #24  
Old 09-27-2009, 02:35 PM
radio nut's Avatar
radio nut radio nut is offline
Born in the wrong decade
 
Join Date: Dec 2007
Location: Lima, Ohio
Posts: 817
Well, I retried my set and I am back to square one. Same problem again, blew my last 1lb4 output tube( too much heater voltage). The cleaner I used last night was an older slow dry type. I even took a hair dryer to it today to make sure it was ready to go.Well, I had bought the last 1lb4 tube that Fair Radio here in town had so I will try to go there and search the "back stock" to see if I can come up with another. In the meantime I am going to unsolder one end of every cap in the set and use my heathkit to see if maybe that cleaner although it was not the lubricating type, being it was slow drying did soak into a cap and short it out.The one thing I would really like to ask someone from Philco is why was this set not a "clean "series string as far as heaters went.Why all the side taps into B+ lines and junctions to IF secondaries?I was thinking that my overvolting issue was from a leaky cap tapped into a B+ line.I guess I will find out soon(not soon enough)!
Reply With Quote
  #25  
Old 09-27-2009, 03:23 PM
rollei35guy rollei35guy is offline
...
 
Join Date: May 2008
Posts: 86
Sorry to hear that. How did it go out? Was it operating for a wile? Is that cap still getting hot?

Quote:
Originally Posted by radio nut View Post
The one thing I would really like to ask someone from Philco is why was this set not a "clean "series string as far as heaters went.Why all the side taps into B+ lines and junctions to IF secondaries?I was thinking that my overvolting issue was from a leaky cap tapped into a B+ line.I guess I will find out soon(not soon enough)!
I was puzzled by the complexity of the heater string too until I realized it's a directly heated cathode. In other words the heater and the cathode is the same element. So you have both the heater and signal on the same element.

You might well be right about the caps shorting out either from cleaner or age. It's possible that they are good initially when you turn on the set but break down after being at working voltage.

If you can figure out what the filament resistance should be on the 1lb4, you could wire in a resistor of similar value as a dummy filament so you could trace out the problem with out burning out another 1lb4. On the other hand you might burn out something else.
Reply With Quote
Audiokarma
  #26  
Old 09-27-2009, 04:01 PM
radio nut's Avatar
radio nut radio nut is offline
Born in the wrong decade
 
Join Date: Dec 2007
Location: Lima, Ohio
Posts: 817
How did it go out ? As soon as the rect. "hit". Yes the cap started getting hot again.It did not even hold long enough to get sound. Last night I left it running for 20-30 minutes before I turned it off and used cleaner.I did not think of cheating the filament line with dummies, I am going to try that, thanks.
Reply With Quote
  #27  
Old 09-27-2009, 05:48 PM
rollei35guy rollei35guy is offline
...
 
Join Date: May 2008
Posts: 86
Quote:
Originally Posted by radio nut View Post
How did it go out ? As soon as the rect. "hit". Yes the cap started getting hot again.It did not even hold long enough to get sound. Last night I left it running for 20-30 minutes before I turned it off and used cleaner.I did not think of cheating the filament line with dummies, I am going to try that, thanks.
You mentioned a resistor had been wired into the circuit but was on the topside of the chassis? And that the insulation was not well protected?

Maybe there are other 'presents' like that? Wires or solder connections close enough together that might cause an intermittent short if moved slightly?

I'm just guessing.

I would suggest replacing all of the electrolytics and wax coated caps. Add in the ceramic and mica's you are finding bad and that's just about all of them!
Reply With Quote
  #28  
Old 09-27-2009, 05:49 PM
rollei35guy rollei35guy is offline
...
 
Join Date: May 2008
Posts: 86
Don't suppose you could post some pictures?
Reply With Quote
  #29  
Old 09-27-2009, 06:26 PM
radio nut's Avatar
radio nut radio nut is offline
Born in the wrong decade
 
Join Date: Dec 2007
Location: Lima, Ohio
Posts: 817
I have done about 100 radios so far. I always replace wax and electro. caps first. Then check tubes and go from there.The resistor that I mentioned I already replaced under the chassis like it should have been(it was also the wrong resistance).I am going to recheck all solder connections for excess solder- shorts and any sort of self-inflicted stupidity. I do not have a digital camera yet. realistically I need one but I have other financial resposibilities ahead of it.
Reply With Quote
  #30  
Old 09-27-2009, 06:47 PM
rollei35guy rollei35guy is offline
...
 
Join Date: May 2008
Posts: 86
Quote:
Originally Posted by radio nut View Post
I have done about 100 radios so far. I always replace wax and electro. caps first. Then check tubes and go from there.The resistor that I mentioned I already replaced under the chassis like it should have been(it was also the wrong resistance).I am going to recheck all solder connections for excess solder- shorts and any sort of self-inflicted stupidity. I do not have a digital camera yet. realistically I need one but I have other financial resposibilities ahead of it.
Sorry, i got the impression that the electrolytics were original. My mistake. That eliminates a lot of issues right there.

Understand the financial responsibilities side. All too well. I was just curious as to what it looked like under there.

It's a puzzlement for sure that it worked for 30 minutes last night but today POW. If I think of anything I'll let you know. Like I said yesterday it sure would be nice to have some voltage readings at certain points.
Reply With Quote
Audiokarma
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 09:47 AM.



Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
©Copyright 2012 VideoKarma.org, All rights reserved.