Some sets of the late forties early 50s use little 3/4" square IF transformers that had "integrated" silver mica capacitors that after many years go bad because the silver oxidizes or something and migrates from one side of the cap to the other cap.
( dreaded silver mica disease)
If this is the case the IF transformers need to be modified.
Agree with Peter. A weak 12SQ7 normally makes little difference in radio operation. A tube tester is much harder on this tube than a radio. In a radio 12SQ7 draws very little current.
Norm
:Describe that crackling... is it more like bursts of crashing static?.
:What radio are you working on?
:
:Some sets of the late forties early 50s use little 3/4" square IF transformers that had "integrated" silver mica capacitors that after many years go bad because the silver oxidizes or something and migrates from one side of the cap to the other cap.
: ( dreaded silver mica disease)
:If this is the case the IF transformers need to be modified.
:Describe that crackling... is it more like bursts of crashing static?.
:What radio are you working on?
:
:Some sets of the late forties early 50s use little 3/4" square IF transformers that had "integrated" silver mica capacitors that after many years go bad because the silver oxidizes or something and migrates from one side of the cap to the other cap.
: ( dreaded silver mica disease)
:If this is the case the IF transformers need to be modified.
Static from mica caps can happen anytime. When a radio is first turned on tubes aren't up to full emission so they draw less current. Less current means higher B+ voltage. Amount of B+ can have an effect on when static starts. It can work the other way also. Static at first then goes away.
Norm
:It's an Admiral 5J22. The sound is more or less a consistant static. I had first supsected the integrated capacitors in the IF cans, but wouldn't they produce crackling when the set is first powered on, rather than after 2 minutes or so.? This behavior is consistant.
:
::Describe that crackling... is it more like bursts of crashing static?.
::What radio are you working on?
::
::Some sets of the late forties early 50s use little 3/4" square IF transformers that had "integrated" silver mica capacitors that after many years go bad because the silver oxidizes or something and migrates from one side of the cap to the other cap.
:: ( dreaded silver mica disease)
::If this is the case the IF transformers need to be modified.
:Hi
:
: Static from mica caps can happen anytime. When a radio is first turned on tubes aren't up to full emission so they draw less current. Less current means higher B+ voltage. Amount of B+ can have an effect on when static starts. It can work the other way also. Static at first then goes away.
:
:Norm
:
::It's an Admiral 5J22. The sound is more or less a consistant static. I had first supsected the integrated capacitors in the IF cans, but wouldn't they produce crackling when the set is first powered on, rather than after 2 minutes or so.? This behavior is consistant.
::
:::Describe that crackling... is it more like bursts of crashing static?.
:::What radio are you working on?
:::
:::Some sets of the late forties early 50s use little 3/4" square IF transformers that had "integrated" silver mica capacitors that after many years go bad because the silver oxidizes or something and migrates from one side of the cap to the other cap.
::: ( dreaded silver mica disease)
:::If this is the case the IF transformers need to be modified.
I would use 82 pf or some other standard value. IF Transformers are adjustable so exact value isn't critical.
Norm
:I think I know what to do now. The caps are 75pf. Since I can't get that exact value, should I go higher or lower in value?
:
:
::Hi
::
:: Static from mica caps can happen anytime. When a radio is first turned on tubes aren't up to full emission so they draw less current. Less current means higher B+ voltage. Amount of B+ can have an effect on when static starts. It can work the other way also. Static at first then goes away.
::
::Norm
::
:::It's an Admiral 5J22. The sound is more or less a consistant static. I had first supsected the integrated capacitors in the IF cans, but wouldn't they produce crackling when the set is first powered on, rather than after 2 minutes or so.? This behavior is consistant.
:::
::::Describe that crackling... is it more like bursts of crashing static?.
::::What radio are you working on?
::::
::::Some sets of the late forties early 50s use little 3/4" square IF transformers that had "integrated" silver mica capacitors that after many years go bad because the silver oxidizes or something and migrates from one side of the cap to the other cap.
:::: ( dreaded silver mica disease)
::::If this is the case the IF transformers need to be modified.
If the case happens to be a must have exact value, then Mouser Electronics at www.mouser.com has the 75pf micas p/n 5982-15-500V75 at 56 cents each.
Radiodoc
::Hi
::
:: I would use 82 pf or some other standard value. IF Transformers are adjustable so exact value isn't critical.
::
::Norm
::
:::I think I know what to do now. The caps are 75pf. Since I can't get that exact value, should I go higher or lower in value?
:::
:::
::::Hi
::::
:::: Static from mica caps can happen anytime. When a radio is first turned on tubes aren't up to full emission so they draw less current. Less current means higher B+ voltage. Amount of B+ can have an effect on when static starts. It can work the other way also. Static at first then goes away.
::::
::::Norm
::::
:::::It's an Admiral 5J22. The sound is more or less a consistant static. I had first supsected the integrated capacitors in the IF cans, but wouldn't they produce crackling when the set is first powered on, rather than after 2 minutes or so.? This behavior is consistant.
:::::
::::::Describe that crackling... is it more like bursts of crashing static?.
::::::What radio are you working on?
::::::
::::::Some sets of the late forties early 50s use little 3/4" square IF transformers that had "integrated" silver mica capacitors that after many years go bad because the silver oxidizes or something and migrates from one side of the cap to the other cap.
:::::: ( dreaded silver mica disease)
::::::If this is the case the IF transformers need to be modified.
:
:If the case happens to be a must have exact value, then Mouser Electronics at www.mouser.com has the 75pf micas p/n 5982-15-500V75 at 56 cents each.
:
:Radiodoc
:
IF transformers with discrete condensers inside usually have either mica or tubular ceramic units. These almost never fail. Also, if they're discrete, there's no way the primary and secondary can short together via this route, since the two condensers are nowhere near eachother. Normally this is the kind of short that causes crackling. On occasion a condenser, whether discrete or integral, can go bad on its own and cause crackling anyway, by causing a short across either the primary or the secondary, but not between the two. Voltage across the primary or across the secondary is not at all as great as the difference between the two, and so arcing shorts don't usually take place in this way. Another crackling problem you might get is when an integral condenser gets corroded, and doesn't make proper connection with contact springs that hold it in place.
Check your condensers. If they're built into the base of the IF (integral), definitely get rid of them. Those are nasty. Whether they corrode or short, they're a headache. If they're discrete components, though, you may want to test them, first. The voltage source you build costs a few dollars more than replacement condensers, but you can use it over and over again to test other non-electrolytic condensers (electrolytics often have too much leakage for this test). Also, you say that you re-capped the set. Make absolutely sure that you replaced all condensers, and not just those in the power supply or audio section. Every one counts. Normally it is not necessary to replace mica condensers (the rectangular units with colored dots), but occasionally these are actually paper units. I don't recommend that you replace this type of condenser every time, but always test this kind to be sure that it isn't a leaky paper unit. Never overlook it. Your DC power supply and your volt meter will come in handy here, and will tell you if any of these are bad. Actually, for a DC power supply, I use my tube tester. Tube testers come in many variations, though, and not all can be used as power supplies. With mine, any pin connected to a lever that's thrown up is connected to one side of the high voltage (on an EICO 625, selector switch position #4 yields 200 volts AC). Any lever thrown down connects its pin to the other side of the high voltage supply. Connect a diode to one side, and your condensers and resistor after this. The condensers should connect to the other side to form a filter. If the diode has the paint line facing away from the tester, then it, and the resistor afterward will be positive. The other side of the high voltage supply will be the negative side.
Also, if you hear a crackling sound, and it only comes about after the set has been on for a few minutes, you may have an element to element short in one of the tubes. When you test your tubes in the conventional way, you don't do an element to element test. With an emissions tester, all of the grids and the plate are connected together. Any shorts between any of these will not show up. If your tester is at all like the EICO 625, you perform an element to element shorts test like this: Throw all levers down. Throw the lever corresponding to the tube pin (element) you want to test up. If the neon light lights up, then you have a short. It is best to have the heater running in order to find a hot tube short, so keep one of the heater pin levers in the center, and the other down, and adjust for proper voltage (connect the heater in the normal way). Tap the tube while making these tests. Loose elements will cause the shorts light to flicker. If you ever test a tube that has one element connected to two pins, you must throw both pin levers up or you will get a short indication due to the connection between the two pins. One tube with such a configuration is the 50C5. Its control grid is connected to two pins.
If you ever wish to test the heater for continuity (say, in a metal tube, or in a battery tube, where it's difficult to see the filament), keep one heater pin lever down, and throw the other up. The shorts light will light if the heater is good (when performing a heater continuity test, though, the heater will not light up...only enough current is sent through it to light the neon light). For multi-tap heaters, like that found in the 35Z5, you can check each segment by throwing the end pins up, one at a time. Leave the center pin lever down, and also the other end not being tested. For the 35Z5, pins 2 and 7 are the ends of the filament, and pin 3 is the center tap (not really in the center, but somewhere in between). When testing 7, leave 2 and 3 down. When testing 2, leave 3 and 7 down. The first test will test the segment between 7 and 3, and the second will test the segment between 3 and 2.
NEVER EVER PRESS THE TEST BUTTON WHEN MAKING SHORTS TESTS! If the shorts light is lit, pressing the test button could damage the tester or the tube.
Take a look at the EICO 625 schematic on this web site under References. If your tester differs from this, and you lack instructions, tell me your model number, or send me a schematic if you have one. Then I can come up with instructions for your tester.
Thomas
An RC coupler.
If the crashing goes away.. you know that was the cause.
lTake a ook here for info and values... very simple.. I have done this it works fine. ...and Norm wrote it.
http://www.antiqueradios.com/chrs/journal/transformers.html
Thomas, I did recap all the paper and electrolytics (8 caps included the multi-section) and I my tester is the Eico 625 (you must be a mind reader). One of the IF cans appears to have the integrated caps because I can see metal strips through the clear plastic. On the other can, I can't see because the bottom is brown plastic.
My question is can I pull the top of the IF can off to see what's inside? I know I'll have to unsolder all leads to the cans when I replace the integrated caps.
Also, Peter if you're reading this, do you or other radio restorers get together locally or have repair clinics? I live in your general area. I'm aware of the NJ ARC in Princeton, but I'm unable to make the monthly meetings.
:If you think you might have a defective IF transformer with silver mica disease... you can do a quick simple by-pass test to determine if that is your problem.
:Simply by-pass the suspected IF transformer with two resistors and cap.
:
:An RC coupler.
:
:If the crashing goes away.. you know that was the cause.
:lTake a ook here for info and values... very simple.. I have done this it works fine. ...and Norm wrote it.
:http://www.antiqueradios.com/chrs/journal/transformers.html
:
... so whatever your name is.. lol
I do not know of any local guys around here to meet with so I don't get to go to nything like that .....but it sure would be nice.
How do you know that you live in my area.. from my website?..
whatever... SURE.
... y'know it only takes two people to have a meeting.
.. so I'd be glad to get together here with you ...or at your joint or somewhere else.
.. but you are certainly MOST welcome to come here anytime and bring something you need help with.. gladly.
I'd enjoy that very much.
I guess you already know I live in Haledon, NJ...Where are you from?
here's my number 973-790-7960
Gary
:Dear "Beginner":
:.. ( It must be hard going through life with a name like "beginner"...lol)
:
:... so whatever your name is.. lol
:
:I do not know of any local guys around here to meet with so I don't get to go to nything like that .....but it sure would be nice.
:
:How do you know that you live in my area.. from my website?..
:
:whatever... SURE.
:... y'know it only takes two people to have a meeting.
:
:.. so I'd be glad to get together here with you ...or at your joint or somewhere else.
:.. but you are certainly MOST welcome to come here anytime and bring something you need help with.. gladly.
:
:I'd enjoy that very much.
:I guess you already know I live in Haledon, NJ...Where are you from?
:here's my number 973-790-7960
:
:
Regarding the EICO 625, well, it's a rather common tester, so it isn't uncommon to find someone with one. It does a fine job. It doesn't tell you all of the details, but it gives you a basic idea as to whether a tube is functioning properly or not. If a tube tests out really weak, usually it won't work in a radio. In some circuits, like the 12SQ7 circuit, it doesn't make much differenc (unless the tube tests out as dead). In some cases, like with FM radios, it's better to have a more elaborate tester, but with most things I find that the EIC0 625 does the trick. I have found that certain FM RF amplifier tubes can act drastically different even though they test similarily on my tester.
I recommend replacing all of the resistors in your tester for accurate results, or at least check them for proper resistance. I was often getting weak results on the #2 setting, and this turned out to be due to a drifted resistor. The #2 setting actually still is kind of strict (makes tubes out to be bad when they still work fine), but it works much better now than it did before.
Thomas
:It is not difficult to disassemble an IF transformer. Mark the primary side with a dot of red paint, or take note of numbers if they are labeled on the contacts. Disconnect all wires (noting where they connected). Remove the transformer via clips or screws or nuts. The transformer base is held to the can by bent over segments of the can. Unbend these. Disconnecting the condensers that are molded into the base requires drilling through them. I recommend it. This type of IF transformer is probably one of the worst kinds after 50 years.
:
:Regarding the EICO 625, well, it's a rather common tester, so it isn't uncommon to find someone with one. It does a fine job. It doesn't tell you all of the details, but it gives you a basic idea as to whether a tube is functioning properly or not. If a tube tests out really weak, usually it won't work in a radio. In some circuits, like the 12SQ7 circuit, it doesn't make much differenc (unless the tube tests out as dead). In some cases, like with FM radios, it's better to have a more elaborate tester, but with most things I find that the EIC0 625 does the trick. I have found that certain FM RF amplifier tubes can act drastically different even though they test similarily on my tester.
:
:I recommend replacing all of the resistors in your tester for accurate results, or at least check them for proper resistance. I was often getting weak results on the #2 setting, and this turned out to be due to a drifted resistor. The #2 setting actually still is kind of strict (makes tubes out to be bad when they still work fine), but it works much better now than it did before.
:
:Thomas