Can't figure out where to look next with problem with an Admiral 5X11. This chassis uses loctal tubes. Have recapped and retubed. Am able to align the IF with no problem, but get no output trying to align the higher frequencies. Radio also crackles intermintently regardless of volume level. No signs of tube shorts or arcing in a dark room. Any suggestions on what to look for?

Thanks. Jim

:Can't figure out where to look next with problem with an Admiral 5X11. This chassis uses loctal tubes. Have recapped and retubed. Am able to align the IF with no problem, but get no output trying to align the higher frequencies. Radio also crackles intermintently regardless of volume level. No signs of tube shorts or arcing in a dark room. Any suggestions on what to look for?
:
:Thanks. Jim

"Radio also crackles intermintently regardless of volume level"

Sonds like your If's have the dreaded "silver mica disease" I had a Motorola 56X13U, that sounded like crashing static, i opened up the little 1" square If's and eliminated the cap, and replaced them with external mica caps. Do a search for silver mica disease, or silver mica migration, you will find all kinds of info on this.

:It couldbe that the sockets need cleaning.

Locktal tubes use a very small pin and if the radio was stored incorrectly, the pin to socket interface can show corrosion. It would be a good idea to try a simple fix - clean the sockets with tuner spray and remove and replace the tubes a few times.

:Can't figure out where to look next with problem with an Admiral 5X11. This chassis uses loctal tubes. Have recapped and retubed. Am able to align the IF with no problem, but get no output trying to align the higher frequencies. Radio also crackles intermintently regardless of volume level. No signs of tube shorts or arcing in a dark room. Any suggestions on what to look for?
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::Thanks. Jim
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:"Radio also crackles intermintently regardless of volume level"
:
:Sonds like your If's have the dreaded "silver mica disease" I had a Motorola 56X13U, that sounded like crashing static, i opened up the little 1" square If's and eliminated the cap, and replaced them with external mica caps. Do a search for silver mica disease, or silver mica migration, you will find all kinds of info on this.

Here's the schematic: http://www.nostalgiaair.org/PagesByModel/116/M0000116.pdf

Does this set have those small IF xfmrs, about 1" square? Those are the type that are prone to the silver mica disease.

To troubleshoot for the disease, here's a couple of approaches. First, with an ohmeter, check for any leakage between the primary and secondary of the IF. (Since the ohmeter uses a low voltage, this probably won't prove that the xfmr is good.)

Next, hook up a voltmeter to the secondary (grid) connection of the xfmr. Watch for any plate voltage leaking through. If you have one, use an analog voltmeter or VTVM so that you can better observe any voltage changes.

Larger slug tuned IF transformers also sometimes have permanent condensers. Check the transformer if it's slug tuned, no matter what size it is. You may find discrete components, and then again you may find the dreaded exposed silver mica sheets, sandwiched between springs, or molded into plastic. Sometimes they short and sometimes they corrode open. Either will cause static and poor performance. A short is more likely to kill all reception. An open will destroy peaking of the coils, but the coils will still probably pass some of the signal.

Strange, though, that you can peak the IF transformers, but you can't pass radio signals through them. If you can pass an IF through all of the coils, you should be able to pass a radio signal through as well, even if it is faint. A short or severe other malfunction probably won't let your generator signal through, either, though you can sometimes crank the generator signal up pretty strong. If you are unsure of things, you can perhaps substitute some known-to-be-working IF transformers and see if the radio will work that way. It doesn't matter what kind or size of transformers they are as long as they can be tuned to the frequency used in that radio. They can be slug tuned or capacitor tuned.

Thomas