Do not operate the radio until you remove 7Z4 from the radio. This will remove the load from high voltage winding. See if the transformer stays cool without this tube? Your transformer will be ok if it doesn't overheat with 7Z4 removed.
Test your 7Z4, especially for cathode to filament shorts. Be sure replacement electrolytic filter caps have high enough voltage rating and are installed in correct polarity. I would use 450 volts. Don't increase the cap value connected to 7Z4 very much above the original. More capacity will increase surge current which will damage the tube in time.
Norm
:I have one of the above mentioned and replaced the "3 in 1" caps with comperable rating electrolytics. My previous problem was soe flashing going on in the 7Z4 rectifier. Now no flashing but the new caps (I put them in the old housing) are getting warm, tube fillaments seem too dim and I was starting to get a hot smell.
: I'm no pro by any means but usually can fix what I set my mind to if I have guidance, a schematic or both. :)
: Thanks,
: Loren
Caps should be much higher voltage unless a cathode bypass on your audio output tube. Others are best rated 450 volts. Electrolytic caps can act like this and heat if they have been around for years.
Even though new, I don't use electrolytic caps made more than 20 years ago. Some older ones will reform and may by now be ok? If these are NOS and don't stay cool use modern replacements.
Norm
: The 7z4's I have are NOS. The transformer stayed cool even with it in. I nearly toaste it about 25 years ago so I do watch that! :) The caps I used were mostly identical in value. The only difference was from 20mfd @ 25V to 22mfd @ 50V. What gets me is the new caps getting warm. I put the negative to the original "tower" case. Frustrating. I must have done something wrong but without a schematic I'm dependant on other's advice. :)
::Hi Loren
::
:: Do not operate the radio until you remove 7Z4 from the radio. This will remove the load from high voltage winding. See if the transformer stays cool without this tube? Your transformer will be ok if it doesn't overheat with 7Z4 removed.
::
:: Test your 7Z4, especially for cathode to filament shorts. Be sure replacement electrolytic filter caps have high enough voltage rating and are installed in correct polarity. I would use 450 volts. Don't increase the cap value connected to 7Z4 very much above the original. More capacity will increase surge current which will damage the tube in time.
::
::Norm
:Hi Loren
:
: Caps should be much higher voltage unless a cathode bypass on your audio output tube. Others are best rated 450 volts. Electrolytic caps can act like this and heat if they have been around for years.
:
: Even though new, I don't use electrolytic caps made more than 20 years ago. Some older ones will reform and may by now be ok? If these are NOS and don't stay cool use modern replacements.
:
:Norm
:
:: The 7z4's I have are NOS. The transformer stayed cool even with it in. I nearly toaste it about 25 years ago so I do watch that! :) The caps I used were mostly identical in value. The only difference was from 20mfd @ 25V to 22mfd @ 50V. What gets me is the new caps getting warm. I put the negative to the original "tower" case. Frustrating. I must have done something wrong but without a schematic I'm dependant on other's advice. :)
:::Hi Loren
:::
::: Do not operate the radio until you remove 7Z4 from the radio. This will remove the load from high voltage winding. See if the transformer stays cool without this tube? Your transformer will be ok if it doesn't overheat with 7Z4 removed.
:::
::: Test your 7Z4, especially for cathode to filament shorts. Be sure replacement electrolytic filter caps have high enough voltage rating and are installed in correct polarity. I would use 450 volts. Don't increase the cap value connected to 7Z4 very much above the original. More capacity will increase surge current which will damage the tube in time.
:::
:::Norm
You should be ok. There are only a few things that cause good electrolytic caps to heat, too high voltage, wrong polarity or AC. You used 450 volt caps, have polarity correct and have a good 7Z4. Be sure they aren't connected to AC, pins 3 or 6 on 7Z4.
Have you tried the radio again. Even though new, caps not used in several years take time to reform. Usually the radio does this in a couple minutes. After that caps shouldn't heat. You are right not to leave the radio on if caps get warm.
Norm
: Hi Norm,
:The caps I used were all brand new electrolytics. They were all of the original, 450V and farad ratings except for the two that were originally 20@25V. I went with higher rated 22@50V. The NOS is the rectifier tube. I was reading about where the caps will be isolated instead of to ground in the tech help section. Mine is like that but I didn't ground it. I did however tie all the negatives together which goes to a transformer output. I didn't understand why he'd only use one half of a double cap though.
: Thanks
: Loren
:
::Hi Loren
::
:: Caps should be much higher voltage unless a cathode bypass on your audio output tube. Others are best rated 450 volts. Electrolytic caps can act like this and heat if they have been around for years.
::
:: Even though new, I don't use electrolytic caps made more than 20 years ago. Some older ones will reform and may by now be ok? If these are NOS and don't stay cool use modern replacements.
::
::Norm
::
::: The 7z4's I have are NOS. The transformer stayed cool even with it in. I nearly toaste it about 25 years ago so I do watch that! :) The caps I used were mostly identical in value. The only difference was from 20mfd @ 25V to 22mfd @ 50V. What gets me is the new caps getting warm. I put the negative to the original "tower" case. Frustrating. I must have done something wrong but without a schematic I'm dependant on other's advice. :)
::::Hi Loren
::::
:::: Do not operate the radio until you remove 7Z4 from the radio. This will remove the load from high voltage winding. See if the transformer stays cool without this tube? Your transformer will be ok if it doesn't overheat with 7Z4 removed.
::::
:::: Test your 7Z4, especially for cathode to filament shorts. Be sure replacement electrolytic filter caps have high enough voltage rating and are installed in correct polarity. I would use 450 volts. Don't increase the cap value connected to 7Z4 very much above the original. More capacity will increase surge current which will damage the tube in time.
::::
::::Norm