Howdy all! My Silvertone 1828 has blown two fuses in the two months that it has been working. I've checked everything and all is good. I'm using 1-amp slo-blo fuses. This is a 14 tube radio and it appears to pull just under 1 amp on power up. Is it safe to start using a 1.5 to 2 amp fuse? Nothing gets warm on power on or during operation except the tubes of course. Is a larger rated fuse okay?
Thanks, Johnny

You are saying everything is okay .. The rectifier tube could be shorting maybe. A fuse does flex if it's near the rated blow point. After a few times of this, it gets weaker and will just let go. You might just put your meter in-line without the fuse, and see just how much it's drawing on start up. Tap on that rectifier tube too, see if it's arcing.

:You are saying everything is okay .. The rectifier tube could be shorting maybe. A fuse does flex if it's near the rated blow point. After a few times of this, it gets weaker and will just let go. You might just put your meter in-line without the fuse, and see just how much it's drawing on start up. Tap on that rectifier tube too, see if it's arcing.

You might want to put an external fuse in series with the Ammeter.
Lewis

A radio draws a lot more than its normal rated current when it is first turned on cold and also when it is turned off and then right back on warm (rectifier is hot, electrolytics discharge, and then the fully functional rectifier charges them up again immediately, instead of gradually, like it would if it was warming up from a cold start). If the fuse blows when the radio is turned on cold, you might consider a larger fuse. If the fuse blows only after a quick off-on while the set is warm, try to avoid doing this and probably you can keep the fuse at its current value. Keeping the fuse at as low a value as you can affords more protection, but you don't want it to be an annoyance.

Another thing to consider is whether you increased the electrolytics from their original values significantly or not. If you did, you might consider reducing their values to what was originally specified.

Finally, a good way to protect the radio is to fuse the transformer with a big enough fuse that it doesn't blow all the time, and then put a #47 pilot lamp in series with the transformer center tap (which will protect the delicate HV winding better than a robust fuse on the line cord will). The pilot lamp has interesting characteristics. It is very delicate, and will blow easy (over 150 mA...which might not be what your transformer is rated for, but it can probably dish that out for a brief moment if overloaded), but its resistance increases as current increases, so an initial current rush will see low resistance, and so the bulb won't likely blow. However, sustained current rush will light the bulb and blow it. I can't remember if it was on here or somewhere else, but I read somewhere that 'old timers' used #47 pilot lamps to protect the HV winding in Zenith radios that use the 6X5 rectifier.

T.

:Howdy all! My Silvertone 1828 has blown two fuses in the two months that it has been working. I've checked everything and all is good. I'm using 1-amp slo-blo fuses. This is a 14 tube radio and it appears to pull just under 1 amp on power up. Is it safe to start using a 1.5 to 2 amp fuse? Nothing gets warm on power on or during operation except the tubes of course. Is a larger rated fuse okay?
:Thanks, Johnny

Thanks to all! That answers my questions precisely. And yes Thomas...The fuse was blowing when turned off and then turned on a few seconds later while the radio was still warm.

That 14-tube set is a beast: http://www.nostalgiaair.org/PagesByModel/774/M0016774.pdf Two stages of audio: two 45s in push-pull for the final, another two 45s in p-p in the first audio (driver) section, etc. Does the label specify the operating current? I'd want a slo-blo fuse, the next size larger than the rated current.

'Course, there was no fuse in the original design, so presumably you are adding one. If there is no rated current on the label, I would try a 1.5-A slo-blo, and see if that holds.

You could also add a current-limiting thermistor in the line supply. My usual CL-90 would be a little puny for this set - so you'd need to pick one with a little higher rating. Mouser and DigiKey sell them.
Doug

::Howdy all! My Silvertone 1828 has blown two fuses in the two months that it has been working. I've checked everything and all is good. I'm using 1-amp slo-blo fuses. This is a 14 tube radio and it appears to pull just under 1 amp on power up. Is it safe to start using a 1.5 to 2 amp fuse? Nothing gets warm on power on or during operation except the tubes of course. Is a larger rated fuse okay?
::Thanks, Johnny
:
:Thanks to all! That answers my questions precisely. And yes Thomas...The fuse was blowing when turned off and then turned on a few seconds later while the radio was still warm.