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and this is why we use safety caps

gadget73

gadget73

junk junkie
Subscriber
Kcdonahue gave me this old Bogen tuner to fool with. I started cleaning it up a bit, but this is what I found on the bottom side. The original line to chassis capacitors are 0.01uf ceramic caps of unknown voltage, plus a 0.047uf 600f (the green one) from one side of the line to chassis. This is what power line transients do to these caps. I forgot to grab a pic of it, but the ceramic cap under the green one has the whole side blown off. `
 

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Yes, exactly!

Thanks for the lesson in pictures.

There is a reason that they are called safety rated capacitors.
 
Yikes! That looks like some of the power supply issues I found in my Sony PS-X70, which I think must have been hit by a lightning surge at some point. Bet that tuner did a few interesting things before it shut down!
 
Excellent illustrative reminder of what could happen when you turn your head!! Gotta pick up a few more :yes:
 
Wow, thanks for the pics Gadget!

In addition to the importance of properly installed and rated safety caps, this also illustrates the importance of inspecting vintage gear before even thinking about powering them up...

KC
 
I figured the pics might be helpful. I don't know if there is any further damage. I'll check the power transformer tonight after I chop those melted caps out and see what it has to tell me.
 
gadget73 said:
Kcdonahue gave me this old Bogen tuner to fool with. I started cleaning it up a bit, but this is what I found on the bottom side. The original line to chassis capacitors are 0.01uf ceramic caps of unknown voltage, plus a 0.047uf 600f (the green one) from one side of the line to chassis. This is what power line transients do to these caps. I forgot to grab a pic of it, but the ceramic cap under the green one has the whole side blown off. `
Click to expand...

Cool... good pics... Did the green one go too, or is it shrapnel from the ceramics? No fuse in that guy, I'm guessing....

Regards,
John
 
Green one visibly looks OK, it just has char marks from the one under it blown up. I don't trust it for a second though. And nope, no fuse yet.
 
I might suggest that you remove those green tubular capacitors and toss them into the bin. If they make a sound when they hit the bottom, they were bad. But seriously, they are Sangamo Type 33 paper capacitors. They will be leaky and no good. Do yourself a favor and toss them please! New film capacitors are inexpensive and tons better.
 
They are getting replaced. I don't trust old paper caps as far as I can throw them. I just posted the pics because I found the damage to be interesting and hopefully serve as a visual reminder of why some parts need to be updated.
 
That old Bogen is a soldier. Transformer is fine, and I was able to find a 6AB4 and borrow a 6X4 to test it. it came up OK on the variac and it actually works fairly decent. It will get a further refresh but for a test run with original 55 year old parts I was impressed.
 
Back in the day of that equipment, my father told me that it was thought that 600VDC caps were adequate for powerline work. Today it's 1.4KVDC. I once used a 400VDC cap across the line, it lasted a few weeks... A fuse in that equipment got taken out as well, probably a good thing. :)
 
kcdonahue said:
Wow, thanks for the pics Gadget!

In addition to the importance of properly installed and rated safety caps, this also illustrates the importance of inspecting vintage gear before even thinking about powering them up...

KC
Click to expand...

Hear hear... I second that...
 
wa2ise said:
Back in the day of that equipment, my father told me that it was thought that 600VDC caps were adequate for powerline work. Today it's 1.4KVDC. I once used a 400VDC cap across the line, it lasted a few weeks... A fuse in that equipment got taken out as well, probably a good thing. :)
Click to expand...

With all the switch-mode power supplies, CFL lamps, and other transient-generating modern electronics out there, you really do need to have 1.4K or higher voltage rating on any cap across the power line. Things can get ugly out there sometimes...
 
GordonW said:
With all the switch-mode power supplies, ... transient-generating modern electronics out there, you really do need to have 1.4K or higher voltage rating on any cap across the power line. ...
Click to expand...

I'm sure that old fashioned vacuum cleaner motors with brushes (the ones inside the motor), washing machine motors and solenoids and relays would dish up big transients as well. Many tube AM radios with caps across the line would still work even after those caps would explode :yikes: You'd find confetti inside the radio under the chassis...
 
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