Hello all,
Couple of months ago I fired up my Beard P-35 II for the first time in too many years. Probably 15 years ago I replaced the known failure regulators with higher rated models, then had no further problems for a good while.
When I hit the power switch, the 500MA fuse HT fuse blew on one channel.
I suspect the 47uf electrolytic between the power supply and audio circuit, so I ordered 2.
While looking inside, I noticed that these (pic) capacitors look bad. Have ordered these: DME4P1K-F Cornell Dubilier - CDE | Mouser.
Could anyone jump in and confirm the choice? I did not know what the marking "fo=4.9MHz" on a capacitor is intended to represent? Looks like it has been hot around there.
Thanks for any additional insight - Robert
Couple of months ago I fired up my Beard P-35 II for the first time in too many years. Probably 15 years ago I replaced the known failure regulators with higher rated models, then had no further problems for a good while.
When I hit the power switch, the 500MA fuse HT fuse blew on one channel.
I suspect the 47uf electrolytic between the power supply and audio circuit, so I ordered 2.
While looking inside, I noticed that these (pic) capacitors look bad. Have ordered these: DME4P1K-F Cornell Dubilier - CDE | Mouser.
Could anyone jump in and confirm the choice? I did not know what the marking "fo=4.9MHz" on a capacitor is intended to represent? Looks like it has been hot around there.
Thanks for any additional insight - Robert
Attachments
You will be fine with what you ordered, but a better picture showing more parts around that cap would confirm.
Also while you probably do need to re-cap, I would suspect you have a bad EL84, and that is what took out the fuse.
Also while you probably do need to re-cap, I would suspect you have a bad EL84, and that is what took out the fuse.
So that cap looks like it's rated for 250V AC and potentially carries an X rating. These are referred to as "safety capacitors".
The cap you've chosen doesn't carry those ratings. Whether or not that matters is really tough to determine from a picture, but a tube amplifier manufacturer would probably already have a 0.1uF film cap in their inventory, so they've gone to the trouble to get an X rated part, so I think it's reasonable for you to do the same.
An externally hosted image should be here but it was not working when we last tested it.
The cap you've chosen doesn't carry those ratings. Whether or not that matters is really tough to determine from a picture, but a tube amplifier manufacturer would probably already have a 0.1uF film cap in their inventory, so they've gone to the trouble to get an X rated part, so I think it's reasonable for you to do the same.
All,
Thanks for the feedback. Am on Mouser, can't seem to find an X rated category. There is an arc protection cap, but it is SMD so would be difficult to mount.
Will check the tubes. A short through the 47uf looks like it would result in B+ to ground, that was my thought behind ordering those.
Additional Pics (not) added, having trouble uploading
Thanks for the feedback. Am on Mouser, can't seem to find an X rated category. There is an arc protection cap, but it is SMD so would be difficult to mount.
Will check the tubes. A short through the 47uf looks like it would result in B+ to ground, that was my thought behind ordering those.
Additional Pics (not) added, having trouble uploading
FWIW, the F0 = 4.9 MHz. marking is the part's self resonant frequency. Real world capacitors are not ideal and exhibit some inductance. Inductance and capacitance together form a resonant circuit.
Ordered two different caps, which to use?
The WIMA caps appear to be more similar to the caps currently in the amp, but have short leads.
The black caps would be easier to install, have a slightly higher voltage rating.
Both carry the X2 ratings, I did not realize that the black caps would have X2 when I ordered.
Any reason I should use the WIMA vs the black ones?
The WIMA caps appear to be more similar to the caps currently in the amp, but have short leads.
The black caps would be easier to install, have a slightly higher voltage rating.
Both carry the X2 ratings, I did not realize that the black caps would have X2 when I ordered.
Any reason I should use the WIMA vs the black ones?
