Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: okguitarman on September 26, 2018, 09:01:07 pm

Title: Rectifier?
Post by: okguitarman on September 26, 2018, 09:01:07 pm

 Cathode bias push pull 6v6s 5e3
The cap 25/25 exploded beside the 250 ohm 5 watt res. on cathode, bad hum started then power tubes started to red plate
shut it down couldn't find any reason. I changed power tubes same results changed rec. tube and back to normal can someone explain this?

Title: Re: Rectifier?
Post by: tubenit on September 27, 2018, 08:22:26 am

Not sure what you are saying?   Are you saying it originally worked fine and then developed a problem with cathode cap and red plating ............. BUT now is working properly again as it did originally? 

Please clarify?   

Did you check voltages when it was not working right?   And compare the voltages to either when it was working right originally OR to what should be within normal limit voltages for a 5E3? 

I would want a 25uf/50v or 25uf/100v cathode caps for the 6V6's instead of 25uf/25v.  Was the cathode cap in backwards?   (that can cause them to explode)

With respect, Tubenit

Title: Re: Rectifier?
Post by: shooter on September 27, 2018, 08:47:49 am

Quote

changed rec. tube and back to normal

well, you could put the old rec tube in and see if things explode again, or, you could just play.
As Tubenit says; 50vdc is a better cathode cap value

Title: Re: Rectifier?
Post by: Willabe on September 27, 2018, 09:29:53 am

The cap can not lay directly right on the K R, if it does it will heat up and will shorten it's life span.

A 25v cap laying on the K R is asking for trouble. 

Title: Re: Rectifier?
Post by: okguitarman on October 06, 2018, 09:36:47 am

installed 50v cap not touching res. so far so good!  Thanks