Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Stuff4bikes on June 26, 2021, 12:08:56 am

Title: Series filament amp
Post by: Stuff4bikes on June 26, 2021, 12:08:56 am

I have this little Packard bell amp......I DON'T USE IT WITH MY GUITAR........AND I POWER THROUGH A CURRENT LIMITER WITH AN ISOLATION TRANSFORMER......I use the amp to test unknown output transformers....I ran my Packard bell console record player through the amp and it sounded decent....

So here is my question.....
How would you wire a three prong cord to this? And after i got the amp I changed the 50C5 cathode resistor and added
25/50v cap. Originally it was soldered to the center post of the output tube but I TRIED grounding it to chassis and it didn't like that. Just curious

Title: Re: Series filament amp
Post by: PRR on June 26, 2021, 12:53:32 am

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Title: Re: Series filament amp
Post by: Stuff4bikes on June 26, 2021, 12:57:06 am

So just leave the amp as is and add the 3 prong cord.....no need to run the heaters through the neutral?

Title: Re: Series filament amp
Post by: acheld on June 26, 2021, 10:04:50 am

Looking at PRR's schematic:   at the end of the line of series heaters, schematic shows current going to ground, which is shared with secondary "neutral." 

Title: Re: Series filament amp
Post by: Stuff4bikes on June 26, 2021, 10:40:21 am

I noticed that about 5 seconds after posting...jumped the gun when I didn't see a "tail" coming from the filaments.