Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Dead Short on July 14, 2019, 07:04:42 pm
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First time build! I just completed my 1st amp build. A simple 5f1 Tweed. I wanted to thank all on this board as you all saved me tons of time and mistakes. I made a few mods to it along the way. I added a NFB toggle, a independent on/off switch and a three way rotary switch for 4/8/16 ohm speaker selection. Ran out of room on the chassis. I checked continuity, grounds and voltages all the way around. Everything was spot on except the ac voltage on the filament circuit. It measured 3.4 vac not 6.3? I used a Classictone 40-18019 PT.. (green wires). I fired it up and the amp works perfectly---no humms WSE! Any harm in running at 3.4 vac to heaters? Everything seems to be in order otherwise. Thanks in advance
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Don't measure filament voltage with one probe on chassis because that only measures half the voltage. Instead, measure across the tube socket, ie, for the 6V6 put one probe on pin 2 and the other probe on pin 7. Then you'll see all the filament voltage.
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Thanks Sluckey, all the reading and vids I watched I didn't pick that bit up...I knew it was something I should have known..Amp sounds great. I am now deflated since that project is done..It was a ton of fun building it. Just a matter of time before I start a new build, but a bit more complex...although I dont need another amp...any suggestions on a next build thats fun and affordable?
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Hoffman has several nice projects. Or you may find something interesting on my website. You may find that you always need just one more amp. :icon_biggrin:
How 'bout showing us some pics of your build? We like that stuff.
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Pics
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Pics
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More pics
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Waiting for 112 - Tweed Cab to come in, (vintage Jensen C12R speaker)
then touch up cosmetics - let her rip
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Last pic.
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Wow! Wish my first amp had looked that good.
One cosmetic tip... Put those star washers (switches and jacks) on the inside of the chassis for a cleaner look.
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Thank you Sluckey!
I noticed that washer foul! Moving those is on my list. I was focused purely on mechanics and nothing of cosmetics when I put those things on the outside. I was in a zone. 🎯
This amp really sings I am very happy with the outcome.
I will post more pics when clean it up and mount it a cab....
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Just for the heck of it and since I have the 15w PT and OT(40-18031/40-18019) I am going to swap some tubes. If I use a change the rectifier to a gz34 and output tube to a 5881 and switch the impedance switch to the 16 ohm tap, will I have to re-bias the cathode resistor or could I just plug and play?
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> change ....output tube to a 5881
What do you gain? 5 Watts to 9 Watts? That won't put your record in the Top Ten.
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True that! Especially since my playing is novice at best😅. I gues I am just bored and looking for something to tinker with...maybe I will build another amp entirely instead and give it to someone who can play but can't afford a beauty!
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:laugh: