THat looks exactly like Mine, V1b not unsed !
I replaced the 3 80uf filtering caps, because I simply assumed they would be out considering their age. I have to order the two 40 + 40 and a 10fu @450 on the preamp.
I intend to rebuild the preamp section to approach a Twin Normal section. I may use the available v1b for a different input, maybe a 2.7/.68 bypass...
Hum when connecting to input
Moderators: pompeiisneaks, Colossal
Re: Hum when connecting to input
THat looks exactly like Mine, V1b not unsed !
I replaced the 3 80uf filtering caps, because I simply assumed they would be out considering their age. I have to order the two 40 + 40 and a 10fu @450 on the preamp.
I intend to rebuild the preamp section to approach a Twin Normal section. I may use the available v1b for a different input, maybe a 2.7/.68 bypass...
I replaced the 3 80uf filtering caps, because I simply assumed they would be out considering their age. I have to order the two 40 + 40 and a 10fu @450 on the preamp.
I intend to rebuild the preamp section to approach a Twin Normal section. I may use the available v1b for a different input, maybe a 2.7/.68 bypass...
Re: Hum when connecting to input
Stevem wrote: ↑Fri Jan 28, 2022 7:53 pm The volume control is right after the first gain stage in that amp, either that first preamp tube is bad ( V1 ) or the amp has a bad power supply filter cap .
It may just be C34 the 10uf 400 volt filter that powers that tube V1.
YOU where ded on ! I changed that 10uf@400 on V1 and, the amp is now silent, maybe the quietest amp I ever had !
My first guess is that it’s that preamp tube.
-
Stevem
- Posts: 4750
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Hum when connecting to input
Good news to hear!
Enjoy!
Enjoy!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Hum when connecting to input
Unloading a coupling cap will produce full DC voltage on “downstream “ end of lifted, no?Stevem wrote: ↑Fri Jan 28, 2022 11:38 pm Well also any of the coupling caps right after the plate of V1a, V1b or V2a could be leaky and passing low DC voltage down stream to the next gain stage.
Unsolder the down stream end of each of these cap and see if you measure any dc voltage above .035.
If you start by lifting the down stream end of C2 ( .022 uf) on V1a and the hum stops then that cap is leaky.
Re: Hum when connecting to input
Forgive me if this is the wrong place to jump in...new here!
I am building no actually retro modding a DRRI with Mojotone blackface small parts kit. I want to use shielded cable in spots as suggested elsewhere here. Where do I find 20-22 gauge shielded wire to purchase?
Thanks,
I am building no actually retro modding a DRRI with Mojotone blackface small parts kit. I want to use shielded cable in spots as suggested elsewhere here. Where do I find 20-22 gauge shielded wire to purchase?
Thanks,
Rich
Clayton Custom Cabs
Clayton Custom Cabs
-
Stevem
- Posts: 4750
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Hum when connecting to input
Monotone has 22 ga Mic cable for 47 cents per ft.
It’s has 2 conductors and the shield wire.
Don’t forget some shrink tubing to get the ends nice.
It’s has 2 conductors and the shield wire.
Don’t forget some shrink tubing to get the ends nice.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
-
Reeltarded
- Posts: 10017
- Joined: Sat Feb 14, 2009 4:38 am
- Location: GA USA
Re: Hum when connecting to input
In the future if anyone is trouble shooting input grounds the easy way is plug in a guitar and with the volume open a little touch the plug with a wire that is touching the chassis
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.