I know you guys like schematics when troubleshooting but the schematic is the same classic 5F1 drawing from Fender that everybody knows. The main difference is no tube rectifier here.
Thanks in advance.
Custom 5F1 build with no sound
Moderators: pompeiisneaks, Colossal
Custom 5F1 build with no sound
So I jerry-rugged a 5F1 circuit into an Epiphone Valve Junior and I have no sound. The amp powers on with no shorts and there is the faintest hum at the speaker but no other audio. I followed the schematic and cannot figure out where I must’ve went wrong so I’m asking for any experienced eyes to take a quick glance at my project amp, perhaps someone will see something that’s amiss:
I know you guys like schematics when troubleshooting but the schematic is the same classic 5F1 drawing from Fender that everybody knows. The main difference is no tube rectifier here.
Thanks in advance.
I know you guys like schematics when troubleshooting but the schematic is the same classic 5F1 drawing from Fender that everybody knows. The main difference is no tube rectifier here.
Thanks in advance.
Last edited by Yoda on Fri May 28, 2021 2:21 am, edited 1 time in total.
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thetragichero
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Re: Custom 5F1 build with no sound
how are your voltages? ie high voltage where it should be, zero(or low) voltage where it should be, ac voltage on heaters?
PRR wrote: Plotting loadlines is only for the truly desperate, or terminally bored.
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Stevem
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1 others liked this
Re: Custom 5F1 build with no sound
It looks like you have no chassis ground for the last filter and the 470 ohm resistor.
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: Custom 5F1 build with no sound
I see the same. Ground the ring (sleeve) of the input jack or jumper it to the two main filter caps. I am assuming the green wire at the top of the rectifier bridge is grounded to chassis. The other end of the green wire is not in the picture.
When you get that sorted out, if you have 50/60Hz hum, it's from the filament supply. Move the black ground wire from the two 100Ω resistors off the ground buss. Just ground that to any convenient point on the chassis.
Also, it looks like the chassis is painted or coated. You must scrape it to bare metal to make a proper ground.
Re: Custom 5F1 build with no sound
There are several more grounds missing too... unless there are some under board jumpers.
Re: Custom 5F1 build with no sound
These rumors are groundless.
I build and repair tube amps. http://amps.monkeymatic.com
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Stevem
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Re: Custom 5F1 build with no sound
They may be ROOTED in fact, we will have to wait for the OPs reply.
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: Custom 5F1 build with no sound
So the only jumpers under the board are a wire running from the B+3 node to the two 100k plate load resistors.
These are exactly the answers I was looking for, I knew seasoned eyes would catch things I missed. I’ll implement a couple changes and see if that fixes things.
Oh and forgive the sloppy routing on the input and volume control wires I will clean it up later.
These are exactly the answers I was looking for, I knew seasoned eyes would catch things I missed. I’ll implement a couple changes and see if that fixes things.
Oh and forgive the sloppy routing on the input and volume control wires I will clean it up later.
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Custom 5F1 build with no sound
There’s a very easy test to determine if a tube stage is working .
It’s called a pop test and no meters are needed just a screw driver.
To make such a test you start at the output stage, so in your case if the output tube is working and you touch the screwdriver tip to pin 5 you will hear a very light pop or tick noise out of the speaker.
If that works then move up stream to the preamp tube and touch pin 2, now if things are working you will hear a louder pop noise.
If that checks out then turn full up the volume control and touch pin 7 and the pop should be much much louder if all is well!
I can tell you right now that the junction of your preamp cathode resistors off of pins 3 and 8 look like they have no ground which is needed.
I am also somewhat concerned that once you do basically get the amp working that it will start oscillating due to the close mounting of the input jack and it’s tip connection point to the preamp section in your rebuild.
It’s called a pop test and no meters are needed just a screw driver.
To make such a test you start at the output stage, so in your case if the output tube is working and you touch the screwdriver tip to pin 5 you will hear a very light pop or tick noise out of the speaker.
If that works then move up stream to the preamp tube and touch pin 2, now if things are working you will hear a louder pop noise.
If that checks out then turn full up the volume control and touch pin 7 and the pop should be much much louder if all is well!
I can tell you right now that the junction of your preamp cathode resistors off of pins 3 and 8 look like they have no ground which is needed.
I am also somewhat concerned that once you do basically get the amp working that it will start oscillating due to the close mounting of the input jack and it’s tip connection point to the preamp section in your rebuild.
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: Custom 5F1 build with no sound
Those two missing grounds were all I was missing, you guys are miracle workers!
I also had concerns about the input jack tip being so close to the turret board but didn’t know what to look out for. How would I know if the amp is oscillating?
I also had concerns about the input jack tip being so close to the turret board but didn’t know what to look out for. How would I know if the amp is oscillating?