anyone have experience with the 5f1 circuit and noise/hum?

[rockstah]

hey guys,

mine sounds like it has bad ground but after going through it, giving it a cap job, checking and rechecking i cant figure why the thing makes so much hum noise? it's a Kendrick 118 kit. any ideas for me to try?

here is a sound clip: started with the volume at 9 o'clock, then 12 then pushing 3 o'clock. the guitar is on 10 through out.

Code: Select all

http://www.soundclick.com/bands/page_songInfo.cfm?bandID=699407&songID=8269709

Mark

[jjman]

You need to have nothing plugged in to judge the amp's hum. Does it hum the same when there is nothing plugged in to it's input?

[rockstah]

You need to have nothing plugged in to judge the amp's hum. Does it hum the same when there is nothing plugged in to it's input?

yes the hum the hum is the same with nothing plugged into the amp.

[rockstah]

[IMG:800:600]http://i24.photobucket.com/albums/c44/m ... C00549.gif[/img]
more here - http://s24.photobucket.com/albums/c44/m ... amian/5f1/

[M Fowler]

Then check the first filter cap connection for bad solder.

[rockstah]

Then check the first filter cap connection for bad solder.

checked and rechecked it -

how do these look?

5f1 voltages.

V1
Pin1 194
Pin2 0
Pin 3 1.4
Pin 4/5 3.1ac
Pin6 195
Pin7 0
Pin8 1.3
Pin9 3.1ac

V2
Pin1 20dcv
Pin2 3.1ac
Pin3 364
Pin4 323
Pin5 0
Pin6 0
Pin7 3.1ac
Pin8 20dcv

V3
Pin1 0
Pin2 365
Pin3 0
Pin4 332ac
Pin5
Pin6 329
Pin7 365

[Structo]

Ok, this is a Champ right?

You have a 12ax7 and a 6V6 and the 5Y3 rectifier, right?

So this is cathode biased.
What value cathode resistor is on the 6V6?
Is that the black resistor? Should be at least a 5 watt resistor.

Lead dress is a nightmare in those cramped chassis.

I would try to twist the heater wires tight and try to run them away from any signal wires or devices.
What kind of heater circuit is in that anyway?
Hopefully it isn't like the real Champs and uses the chassis for part of the heater circuit.

If it does I would wire the heaters with two wires.
Does the heater winding have a center tap? Green w/yellow stripe possibly?

If not then you will need to make an artificial center tap by soldering a 100 ohm resistor from each heater wire to ground, then on to the tubes.

You probably would rather be working on your Plexi about now, eh?

[John_P_WI]

If it does I would wire the heaters with two wires.
Does the heater winding have a center tap? Green w/yellow stripe possibly?

If not then you will need to make an artificial center tap by soldering a 100 ohm resistor from each heater wire to ground, then on to the tubes.

You probably would rather be working on your Plexi about now, eh?

My thoughts exactly Tom.

Don't worry, Mark will pull off some convincing VH1 and VH2 tones out of it....

[rockstah]

Ok, this is a Champ right?

1.You have a 12ax7 and a 6V6 and the 5Y3 rectifier, right?

2. So this is cathode biased.
What value cathode resistor is on the 6V6?
Is that the black resistor? Should be at least a 5 watt resistor.

Lead dress is a nightmare in those cramped chassis.

3. I would try to twist the heater wires tight and try to run them away from any signal wires or devices.
What kind of heater circuit is in that anyway?
Hopefully it isn't like the real Champs and uses the chassis for part of the heater circuit.

If it does I would wire the heaters with two wires.
Does the heater winding have a center tap? Green w/yellow stripe possibly?

If not then you will need to make an artificial center tap by soldering a 100 ohm resistor from each heater wire to ground, then on to the tubes.

You probably would rather be working on your Plexi about now, eh?

1. yes
2. it’s the resistor that came in the kit 470 ohm I think it’s a 2-3 watt though I believe.
3. I was thinking of redoing the heaters as well
It has two wires and yes a yellow green ct wire is grounded.

This amp has been bugging me for a while. It has never worked properly since putting it together!

[M Fowler]

Voltages are not that bad V1 is spot on.
V2 a little high at pin 3
V3 has higher voltage at 365 compared to about 325vdc on pin 2 and pin 8 not pin 7 as you reported.

I blew the picture up and cannot see anything other than already mentioned filament wondering if you have CT or not otherwise a pair of 100R should be used.

Mark

[rockstah]

Voltages are not that bad V1 is spot on.
V2 a little high at pin 3
V3 has higher voltage at 365 compared to about 325vdc on pin 2 and pin 8 not pin 7 as you reported.

I blew the picture up and cannot see anything other than already mentioned filament wondering if you have CT or not otherwise a pair of 100R should be used.

Mark

the pt does have a heater ct which is grounded.

[M Fowler]

I have one suggestion and that is to move the V1 wires away from the output jack and keep input away from output but that is the way this creature was designed, might help?

[rockstah]

I have one suggestion and that is to move the V1 wires away from the output jack and keep input away from output but that is the way this creature was designed, might help?

thanks - i am basically rebuilding it one more time right now.

[M Fowler]

It really shouldn't be needed but shielded wire for the input jack and to the volume control if you cannot locate any other source for the hum. The hum has to be in the output end if it hums all the time at the AC source so the filter cap and volume knob doesn't change anything.

I edited should to shouldn't sorry. Mark

[rockstah]

It really should be needed but shielded wire for the input jack and to the volume control if you cannot locate any other source for the hum. The hum has to be in the output end if it hums all the time at the AC source so the filter cap.

i did shield both grids of v1 and i replaced the caps completely but i agree it seems and sounds like it is in the output section.