Deluxe Reverb clone Hum?

[psychepool]

I made a single channel deluxe reverb clone. (aka AX84 California dreamer)
The schematic is almost same with this.
http://ax84.com/media/ax84_m274.pdf

It has 2 difference points.
I use SS rectifier instead of tube rectifier.
And has no 50K master volume. It is replaced with 47K resistor to ground.


When I turn the standby on, there's low frequency hum noise.
In my experience, it seems like hum from the bad power supply or bad ground
Not earthquaking loud but still loud.

I can hear the guitar sound from the speaker. All knobs are operate normally.
But the output is not loud enough.
And the sound is not smooth. Tearing like a fart.

No problem is checked from the plate voltage and the bias.
The 8pin of 6v6(it connected to the chassis with 1 ohm) has 20mA.
And the plate voltage(OT secondary) has 400vdc.
The 5pin has -34~35vdc. they are almost ideal.

Main power supply electrolytic is JJ Tesla 40/20/20/20uF multi-section.

Input~PI ground is combined and earthed near input jack.
Output jack ground is earthed near output jack.
Power jack ground is earthed near Power jack.
Power supply multi-cap/bias circuit/PT main center/Heater center(it has center tap in the PT : 3.15-0-3.15) grounds are earthed at the same point(PT bolt)



Can you figure out the reason with these informations?
I originally made it with princeton reverb. And except the preamp, I remove all components and remade with Deluxe reverb(AX84 California Dreamer).
There's no matter when it was Princeton reverb.


Give me advise please.

[frankdrebin]

the simplest thing to do is getting a scope,imho is essential for building amps.
anyway,are the filaments of power tubes in phase?
It could be a bad soldering or a ground in the wrong spot.
The multicap is not a good idea in terms of good grounding.
The ground from the output jack is better connected directly to the main PS/center tap ground,and the jack isolated from chassis.
In the schem i see an elevated heater center tap AND a ground connection as well:its one or the other!
look if you did that double connection.

[Stevem]

If you have a meter that can read frequency what is showing up across the speaker output, 60 HZ AC related hum, or 120 HZ power supply rectified hum?
100 HZ is close to low E on your guitar , is that what you hear?

[drew]

Post some photos.

[epis]

That 50k master is wrong, should be at least 500k. Just remove from circuit your 47k resistor.
About the hum, I bet it's reverb circuit ground.

[Craig B]

I looked at the schematic after reading frankdrebin's first post. It shows the heater wiring grounded through two 100 ohm resistors...and through the transformer heater ground wire (usually green wire with yellow tracer). Only one of these heater ground systems should be used.
I built a similar amp using the schematic at the Hoffman website. He used a 47k resistor to ground instead of the master volume. The resistor value was chosen because it is a substitution for the ground resistance of the tremelo circuit which was removed from the original fender design. So maybe the schematic 50k value for the master volume is good.
I also used the 40/20/20/20 JJ cap can without noticeable hum. It is not "best practice" but worked fine in this medium gain circuit.
Happy troubleshooting,
Craig

[psychepool]

Thanks all!
I must apologize for faithless description.

The heater in my PT is not like that schematic.
My PT has center tap for the heater wire. It is 3.15-0-3.15.
I wasn't use 100R reisistor for heater ground.

Basically, I think the hum is occurred by bad soldering.
But the tester couldn't find the bad connection.

It could be a bad soldering or a ground in the wrong spot.
The multicap is not a good idea in terms of good grounding.
The ground from the output jack is better connected directly to the main PS/center tap ground,and the jack isolated from chassis.

When this amp was Princeton Reverb, there's no hum and no noise.
The ground point is the same with when it was PR.
And also used JJ multi-cap.

If you have a meter that can read frequency what is showing up across the speaker output, 60 HZ AC related hum, or 120 HZ power supply rectified hum?
100 HZ is close to low E on your guitar , is that what you hear?

I have no tools for check frequency but may be it's 120hz power supply rectified hum according to your description.
It is lower than low E.

Post some photos.

I have a photo but the chassis is very narrow so the photo couldn't show the state.
I'll try to take better photo for show you it's state.

That 50k master is wrong, should be at least 500k. Just remove from circuit your 47k resistor.
About the hum, I bet it's reverb circuit ground.

Ok, I'll try to check the reverb circuit intensively.

I looked at the schematic after reading frankdrebin's first post. It shows the heater wiring grounded through two 100 ohm resistors...and through the transformer heater ground wire (usually green wire with yellow tracer). Only one of these heater ground systems should be used.
I built a similar amp using the schematic at the Hoffman website. He used a 47k resistor to ground instead of the master volume. The resistor value was chosen because it is a substitution for the ground resistance of the tremelo circuit which was removed from the original fender design. So maybe the schematic 50k value for the master volume is good.
I also used the 40/20/20/20 JJ cap can without noticeable hum. It is not "best practice" but worked fine in this medium gain circuit.
Happy troubleshooting,
Craig

I apologize for it. I don't connect the heater ground like that schematic. Thanks!



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I think it is very mysterious situation.
DR version is made same with PR version, just exception the PI and the output ciruit. But when it was PR version, there's no hum noise and all function is fine.

[Stevem]

Low E on a guitar is 82.4 HZ !