Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Hebert on October 05, 2019, 08:22:54 am
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I can't get distortion out of my new 5e3 build. I tested the DC voltages. all the numbers look right on or within 10%. except for pin 7 of V2. it is about 3 rather than the 17 to 20 expected. I then tested the resistors above pin 7 and they are fine. perhaps I need to resolder them? would this pin cause my problem? perhaps putting a 12ax7 in V1 would help with distortion? thanks
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except for pin 7 of V2. it is about 3 rather than the 17 to 20 expected.
That's a problem. What is the voltage on pin 8?
Check for wiring error or incorrect component value.
Post some pics.
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hi, 8 pin is 47, the resistors above are normal perhaps my soldering is not solid?
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hi, 8 pin is 47, the resistors above are normal perhaps my soldering is not solid?
You cannot accurately measure the voltage on pin 7, even with a $500 Fluke. But 3 volts indicates a wiring error or wrong component value, or very cheap meter. If there was really only 3 volts on pin 7 that tube would be in hard cutoff and you would have no sound.
I don't know what you mean by "resistors above". Show us some hi-rez pics.
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Your meter causes the funny reading on pin 7.
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hi, 8 pin is 47, the resistors above are normal perhaps my soldering is not solid?
You cannot accurately measure the voltage on pin 7, even with a $500 Fluke. But 3 volts indicates a wiring error or wrong component value, or very cheap meter. If there was really only 3 volts on pin 7 that tube would be in hard cutoff and you would have no sound.
I don't know what you mean by "resistors above". Show us some hi-rez pics.
if this is true then perhaps the voltage is fine since all the others are good. still left with no distortion. do you think using a 12ax7 in v1 might help?
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hi, 8 pin is 47, the resistors above are normal perhaps my soldering is not solid?
You cannot accurately measure the voltage on pin 7, even with a $500 Fluke. But 3 volts indicates a wiring error or wrong component value, or very cheap meter. If there was really only 3 volts on pin 7 that tube would be in hard cutoff and you would have no sound.
I don't know what you mean by "resistors above". Show us some hi-rez pics.
I meant that the resistors 1m, 1.5k and 56k were tested and are correct
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still left with no distortion. do you think using a 12ax7 in v1 might help?
yes
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The volume controls are interactive on a 5E3, so make sure the volume control on the channel your NOT plugged into is turned all the down/off/0.
Even with a 12AY7 a 5E3 will distort pretty easily.
You can always put in any 12 _ _ 7 with no harm.
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thanks all for the comments and here is a drawing of where I am getting 3 volts. just noticed that the .022 should not be k but uf, it is a capacitor
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Your drawing shows the 1k5 resistor connected to pin 7 v2 & the 1m, that should not be. It connects to the .1 & pin 8. double check drawing & connection. . Joe
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I'm sorry I drew it unclear I should not have even included the 1.5k. I just left it floating there in the drawing, it does go down to pin 8. The dotted line is under the board and connects the 1m to the capacitor
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I think as suggested earlier if you post some pictures it will help.
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do you think using a 12ax7 in v1 might help?
It seems there is a problem with your circuit, so try to fix that first, rather than trying to change the original circuit.
First test though - have you tried with another guitar?
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I'll just say this... My 5E3 is really loud before it begins to distort. Way too loud to play in my house.
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I just checked all the ohms of my resistors to see if they are right and they are except for the two 1m's connected to two input jacks. they have no reading at all. is there a reason for this? is there something about resistors soldered into jacks that makes them unreadable? weird that they could be acting this way.
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Does that mean they read zero ohms (shorted) or infinity ohms (open)?
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1m resistors on the input jacks go from 1 to 0.00 after they are touched by the meter which is set to 2000k. the 1m resistor on the board tests as it should 1000k
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1m resistors on the input jacks go from 1 to 0.00 after they are touched by the meter which is set to 2000k. the 1m resistor on the board tests as it should 1000k
That's most likely due to the switching jack on the input. If wired as per the schematic, that 1M resistor will be shorted out if nothing is plugged into the HI jack. When you plug in a cable the jack switch opens and removes the short across that resistor. Then the resistor will read correctly.
If that resistor really was zero ohms, you would have no sound at all! Ain't no problem here.
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1m resistors on the input jacks go from 1 to 0.00 after they are touched by the meter which is set to 2000k. the 1m resistor on the board tests as it should 1000k
That's most likely due to the switching jack on the input. If wired as per the schematic, that 1M resistor will be shorted out if nothing is plugged into the HI jack. When you plug in a cable the jack switch opens and removes the short across that resistor. Then the resistor will read correctly.
If that resistor really was zero ohms, you would have no sound at all! Ain't no problem here.
thank you
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I fixed it. thank you for all your help, this is really fun building amps. I found that the ground connection between the ground bus filter b+ 1 and the b+ 2 was not solid. once I made it solid, distortion starts at about volume 4 (bright). I had no idea that solid ground connections would do that. learned a lot. thanks again.
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Glad you got it sorted.