Hi , I could use some help on this hum problem. With the volume turned all the way down there is an annoying hum with or without the guitar plugged in.
Thanks for any advice.
hum
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Randy Magee
- Posts: 222
- Joined: Thu Feb 16, 2006 12:05 pm
- Location: Leland, MS
Re: hum
Can you tell if it's 60 cycle or 120 cycle hum? 60 cycle would be a problem with the filament circuit, provided the filaments are VAC. !20 cycle hum would be in the power circuit, i.e. a bad filter cap or a grounding issue... could also be a badly mismatched set of power tubes...
Randy Magee
Re: hum
Thanks for the replies. The Heybouer has always had a mechanical hum but when the transformer set was in a TW style aluminum chassis I never heard a hum coming out of the speakers. I now have the set in a cleaned out steel Blues DeVille chassis. I had to put the OT at front center of the chassis. I'll try reorienting the trannys. I'll keep y'all posted. Thanks
Re: hum
You know about the "headphone" trick?
From our friends over at AX84:
This is the best way to find the quietest place to put a reverb, output, driver, or any other signal transformer to get the least hum. CAUTION: THIS INVOLVES WORKING ON THE AMP WITH WALL VOLTAGE PRESENT. WALL VOLTAGE CAN BE FATAL.
First set up the power transformer. If it's not installed yet, all the better, but if it is, this will still help. If the PT is not installed, wire up the primaries to a power cord, but do not wire up any secondaries-- tape the ends of the secondaries. If the PT is installed, fine, just make sure there is no circuit on any of the secondary leads (pull all tubes, and disconnect leads and tape them as necessary).
Now set up the signal transformer (output, reverb, whatever). Hook one set of OT secondaries (your choice, but I usually go from ground to the highest impedance tap, don't worry about impedance matching here!) to a set of headphones. Tape the primary leads.
Put the headphones on, plug in the power cord, and start moving the signal transformer around. Try it all over the chassis, and also rotate it. While you might expect the least hum with the transformers as far from each other as possible and at right angles (and that may be the case for you), it might come at an odd angle and/or position. Sometimes the least hum occurs when the transformers are side by side. When you find the quietest spot, use a permanent marker to mark where the mounting holes should be.
If you have more than one signal transformer, repeat this for each one. When you're finished, unplug the PT. That's it!
From our friends over at AX84:
This is the best way to find the quietest place to put a reverb, output, driver, or any other signal transformer to get the least hum. CAUTION: THIS INVOLVES WORKING ON THE AMP WITH WALL VOLTAGE PRESENT. WALL VOLTAGE CAN BE FATAL.
First set up the power transformer. If it's not installed yet, all the better, but if it is, this will still help. If the PT is not installed, wire up the primaries to a power cord, but do not wire up any secondaries-- tape the ends of the secondaries. If the PT is installed, fine, just make sure there is no circuit on any of the secondary leads (pull all tubes, and disconnect leads and tape them as necessary).
Now set up the signal transformer (output, reverb, whatever). Hook one set of OT secondaries (your choice, but I usually go from ground to the highest impedance tap, don't worry about impedance matching here!) to a set of headphones. Tape the primary leads.
Put the headphones on, plug in the power cord, and start moving the signal transformer around. Try it all over the chassis, and also rotate it. While you might expect the least hum with the transformers as far from each other as possible and at right angles (and that may be the case for you), it might come at an odd angle and/or position. Sometimes the least hum occurs when the transformers are side by side. When you find the quietest spot, use a permanent marker to mark where the mounting holes should be.
If you have more than one signal transformer, repeat this for each one. When you're finished, unplug the PT. That's it!
Re: hum
I removed the bigger OT from the front of the chassis and used a smaller sized OT instead and mounted it TW style- still hummed
I swapped out the PT- still hummed --- It had to be something simple then like a ground hum.
The problem was that I was using all the B+s on a can cap with the can ground point near it and the preamp ground near the input. I tried using a separate cap for the B+1 with its own ground point and grounded the can (screens,PI,and V1) along the preamp buss going near the input. This fixed just about all of the hum. Finally.
Has anyone had trouble using B+1 on the same can as the rest of the amp?
Thanks for your thoughts on this.
I swapped out the PT- still hummed --- It had to be something simple then like a ground hum.
The problem was that I was using all the B+s on a can cap with the can ground point near it and the preamp ground near the input. I tried using a separate cap for the B+1 with its own ground point and grounded the can (screens,PI,and V1) along the preamp buss going near the input. This fixed just about all of the hum. Finally.
Has anyone had trouble using B+1 on the same can as the rest of the amp?
Thanks for your thoughts on this.
Re: hum
Well yes, the grounding scheme is very important as you found out.
There are a few different schools of thought about grounding at various points and you can see merit in all of the successful ones.
In other words, there are more than one way to skin a cat.
I call the ones that are successful as the ones that don't hum loudly when on.
Having the preamp tubes ground near the input is good because that is the quietest place in the amp.
The power tube filter grounds usually are best suited going near the filter caps location.
There are a few different schools of thought about grounding at various points and you can see merit in all of the successful ones.
In other words, there are more than one way to skin a cat.
I call the ones that are successful as the ones that don't hum loudly when on.
Having the preamp tubes ground near the input is good because that is the quietest place in the amp.
The power tube filter grounds usually are best suited going near the filter caps location.
Tom
Don't let that smoke out!
Don't let that smoke out!
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diagrammatiks
- Posts: 558
- Joined: Sun Mar 27, 2011 12:28 am
Re: hum
A shared can with body ground is pretty much the worst way to ground an amp
Re: hum
Maybe the reason the heyboer PT didn't hum in the TW chassis is because I wasn't using a can cap at the time. Should I use another separate cap for the screens also? As it is now the screens are in the cap along with the PI and V1.
Re: hum
I love this !labb wrote:You know about the "headphone" trick?
From our friends over at AX84:
This is the best way to find the quietest place to put a reverb, output, driver, or any other signal transformer to get the least hum. CAUTION: THIS INVOLVES WORKING ON THE AMP WITH WALL VOLTAGE PRESENT. WALL VOLTAGE CAN BE FATAL.
First set up the power transformer. If it's not installed yet, all the better, but if it is, this will still help. If the PT is not installed, wire up the primaries to a power cord, but do not wire up any secondaries-- tape the ends of the secondaries. If the PT is installed, fine, just make sure there is no circuit on any of the secondary leads (pull all tubes, and disconnect leads and tape them as necessary).
Now set up the signal transformer (output, reverb, whatever). Hook one set of OT secondaries (your choice, but I usually go from ground to the highest impedance tap, don't worry about impedance matching here!) to a set of headphones. Tape the primary leads.
Put the headphones on, plug in the power cord, and start moving the signal transformer around. Try it all over the chassis, and also rotate it. While you might expect the least hum with the transformers as far from each other as possible and at right angles (and that may be the case for you), it might come at an odd angle and/or position. Sometimes the least hum occurs when the transformers are side by side. When you find the quietest spot, use a permanent marker to mark where the mounting holes should be.
If you have more than one signal transformer, repeat this for each one. When you're finished, unplug the PT. That's it!