Quote from: RookieRecurve on Today at 10:08:52 AMIs grounding necessary here?  Is the lack of a metal enclosure going to introduce a bunch of noise?  Will the lack of an earth-ground make this amp noisy?

Yes, the ground side of your Voltage output should be connected to the Mains Safety Ground. Without that ground, a guitar will pickup hum and you may get a mild shock or tingle when you touch something that is grounded (like a microphone) while holding the guitar.

I have a question regarding grounding of my setup.  As some of you know, I scavenged a stepdown transformer from an old Dell powered computer speaker (120 to 17), and added a full-bridge rectifier to change that to DC.  Finally, that will be regulated down to 16vdc using a buck converter.  This will then feed the amp (once I assemble it), and feed an external speaker.  The current transformer does not have a grounding plug, a fuse, or a power switch. The enclosure that I am using is plastic.  I am planning to add a power switch and an inline fuse, but am unsure about a ground.  I know from working with tube amps, that the voltages in there are lethal, and therefore grounding protects people from high voltages.  In the case of this amp, after the first stage of the transformer, the voltages are around 17VAC.  Is grounding necessary here?  Is the lack of a metal enclosure going to introduce a bunch of noise?  Will the lack of an earth-ground make this amp noisy?

Thanks for the help with this.  I bought a DIY full-bridge rectifier kit, and powered up the transformer.  My output voltage is 25.3 VDC, so I will definitely need to step that down.  I order up an inexpensive buck converter that is adjustable down to 3.2v, so I will easily be able to step this voltage down to the 16vdc that I am going to need.

Quote from: The Dude on July 24, 2024, 06:57:15 PMThat's not corrosion. It's flux. Not a problem. If you turn the master all the way down (as Juan suggested) is the noise still present? Also, grab the top of those caps and give them a SLIGHT wiggle. That might tell you if any are loose.

One of the connections is pushed through on C31, and it looks like it's taken a piece of the PCB off with it. There's a flake of it attached to the solder.

If I turn the master up, there's some pops and squeals that get louder. This I did after jiggling the cap; I haven't heard that yet. Turning the master down stops that, but the buzz continues unaffected.

There are some pictures and a gut shot here:  http://inspireformation.blogspot.com/2012/08/electro-harmonix-freedom-brothers-photos.html

I can't say whether the schematic is the same as the Mike Mathews Freedom amp.

Is it the Electro Harmonix Freedom amp?
There are a couple gut pictures floating around.

Never heard of Freedom "Brothers" though.

Post a picture or two for identification.

FWIW: Unless board mounted and covered up, there is usually an accessible hole in the center of a 9 pin socket. You can use a chop stick or something of the sort to help push the tube out of the socket from the bottom side.

That's not corrosion. It's flux. Not a problem. If you turn the master all the way down (as Juan suggested) is the noise still present? Also, grab the top of those caps and give them a SLIGHT wiggle. That might tell you if any are loose.

Good.
To my ears it's too buzzy raspy rather than deep hummy, I suspect you lost some ground between amp input and preamp

What happens if you set Master to 0?

What if you short power amp input terminals together?

Trying to find *where* buzz gets in.
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I turned on the board with the speaker disconnected, and I could hear a similar buzz (quieter, obviously) that seemed tk be coming from the transformer... does that help?

Turning the pots didn't affect the speaker buzz at all...

By short the power amp input terminals you mean connect them? And see if it buzzes or am I checking voltage at the speaker leads again? Forgive my inexperience - I know basic circuitry and can do house wiring and car stereos, but that's about as much troubleshooting as I've done.

Quote from: The Dude on July 23, 2024, 10:29:36 PMThat sounds like poor power supply filtering to me. I'd check caps C30, C31, C26, & C27. First, make sure they are properly soldered to the circuit board. It's quite possible you just have a cracked solder joint on one of the caps.

Ok, so it looks like some corrosion (?) on the solder, and some of the connections aren't pretty. I think there might also be problem spots on the bass pot and what I think are fuses(?) Have a look at these pictures and tell me what you think: https://flic.kr/s/aHBqjBBdor