Search found 1237 matches
- Sun May 05, 2024 6:26 pm
- Forum: Technical Discussion
- Topic: JJ E34L (brand new) emitting a white light - has anyone seen this before?
- Replies: 5
- Views: 134
Re: JJ E34L (brand new) emitting a white light - has anyone seen this before?
Very unlikely to be a spot of contamination on the cathode/plate/etc. The white color of the light indicates a temperature over 5000K of the source. There's no reactive gasses in there to speak of to support a reaction that vigorous if it passes audio at all. It's very, very, very likely to be an ar...
- Wed May 01, 2024 11:52 pm
- Forum: Technical Discussion
- Topic: Can I use 6v6's in a 69 Super Reverb ?
- Replies: 16
- Views: 396
Re: Can I use 6v6's in a 69 Super Reverb ?
"Can I use them?" is not the question. Of course you can.
The question is how long they'll last.
The question is how long they'll last.
- Sat Apr 27, 2024 4:12 pm
- Forum: Technical Discussion
- Topic: Add an HT Fuse?
- Replies: 10
- Views: 364
Re: Add an HT Fuse?
I'd be interested in commentary regarding fusing the rectified DC line vs. both HT legs of the secondary (AC). It goes back to that "what are you trying to protect?" thing. A fuse in the rectified DC line can only stop current flow between the rectifiers and whatever is after them, presumably both ...
- Fri Apr 26, 2024 8:15 pm
- Forum: Technical Discussion
- Topic: Add an HT Fuse?
- Replies: 10
- Views: 364
Re: Add an HT Fuse?
Why do a lot of guitars amp circuits do not have an HT fuse, while others do have them? I believe that it's an economic decision based on trading off the cost of a fuse, holder, and wiring plus some number of warranty calls on the fuse setup, versus the warranty savings of the small percent of amps...
- Sat Apr 13, 2024 7:20 pm
- Forum: Technical Discussion
- Topic: Regarding the B+mosfet reducer and power ground
- Replies: 10
- Views: 416
Re: Regarding the B+mosfet reducer and power ground
That's a clearer explanation of what I was worried about. If the bias is a tap, not a separate winding then the whole bias generation rectifier/filter/is pulled down by the zener setup. The bias voltage is shifted. I - think - what I wrote is consistent with that, at least from the perspective of to...
- Sat Apr 13, 2024 2:28 pm
- Forum: Technical Discussion
- Topic: Regarding the B+mosfet reducer and power ground
- Replies: 10
- Views: 416
Re: Regarding the B+mosfet reducer and power ground
I ... think... that moving only the PT high voltage center tap was the right thing to do for everything except possibly the bias. How is your bias voltage generated? Is the output stage cathode biased? Is it fixed bias? If fixed bias, does the bias voltage come from a tap on the high voltage winding...
- Thu Apr 11, 2024 10:32 pm
- Forum: Technical Discussion
- Topic: Regarding the B+mosfet reducer and power ground
- Replies: 10
- Views: 416
Re: Regarding the B+mosfet reducer and power ground
I'm having some trouble visualizing exactly how you have it hooked up. Can you post even a quickie, crude sketch so I don't mis-visualize it? If I'm visualizing correctly, the MOSFET reducer installed in the ground-to-PT/CT should have no effect on the circuit at all - as long as you tie nothing but...
- Mon Apr 08, 2024 7:11 pm
- Forum: Technical Discussion
- Topic: Paging RG Keen/UL700 pcb/wiring question.
- Replies: 13
- Views: 4546
Re: Paging RG Keen/UL700 pcb/wiring question.
Got it, replied.
- Fri Apr 05, 2024 8:45 pm
- Forum: Technical Discussion
- Topic: New design humming - help requested
- Replies: 20
- Views: 637
Re: New design humming - help requested
I believe it's the best practice, yes. Star grounding is not the only way to get a hum-free setup. It's just the only way that is known to work ahead of building and trying. I like the term I heard here - "constellation grounding". This is a handier way to wire grounds with very, very, very nearly t...
- Fri Apr 05, 2024 1:35 pm
- Forum: Technical Discussion
- Topic: New design humming - help requested
- Replies: 20
- Views: 637
Re: New design humming - help requested
Yep, PCB grounding scheme is the most likely culprit. It may be the PCB combined with how your connections to chassis ground is done. I can't figure it out from the diagrams either (no part designators shown), but one possible issue might be grounding the tremolo depth pot (and in fact the whole tre...
- Thu Apr 04, 2024 11:24 pm
- Forum: Technical Discussion
- Topic: Testing power supply before completion
- Replies: 14
- Views: 484
Re: Testing power supply before completion
Don't forget to drain those filter caps! Even better, permanently install a 220K 3W resistor across the first filter cap to always drain whenever the amp is off. + 1 on the drain-down resistor. The life you save could be your own. I like to put an LED in series with the 220k to have a glowing indic...
- Mon Apr 01, 2024 10:06 pm
- Forum: Technical Discussion
- Topic: Lead Dress for Star Grounding
- Replies: 5
- Views: 262
- Mon Apr 01, 2024 4:52 pm
- Forum: Technical Discussion
- Topic: Lead Dress for Star Grounding
- Replies: 5
- Views: 262
Re: Lead Dress for Star Grounding
Good planning! Running extra ground wire is the bane of star grounding. And good thinking - ideal versus real world is always a consideration. If it were me, I would feel free to bundle the ground wires neatly as they head back to the star ground point, with two exceptions. I would route the PT cent...
- Mon Apr 01, 2024 1:43 pm
- Forum: Technical Discussion
- Topic: Schematic interpretation, PT 125V and 120V Primaries
- Replies: 8
- Views: 264
Re: Schematic interpretation, PT 125V and 120V Primaries
Haven't been able to find the answer online. The PT has a 125V and 120V primaries. Does the attached schematic show the 125V (BLUE) connected to the switch, or is the 120V (Brown) connected, or are both connected? If some one could explain the reasoning behind the 125V primary when the US power sup...
- Tue Mar 26, 2024 2:42 pm
- Forum: Technical Discussion
- Topic: The Lost Art of Cable Lacing
- Replies: 17
- Views: 1045
Re: The Lost Art of Cable Lacing
I just use it because I think it looks nice. But apparently lacing is longer lasting than nylon zip ties, and less prone to cutting into the wires' jackets than zip ties. These are not likely to be reasons to use lacing in home-built gear, though. In industry, zip ties have the huge economic advanta...