Dragon1 wrote: ↑Wed Apr 03, 2024 2:42 am
Question:
What are these abbreviations ???
LNFB
GNFB
Thanks Brian
Local negative feedback. In an ODS, this is the 20M-.047u-20M network at V1b from plate to grid. But one of the main distinguishing features of #183 is it has no LNFB. you could make that switchable since I see you already have the network in place.
Global negative feedback. The 4k7 resistor connected between the OT secondary and the PI.
Truly don't mean to be rude or unwelcoming, but this answer is easily found with the search function in numerous threads as well as Google. At some point people may become less inclined to answer. It would go a long way to look around here for yourself and if still unsure, then ask for help and explain how you attempted to figure it out.
I see Whopperplate has already included Aiken's glossary in an Electronics Glossaries post in the FAQ section, so maybe the new one I just added could be deleted. OTOH, maybe Aiken's guitar amp specific glossary deserves its own FAQ post.
I see Whopperplate has already included Aiken's glossary in an Electronics Glossaries post in the FAQ section, so maybe the new one I just added could be deleted. OTOH, maybe Aiken's guitar amp specific glossary deserves its own FAQ post.
I can certainly delete it if seen as unnecessary. I worry that many of these resources will go away as all of the links to Trainwreck photos have, for instance.
Thank you dbharis, I know right where this is. I’ve been thru the posts again
And again x100. I don’t remember seeing these terms.
Anywhere. Thank you for the answers.
Brian
Colossal wrote: ↑Wed Apr 03, 2024 11:32 amI worry that many of these resources will go away as all of the links to Trainwreck photos have, for instance.
Could post a .pdf version. That may be fine as long as the source is identified.
Good news, finally finished, still have to wire the footswitch though.
Bad news, I turn on the standby and the test light does nothing, amp make no sound or hum.
Turn on the power switch and the light blinks a little, amp still makes no noise or hum. Then if I wait about 30seconds the 22K resister on the right side of the power board starts to smoke. So I turn it off, I got to check 6L6"s, they are 480v. Didn't check anything else as of yet. If I take off the B+3,4,5 wires the resister doesn't get hot, so I'm assuming the problem comes somewhere from the preamp board.
I don't understand how the standby switch works if there's no power to it. Both sides come from the power board which has no power until the power switch is turned on.
Do you turn on the power first and then the standby???
Brian
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Last edited by Dragon1 on Thu Apr 11, 2024 8:49 pm, edited 1 time in total.
Immediately, I see you don't have your heaters wired up. That is typically not shown on layouts bc it is assumed the builder knows that.
That would not cause your smoking resistor. The problem is likely on or under your power supply board. I suggest looking for shorts to ground first.
Looks like you are missing some jumpers on the power supply board unless they are underneath.
Look closely at your layout and you actual board. Double check every connection and part orientation. Then mark your layout as you go.
Not to pile on but a lot of these solder joints don't look great and lead dress leaves a lot to be desired. First goal is to get a working amp, then clean things up.
-Dan
Last edited by dbharris on Fri Apr 12, 2024 12:31 am, edited 1 time in total.
Jumpers are all underneath the boards. All you guys run your wires under the boards and it's hard for us to see where they go.
OK, I see what I missed, (heater wires) I'll take care of it tonight.
Again, I am new at amp building, have done pedals, guitars, cars and choppers but this is my first amp. I and others seek your guidance and support for
this opportunity so don't be too harsh when replying as we are trying to learn what you already know.
Thank you for your replys.
Brian
Dragon1 wrote: ↑Fri Apr 12, 2024 12:28 am
Jumpers are all underneath the boards. All you guys run your wires under the boards and it's hard for us to see where they go.
OK, I see what I missed, (heater wires) I'll take care of it tonight.
Again, I am new at amp building, have done pedals, guitars, cars and choppers but this is my first amp. I and others seek your guidance and support for
this opportunity so don't be too harsh when replying as we are trying to learn what you already know.
Thank you for your replys.
Brian
Hi Brian,
I don't think any of the replies were harsh or had any ill-will but having said that I think the real concern here is that the heaters are a fundamental part of tube amplifiers and not knowing (or missing them) demonstrates a lack of basic understanding of how these amps work. I am also new to this and remember building my first amp (Tweedle Dee)... I spent days going back and forth verifying every connection and double-checking pictures of real amps before I plucked up the courage to turn the damn thing on. I am still terrified every time I fire up a new amp as these things contain lethal voltages and are no joke.
I hope you understand my concern. This whole community is extremely helpful but you still need to do some of the work on your own. I would suggest reading up on some basic tube amp design before proceeding. There are many resources available, this being one o them https://www.valvewizard.co.uk/
In order to build any tube amp, its imperative to know the fundamentals of tube amp technology. Thevenin etc.
While I applaud your desire to build an amp of this complexity, without having a grasp of the basic fundamentals, its like building a car without tires, and asking why.....
The good thing is that the learning experience is priceless. And experience is the aggregate of fuckups, I know have learned a lot over the years.
Don't be too hard on yourself, Step back, study and tackle the rest of the amp. You got this.
Last edited by jelle on Fri Apr 12, 2024 2:01 am, edited 1 time in total.
