Drive voltage vs. bias voltage

[Enzo]

He's one of those island people, almost in Canada.

[Dave H]

I have one! I was using it to monitor the output for clipping and using my 87 to measure voltages. Had I put the scope on the grids, well...

If your scope has two channels you could monitor the output and the grid. It should look something like the sim below.



Edit:
Here's a plot with it driven harder. The flat at the top of the blue trace is where the signal is clipped by the EL84 grid. The section of the blue trace extending from -16V to -35V will be clipped off by your zener mod.

[Chuck H]

Mine is a a dual trace, but the older over/under type. I'd need to find my other scope probe for that I haven't seen it since my last move four years ago.

And I did scope the grids, but just to LOOK at the waveform. Not at the same time as the plates. I'm using 10k grid resistors so the clamp at the grid looks a little more crowned at first. then flattens.

Remember guys, I'm not a tech in a shop. I'm pretty amateur. But yeah, I should look for that other probe (it's even the clippy do tip type )

I had actually considered the RMS thing. When the math didn't add up exactly that's when I became confused. Then, after posting I remembered the slightly different reading by measuring directly between the cathode and grid, rather than the cathode and ground. That math looked better.

[nsubulysses]

Remember guys, I'm not a tech in a shop. I'm pretty amateur.

If you've been building and working on amps for a couple decades I would assume you know more than most techs at most shops. Give yourself some credit !

Having these types of discussions on MEF for years doesn't hurt either

With the exception of meeting Enzo in person once, I've learned 1000X more from reading here vs. any tech/electronics person I've ever met in real life.

[Chuck H]

If you've been building and working on amps for a couple decades I would assume you know more than most techs at most shops. Give yourself some credit !

Having these types of discussions on MEF for years doesn't hurt either

With the exception of meeting Enzo in person once, I've learned 1000X more from reading here vs. any tech/electronics person I've ever met in real life.

Oh, absolutely! Some of the "professionals" I meet say things that clearly demonstrate a strictly rote understanding, and occasional misconception. I politely hold my tongue, but the whole time I'm thinking "I sure hope they don't get themselves hurt or into any real trouble". I've mentioned before that there's a guy here on Whidbey that works on vintage amps that goes by some moniker like Wild Bill or some such (No relation to the Wild Bill that use to post here I'm sure!). I approached a guy after a gig once. He was playing a Super Reverb and it sounded awful. Clearly in need of new filters and probably some tubes, maybe check for resistor drift, etc. It didn't sound "right" and it had the original two prong power cord! I told him "I can fix up that amp if you're interested." He responded, with some indignance that "Wild Bill just went through this amp. It's all great." I heard another conversation between a couple of other gigging guitar players that were talking about his "services". I got the impression that the guy is all about keeping vintage filters, tubes and power supply design unless it's non operational. And then you should replace such things with only vintage parts. Stock is best, even when it means NOS filter caps!?! Just stupidly uneducated and borderline dangerous shizzle on the matter. This guy must have some game because I got the impression these guys had drank too much of the KoolAid for me to bother interjecting. Point is, Wild Bill doesn't post here. At least as far as I know. If he did the amps here on Whidbey would be safer and sound better. So yeah, I'm pretty glad my entire history in this avocation is attached to this forum

[The Dude]

I must preface this by saying:

1) I don't know everything.
2) I never will know everything.
3) I'm not afraid to learn or ask questions.
4) I'm not embarrassed or too proud to admit any of the above.

If you don't know something, it's because you haven't learned it yet. That doesn't make you stupid. Stupid is when you think you know everything and, because of that, fail to grow intellectually.

That said, I know these types. There's "a guy" like that in my area, too (and an "infamous forum member" comes to mind). My strategy is usually the same as yours- in that I usually don't engage him in tech conversation. He already knows everything and isn't going to listen to you anyway. I'm content in the fact that much of the gear he fixes comes to my shop to be fixed again.

P.S. Sorry to further derail the thread. You may return to regular programming.

[Chuck H]

He's one of those island people, almost in Canada.

We don't take kindly to that sort a talk 'round here.

[J M Fahey]

I must preface this by saying:

1) I don't know everything.
2) I never will know everything.
3) I'm not afraid to learn or ask questions.
4) I'm not embarrassed or too proud to admit any of the above.

If you don't know something, it's because you haven't learned it yet. That doesn't make you stupid. Stupid is when you think you know everything and, because of that, fail to grow intellectually.

That said, I know these types. There's "a guy" like that in my area, too (and an "infamous forum member" comes to mind). My strategy is usually the same as yours- in that I usually don't engage him in tech conversation. He already knows everything and isn't going to listen to you anyway. I'm content in the fact that much of the gear he fixes comes to my shop to be fixed again.

P.S. Sorry to further derail the thread. You may return to regular programming.

Same here.
I come to this Form to *learn* and if sometimes I seem to disappear for a week or two itīs basically because main fodder on the menu is a week or two long discussion on how to bias a 5E3 or tube rolling or whatever ... old stuff where anything possible has been said and done *long* ago ... then somebody brings a Little Markbass or 1200W active subwoofer, all SMPS and Class D or Class H or whatever and I adjust my glasses and say "well, NOW thereīs something interesting starting on

[Justin Thomas]

I'm just glad "you guys" don't poke fun at us who still are learning that the circuit matters more than the tube and for whom biasing an amp is still not yet a "simple procedure." Best place around for those of us who "had to start somewhere," yet may not ever get to somewhere else!

Class D = Class Dustbin when broken?

Justin