[mcgsxr]

Well, much (ok, ALL) of the technical parts of this discussion are beyond me, but I certainly do appreciate the various links etc.

I bought an old Magnavox SE EL84 amp around 1-1.5 years ago, and have been very happy with it.  I use it with my Bolder modded SB3, and with b200 Visaton speakers.  Even with only 1v rms driving the 1.5-3 wpc into my mid 90's efficient b200's, this is a combo that makes me really happy.

Good music, and cheap too!

[floobydust]

Well the reason I read why screen regulation is problematic when B+ is not regulated is this...  Say your wall is running at 117V and your B+ is 400v and your screen is 255v regulated.  Now suppose the wall voltage climbs to 125v (mine was 126 most of the weekend), your B+ is now 427v and your screen is still 255v.  What just happened to your screen vs. plate? 

 Actually, a fixed screen supply is preferred. This is well documented in older ARRL handbooks and older tube manuals. As an example, RCA's RC-30 manual specifically notes that the excellent performance of their 50-watt AB2 power amplifier is partly the result of a regulated screen supply. You can also find regulated power supplies that provide regulated screen supplies to reduce the ripple in their output. A regulated screen supply also can also be found in numerous amplifiers designed for high-power AM modulators.

 Regards, KM

[JoshK]

Kevin, I am not saying regulation of screen supplies is bad, I actually believe the opposite to be true.  I am just raising a point that needs to be addressed regarding the way in which it is done. 

[floobydust]

Sorry Josh,

 Was no intention to type on your fingers... but just point to a few sources which clarify the advantages of a regulated screen supply.

 Regards, KM

[andrewbee]

Well the reason I read why screen regulation is problematic when B+ is not regulated is this...  Say your wall is running at 117V and your B+ is 400v and your screen is 255v regulated.  Now suppose the wall voltage climbs to 125v (mine was 126 most of the weekend), your B+ is now 427v and your screen is still 255v.  What just happened to your screen vs. plate?

In a tetrode / pentode, screen voltage / regulation is much more important than plate voltage. Well... the 27V difference is not critical on the plate on a competently designed amp ( e.g. tube dissipation not knocking on the door of maximum dissipation value), we are dealing with tubes here, I agree it would not be what it is designed to be but its a little over 5%. I would be more concerned with the heater voltage being excessive. I certainly see your point though.
IMHO 5% one way or the other is not going to spoil the brew. Having said that though, being somewhat anal myself I shoot for +/- 2% in my own stuff.

BTW, have you ever measured your wall at 117VAC? If yes was it at night? I have never seen my AC go below 120V in recent history and it usually hovers around 122VAC. The max I have measured is 125VAC but I know it has swung wildly from time to time in the past, usually low, a brownout at ~90VAC.

[jrebman]

So, still curious if anybody has ever seen a BOM, or has a schematic in some form like a PDF, etc. that I can at least make an atempt at tactilly printing or translating into english directions?  I checked all over, and did not come up with anything but the nearly useless original web page.  If Bas Horneman did do something it must be in his DIY magazine, which is a scanned image, not electronic text.

-- Jim

[andrewbee]

Is this what you are refering to as useless?

http://www.tubeaudio.8m.com/RH84/rh84.html

Can you see the schematic?

Try to right click and then use "save image as" and save it, you now have a .gif that you can print easily.

[jrebman]

Right, that's the site.  No, I can't see it (I'm blind and can't see anything.)  I can't even find anything to click on in order to be able to save it, and even if I did, .gifs don't print well on my tactile printer -- images in PDFs and Word documents print much better, as do things in Visio, etc.

I'm sure it would be completely adequate if I indeed could see it.

-- Jim

[planet10]

Jim,

What kind of format do you prefer for a schematic? I have an almost finished  variation in Vectorworks. It would take me less time to finish that up than to describe the circuit in text (which i could & am willing to do if you prefer, but i'm not anywhere near as slick as some JoeListers). I can export the drawing in a number of formats.

dave

[jrebman]

Dave,

Is this the EF86 version?  No problem if it is, just curious.

There is a new version of my tactile printing software due out anyday now, let me check in with the development team to see what is the preferred format.  It may be some SVG thing, but not sure if that is a supported format yet.

Thanks,

Jim

P.S. -- The package from Bud arrived, so I'll get it out on Friday.

[planet10]

Is this the EF86 version?  No problem if it is, just curious.
Jim

P.S. -- The package from Bud arrived, so I'll get it out on Friday.

If i have to finish a map, i'd prefer to do the EF86 version... force me to poke around inside the amp and see what we actually ended up with.

Look forward to hearing uberFonken,

dave

[andrewbee]

(I'm blind and can't see anything.)

Okay, now I know. Here is a pdf, I hope it works, if not holler back and I will PM you.
as a matter of fact I will PM you with it anyway.

Andrew

[andrewbee]

It did not work so I sent you a PM with it as a pdf.

Andrew