Re: [AMRadio] Re: Modulator design needed
W5OMR/Geoff writes: Is it really that hard, Larry, to delete all of the unnecesary message? ne1s wrote: > Hi Geoff, > As a matter of fact, I try to par particular attention to this, and typically only leave the info i consider pertinent (sp?)from the previous message in the reply. > It is possible that I screwed up on this occaision (if so, please accept my apologies), or that what I think is pertinent & necassary (so that the contest of the reply is > understood) dissagrees with your assessment. (Since you included none of my original posting, I can't tell ;>)) there was a lot of it, for a 1 or two line reply ;-) My contention was, the little blurb at the bottom of every AMRadio Reflector message had been copied like 4 times. Anyway - this conversation isn't gonna do the archive any good, so no harm, no foul ;-) -- 73 = Best Regards, -Geoff/W5OMR A: Yes. > Q: Are you sure? >> A: Because it reverses the logical flow of conversation. >>> Q: Why is top posting annoying in email?
[AMRadio] Re: Modulator design needed
Hi Geoff, As a matter of fact, I try to par particular attention to this, and typically only leave the info i consider pertinent (sp?)from the previous message in the reply. It is possible that I screwed up on this occaision (if so, please accept my apologies), or that what I think is pertinent & necassary (so that the contest of the reply is understood) dissagrees with your assessment. (Since you included none of my original posting, I can't tell ;>)) 73, -Larry/NE1S W5OMR/Geoff writes: Is it really that hard, Larry, to delete all of the unnecesary message?
[AMRadio] Re: Modulator design needed
Never measured the screen current, Dennis, it may well be exceeding the dissipating ratings. That said, I've never had to replace any of the 807's, they're still cranking (in one case after ~10 years of intemittant use), and this is not too much different from where Fender used to run 6L6GC screens in some of their guitar amps. (the 6L6 family is nearly identical electrically to the 807/1625). And in the transmitters I've done this to there's no screen or plate volts on the 807s during standby. 73, -Larry/NE1S [EMAIL PROTECTED] writes: (1) Change screen grid voltage to ~450V, Wow, that's pretty hot for an 807. What kind of screen dissapation numbers are you seeing with this?
Re: [AMRadio] Re: Modulator design needed
In a message dated 3/28/06 1:47:38 PM, [EMAIL PROTECTED] writes: > (1) Change screen grid voltage to ~450V, > Wow, that's pretty hot for an 807. What kind of screen dissapation numbers are you seeing with this? Dennis D. W7QHO Glendale, CA
Re: [AMRadio] Re: Modulator design needed
ne1s wrote: Is it really that hard, Larry, to delete all of the unnecesary message? Why would anyone (or I, for that matter) want to see not twice, not thrice, but FOUR times the blurb that's on every reflector message? I just don't know what the deal is, Brian - people just don't pay attention to what passes in front of their face. -- 73 = Best Regards, -Geoff/W5OMR A: Yes. Q: Are you sure? A: Because it reverses the logical flow of conversation. Q: Why is top posting annoying in email?
[AMRadio] Re: Modulator design needed
Not in mine they don't, Gary, OM ;>) I'm talking fairly extensive mods here: (1) Change screen grid voltage to ~450V, preferably regulated. (plate V is about 550 - 600). Change control grid bias to ~ -50V for proper operating point (~35 - 40mA/tube quiescent). This allows up to 50V of audio on each grid (100V P-P) before going into grid current. (2) Replace adio driver transformer with resistance-coupled phase inverter. I've used the split-load circuit, as well as others, with good results. (3) Feedback from mod xfmr secondary to phase inverter input. Roll off highs in the feedback network so that phase shift don't getcha! (4) Increase 1st audio input resistor, beef up audio coupling & decoupling caps, replace .02 mfd accross mod xfmr secondary with 0.002, yada, yada... Works for me - I did it for my Viking I, and a friends Viking II. Able to modulate the things at 100% cleanly at full rated input. Can't argue with the results! 73, -Larry/NE1S Gary Schafer writes: The 807's in the Viking and DX-100 run in AB2. In AB1 you wont get more than around 45 to 50 watts of audio before they start drawing grid current. In AB2 they will produce 120 watts of audio. 73 Gary K4FMX -Original Message- From: ne1s [mailto:[EMAIL PROTECTED] Sent: Monday, March 27, 2006 1:06 PM To: [EMAIL PROTECTED]; Discussion of AM Radio Subject: Re: Modulator design needed While other tubes may do better, I've had good luck using AB1 807s in VikingI/II/DX-100 class transmitters - they'll do 100% cleanly. -Larry/NE1S Gary Schafer writes: > Just remember if you are going to use a tube phase inverter rather than a > driver transformer the modulator tubes need to be run in AB1 and not AB2. > You can't run any grid current without a driver transformer. > This leaves out 807's as modulators as you can't get very much power out of > them in AB1 but they are fine in AB2 as they are used in most rigs. Dx100 > etc. > > 73 > Gary K4FMX > > >> -Original Message- >> From: [EMAIL PROTECTED] [mailto:amradio- >> [EMAIL PROTECTED] On Behalf Of Peter Markavage >> Sent: Sunday, March 26, 2006 1:34 PM >> To: amradio@mailman.qth.net >> Subject: Re: [AMRadio] Modulator design needed >> >> 12BY7 drives the driver transformer which, in turn drives the EL-34's. >> >> Build a phase inverter, like many of the Hi-Fi amps that don't use a >> driver transformer to drive the EL-34's. >> >> Pete, wa2cwa >> >> On Sun, 26 Mar 2006 13:19:06 -0500 "Mike Sawyer" <[EMAIL PROTECTED]> >> writes: >> > Bob, >> > I suggest you look at the schematics again. The output of the >> > 5763 goes >> > no where near the modulator. I don't have the schematics in front >> > of me but >> > I have done some extensive work in the audio section. >> > Mod-U-Lator, >> > Mike(y) >> > W3SLK >> > - Original Message - >> > From: <[EMAIL PROTECTED]> >> > To: <[EMAIL PROTECTED]>; "Discussion of AM Radio" >> > ; >> > "Discussion of AM Radio" >> > Sent: Sunday, March 26, 2006 12:59 PM >> > Subject: Re: [AMRadio] Modulator design needed >> > >> > >> > Mark, >> > >> > Take a look at a Heathkit Apache schematic, (TX-1), for ideas. >> > >> > There is NO driver transformer. The 5763 driver goes to the Mod >> > transformer >> > and the EL-34s feed it for audio. >> > >> > Bob - N0DGN >> > >> > -- Original message -- >> > From: "W1EOF" <[EMAIL PROTECTED]> >> > > >> > > I've been gifted a nice mod transformer so I can build a modulator >> > for my >> > > Johnson 6N2. I don't have a driver transformer so I'm looking for >> > a design >> > > which doesn't need one. I'm sure the schematics are out there, but >> > I keep >> > > finding ones with the driver transformer. Same with all my old >> > radio books >> > > that I've looked at so far. Can someone point me in the direction >> > of a >> > > good >> > > design that is online, or one that you can share with me via >> > email? >> > > Thanks! >> __ >> AMRadio mailing list >> Home: http://mailman.qth.net/mailman/listinfo/amradio >> Help: http://mailman.qth.net/mmfaq.html >> Post: mailto:AMRadio@mailman.qth.net >> AMfone Website: http://www.amfone.net >> AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb > > > __ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
Re: [AMRadio] RE: Modulator design needed
In a message dated 3/28/06 7:36:46 AM, [EMAIL PROTECTED] writes: > I think if you look at the grid voltage with a scope you will find that it > does go into AB2 on modulation peaks. > Yes, the grids do go somewhat positive but the peaks are badly distorted. Not square clipped but rather rounded off, hence my characterization of AB"1.25" The stock bias supply is not very stiff either so flops around when any grid current is drawn. Dennis D. W7QHO Glendale, CA
RE: [AMRadio] RE: Modulator design needed
> -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] > Sent: Monday, March 27, 2006 10:23 PM > To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; amradio@mailman.qth.net > Subject: Re: [AMRadio] RE: Modulator design needed > > > In a message dated 3/27/06 4:48:02 PM, [EMAIL PROTECTED] writes: > > > > The 807's in the Viking and DX-100 run in AB2. > > > > I know the VII manual sez AB2 but no way with that triode connected 6AU6 > driver (AB1.25 maybe). A popular mod was to replace with a parallel > connected > 12AU7 which doesn't give enough kick either and the stock driver > transformer won't > handle AB2 power levels in any case. The stock VII audio system can > provide > just enough output for good sounding 100% modulation with a hot pair of > 807s and careful adjustment. Regulating the screens at 300 volts will > help a > lot too. Don't know what Heath did about the problem, but note that DX- > 100s > (pair of 1625s) usually sound quite good on the air. > > I modified my VII for proper AB2 operation with a 6AQ5 driver, 5W driver > xformer, negative feedback, and regulated screen and bias supplies. > Works FB but > a non-trivial undertaking. Swapped a pair of EL-34s for the 807s in > another > VII; regulated the screens but left the rest of the audio string original. > Worked just as well as the AB2 mod and MUCH easier to do. > > > Dennis D. W7QHO > Glendale, CA Part of the problem with the Viking II is that the modulation transformer has the wrong ratio. The modulator tubes are not loaded heavy enough and they go into clipping too soon. They designed it that way deliberately, I suppose to get a little high level clipping without the rig being able to severely over modulate. I think if you look at the grid voltage with a scope you will find that it does go into AB2 on modulation peaks. 73 Gary K4FMX
Re: [AMRadio] RE: Modulator design needed
In a message dated 3/27/06 4:48:02 PM, [EMAIL PROTECTED] writes: > The 807's in the Viking and DX-100 run in AB2. > I know the VII manual sez AB2 but no way with that triode connected 6AU6 driver (AB1.25 maybe). A popular mod was to replace with a parallel connected 12AU7 which doesn't give enough kick either and the stock driver transformer won't handle AB2 power levels in any case. The stock VII audio system can provide just enough output for good sounding 100% modulation with a hot pair of 807s and careful adjustment. Regulating the screens at 300 volts will help a lot too. Don't know what Heath did about the problem, but note that DX-100s (pair of 1625s) usually sound quite good on the air. I modified my VII for proper AB2 operation with a 6AQ5 driver, 5W driver xformer, negative feedback, and regulated screen and bias supplies. Works FB but a non-trivial undertaking. Swapped a pair of EL-34s for the 807s in another VII; regulated the screens but left the rest of the audio string original. Worked just as well as the AB2 mod and MUCH easier to do. Dennis D. W7QHO Glendale, CA
RE: [AMRadio] RE: Modulator design needed
Your Right Gary on the out put of AB1 VS AB2 and Since the plate current swing is limited to not drawing grid current one generally ops for better linearity and gain by using a high plate "Z" load in AB1 than in AB2. This also reduces output slightly. It can be accomplished on a modulator by simply unloading the final to draw less current, thereby reflecting a high Z to the modulator. It makes the audio really smooth but a lot less PEP. John, WA5BXO
[AMRadio] RE: Modulator design needed
The 807's in the Viking and DX-100 run in AB2. In AB1 you wont get more than around 45 to 50 watts of audio before they start drawing grid current. In AB2 they will produce 120 watts of audio. 73 Gary K4FMX > -Original Message- > From: ne1s [mailto:[EMAIL PROTECTED] > Sent: Monday, March 27, 2006 1:06 PM > To: [EMAIL PROTECTED]; Discussion of AM Radio > Subject: Re: Modulator design needed > > While other tubes may do better, I've had good luck using AB1 807s in > VikingI/II/DX-100 class transmitters - they'll do 100% cleanly. > > -Larry/NE1S > > Gary Schafer writes: > > Just remember if you are going to use a tube phase inverter rather than > a > > driver transformer the modulator tubes need to be run in AB1 and not > AB2. > > You can't run any grid current without a driver transformer. > > This leaves out 807's as modulators as you can't get very much power out > of > > them in AB1 but they are fine in AB2 as they are used in most rigs. > Dx100 > > etc. > > > > 73 > > Gary K4FMX > > > > > >> -Original Message- > >> From: [EMAIL PROTECTED] [mailto:amradio- > >> [EMAIL PROTECTED] On Behalf Of Peter Markavage > >> Sent: Sunday, March 26, 2006 1:34 PM > >> To: amradio@mailman.qth.net > >> Subject: Re: [AMRadio] Modulator design needed > >> > >> 12BY7 drives the driver transformer which, in turn drives the EL-34's. > >> > >> Build a phase inverter, like many of the Hi-Fi amps that don't use a > >> driver transformer to drive the EL-34's. > >> > >> Pete, wa2cwa > >> > >> On Sun, 26 Mar 2006 13:19:06 -0500 "Mike Sawyer" <[EMAIL PROTECTED]> > >> writes: > >> > Bob, > >> > I suggest you look at the schematics again. The output of the > >> > 5763 goes > >> > no where near the modulator. I don't have the schematics in front > >> > of me but > >> > I have done some extensive work in the audio section. > >> > Mod-U-Lator, > >> > Mike(y) > >> > W3SLK > >> > - Original Message - > >> > From: <[EMAIL PROTECTED]> > >> > To: <[EMAIL PROTECTED]>; "Discussion of AM Radio" > >> > ; > >> > "Discussion of AM Radio" > >> > Sent: Sunday, March 26, 2006 12:59 PM > >> > Subject: Re: [AMRadio] Modulator design needed > >> > > >> > > >> > Mark, > >> > > >> > Take a look at a Heathkit Apache schematic, (TX-1), for ideas. > >> > > >> > There is NO driver transformer. The 5763 driver goes to the Mod > >> > transformer > >> > and the EL-34s feed it for audio. > >> > > >> > Bob - N0DGN > >> > > >> > -- Original message -- > >> > From: "W1EOF" <[EMAIL PROTECTED]> > >> > > > >> > > I've been gifted a nice mod transformer so I can build a modulator > >> > for my > >> > > Johnson 6N2. I don't have a driver transformer so I'm looking for > >> > a design > >> > > which doesn't need one. I'm sure the schematics are out there, but > >> > I keep > >> > > finding ones with the driver transformer. Same with all my old > >> > radio books > >> > > that I've looked at so far. Can someone point me in the direction > >> > of a > >> > > good > >> > > design that is online, or one that you can share with me via > >> > email? > >> > > Thanks! > >> __ > >> AMRadio mailing list > >> Home: http://mailman.qth.net/mailman/listinfo/amradio > >> Help: http://mailman.qth.net/mmfaq.html > >> Post: mailto:AMRadio@mailman.qth.net > >> AMfone Website: http://www.amfone.net > >> AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb > > > > > > __ > > AMRadio mailing list > > Home: http://mailman.qth.net/mailman/listinfo/amradio > > Help: http://mailman.qth.net/mmfaq.html > > Post: mailto:AMRadio@mailman.qth.net > > AMfone Website: http://www.amfone.net > > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb >
[AMRadio] Re: Modulator design needed
While other tubes may do better, I've had good luck using AB1 807s in VikingI/II/DX-100 class transmitters - they'll do 100% cleanly. -Larry/NE1S Gary Schafer writes: Just remember if you are going to use a tube phase inverter rather than a driver transformer the modulator tubes need to be run in AB1 and not AB2. You can't run any grid current without a driver transformer. This leaves out 807's as modulators as you can't get very much power out of them in AB1 but they are fine in AB2 as they are used in most rigs. Dx100 etc. 73 Gary K4FMX -Original Message- From: [EMAIL PROTECTED] [mailto:amradio- [EMAIL PROTECTED] On Behalf Of Peter Markavage Sent: Sunday, March 26, 2006 1:34 PM To: amradio@mailman.qth.net Subject: Re: [AMRadio] Modulator design needed 12BY7 drives the driver transformer which, in turn drives the EL-34's. Build a phase inverter, like many of the Hi-Fi amps that don't use a driver transformer to drive the EL-34's. Pete, wa2cwa On Sun, 26 Mar 2006 13:19:06 -0500 "Mike Sawyer" <[EMAIL PROTECTED]> writes: > Bob, > I suggest you look at the schematics again. The output of the > 5763 goes > no where near the modulator. I don't have the schematics in front > of me but > I have done some extensive work in the audio section. > Mod-U-Lator, > Mike(y) > W3SLK > - Original Message - > From: <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]>; "Discussion of AM Radio" > ; > "Discussion of AM Radio" > Sent: Sunday, March 26, 2006 12:59 PM > Subject: Re: [AMRadio] Modulator design needed > > > Mark, > > Take a look at a Heathkit Apache schematic, (TX-1), for ideas. > > There is NO driver transformer. The 5763 driver goes to the Mod > transformer > and the EL-34s feed it for audio. > > Bob - N0DGN > > -- Original message -- > From: "W1EOF" <[EMAIL PROTECTED]> > > > > I've been gifted a nice mod transformer so I can build a modulator > for my > > Johnson 6N2. I don't have a driver transformer so I'm looking for > a design > > which doesn't need one. I'm sure the schematics are out there, but > I keep > > finding ones with the driver transformer. Same with all my old > radio books > > that I've looked at so far. Can someone point me in the direction > of a > > good > > design that is online, or one that you can share with me via > email? > > Thanks! __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
