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Vic 2




 
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The Slab Bacon
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« Reply #25 on: March 23, 2012, 08:24:44 AM »

An overhaul will require access underneath to replace paper and electrolytic caps anyway. 

Well..................... By the time you remove the 12 bazillion screws that hold the bottom on, replace all of the paper and tubular electrolytic caps, and a few out of tollerance resistors. It's about a half hour more work to do the 12AX7 / 6C4 mod and have good audio. 6AU6s were designed to be RF /IF amplifiers. IIRC the V-1 and V-2 are just about the only thing I can remember them being used for audio in..

V-2s are common as dirt itself and can still be found for $100 or less.
Hell, Skip (K7YOO) even used one to help level out the bumpy road at a hamfest by dragging it around behind his van! !   Grin  Grin
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KM1H
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« Reply #26 on: March 23, 2012, 10:53:09 AM »

Quote
Well..................... By the time you remove the 12 bazillion screws that hold the bottom on, replace all of the paper and tubular electrolytic caps, and a few out of tollerance resistors. It's about a half hour more work to do the 12AX7 / 6C4 mod and have good audio.

I still dont understand the obsession to change something that works to something else that works with no real benefit.
The 12AX7 is not a cheap tube either if you have to buy one while NOS 6AU6 or 6AU6W's are almost a give away if the originals are tired.


 
Quote
6AU6s were designed to be RF /IF amplifiers. IIRC the V-1 and V-2 are just about the only thing I can remember them being used for audio in..

Bull excrement. http://tubedata.tigahost.com/tubedata/sheets/127/6/6AU6.pdf

The various Globes also used it and its forerunners go back to the better AF amps of the early 30's using a 57 as the input stage.
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The Slab Bacon
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« Reply #27 on: March 23, 2012, 11:38:39 AM »

I still dont understand the obsession to change something that works to something else that works with no real benefit.
The 12AX7 is not a cheap tube either if you have to buy one while NOS 6AU6 or 6AU6W's are almost a give away if the originals are tired.
Bull excrement. http://tubedata.tigahost.com/tubedata/sheets/127/6/6AU6.pdf
The various Globes also used it and its forerunners go back to the better AF amps of the early 30's using a 57 as the input stage.

Carl,
      The key word that you are missing is "better". As pentodes they have too much stage gain. Causing hum pick up and other issues. Also the rising plate charactoristics of most pentodes quite often causes distortion issues. I think Johnson's reasoning for using them might have been that it required less stages of amplification to get the voltage gain necessary to drive the AB1 grids of the 807s. Now add the rising plate curve of AB1 modders and you leave yourself open for a lot of distortion in the audio.
You at the very least have to wrap some global NFB around the whole shebang to tame down the distortion products. A lot of people are not comfortable in designing / adjusting NFB circuits, making it easier to do the 'AX7/6C4 mod. Although the specs for triode connecting them kinda look interesting with a Mu of 56.

As far as 'AX7s being expensive, they didn't used to be. Also for this application you do not need the high end "audio grade" ones. Also any BA enthusiast should have at least a box full of good used ones removed from other non ham stuff that was recycled for one reason or another. I have a couple of lunch baggies full of them not counting the NIB ones on the shelf.

As far as some of the older amps using 57s and other pentodes, they didn't sound as good as the ones that used triodes. Also a few of the PA system amps used pentodes in the first stage to help overcome the losses from long mic cords and cables. How often do you remember them having a hum pickup issue...... Most of the 50s and 60s higher end tube amps used 'AX7s, 'AU7s, and 6C4s driving 6L6s. (or one of the many 6L6 variants) The real good ones had a little NFB wrapped around them. They didn't use pentodes. And after all an 807 is nothing more than a 6L6 with a plate cap.
Triodes always seem to have a much more linear plate curve.

Whenever possible, I like to use triodes for audio and tetrodes for RF.

And when you're done with the 'AX7/6C4 mod, you have to put an audio grade knob on the mic gain control for the final icing on the cake..............

Just my $.02 worth........... Wink
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WD8BIL
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« Reply #28 on: March 23, 2012, 01:51:04 PM »

Quote
V-2s are common as dirt itself and can still be found for $100 or less.
Hell, Skip (K7YOO) even used one to help level out the bumpy road at a hamfest by dragging it around behind his van! !     

That was a Viker 1, Slab. Not as common but did the job just as well!
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Steve - K4HX
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« Reply #29 on: March 23, 2012, 11:42:36 PM »

I've given you more. I've given you a clear technical explanation that you've chosen to ignore. That's your problem not mine. If you can't take a joke, that's you're problem, not mine. With all the shots you've taken at people here, please don't play the victim. It's just not you.  Smiley

Let me state it one more time. An external driver has to be neither built or modified. Almost any 10-20 watt amp can be used.  I've done it on a Viking II, 32V, Globe Champion and DX-100 with both tube and solid state amps. The modification/connections take about 5 minutes and are completely non-invasive and can be undone in 5 minutes. If a good transformer is used this set up will easily out perform any internal mods, even very invasive ones. This is not my opinion, it's a fact, one myself and other have proven over and over for decades.

Are there good internal mods? Sure. Why on earth do I have them posted on the web site if I thought they were no good? But the least invasive is to use an external driver.


Steve, your as entitled to your opinion as I am to mine. Id also expected more out of you than childish insults.

IMO adding an external driver which has to be built or modified is a last resort. Changing a few components in the rig is simple and you dont have to worry about RF problems either. An overhaul will require access underneath to replace paper and electrolytic caps anyway.




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Patrick J. / KD5OEI
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« Reply #30 on: March 24, 2012, 10:02:52 AM »

KM1H said: "Considering that you have to hack a 7 pin hole for a 9 pin socket"

Not really, just put it sideways under the chassis with a standoff or use a 6AQ5 as a triode or semi-triode and in any one can case keep the original socket in place. The transformer can be kept as well, optionally putting a resistor or choke in for the 6AQ5 plate current and using capacitive coupling if one wishes to run the 6AQ5 with high current. There are many possible internal mods that are not published that will work without messing up the chassis. I have not looked to see if a 6AQ5 is one of the mods but it would be impractical to publish all of the mods that don't require changing socket sizes.
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KM1H
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« Reply #31 on: March 24, 2012, 01:49:39 PM »

I suggest all doubters actually read those ER articles before offering useful criticism....Ive seen none yet.

One of them takes a good shot at whats been up on AMfone for awhile.

Steve, etal,  you continue to miss the point. New people coming here for advice about their first ever AM rig dont have a room full of outboard gear and tubes hanging around. Many have no interest in making brackets or whatever to hang tubes underneath where its a major PITA to service.....unless you enjoy moving the damn thing around and remove a "zillion" screws.

Steve, we can continue to argue this at the AM dinner and I'll even buy the first round Grin

Carl
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KE7KPB
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« Reply #32 on: March 25, 2012, 12:10:48 AM »

Wow, what did I start. All over some ideas on audio. I'm still learning how to properly tune the darn thing.
With trying to hold a job, raise a family, being trustee for the club and trying to be a good elmer it's hard to find time to work on the am rig but it is a real kick. The one thing I do find interesting is the old ham vs new ham. (SSB), Something store bought is simple in it's operation even with all of the sub menus. Plug and play. I enjoy the old gear because the doesn't cost a grand and you can work on them, and you don't have to send them off the the factory to get them fixed. There are arguments over the tube vs transistors, to mod or not to mod equipment. It's like do you want a Chevrolet or a corvette. It is a real disappointment when you ask a simple question on something that was built in 1952, that's before I was born! and  you get so called experts having a spat on the boards. ( Expert, a drip under pressure) Reminds me of the bully in the sand box. Off my soap box now. What I would like to know is what would the audio sound like before a audio mod and what would it sound like after the mod and is is truly worth the work. There are lots of newer hams that are looking at the boards. Let's set a good example.
Please don't hit me to hard  on the return post.
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KM1H
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« Reply #33 on: March 25, 2012, 01:28:02 PM »

Get those ER issues, read the articles and look at the graph and tables and then decide what you want to do. We have no idea what your voice sounds like and what help it may need.

I dont think insulting those who are trying to help....all of us... is an intelligent move either and its obvious you havent been here long since this is often the norm when there are differing opinions. Its like a big loud family squabble that goes away once the booze is shut off and the main course is put out Grin Roll Eyes
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K6IC
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« Reply #34 on: March 25, 2012, 05:13:50 PM »

Think that most of the fun is done on this thread,  so

HIJACK:
Hi Robert,

I know that you know the city in which you live,  but, ...

Is is possible that there is a typo in the city name for your call in the FCC Database?  Says,  "Billing, MT"

Have fun with the Viking II project.  Vic
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WD8BIL
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« Reply #35 on: March 25, 2012, 08:18:16 PM »

You don't hafta hack anything. A few twist with a good angled reamer is all it takes.
I've done 7 Vikers with a 12AX7 mic amp mod and the tube socket mounting was the least problematic.

The only one I did with outboard audio driver took all of 30 minutes. When I sold it I undid the mod while the guy waited.

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The Slab Bacon
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« Reply #36 on: March 25, 2012, 08:33:08 PM »

Just FWIW, the ultimate goal of most modifications should be to create a voice in the other people's receivers that sounds as close as possible to your natural voice as if you were sitting in the room with them.

Most stock BA rigs had restricted audio "to increase talk power" and do not sound like the sender's in-person voice.

Most modifications (if they are worth doing) are designed to:

1. give the ability to make 100% (or a little more) modulation for maximum talk power.

2. produce as natural of a reproduction of the sender's in-person voice as possible.

If you can get that without modifying the transmitter, then it doesn't need to be modified in any way. But, since most rigs do neither, most hams are always looking for ways to make ther rig sound and perform better. If you can do it with your own hands, you get much more respect than one who just buys stuff and "bolts it on". Just like if you are into hot-rod cars, you are always looking for that little extra to make it faster.

Just my $.02 worth.
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KM1H
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« Reply #37 on: March 25, 2012, 10:28:27 PM »

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Most stock BA rigs had restricted audio "to increase talk power" and do not sound like the sender's in-person voice.

Most were forced into restricting transmitted BW by the ARRL when they went full bore pro SSB and castrated good AM.
Listen to the Space Shuttle if you want poor boosted audio.

All my early SSB rigs, HB or bought were phasing style since their audio wasnt as restricted and could be easily improved a bit within the limit of the PSN.

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The Slab Bacon
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« Reply #38 on: March 26, 2012, 08:31:05 AM »

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Most stock BA rigs had restricted audio "to increase talk power" and do not sound like the sender's in-person voice.
Most were forced into restricting transmitted BW by the ARRL when they went full bore pro SSB and castrated good AM.
Listen to the Space Shuttle if you want poor boosted audio.
All my early SSB rigs, HB or bought were phasing style since their audio wasnt as restricted and could be easily improved a bit within the limit of the PSN.

Duhhhhhhhhh.............. That's why we "modify" them.............. Roll Eyes  Shocked     Huh
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KM1H
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« Reply #39 on: March 26, 2012, 12:51:50 PM »

What.. a little history lesson bothers you? Or are you on the ARRL payroll Shocked
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The Slab Bacon
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« Reply #40 on: March 26, 2012, 01:24:02 PM »

What.. a little history lesson bothers you? Or are you on the ARRL payroll Shocked

Huh? ? ? ? ? ? Huh  Huh I have to say, you lost me on that post Carl.

My being on the ARRL payroll is about as good as your chance of getting pregnant. I often wonder if that was really the ARRL's doing, or just a big hoax.
Many manufacturers advertised that they adjusted the transmitters audio for "increased talk power" If you read my post carefully, you'll notice that I have quotations" around the "increased talk power"

"He who does not learn from history is doomed to repeat it".
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Pete, WA2CWA
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« Reply #41 on: March 26, 2012, 02:40:04 PM »

ARRL had nothing or very little to do with it. Back in the 50's and early 60's when these boatanchors came out, the emphasis from the manufacturers was communications and "communications quality" audio. There wasn't any push back from the users that they wanted wide bandwidth audio. They wanted "talk power". Hence the typical "300 to 3000" response, clippers, and other "can you hear me now boxes" that came out and later rolled in the SSB technology.
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KM1H
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« Reply #42 on: March 27, 2012, 04:30:06 PM »

I disagree about the ARRL as Ive been told by management at various ham companies during 60's era ARRL Conventions that they were threatened in writing to cut back the bandwidth or lose advertising for that TX. When Collins was the first to flip the rest followed.
It even delayed the Viking I release.

Even tho AM was dead by then the people involved werent and some were quite bitter.
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KE7KPB
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« Reply #43 on: March 28, 2012, 08:31:18 PM »

I'm going to capitulate and do the 12ax7 mod. I must a couple dozen of them. Let's see how it works.
One of these days the bands will open up and I can actually work am. So far it's dead as a door nail.
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kb3rdt
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« Reply #44 on: March 30, 2012, 12:15:58 AM »

I'm going to capitulate and do the 12ax7 mod. I must a couple dozen of them. Let's see how it works.
One of these days the bands will open up and I can actually work am. So far it's dead as a door nail.

I hear AM on the bands!
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KE7KPB
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« Reply #45 on: April 01, 2012, 09:16:29 AM »

Hi Carl,
It is dead here in Montana. If I lived on the east coast I guess I would be busy on am but here in the back country with the buffalo and bears Am is a dead mode.  Cry
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KM1H
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« Reply #46 on: April 01, 2012, 10:19:39 AM »

Try different bands
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kb3rdt
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« Reply #47 on: April 01, 2012, 06:49:30 PM »

160 meters be a good start! but Might late in the year static crashes season.. Cry
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KX5JT
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« Reply #48 on: April 01, 2012, 10:09:49 PM »

Hi Carl,
It is dead here in Montana. If I lived on the east coast I guess I would be busy on am but here in the back country with the buffalo and bears Am is a dead mode.  Cry

I work Montana and Wisconsin during the day on 15 meter AM.  Give the high bands a try during the daytime... 21.420 through 21.440 (21.425 is very popular)

Also 20 meter on 14.286 late afternoons.  and 10 meters when it opens on 29.000 plus

You might be pleasantly surprised!
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