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I got this Tranny here, and this VIK II See.




 
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Author Topic: I got this Tranny here, and this VIK II See.  (Read 5970 times)
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Jack-KA3ZLR-
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« on: March 13, 2005, 09:35:33 AM »

Good Sunday Morning to Everyone,

O.K.  One of the Hammond Trannys arrived at my door step friday. Now it's a Hammond 812: Line or 150 ohm MIC to 1 or 2 Grids, Primary is 125/500 (150/600) Secondary is 10K/40/K (12K/48K).

Now i have an 841 coming as well, it hasn't arrived yet, Now my Question is seting the negative Bias Milliage, it will have to be done by resistance, what i was told was 50 to 100K i'm wondering if i shouldn't just put a pot in and set it by hand...any Suggestions..?
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k4kyv
Contributing Member
Don
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« Reply #1 on: March 13, 2005, 02:02:24 PM »

Quote from: Jack-KA3ZLR-
Now i have an 841 coming as well, it hasn't arrived yet


An 841 tube?
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Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

- - -
This message was typed using the DVORAK keyboard layout.
http://www.mwbrooks.com/dvorak
Jack-KA3ZLR-
Guest
« Reply #2 on: March 13, 2005, 02:14:20 PM »

Hi Don,

No an 841 tranny from hammond i'm going to attempt this other type mod on this other Vik II i stole off of epay, Now from what Paul said setting the bias to 35 Ma, I was thinking of using a pot, i was wondering if anybody tryed this...no Biggie...
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Jack-KA3ZLR-
Guest
« Reply #3 on: March 13, 2005, 05:45:02 PM »

While i'm at it here I've seen how alot of mods want the screens connected directly to the 600v B+, I was wondering about adding two OA2's in series on that line as regulators, to stabilize that voltage.

It's the Biasing that's got me stumped, the 807's have a Fixed Bias of -37 volts now.
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Steve - WB3HUZ
Guest
« Reply #4 on: March 13, 2005, 06:20:42 PM »

IIRC, the modulator bias in the Viking II is set by adjusting the screen voltage. This is adjusted via the slider on the big wirewound resistor on the underside of the chassis, just about in the middle.

If you are looking for alternatives, get a look at the schematics for the 32V or DX-100 (it used 1625, a 12v version of the 807). I also have at least one schematic of a hi-fi audio amp that used 807s in the output. I can scan and email or photocopy and USPS.

That said, you may want to mess around with your new trannys first before worrying about the bias on the 807s. You may like what you hear and not feel the need to go any further.
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Jack-KA3ZLR-
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« Reply #5 on: March 13, 2005, 06:43:36 PM »

Thanks Steve,

 I went over to Pauls web site and re-read his mod, I'm not real concerned about the Pulling the gids off the line and re-routing them this one here is fairly stable, but, thinking out loud helps.

 I'll do what you say Steve and i'll watch the scope and see what happens, i'll just put it into place with two 50K resistors and see what happens...
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Jack-KA3ZLR-
Guest
« Reply #6 on: March 13, 2005, 07:22:30 PM »

HELLO HOUSTON..We have Audio here...Hey Steve can i leave this alone with no further adjustments..?

Plate and Grid Currents are FB... Cheesy
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Steve - WB3HUZ
Guest
« Reply #7 on: March 13, 2005, 08:38:30 PM »

Get on the air and we'll have a listen!
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Jack-KA3ZLR-
Guest
« Reply #8 on: March 14, 2005, 05:38:54 AM »

I'm gona try running the Behringer Mic and the small stack on this one and when i get that settled i'll put it on for test...I have to do the relay yet and i'd like to rock this one.

These little trannys are nice and take up no room at all, if it pans out this should be listed on the AM site shouldn't it as another direction for a potential Mod.. It's so easy to do and by all indications and obvious Ops using it, from what i've listened to on the air, It's a Big Plus, with little effort...very little effort...
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Steve - WB3HUZ
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« Reply #9 on: March 15, 2005, 12:01:51 AM »

Cool. Send me details, schematics, connection info and the like and I'll put it up in the Mods section of The AM Window Web Site.

Hope to hear that setup on the air.
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WA1GFZ
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« Reply #10 on: March 15, 2005, 11:39:59 AM »

I built a zener regulated screen supply for my first V2.
I removed the big resistor and mounted an L bracket
with a string of 10 watt zeners and a dropping resistor.
This was the modulator screen supply.
The final screen was a pair of 10 watt resistors back to modulated plate.
30 kohms if I remember.
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Jack-KA3ZLR-
Guest
« Reply #11 on: March 15, 2005, 05:52:49 PM »

Hi Guys,

 Well i'm still waiting on the 841 to come to the door and then i'm going to make a Comparison of the two pick the best, put it on the Air, then depending on that outcome i'll write everything down and submit to Steve for his going over and we'll go from there, and I'm grateful for the understanding here going through this..Much obliged...
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