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PostPosted: Mar Sat 26, 2011 12:51 am 
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hergi wrote:
I have another question, what is the impedance load of the output transformer to the tubes? I'm curious.

Doug


I don't have the Sams folder for the 130, but have the 230A and it says 7500 Ohms to 4, 8, 16, and 32 ohms. The similar DB-230 says 6K Ohms.


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PostPosted: Mar Sat 26, 2011 1:17 pm 
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hergi wrote:
6FW5 has 18W plate dissipation vs 11 for the 6AV5. I might have to try that once I get this thing going.

Doug


That sounds like a winner! 700v plate, 220v screen, too. The increased screen voltage handling (220v vs. 175v for the 6AV5) should definitely help it run cleanly...

Regards,
Gordon.

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PostPosted: Mar Sat 26, 2011 4:22 pm 
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GordonW wrote:
hergi wrote:
6FW5 has 18W plate dissipation vs 11 for the 6AV5. I might have to try that once I get this thing going.

Doug


That sounds like a winner! 700v plate, 220v screen, too. The increased screen voltage handling (220v vs. 175v for the 6AV5) should definitely help it run cleanly...

Regards,
Gordon.


Use the same screen voltage adjustment shown in the Bogen instructions for the 6AV5, so you get the same idling current, and the sound will be clean and stable. The 6FW5 is plug-compatible with 6AV5, just a lot more stable and powerful. The low-bass output when watching a movie on TV is amazing.
Don


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PostPosted: Mar Mon 28, 2011 5:43 pm 
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What is the idle current on the output tubes? I don't have the adjustment instructions just the schematic.

Doug


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PostPosted: Mar Mon 28, 2011 5:59 pm 
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Here is a link to the free schematic with the bias and screen adjustment included http://www.schematicsunlimited.com/down ... ematic.pdf
Don


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 Post subject:
PostPosted: Mar Mon 28, 2011 6:03 pm 
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hergi wrote:
What is the idle current on the output tubes? I don't have the adjustment instructions just the schematic.

Doug


According to this schematic, the idle current for each tube is 10 mA. http://members.shaw.ca/pacifictv5/bogendb130a.jpg With plate voltage of 680 V the idle plate dissipation would be 6.8 Watts.

That would put this amp in the class B mode of operation with a conduction angle of about 183 degrees.

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PostPosted: Mar Mon 28, 2011 6:04 pm 
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Thanks Don! :D

Doug


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PostPosted: Mar Mon 28, 2011 6:11 pm 
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Actually that schematic is a bit different than mine. Mine uses two 5Y3s in parallel and is 605V B+, 150V screen. I imagine the alignment procedure is the same though.


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PostPosted: Mar Mon 28, 2011 6:41 pm 
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hergi wrote:
Actually that schematic is a bit different than mine. Mine uses two 5Y3s in parallel and is 605V B+, 150V screen. I imagine the alignment procedure is the same though.


So yours must be the DB130? http://members.shaw.ca/pacifictv1/bogendb1301.jpg

You could bias the DB130 a bit hotter since the plate voltage is lower than the DB130A.

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PostPosted: Mar Mon 28, 2011 7:13 pm 
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Oh dear, the DB130a is a very different beast! It has 680 volts on the plates and 10mA idle, 1 volt setting on Volt Reg Adj. and 5AR4 rectifier. With 6AV5 tubes, I doubt if it was stable. There are some value changes in the schematic.
My older DB130 is the same as yours, two 5Y3 tubes, a much lower 605 volts on the plates therefore the Volt Reg Adj is set for 1.5 volts which is 15 mA idle current per tube at this lower plate voltage.

From the Bogen DB130 manual
The Damping Factor control changes the effective output impedance from +160 ohms through zero ohms to less than -9 ohms. "Adjust to the setting that sounds best to the listener" "Greatest benefit from settings approaching ultimate damping"
1. Set volume to minimum.
2 Turn DF switch ON
3. use screwdriver to slowly rotate Damping Factor controlin a clockwise direction until DAMP. IND. bulb flashes.
CAUTION: Allow the speaker to oscillate only momentarily. Violent vibration could be detrimental to the suspension system of the speaker.
4. Slowly rotate the DAMPING FACTOR control counterclockwise until the damping indicator bulb stops flashing.
If two speakers are used, set selector to AB so both speakers are connected.
Note: Some speakers ...may not oscillate, especially if voice coli resistance is greater than 9 ohms. Control should be adjusted to extreme clockwise position.

I found if you set it for minimum damping it will give the "pentode boom" strong bass of an old jukebox. This DF feature was only used from the mid to late 1950's
Don


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 Post subject: Re: Bogen DB-130 Mono Amplifer
PostPosted: Feb Tue 13, 2018 11:26 am 
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Sounds like the damping factor adjustment could damage vintage drivers...would it be safe to try per the Bogen manual? Did you find a noticeable difference in sound. JBL D123 12" driver. Any comments?


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