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5687 heater voltage - what's too high [message #30725]

Sat, 26 February 2005 12:01

colinhester
Messages: 1349
Registered: May 2009
Location: NE Arkansas

Illuminati (3rd Degree)

Got the 5687 heater fired up last night. Man, that sure is a pretty sight. I'm using the RCRC filter (2 ohm and 1 ohm in lieu of 5 and 3, respectively - see link below) I measured the voltage and got 13.4VDC. This is supposed to run at 12.6 VDC. Do I need to pad the voltage back, or is this really that critical? I am within 10%. I know this will somewhat shorten tube life due to more heat being generated, but other than that are there any issues I can expect (ie., noise / hum.)

Guinevere should be singing tonight!!!!!!!Colin

http://audioroundtable.com/GroupBuild/messages/397.html

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Re: 5687 heater voltage - what's too high [message #30728 is a reply to message #30725]

Sat, 26 February 2005 12:37

Forty2wo
Messages: 163
Registered: May 2009

Master

Well..See, it's like this. Yea it's high, yea it will shorten tube life. but hey it works. Go for it.
If you promise to fix it someday, I wom't call the tube police...John

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Measuring current [message #30729 is a reply to message #30728]

Sat, 26 February 2005 12:43

colinhester
Messages: 1349
Registered: May 2009
Location: NE Arkansas

Illuminati (3rd Degree)

How does one measure the current drawn? I set my voltmeter to DC current and nothing - a big zero. I know that even if the voltage is too high, the current can be lower and still have the same wattage draw.

Yes mom, I promise to fix it someday......Colin

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heater Voltage [message #30730 is a reply to message #30729]

Sat, 26 February 2005 12:57

PakProtector
Messages: 935
Registered: May 2009

Illuminati (2nd Degree)

hey-Hey!!!,
Since it is drawing about a half an amp, I would stick in another Ohm into the second position. Ought to take it back by ~ a half a volt and that will be quite close enough.
regards,
Douglas

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2 and 2 it is [message #30731 is a reply to message #30730]

Sat, 26 February 2005 13:05

colinhester
Messages: 1349
Registered: May 2009
Location: NE Arkansas

Illuminati (3rd Degree)

I'll throw another 1 ohm 5W resistor in series with the second.

Since we're talking about the heater circuit, I have a question. I'm using 1 ohm, 5W "white coffin" wirewound resistors. Is there a better type of resistor construction, or is this OK for dropping voltage in this application. Will this cause any undue noise?......Colin

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Re: 2 and 2 it is [message #30734 is a reply to message #30731]

Sat, 26 February 2005 13:13

PakProtector
Messages: 935
Registered: May 2009

Illuminati (2nd Degree)

cement block looking things? I got mine from R-S. I think they are 10W...no big deal, this is not a very noise sensitive part of the circuit.
regards,
Douglas

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Re: 2 and 2 it is [message #30736 is a reply to message #30734]

Sat, 26 February 2005 13:23

colinhester
Messages: 1349
Registered: May 2009
Location: NE Arkansas

Illuminati (3rd Degree)

No, they are 5W from Parts Express. I live about 3 exits from their showroom

.....Colin

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Re: 5687 heater voltage - what's too high [message #30741 is a reply to message #30725]

Sat, 26 February 2005 15:00

Wayne Parham
Messages: 18782
Registered: January 2001

Illuminati (33rd Degree)

I'm eagerly watching you on this one, Colin! It's nice to be the bystander on something for a change.

I'll be following in your footsteps, but on this one, I'm lagging behind. Other stuff going on, you know.

Speaking of, how about you and everyone here planning to come to Tulsa in a couple of months? Bring Guinevere with you. We're arranging a get together in April or May, and it won't be expensive at all. No registration fee, just your plane tickets and room. Costs aren't that high so it should be affordable for many people.

Great Plains Audiofest preliminaries

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