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Post by deepdark on Sept 8, 2015 19:36:18 GMT -6
Now I took current between R11 and R7, I got 1,7ma. Again, pretty spot on.
C6 has been changed, just in case, too.
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Post by deepdark on Sept 8, 2015 18:51:55 GMT -6
other side of 8k2 is 19,6ma, pretty spot on, too...
I let it run for about 5 minutes, 'till the resistor began to smoke and there was no change in the current value. It wasn't increasing.
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Post by deepdark on Sept 8, 2015 18:30:15 GMT -6
First current measurement, power supply to the junction of 8k2 is 21,4ma. Looks pretty good so far. I changed the ef86 tube, change 8k2 for another one, changed C5. No luck for now, I'm waiting for the caps to discharge before taking current straight after 8k2.
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Post by deepdark on Sept 8, 2015 16:44:39 GMT -6
One thing i'm thinking. The original schematic recall 30ma for a 400v dc psu. After the rectifier i got 395v. Maybe i'm about 30ma and the excess of current is heated through the 8k2 which set it to the edge of it's limit. Just some thoughts here.
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Post by deepdark on Sept 8, 2015 15:25:55 GMT -6
Is heaters can have something to do? Exemple, if they are at 7,3v?
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Post by deepdark on Sept 8, 2015 15:24:07 GMT -6
Allright. Basically, since voltages looks good everywhere, i'll have to check current at some point around e88cc i guess, once i get where it all screw off things?
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Post by deepdark on Sept 8, 2015 15:02:47 GMT -6
No luck with the tube. I replaced the e88cc and it is still hot and smell. Mo more fume, thought. C4 and c5 bloc dc, all voltages are spot on. B+ is 305v. I'll have to test current before and after 8k2 to see of there is something weird.
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Post by deepdark on Sept 8, 2015 12:58:52 GMT -6
Does a 1176 that prone to pick up noise (a least, when looking at the circuit noise)??
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Post by deepdark on Sept 8, 2015 11:37:10 GMT -6
didn't tried yet the input/output of the apogee.
So what we are taking is the noise picking by the transformers, cables, etc. In other words, noise Inside the circuit and psu
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Post by deepdark on Sept 8, 2015 8:55:46 GMT -6
Oh and by the way, I know this isn't really scientificaly accurate or anything else, it's just a good first impression
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Post by deepdark on Sept 8, 2015 8:54:54 GMT -6
Hi there quick one for you folks
Just curious about one thing. While testing the gear I build, I use the following setup: Output of my apogee ensemble to the input of whatever I build, let's say, a compressor, and the output of the compressor to the input of the apogee. I open up a session in Logic pro, set my in/out plugin to rout the compressor and then, open up a freq. analyser plugin (Melda) to take a look at the general audio frequency and all other stuff.
Anyway, The first thing I do is to only plug the output of the compressor to analyse the noise. There is always that 60hz (I'm in canada) bump, while no signal passing through of course, just looking at the noise of the circuit. What is that 60hz? Hum from the main ac? I don't hear any hum, and of course, while pluging the input and passing a signal, let's say a sine wave or a pink noise, there is no more 60hz bump.
Just curious what it is. Maybe I'm just looking at the main hum from the circuit, and while looking at the meter, I generaly see some -92db signal (noise), depending of the gear i check.
Again, just curious
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Post by deepdark on Sept 7, 2015 12:06:14 GMT -6
Oh and the fact my b+ is a little higher than the schematic could also influence that.
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Post by deepdark on Sept 7, 2015 12:04:59 GMT -6
Oh and by the way, is it possible a tube consume, say, 20ma instead of the 18,5 ma? So about 1,5ma. Not a big deal. I guess different batch, brand, different reading and the fact resistors never read exactly the right value, right? That is what i said. The 20ma was a rough calculation of 165vdrop across a 8k2 resistor. Then comparing with the schematic value, i was simply thinking about the fact that different tube brand and batch, nos or brand new, could cousume more or less of the specified current.
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Post by deepdark on Sept 7, 2015 11:53:53 GMT -6
1,5ma is only a rought calculation within ohms law. I didn't measure it yet. Its only the consumption given the actual vdrop and the resistor value. So yes, it could be a dead short because vdrop is allright and all other one. So excess curent would evacuate in form of heat i think.
1,5ma could be explain by the resistive parts of the circut, the layout, the fact tesistor never has the exact value they are rated,mthe tube itself, etc.
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Post by deepdark on Sept 7, 2015 11:42:39 GMT -6
Cathode was about 3,8 or 3,9 v. Schematic recall for about 3,7v oh and c5 (1uf) block all dc so no leakage here
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Post by deepdark on Sept 7, 2015 11:32:04 GMT -6
Oh and by the way, is it possible a tube consume, say, 20ma instead of the 18,5 ma? So about 1,5ma. Not a big deal. I guess different batch, brand, different reading and the fact resistors never read exactly the right value, right?
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Post by deepdark on Sept 7, 2015 11:21:52 GMT -6
Thanks. You're right. I tend to suspec the layout 'till i test all voltages and current. Yes, voltages drop are all good, with ohms law, it gave good current guess. I calculate 3 watts across 8k2 given the reading voltage drop i got (about 165v) which give about 20ma. 165v through 20ma is about 3,3W. So were trouble may be occuring is between 8k2 and the plate? If a short at the plate of the tube is occuring, then what, current will flow from plate to the resistor, or current will build up at the plate resistor? As i said, all voltages look good and ohms law tells me current across resistor looks fine.
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Post by deepdark on Sept 7, 2015 6:53:04 GMT -6
Welp, my brain imagined that I see. My bad! No trouble. Thanks for thé help by the way.
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Post by deepdark on Sept 7, 2015 6:51:19 GMT -6
You tried another tube right? Note yet. I wanted to be absolutely sure my circuit is ok before swaping tube. Is a damaged or non working tube could increase current at thé anode resistor? Even voltages are OK? Thé resistor will evacuate thé over current on form of heat?
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Post by deepdark on Sept 6, 2015 16:58:14 GMT -6
Since you said it was measuring 7K, that's unlikely. The drop in resistance is almost definitely due to the multiple parallel paths from B+ to ground. What do i said measuring 7k?
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Post by deepdark on Sept 6, 2015 16:36:56 GMT -6
One thing i'm thinking. First start up, i wired b+ the other side of 8k2, so straight at the anode. I'm wondering if i damaged the resistor or something else
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Post by deepdark on Sept 6, 2015 16:16:46 GMT -6
Yup, once the maintensnce will be finished
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Post by deepdark on Sept 6, 2015 12:39:59 GMT -6
By the way, according to maths, my power cunsumption acriss 8k2 loks to be 3w. According to what you think, i'll have to check current between psu and the juction of r11 and r7' to be sure to read about 20ma. And current after r11 to the joction of plate/r9/c5. Should be about 18,5ma. If i consume more than 3w, let's say 6w through r11, then i should read about 35ma.
but i'm pretty sure b+ will be right for one reason. My psu is RC topology made of five section of 1k resistors/1w and five caps of 47uf. After the rectifiers i got 395v and i need to drop about 95v, at 20ma. 95v/20ma gives 4700k/5 = 950ohm each. Total piwer is 95v x 20ma = about 2w. Less than 1/2w per section and i put 1w resistors.
Is the wire i used can be the culprit? I put some 22ga/300v rated.
And my heaters are at about 7,3v
lastly, how long after shutting off filter caps take to discharge? Do they fully discharge over time?
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Post by deepdark on Sept 6, 2015 11:35:02 GMT -6
ok I make some more test. Put the B+, with no tube, it's the same as running unloaded, no smoking resistor, of course. Then. after discharging the psu caps, I pull in the tubes and make some measurement. As I said, all voltages are spot on.
E88CC plate = 143v E88CC cathode = 3,9v EF86 Anode = 82v EF86 grid 3 (pin 1) = 101v Ef86 catode = 1,6v
R11 vdrop = 165v R7 vdrop = 83v R2 vdrop = 136v R12 vdrop = 116v R9 vdrop = 43v R14 vdrop = 8v
8K2 didn't make smoke that time, but it remains pretty hot and there is a burning odor. It's a wirewound with a flame retardant coating on it.
What do you guys think about those values?
E88CC side of C5 is 143v, the other side read 0v (so C5 bloc all dc current)
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Post by deepdark on Sept 6, 2015 9:46:59 GMT -6
While loaded it's about 310v
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