Nice.
Actually, I'm using two 48Ohm resistors in series 😀
I am almost done. Just need to hook up the pentode.
You can draw schematics with Digi-keys' Scheme-it for free
Scheme-it | Free Online Schematic and Diagramming Tool | DigiKey Electronics
Scheme-it | Free Online Schematic and Diagramming Tool | DigiKey Electronics
There you go!
Always listen to KodaBMX.
That's my advice.
Rarely wrong.
Often subtle.
Good DIY'er
GoatGuy
Disappointing news:
It sounds basically the same as before.
My multimeter also died on me.
Well, that was fast.
HERE is the 'next version', with numbered test points, so we can
use the 'same language' when talking about measured values.
-= GoatGuy ✓ =-
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I only have my Arduino-based multimeter to test voltage and it only goes up to 40V. I will test a few and tell you.
The no sound was because of pentode's anode being disconnected from the B+.
Well, brother DIY'er, it is time to buy a proper multimeter. You need not spend more than $14 on one. I used a small — but quite satisfactory — $9.99 one purchased from the now defunct Radio Shack, some years ago. Took lil' flat 'coin' batteries. Did everything.
But a slightly better model would be ( Digital Multimeter Multi Tester Voltmeter Ammeter Ohmmeter with LCD Back Light 700819594799 | eBay )
Yuck. Ebay.
But eleven bucks.
You might notice that I also updated the capacitor annotations to actually have something other than 'C 1' for all caps!
🙄 Silly me.
-= GoatGuy ✓ =-
Triode cathode bias voltage: 1.577V
12AQ5 cathode resistor voltage: 4.080V
I think the problem is with the 12AQ5s as they're not drawing much current.
I might not buy the 6L6GC ($9) and save up for an old but highly accurate and awesome GW Instek GDM 450A.
www.esam.ir/item/16445703/مولتی-متر-INSTEK-GDM450Aتایوانی
It's about $30.
It will take 2 months to buy this though .-.
I'm 17 and don't get much monthly allowance ($25).
Will make a resistive divider to try and measure the high voltages with my DIY multimeter which has great accuracy (16bit ADC with calibrated 11.1M-1M resistive divider)!
PS... using a simple voltage divider, you can safely test higher voltages with your ~Arduino~ based multimeter. 2 resistors.
Here's the diagram
(ps - you do NOT need precision 'absolute', but relative value accuracy. It is an all-too-common fallacy to lust for absolute precision in measurement, when it is hardly ever required. I used to be 'in metrology'. )
Here's the diagram
(ps - you do NOT need precision 'absolute', but relative value accuracy. It is an all-too-common fallacy to lust for absolute precision in measurement, when it is hardly ever required. I used to be 'in metrology'. )
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Yes, i'm currently trying to measure the test points.
You are right! But hey, everyone loves good accuracy 🙂
Because of the crude voltage divider, I have to round the numbers and stuff.
TP8-12AQ5s' anodes (transformer's primary through the coil): ~150V
TP2-Pentode's cathode: ~80V
TP10-12AQ5s': 0.00V
TP1-Triode's cathode: 1.577V
TP3-Triode's anode: ~80V
TP4-Pentode's screen: ~150V
TP5-6-8-12AQ5s' screen: ~140V
TP9-12AQ5s' cathode: ~4.2V
TP11-Transformer's output: 0.00V
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Not sure this has been mentioned before, but I think you can't just put three tubes in parallel like this and expect them to share the load. There's always differences in gain and how much negative Vgk they need for a specific current.
The way it is now, the hottest tube will conduct all the current and cut off the others, and could even cause grid current on one or two. That will load down the preamp and cause massive distortion.
Pull out two of the three tubes and it probably gets a lot better.
Jan
The way it is now, the hottest tube will conduct all the current and cut off the others, and could even cause grid current on one or two. That will load down the preamp and cause massive distortion.
Pull out two of the three tubes and it probably gets a lot better.
Jan
The way to do this is to give each tube is own Rk and couple the grids via individual caps, so each tube can get to the autobias that fits its characteristics. You can then connect the anodes together if you wish.
Jan
Jan