jensenmann
Karlsruhe, Germany
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« Reply #20 on: May 18, 2009, 12:36:45 pm » |
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Good ideas thanks! What did you pay for your torodial? Here's the enclosure I'll be using. Old geiger counter, hope it's not radioactive...   app 40€ |
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Jens >The tubes of course don't care what frequency they distort |
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eskimo
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« Reply #21 on: November 12, 2009, 05:34:59 pm » |
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Some in progress(after a looong hiatus) pics:   |
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« Last Edit: November 12, 2009, 06:04:54 pm by eskimo »
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eskimo
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« Reply #22 on: November 14, 2009, 05:09:53 pm » |
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PSU question: The values I should be getting in black, the values I am getting in red. Note: -The PT secondary gives 128VAC instead of the 117VAC on the original. I assumed that was close enough. -R21 is 6,8K 5W instead of the 7K on the schem. -I'd miswired the PT secondary on the first powerup which fed the circuit, 250VAC, can that have messed up the caps? I did hear a weird sissling sound coming from them before I hurried and shut it off. Any ideas?  Schematic: http://eskimo.creotia.com/438C.jpg |
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schmidlin
Ohio
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« Reply #23 on: November 15, 2009, 09:41:35 am » |
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Are these voltages under load, ie with the tubes in it?
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perception > reality
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eskimo
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« Reply #24 on: November 15, 2009, 11:31:28 am » |
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No, I didn't dare put them in yet, could it be as easy as that?
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Kingston
Helsinki, Finland
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« Reply #25 on: November 15, 2009, 12:22:43 pm » |
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Yes indeed. Ohms law is as easy as that.
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eskimo
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« Reply #26 on: November 15, 2009, 12:52:23 pm » |
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doh.  Well, even with the tubes in the numbers are way off. From left to right: 299, 209, 330. |
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eskimo
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« Reply #27 on: November 16, 2009, 06:38:39 pm » |
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badabump
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schmidlin
Ohio
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« Reply #28 on: November 16, 2009, 10:09:38 pm » |
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Well, here goes: Check your heater voltage carefully. If it close to 6.3, you can bump up R20 & R21 up to get you where you need to be. If you are getting 7 volts or so, you have several not-very-good options such as a padding your AC-in via power resistors or a variac. Or get a custom (yikes) PT wound. My guess is you are suffering from an overly-ambitous home power supply company, common here in the States, too. Check your wall AC or even question your VOM. As a side note, your PT being so close to the signal tubes has me wondering if you will get some residual noise from it. Separation is your friend. Hope this helps.  |
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perception > reality
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PRR
Maine USA
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« Reply #29 on: November 16, 2009, 11:06:48 pm » |
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Your power transformer is better than the original. 117VAC peak-doubled should be over 300VDC, not the 255V shown on the original: they used a lame transformer (but good enough).
Put about 500 ohms 1 Watt in between the 117/125V lead and the two-diode point. With load (tubes), this will come down into the 230VDC-280VDC zone. Fiddle the resistor to get closer. It does NOT have to be 255VDC exact: in fact 200VDC or 300VDc would be fine.
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« Last Edit: November 16, 2009, 11:13:00 pm by PRR »
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eskimo
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« Reply #30 on: November 16, 2009, 11:38:34 pm » |
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Much appreciated! Did some more measuring. The wall socket gives me 230V(as expected), the primary is wired for 240V though which explaines why my heaters are a tad low at 5,9VAC. Thanks for the resistor tip PRR.  Right now it's wired like this:  If I use the Blu/Yel 110V tap instead(or connect brown to black/red instead of black) I should get 230V right? (sorry for the noobness) |
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PRR
Maine USA
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« Reply #31 on: November 16, 2009, 11:45:07 pm » |
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No big deal, but yes, do this:
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eskimo
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« Reply #32 on: November 17, 2009, 05:16:07 pm » |
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So I've gotten a useful mic signal out of the thing. No compression in sight yet though. I assume I've messed my wiring of the pots(threshold, attack, release).  In P1 and P2, does pin 2 connect to 1 or 3? As for P3, does 1 or 3 go to R15? |
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PRR
Maine USA
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« Reply #33 on: November 17, 2009, 08:52:26 pm » |
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> does pin 2 connect to 1 or 3?
For smoke-test: either. If it is "wrong", the knob turns "backward", but the limiter still limits.
You could leave the wiper un-connected. That gives long attack long release.
Put the junction of R10 R11 to ground. That gives a threshold of "nothing": any medium-strong signal will make DC on C4 and the input grids.
You'll want control someday, -after- you get it "working".
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eskimo
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« Reply #34 on: November 23, 2009, 01:36:23 pm » |
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Tried that but no difference.
I noticed now that if I really slam it, like bass straight through on high gain, I can hear a vague compression. So it seems to do something, but extremely little of it.
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eskimo
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« Reply #35 on: November 25, 2009, 11:38:26 am » |
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I installed a VU (well almost, peak signal meter) and it seems to respond well. Reacts to threshold level. Attack and release works as expected. I still can't hear it though. Does that give any clues where the problem might be?
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skal1
Birmingham,uk
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« Reply #36 on: November 25, 2009, 02:04:20 pm » |
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Have you checked pin 1 and 6 of the v2 under compression / no compression ?
when under compression pin 1and 6 should rise .
skal1
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eskimo
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« Reply #37 on: November 25, 2009, 02:17:52 pm » |
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1 is 60V when idle and 6 is 55V. It's kinda critical that both sides are in balance right?
Anyway, both side go up to 300ishV under full compression.
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skal1
Birmingham,uk
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« Reply #38 on: November 25, 2009, 04:49:57 pm » |
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1 is 60V when idle and 6 is 55V. It's kinda critical that both sides are in balance right?
So they say. Was this v1 or v2 ? schematic says 150v on both plate  your readings are low for v2 according to the schematic at idle. skal1 |
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