| Rev. 6 update [message #30448] |
Fri, 11 February 2005 10:39  |
PakProtector
Messages: 935
Registered: May 2009
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Illuminati (2nd Degree) |
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Hey-Hey!!!,
I found a few causes of noise. part was a routing. I ran the choke leads too close to the voltage refrence boards. I moved this and a lot of it went away. the other was harder to figure. I changed the orientation/location of some of the bits on the voltage ref. boards. They were picking up interferance and pluging it in where the circuit was quite sensitive.I think the last can be adressed with a seperate filament TX. I have two 6.3 and a 5VAC winding in series feeding a bridge and I *SUSPECT* that if it were on a different core I would be free of its infulence. Also, the active load/output buffer works best with a 12GN7 and a 12BY7 instead of two of each. Now to re-wire and plug in the 7788's I have in place of the 12GN7's. 50 mA/V gm ought to help...instead of 36 mA/V. If I can avoid creating an RF oscillator.
regards,
Douglas
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| 7788 [message #30453 is a reply to message #30451] |
Fri, 11 February 2005 12:21  |
PakProtector
Messages: 935
Registered: May 2009
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Illuminati (2nd Degree) |
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that valve is a high-gm pentode( or perhaps a beam tetrode, I can't see all the grid posts to determine if it has a supressor grid or beam plates ). I think it goes by E180F as well. The D3a is another. High mu triode connected too. Not exactly a common valve in the States though. Don't worry about the sauce, it's not tooo spicy.
regards,
Douglas
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| Re: 7788 [message #30464 is a reply to message #30457] |
Fri, 11 February 2005 14:06 |
Damir
Messages: 1005
Registered: May 2009
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Illuminati (2nd Degree) |
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SPICE is fantastic thing if someone knows how to use it properly/limitations...
There are many HQ tubes not known enough to "wider audience", but that`s not a bad thing to DIY-ers, some good tubes can be found cheap. And pentodes are not that "bad" in spite of popular "myth". Some types Doug mentioned (E810F, D3a...) and some others (E180F, E280F-simylar to D3a, even EF184) are surprisingly good, see for example "High-Gm driver pentodes test data" report by Pete Millett. And for the trannies - if I remember correctly, they have 800Vct/100mA taps...LCLC or so, and we are close to 310V DC/95mA - I see nice 2A3 monobloc, we`ll see... Picture: EL8 Valvo, 6463 Telefunken, D3a Valvo/Siemens, E280F Valvo/Siemens... Too bad, I have just one pair of each kind.
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| Insanity... [message #30466 is a reply to message #30464] |
Fri, 11 February 2005 14:22 |
PakProtector
Messages: 935
Registered: May 2009
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Illuminati (2nd Degree) |
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I have a single pair of 7788. And at $30 each for spares, this is the rarest tube I have considered using in one of my experiments( when replacements are sooooo bloody 'spensive ). I have not done it yet though.... SE 2A3 maybe for the TX's...or PP 45. Did I mis-understand? It looks like all four got sent to one person, and the other three ov you will have to wait for an individual shippment.
regards,
Douglas
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| that's not so good... [message #30472 is a reply to message #30468] |
Fri, 11 February 2005 14:40 |
PakProtector
Messages: 935
Registered: May 2009
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Illuminati (2nd Degree) |
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Been thinking. With L-C filter, 310VDC@ 100 mA is available. This is fine for an AB1 pair of 6V6's. Use the 325 taps, Class A with: 6V6, EL84, 1619/1624 and a few others I have not thought of often. Plenty of uses. They were meant to be versatile, remember?
regards,
Douglas
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| Sauce... [message #30473 is a reply to message #30451] |
Fri, 11 February 2005 14:47 |
PakProtector
Messages: 935
Registered: May 2009
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Illuminati (2nd Degree) |
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hey-Hey!!!,
Don't ever worry about being Lost. Even if you feel lost, the effort required to make you feel 'found' is helpful to both sides.Besides, look at the list of folks who have done interesting things. A very large fraction of these folks were teachers( at some level ) and were constantly exposed to students. Once, when the students were removed so a group of scientists could work w/o distraction, no further discoveries came from them. Richard Philips Feynman is a fine example of this effect. Look at 'The Feynamn Lectures on Physics'.
regards,
Douglas
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