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PostPosted: 22 Mar 2014, 01:47 
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laurie54 wrote:
I'm still waiting for the 6as7 to get my build out the gates. The trans came today and i am looking at a chain of RC's, load res, meters, and lots of wire. Just double checking the wiring before powering on. I have a variac so am using it to fine tune the B+ rail as the trans is a Hammond 270FX. Somewhat overkill i know but I like to have cooler running trans and may be put to use in other builds so good to see what it is made of. This means of coarse i have 550v not 450vac so i need to drop a bit more V's in the filter. Which is what i am spending the eve doing. Carefully! I salivate each time i see those RCA NIB's you picked up not to mention Sophia. A beautiful build mwhouston.

Keeps us in formed and add some images. Thanks for the nice compliment. I sold the HP amp but are missing it. I may have to build another.

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Projects:180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp |


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PostPosted: 22 Mar 2014, 03:15 
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Joined: 09 Oct 2012, 19:43
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Location: Vancouver Canada
I hope i can do justice to the amps you and Nordic have finished. After years of SS i still like a compact build. I know it isn't preferred for many reasons, as heat, ease of room to work, modes, etc. and i do agree. On the other hand i know the value of getting each stage closer together in the signal chain, making allowances for heat and physical size etc., I guess time will tell what comes into fruition but getting there really is the fun part. This pic, if it gets on page, --- is a concept drawing i have in a series for this build. On the pwr end, Corcom line filter (a must have), fuse (must have), over sized trans, and lots of filtering with a nice big tank at the end of the chain. The sig path is however looking like the letter Z. I can put the "input" in the front with vol and HP-jack, which would eliminate one leg of the Z. A top view looks promising.


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PostPosted: 22 Mar 2014, 03:30 
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Not sure if that qualifies as a pic but i can't get a pdf to work. Sorry.


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PostPosted: 22 Mar 2014, 06:27 
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laurie54 wrote:
Not sure if that qualifies as a pic but i can't get a pdf to work. Sorry.

Choke?

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Projects:180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp |


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PostPosted: 22 Mar 2014, 08:13 
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No. It's RC right threw. The original was 6.8uF / 330R2W / 100uF / 330R2W / 100uF / 1.250R5W / 470uF. NOW to be,, 6.8uF / 560R5W / 100uF / 560R5W / 100uF / 1.5K to 1.8K 10W / 470uF. I sure am glad this trans has a 125volt tap on the primary though. Line here is 119v+ and even driving the 125v tap,, HV output is 590Vac from pri. under full 52mA load. With the two 330R's, voltage at load is 222vdc. I changed them to some 470's I had and V+ fell to 190vdc so i am sure 560R's will do it and the 5W will handle the bit extra heat due to larger V drop. Any more I can trim using the 1.5K.


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PostPosted: 22 Mar 2014, 16:50 
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laurie54 wrote:
No. It's RC right threw. The original was 6.8uF / 330R2W / 100uF / 330R2W / 100uF / 1.250R5W / 470uF. NOW to be,, 6.8uF / 560R5W / 100uF / 560R5W / 100uF / 1.5K to 1.8K 10W / 470uF. I sure am glad this trans has a 125volt tap on the primary though. Line here is 119v+ and even driving the 125v tap,, HV output is 590Vac from pri. under full 52mA load. With the two 330R's, voltage at load is 222vdc. I changed them to some 470's I had and V+ fell to 190vdc so i am sure 560R's will do it and the 5W will handle the bit extra heat due to larger V drop. Any more I can trim using the 1.5K.

Sounds about right. When doing the final trim I start with a huge value then step it down to what is required. I think in my PS, after the choke, I used two 1K resistors between caps.

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Projects:180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp |


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PostPosted: 22 Mar 2014, 22:59 
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I looked for 560R and as luck would have it,, i find no 560 but, two 1K's. You have been peeking in my bin. Thank you, and Good choice In they go with 1.5K = 167vdc (still under load) and with 1.8K replacing 1.5K = 155vdc. Lots of range within acceptable limits. I am noticing however rather than using a variac, ( exl tool for working on unknown equipment ++) Personally i would feel using the R = lamp in series method would work very well. The 5v4 takes so long to come up that: 1-having shook the tube for loose spare parts, cracks etc, 2-check and recheck wiring and sch, 3- proper monitoring for key points in the chain from at ac into tube, dc out of tube, dc at the end at load, good reflexes and, the leap well re-hurst "click" is a must happen. It is, when that feeling leaves, that accidents happen. I believe in "" if it can happen, it will "", It comes in handy often!


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PostPosted: 23 Mar 2014, 00:53 
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laurie54 wrote:
I looked for 560R and as luck would have it,, i find no 560 but, two 1K's. You have been peeking in my bin. Thank you, and Good choice In they go with 1.5K = 167vdc (still under load) and with 1.8K replacing 1.5K = 155vdc. Lots of range within acceptable limits. I am noticing however rather than using a variac, ( exl tool for working on unknown equipment ++) Personally i would feel using the R = lamp in series method would work very well. The 5v4 takes so long to come up that: 1-having shook the tube for loose spare parts, cracks etc, 2-check and recheck wiring and sch, 3- proper monitoring for key points in the chain from at ac into tube, dc out of tube, dc at the end at load, good reflexes and, the leap well re-hurst "click" is a must happen. It is, when that feeling leaves, that accidents happen. I believe in "" if it can happen, it will "", It comes in handy often!

My technique is; cover eyes, look away, hold a big breath and turn it on.

_________________
Projects:180W RAW Class D amp | "Illusion" - 6SN7 SRPP preamp in a plastic jiffy box | “Salt Cellar” - Mono 807 triode integrated amp |
"Rosso" - E88CC SRPP preamp |


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PostPosted: 23 Mar 2014, 03:23 
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Location: Vancouver Canada
I can see i need to keep an eye out for certain tubes. I love the glow but not all tubes of the same number are made such that they show off the glow. It's nice the 5v4 and the 6as7 are both available in the stubby and the bottle neck/head type though.


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PostPosted: 24 Mar 2014, 08:22 
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Location: Vancouver Canada
[/quote]Keeps us in formed and add some images. Thanks for the nice compliment. I sold the HP amp but are missing it. I may have to build another.[/quote]

Did it go out the door with the 6080, or the S shaped 6as7? The reason I ask is my 6as7 "S" has not yet come in so i am thinking of changing to the stubby which is in stock.


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