Chris,
Looks great! Makes me think about starting another tube coil.
BrianB
> On Dec 23, 2018, at 11:41 PM, Chris Reeland <chrisreeland@xxxxxxxxx> wrote:
>
> Hi all,
>
> It has been a while since I posted anything... been lurking though and got
> some updates here...
>
> I have made a decision on my small 304 VTTC about 3 weeks ago. Inspired by
> Steve White's 833A and Dave's 810 to be easier to set up and be much more
> portable I have made several changes. I will admit it is not a thing of
> beauty, but I am mostly concerned with being functional.
> I have also greatly simplified it. Removing several extra monitoring
> meters. I am now confident in how all is running, that I don't need them.
> Only have two meters now. A meter to monitor filament voltage is a must in
> my opinion. And I have a current meter monitoring input on the variac, to
> monitor efficiency, which is something I have also made a major decision on
> this coil. Also removed extra different type of tube socket, simplified my
> experimental extra adjustable grid leak setup and several other small
> changes. So back to the efficiency monitoring... I have decided even though
> I have achieved a maximum of 42" with this small coil, the efficiency is
> terrible at 25A, even with several PF caps added. I can't even imagine what
> it would draw with out them, if the 120 line was capable of higher amps and
> proper breaker. The other efficiency issue and I also consider a health
> problem is the MOT. I was using a fairly large 20 amper variac with 140V
> input. The variac handles this no problem. The MOT now though, is being
> pushed very hard, no bad sounds, but definitely being pushed. Run times
> even at reduced rates limits run time to about 5 minutes max. MOT is then
> extremely hot, even with the full time fan I have mounted above it. Takes
> at least 35 minutes to cool way down and it is still hot some! Like I said,
> extremely hot! The tube handles the low rate just fine though. The run
> times are even shorter if rates are up on MOT, and now tube is starting to
> be pushed hard. Also extremely finicky and hard to tune in for maximum of
> 42". Most times I can only tune to 36" while it still draws 25A w/PFC. So I
> have decided to make this coil much more usable run time wise and much more
> efficient running. I have gone back to the original 10 amp variac using the
> 120 setting. It also has a 140 setting, but my variac and the MOT does not
> like this as I have run into this in the past quite a bit ago. Both made
> unpleasant sounds, and again efficiency was really terrible again. Don't
> remember exactly how bad amp wise and how much PFC was tried but it was not
> good. So it is strictly now only using 120 input on this 10 amper. Since
> this is smaller and with the changes to coil layout, I am able to squeeze
> this on the coil board attached with wing nuts, so it can be removed in
> Hi all,
>
> It has been a while since I posted anything... been lurking though and got
> some updates here...
>
> I have made a decision on my small 304 VTTC about 3 weeks ago. Inspired by
> Steve White's 833A and Dave's 810 to be easier to set up and be much more
> portable I have made several changes. I will admit it is not a thing of
> beauty, but I am mostly concerned with being functional.
> I have also greatly simplified it. Removing several extra monitoring
> meters. I am now confident in how all is running, that I don't need them.
> Only have two meters now. A meter to monitor filament voltage is a must in
> my opinion. And I have a current meter monitoring input on the variac, to
> monitor efficiency, which is something I have also made a major decision on
> this coil. Also removed extra different type of tube socket, simplified my
> experimental extra adjustable grid leak setup and several other small
> changes. So back to the efficiency monitoring... I have decided even though
> I have achieved a maximum of 42" with this small coil, the efficiency is
> terrible at 25A, even with several PF caps added. I can't even imagine what
> it would draw with out them, if the 120 line was capable of higher amps and
> proper breaker. The other efficiency issue and I also consider a health
> problem is the MOT. I was using a fairly large 20 amper variac with 140V
> input. The variac handles this no problem. The MOT now though, is being
> pushed very hard, no bad sounds, but definitely being pushed. Run times
> even at reduced rates limits run time to about 5 minutes max. MOT is then
> extremely hot, even with the full time fan I have mounted above it. Takes
> at least 35 minutes to cool way down and it is still hot some! Like I said,
> extremely hot! The tube handles the low rate just fine though. The run
> times are even shorter if rates are up on MOT, and now tube is starting to
> be pushed hard. Also extremely finicky and hard to tune in for maximum of
> 42". Most times I can only tune to 36" while it still draws 25A w/PFC. So I
> have decided to make this coil much more usable run time wise and much more
> efficient running. I have gone back to the original 10 amp variac using the
> 120 setting. It also has a 140 setting, but my variac and the MOT does not
> like this as I have run into this in the past quite a bit ago. Both made
> unpleasant sounds, and again efficiency was really terrible again. Don't
> remember exactly how bad amp wise and how much PFC was tried but it was not
> good. So it is strictly now only using 120 input on this 10 amper. Since
> this is smaller and with the changes to coil layout, I am able to squeeze
> this on the coil board attached with wing nuts, so it can be removed in
> about 2 minutes if I need to borrow it for something else. Did the same for
> a variac on the filament transformer. Same wing nuts and can be borrowed if
> needed. So now strictly limited to just 120V on a 10A variac, I also made a
> decision to not use any PFC if possible to make things simpler.
> So all this, also means that I need to retune the tank capacitance. Did
> some crude calculations, and decided on what I need approximately uF wise.
> Still keeping and using the same vacuum variable cap in conjunction with a
> fixed tank cap for fine tuning. The calculated mica cap required I did not
> have even though I have a whole mess of them. Seems like you can never have
> enough on hand :-) So I searched around online and found a couple. Had no
> choice on package type for the micas. It is a 292 type. I was using a F3
> type mica for the tank and another for the BP. Decided to get the 292 for
> the tank and another for the BP, so they match package wise. Next thing to
> figure out was how to mount this different type of mica. Decided to make I
> guess I will call a RF deck made out of a piece of scrap metal laying
> around. This greatly simplified connections, while mounting securely. I
> started to make all these changes 2 weekends ago. Just worked on, on and
> off, a bit at a time with some small tests at times. Last night got done
> with all changes physically. And it was time for running new complete
> setup. Very pleased now, with just some minor tuning so far. I just picked
> a random 304 tube that I have to run. I am going to roll all 304's that I
> have again, as they all have to be retuned to new setup. I will post
> rolling results later eventually when I get through them all. Also
> recently picked up more also. The tuning required on the one tube that I
> have tried so far is completely different. It is much easier to tune in for
> maximum output and efficiency. Much more flexible also for achieving
> maximum efficiency with slightly reduced output. I can now also, it seems
> like, I can run this coil indefinitely so far... I ran this coil non-stop
> for 1 hour and 20 minutes at different rates at times. The MOT when I shut
> down was just kinda hot, not bad at all. Checked MOT 7 minutes later while
> the fan was still on and it was already just lukewarm.
> Thrilled about this. Not going release the magic smoke now...
> Here are a few numbers on performance currently that will probably change
> just a bit as I "play" with this more.
>
> Maximum output length now currently is 31"@12A
>
> Best efficiency tuning wise so far is 28"@9A
>
> And yes, I am not going to bother with any PFC, achieved this goal...
>
> Did not expect this kind of efficiency, I will admit, and thrilled about
> running non-stop. A much more portable and useful coil and takes up way
> less on the bench:-) While not a 36"-42" coil anymore, it is a better small
> coil now. Bigger streamers is the goal on the next VTTC project that is
> nearly done. Everything is better setup for this also. Just need to wait
> for Spring. I don't like coiling outdoors in the Winter. Can not
> concentrate as well and more likely to make a major mistake as well in my
> opinion, as this one must be run outside. Don't have anywhere big enough to
> do indoors for this one. Also I have been gathering parts up still for the
> next bigger VTTC, no real work on it yet, still hunting parts... getting
> there though... piece by piece...
> Another reason to change this coil is to have something to do while waiting
> for Spring. I can now spend a lot time experimenting now since it seems
> like I can run indefinitely if I want to.
> No more short run times, with very long cool down times and possibly
> ruining the MOT.
>
> Here are a few links to pictures of new setup. Again, I will admit not very
> good to look at, but very functional.
>
> https://photos.app.goo.gl/Zv5fZ6dKBgWjgm538
>
> https://photos.app.goo.gl/qtMTShdJAc4h5A7a8
>
> https://photos.app.goo.gl/7XbGxT7YRt43yqdt7
>
> Hope this all makes sense...tried to edit all mistakes I could find
> here...may have missed a couple of "strays":-)
>
> Chris Reeland
> Ladd Illinois USA
>
> Sent from my LG V20
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