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*my* Tubelab SE build...

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You can get mylar kits at Radio Shack, but the little thermal pads from Mouser/Digikey are better (no grease). Typically you would use 4-40 screws and nuts. These come with the Rat-shack kits along with the washer. Note that you only need them for the heat sink on the Schottky rectifier and regulator and even there you can get away with only doing one. The FETs are insulated packages and the CCSs can short to each other since they both see full B+ anyway. This does make the heat sink "live", just like the SSE. If you don't want that, then you would need pads for those too.
 
I have an extra motor run capacitor. I could probably get it to you for $10 all said and done shipped out the door. Shoot me an email if you want it. Otherwise I am going to toss it up in the classifieds.

For the other capacitor you bought as a snap in...couldnt you straighten the legs out. Not sure how successful you would be at doing that but it might work.
 
If you have a "real" electrical supply store, like for contractors and manufacturing, they will likely have it. There is a local surplus store near me that had boxes of used ones, but they were smaller 3-4uF types. I got mine from eBay in the end so that I could find a large, round one. I believe that shipping was free and the total was less than half of what Mouser wants for the same cap.
 
Nic - The snap in leads are really thick buggers, even if I did straighten them out, they wont fit into the pads - I'd have to drill them out. Which I'm still considering doing. I think I may take you up on that offer - what is the value of the run cap?

Russ - I looked a couple up and called them. When I asked about motor run caps, well lets just say I had to repeat the question a few times... Just did a quick ebay search - not many choices in the > 60uf range.
 
oldmanStrat said:
Russ - I looked a couple up and called them. When I asked about motor run caps, well lets just say I had to repeat the question a few times... Just did a quick ebay search - not many choices in the > 60uf range.

I got all of mine from "supplystuf". I don't see any 100uF listed right now, but here is an oval 80 and a round 90 440VAC:

http://cgi.ebay.com/POCF80-Oval-80-...de948cb&_trksid=p4634.c0.m14.l1262&_trkparms=|301%3A1|293%3A1|294%3A30

http://cgi.ebay.com/PRCF90-Round-90...07f7674&_trksid=p4634.c0.m14.l1262&_trkparms=|301%3A1|293%3A1|294%3A30

I am using the latter in my SSE and as you can see it is huge. 440VAC is way overkill, especially for a TSE, but it does the deed. Here is a smaller 70uF 370VAC oval if space is an issue:

http://cgi.ebay.com/POC70-Oval-70-u...ea9ecb4&_trksid=p4634.c0.m14.l1262&_trkparms=|301%3A1|293%3A1|294%3A30

Just go into his eBay store and search the capacitor section for "80 uf" or whatever. Remember that 370VAC is good up to at least 520VDC though probably 10-20% higher than that. 440VAC is good up to at least 620VDC.
 
Hmm, I think I found an error on the tubelab website.

I was trying to check if the value of C4 (rectifier output cap) was ok for my 300B application and I found that there two different numbers spec'd on different pages.

The parts list shows 47uf, and mentions a table that I can't find.
The tubes and transformers page (where I think the mystery table should be) only mentions cap values for the 45 & 2A3 - but the suggested initial value is 4.7uf - a decade different than the parts list...

So - my question is what is the right cap value for the Rknize transformer (330-260-0-260-330) for my 300b's. I'm using a hammond 10h choke @ 155ohms - and eventually a motor run cap ;)
 
If you look carefully, what he is talking about is starting with a smaller cap to drop the B+ slightly if you have too much voltage on the HT winding, such as those "hot" Hammond transformers. When you lower the value of the first C in a CLC (or "pi") filter, the filter starts acting more like an LC filter with more of the work being offloaded to the choke. While a CLC filter will give you nearly 1.414 times the RMS AC voltage of the transformer winding, an LC filter will give you about the same DC voltage as the RMS AC voltage of the winding. A great way to play around with this is to fire-up PSUD and pay around with various values on the first cap.

To answer your question, I am using the specified 47 (forty-seven) uF. ;)
 
rknize said:
If you look carefully, what he is talking about is starting with a smaller cap to drop the B+ slightly if you have too much voltage on the HT winding, such as those "hot" Hammond transformers. When you lower the value of the first C in a CLC (or "pi") filter, the filter starts acting more like an LC filter with more of the work being offloaded to the choke. While a CLC filter will give you nearly 1.414 times the RMS AC voltage of the transformer winding, an LC filter will give you about the same DC voltage as the RMS AC voltage of the winding. A great way to play around with this is to fire-up PSUD and pay around with various values on the first cap.

Good info... Can you model transformers with PSUD? I suppose it is a windoze program too...

Originally posted by rknize
To answer your question, I am using the specified 47 (forty-seven) uF. ;)

Excellent ! That I have. What did your B+ work out to be?
 
oldmanStrat said:


Good info... Can you model transformers with PSUD? I suppose it is a windoze program too...


It is, but it works just fine in WINE. ;)

Excellent ! That I have. What did your B+ work out to be?

This post shows that transformer in both modes on the TSE with this CLC arrangement:

47uF - 10H, 82ohm - 220uF

http://www.diyaudio.com/forums/showthread.php?postid=1803717#post1803717

The 300B results are a little high because I wasn't biasing them very hard (they weren't my tubes). I was later brave enough to set them at 80mA each:

http://www.diyaudio.com/forums/showthread.php?postid=1804760#post1804760
 
I don't mean to hijack the thread but I have a related question on the motor run caps.

are there any smaller options for this supplemental capacitor? my real estate is bit tight so i'm looking for something that is less than 1.5" in diameter. all the caps that i've come across are about 2-2.5". i would prefer to mount it under the chassis (which is only 1.5" high).

TIA
 
discomonkey said:
I don't mean to hijack the thread but I have a related question on the motor run caps.

are there any smaller options for this supplemental capacitor? my real estate is bit tight so i'm looking for something that is less than 1.5" in diameter. all the caps that i've come across are about 2-2.5". i would prefer to mount it under the chassis (which is only 1.5" high).

TIA


Try an oval, the one rknize just posted: ebay oval cap might be the ticket. email the guy and ask him for dimensions...
 
http://www.mouser.com/Search/Refine.aspx?N=254298&Keyword=UNL6W&FS=True

I've used the 30uF @ 600V before. It's about 1.3" x 2.1". They get expensive quickly above that, but they are quite compact. The 80uF is 2" x 2.5".


These are not oil-filled like the motor run caps are, which is probably why they are smaller. They will work just fine in our application.
 
can a solen fast cap be used in this application?

Yes, they work very well as a filter cap.

what is the benefit to the oil? [/B]

Cooling. A motor run cap has to swing the full 370/440 or whatever volts 60 times per second. They are used for balancing the Q-factor of electrical motors so that they don't cause phase shifts in the power service (since induction motors are purely inductors). Some utilities actually have a surcharge for industrial power if a site has too much inductive loads.

We are just using them in a filter network, in this case on the "easy" end of a CLC filter. Heating is not really an issue.
 
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