Tubelab SSE inrush current limiters.

[syyma]

I'm in the parts ordering for my Tubelab Simple SE build, inrush current limiter (KC009L-ND) just out of stock from DigiKey, lead time will be Nov-6-2009. Can I pick the one with a different value?
There is one from Ametherm, DigiKey P/N: 570-1073-ND but at a higher resistant value. Any recommendations are more then welcome.

[rknize]

For use on the transformer primary, those should be fine. For use on the secondary, it might be a little high. Even the CL90 is going to have a fairly high resistance since it is rated for 2A and we draw less than 200mA. Maybe MF72-200D9 (570-1073-ND) would be more appropriate for that location.

[Doc Jr 8156]

Try Allied Electronics for availability. Russ, what is the effect of not installing an in-rush current limiter on the "red/yellow" wire if using a Hammond transformer? Godspeed.

John Revilla

[rknize]

The idea of putting on there is to make the life of the B+ rectifier easier. It limits the current to charge the power supply caps. This is helpful for tube rectification, since current-production tubes don't seem to handle that power-on surge very well when the cathode is still not quite up to temp (causing arcing).

[ChrisA]

Originally posted by syyma
I'm in the parts ordering for my Tubelab Simple SE build, inrush current limiter (KC009L-ND) just out of stock from DigiKey, lead time will be Nov-6-2009. Can I pick the one with a different value?
There is one from Ametherm, DigiKey P/N: 570-1073-ND but at a higher resistant value. Any recommendations are more then welcome.

Ametherm will give you free samples. I had them send me a couple dozen in assorted values. (Yes, I really will experiment with them and then spec their part in any design I publish.)

The spec'd KC009L is not really correct for the secondary side of the transformer anyway. There is not enough HT current to heat it to operating temperature. There is good info on the Ametherm web site about selecting the correct part, and you can't beat the price either. http://www.ametherm.com/

I already ask about operating voltage. Their support person said it does not matter as the parts are spec'd by current. I doubt he was 100% correct but our amps don't go into the kilivolt range so I think we will be OK using thermistors across a "mere" 500V

Also if you think about it, placing one of these on the primary side has the desired effect of limiting the B+ current. I'm not sure you even need one on the secondary side. Although there is something to be said for "belt and suspenders" designs

[rknize]

Originally posted by ChrisA
The spec'd KC009L is not really correct for the secondary side of the transformer anyway. There is not enough HT current to heat it to operating temperature. There is good info on the Ametherm web site about selecting the correct part, and you can't beat the price either. http://www.ametherm.com/

I suggested MF72-200D9. What do you think?

Originally posted by ChrisA
Also if you think about it, placing one of these on the primary side has the desired effect of limiting the B+ current. I'm not sure you even need one on the secondary side. Although there is something to be said for "belt and suspenders" designs

Not really. The thermistor is plenty toasty from powering the heaters long before the 5AR4 comes up. If you are using SS rectification or if you have a separate transformer for B+, then that would work.

[syyma]

Hi All,
I finally finished my Tubelab Simpe SE, up and running for about two weeks.
Many thanks to Tubelab's George who comes up with this great board,reommendation form Russ, ChrisA and John Revilla. Thank you again for all you guys.

[rknize]

Looks nice. Enjoy!

[Doc Jr 8156]

Wow! What a nice looking amp. I like the wood panel execution. I bet this amp sounds excellent as well. Godspeed.

John Revilla

[syyma]

Thank you for your kind words. The frame was made out of red oak from my garage's scraps box. The holes on the side panels are for removed the marks and dings, getting better airflow for the two 10M45 and the board, also easier for me to carry, it's heavy and heavier then I expected. The Hammond steel plate just unable to holding all the irons without sagging, I end up put a strip of maple to support those three transfomers.
This amp sounds excellent with Chinese 6L6GC and JJ EL34L so far, will explore other tubes later, for now I'm enjoy the music first.