Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: shooter on February 16, 2018, 09:23:40 pm

Title: avoiding inrush
Post by: shooter on February 16, 2018, 09:23:40 pm

if I keep OHM happy does this work?  30sec TD is tweakable
EDIT: trying to keep secondary from spiking, trying not to have to || caps, using 500vdc, unloaded is cal'd at 510vac

thanks

Title: Re: avoiding inrush
Post by: PRR on February 17, 2018, 11:06:24 am

Depending on values of R, it may do almost nothing for that first cap.

Seems to me that more/fancier caps may be cheaper than a delayrelay and 50W resistor. Remember that non-electro motor caps in this range are coming down in price; there's a post I think in the Tools section.

Title: Re: avoiding inrush
Post by: shooter on February 17, 2018, 12:13:41 pm

thanks, I have some cheepeezz,  and it is a Mr Goldburgy circuit, it just seems like there should be a simplish way not to get such a large V spike waiting for slow analogs.
when the PT gets here I will experiment with the DL and see what's up.

I like 50 to 100uf at the 1st tap, but it takes 4 50's, or 4 100's to get there.   

Title: Re: avoiding inrush
Post by: kagliostro on February 17, 2018, 12:14:12 pm

Why use a delay relay

on old VOX there was a component called Brimistor (CZ 4 on the VOX AC50)

http://www.voxac50.org.uk/brimistor.htm (http://www.voxac50.org.uk/brimistor.htm)

nowaday I think an NTC can be used as sostitute

--

In this old thread was discussed an alternative path to find a solution

http://el34world.com/Forum/index.php?topic=12395.msg115393#msg115393 (http://el34world.com/Forum/index.php?topic=12395.msg115393#msg115393)

(http://el34world.com/Forum/index.php?action=dlattach;topic=12395.0;attach=25926;image)

Quote

EDIT: Here something that may be of your interest

http://el34world.com/Forum/index.php?topic=12801.msg119862#msg119862 (http://el34world.com/Forum/index.php?topic=12801.msg119862#msg119862)

http://www.electrojumble.org/DATA/STC_Brimistors_CZ_Types.pdf (http://www.electrojumble.org/DATA/STC_Brimistors_CZ_Types.pdf)

http://www.electrojumble.org/data/stc_thermistors_gen_info.pdf (http://www.electrojumble.org/data/stc_thermistors_gen_info.pdf)

http://docs-europe.electrocomponents.com/webdocs/002a/0900766b8002a5a8.pdf (http://docs-europe.electrocomponents.com/webdocs/002a/0900766b8002a5a8.pdf)

Franco

Title: Re: avoiding inrush
Post by: shooter on February 17, 2018, 02:26:56 pm

Thanks Franco, nice links

I like this;

Quote

Whether the brimistor really worked as intended is a moot point

:l2:

Is that the part that needed the "oil pan" under it?  seems there was a thread sometime ago that did :dontknow:

Title: Re: avoiding inrush
Post by: kagliostro on February 17, 2018, 04:47:46 pm

I think I remember something about the "oil pan"

but to me seems that the involved component wasn't a Brimistor

Quote

EDIT: I just remembered ..... the component was the grid leak

http://el34world.com/Forum/index.php?topic=18218.msg185619#msg185619 (http://el34world.com/Forum/index.php?topic=18218.msg185619#msg185619)

Franco

Title: Re: avoiding inrush
Post by: shooter on February 17, 2018, 06:03:38 pm

you have a beautiful mind my friend :laugh:

I was close, it's round :icon_biggrin:

Title: Re: avoiding inrush
Post by: trobbins on February 17, 2018, 11:15:27 pm

Its a very long time to try and clamp B+ before indirectly heated output stage valves start to conduct sufficiently.  NTC/brimisters won't help as they only influence initial surge.

I used a shunt load for one amp to avoid the typically used delayed relay.  I had all the parts, although would've been nicer with a pcb.  I just didn't want to do series connected main filter caps, and as in your situation, the VAC to switch is really too high for most common relays meant for 240VAC as they get exposed to capacitor in-rush.

 https://www.dalmura.com.au/static/HV%20DC%20shunt%20load.pdf (https://www.dalmura.com.au/static/HV%20DC%20shunt%20load.pdf)

Title: Re: avoiding inrush
Post by: kagliostro on February 18, 2018, 05:47:32 am

Thanks Tim

Franco

Title: Re: avoiding inrush
Post by: shooter on February 18, 2018, 10:17:07 am

thanks for the link, archived