Author: Felipe Ceglia - PY1NB <felipeceglia2@gmail.com>
Date: Tue, 23 Feb 2010 10:34:04 -0300
Hi folks, Regarding this recurring topic about soft starting... How can one determine if it is needed or not? Should HV be soft-started as well? What would be the best math to determine the soft-star
As far as possible, USE ONE!!!!! First, the cold resistance of a tube's filament is as low as one tenth of the warm filament, so inrush currents can reach 10 times the operating value. Second, inrush
Hi Guys, FWIW, I had to re-build my rectifier stack at least twice before I finally incorporated a soft-start / step-start scheme in the primary of my B+ transformer... The p.s. is a full-wave rectif
Author: Felipe Ceglia - PY1NB <felipeceglia2@gmail.com>
Date: Wed, 24 Feb 2010 09:21:39 -0300
Folks, Thank you for your replies. Is there a way to calculate what R values and relay contact Amp rate should I need? Also, if the primary is feed with 110+110 volts, I should use one R on each prim
The power supply for the Ten Tec Titan 425 (1980 vintage) uses a 20 ohm 25W resistor in series with one side of the primary. I haven't one apart for a while, but I recall the relay contacts looking l
Yes, there is. The most endangered part are the rectifiers. The specification includes a current value called " non repetitive peak current", usually with a time limit of about a cycle or so. Use tha
Hi Alex, I didn't see anyone reply to your suggestion to add a one ohm resistor in the plate transformer primary so I will. This is a really bad idea from voltage regulation viewpoint. It would be th
The AL-1200 has a simple Soft-Start circuit, one resistor and a relay. Download the manual from the MFJ site and see how simple it is. 73, Dick, W1KSZ _______________________________________________
You can purchase time delay relays, build a small RC circuit to turn on a transistor that keys a relay. Essentially you have a circuit that has a resistor in series with the primary of the plate tran
By the way, an old trick that was used in tube type TV sets was to install a thermistor in series with the mains. It had a cold resistance of a few tens of ohms when cold, dropping to an oh or two af
ORIGINAL MESSAGE: REPLY: That thermistor was not used for soft start. It was part of the degaussing system and had very poor reliability. I changed hundreds of them over the years. Not recommended. 7
I'll bet you replaced almost as many, if not more than tubes. Typically the set would just quit rather than some indication of imminent failure that tubes often gave. Yes, I also repaired tube type T
ORIGINAL MESSAGE: REPLY: I replaced so many I even remember the RCA part number after more than 30 years: 107191. 73, Bill W6WRT _______________________________________________ Amps mailing list Amps
Herzog says there is confusion. There are thermistors of a type that measure 25 to 100 ohms when cold, and drop to an ohm or two when hot. My last one has been keeping my outdoor light, 25 feet up un
No so. I had a RCA CTC-9 (Circa 1959-60) with a 21" round crt that used a thermistor in the transformer's primary and it did open up. Not having a replacement handy I just shorted the leads and power
Hi Alex, no, I didn't forget what inrush protection is; that is why I suggested the 25 ohm resistor and shorting relay. You are the one suggesting installing a one ohm resistor and leaving it in the