On Thursday, September 14, 2017 at 1:10:23 PM UTC-4, John Robertson wrote:
On 2017/09/14 6:46 AM, John-Del wrote:
On Wednesday, September 13, 2017 at 8:29:21 PM UTC-4, Jeff Liebermann wrote:
On Wed, 13 Sep 2017 08:33:57 -0700 (PDT), wrote:
im working on a arcade game board . the tip 120 for an eject soleniod is driven right off the processor leg, no pre -driver transistor. didnt even think that was possible, maybe that why it blew. is there a mosfet i can replace the tip120 with?
thanks
I don't like using darlingtons for power drivers. A momentary shorted
load, and the darlington blows up from too much current. This article
should provide some detail:
http://www.sensitiveresearch.com/elec/DoNotTIP/index.html
I can't offer any specific recommendations without some clue as to the
processor output voltage and current capabilities, the solenoid specs,
and the operating voltage.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
I wouldn't worry about using a Darlington as a coil driver. Arcade games are generally quite robust (the monitors generally the weakest point) and they've been using them for years with no issues. They used to use relays or even high current leaf switches to drive coils but relays and switches have a finite life.
Well, actually. no, arcade games (pinball games) using TIPs and other
BJTs have a nasty habit of failing and cooking their coils and the
circuit board. Many of us in the trade are getting around to finally
ripping out all these dinosaurs and replacing them with modern devices.
It has taken me far too long to realize I am not doing customers a
favour by leaving old tech in their games. As the link Jeff provided you
get up to 4VDC drop across the BJT so a MOSFET with less than 1V drop
will give you more pop too!
Most of the aftermarket replacement boards are using MOSFETs except for
a few holdouts whose quality suffers in other areas too.
Still for the OP who has a CHEXX game the TIP120 should last forever, it
has at most a 1A draw, and we have never replaced one in the 30 odd
years I've been servicing CHEXX boards.
John :-#)#
--
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John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
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"Old pinballers never die, they just flip out."
From about 1982 until he sold the company about 8 years ago, I did all the electrical work for a vendor who became a very good friend of mine. The vast majority of the work I did for him were monitor failures. Most of the electrical work he did was swapping out game boards, converting cabinets and replacing hard drives. He would shop the pinballs as they were rotated or were pulled for failures and if there was a problem beyond lamps, rubbers, solenoids etc. I'd get the board.
I rarely saw shorted Darlingtons. I agree that MosFets are better suited to switching, but other than upgrading the ratings of the replacements, we never felt the need to do wholesale replacements of Darlingtons that would most likely last the life of the game. It was far easier to deal with them individually.