Hello everyone, As you may know, from my previous posts I am trying to build a layout powered by old MRC Throttlepacks (for HO). Hence, I am building some hand-held transistor throttles to provide power for my N-Scale locos with can motors. My situation: I found a circuit diagram for a two-transistor throttle in the old Kalmbach Electronics Projects for Model RRs book. My problem: I can't find an appropriate transistor for the second transitor in the circuit. That means I found a potentiometer for the first transistor. But the second is an NPN 0.5 watt, 40 volt. When I look in the electronics parts catalogs from either Mouser or Digi-key, they don't list these that way. They only have the transistor number. Can anyone help me figure out the correct transistor to use? For all of you who I know will suggest I switch to DCC, I'd love to do it, but it's out of the financial question for now. Thanks in advance.
Clifton, is´nt there any maker, component ID or number for that second transistor, in the circuit diagram? If so, it must be possible to find a replacement ID in some makers catalogue (I believe) ------- Helge SR&WF NARA member #5
Clifton, look in phone book for an electronics supply or distributer out there. See if they carry or have a catalog for Optek Technology Inc. Dallas, Texas. We made all kinds of transistors, photo cells, emitters, detectors, all miniture stuff. Post any numbers you see, maybe we can identify it.
Helgek, I looked in the book again and no such luck. The only reference to a specific part is in the parts list and I was left with the cryptic NPN, half watt, 40 volt transistor. I am building a throttle to use in N-Scale, and that is the recommended transistor for that scale. The book also recommends a NPN, 1 watt, 40 volt high-gain transistor , such as Texas Instruments TIS92. Hopefully this added info can help narrow my search. Watash, I need your opinion. Considering the copyright date of this book was 1974, before can motors made their entrance, do you think I could just build the HO version? The book also contains a recommended transistor types which fails to include the TI transistor or provide any leads for the one recommended for N-Scale. The question is: do I need the precise transistor or is there something that's close that I could use? I'm not that familiar with electronics, so I figure why not ask. Thanks in advance for your help. BTW, I'll check out the suggestion you gave, Watash. Regards,
Not being completely familiar with the circuit design, but being familiar with the basic problem, you should be able to substitute a different transistor for the onw shown without any problems. It's a case of "close is good enough". If you were building a sophisticated radio system or such, the answer would be different. Just make sure that the VBE is at least 40 like your circuit shows, and check to make sure that the "beta", "gain", or "hfe" is "up there", then you should be O.K. What's "up there"? 40 or 50 are typical "grunt" transistors, and anything over 100 could be considered a higher-gain transistor. A darlington transistor should show a gain of at least 1,000. The most important things will be voltage and power dissipation. Mark
Clifton, just a short comment. As Mark said "close is good enough". I can not find the TIS92 in my catalogues, but there are some that might match your need like Philips BC635 or BCX54-16, Philips BSR41 or Motorola 2N1613. They are all 1 W except for 2N1613 which is 3 W. 40 - 60 V and a minimum hfe varying between 40 and 100. Good Luck! ------ Helge SR&WF NARA member #5
Clifton I sure wouldn't use that throttle design if it from 1974. Check around for a more up to date design. Look in the NTRAK throttle book for some simple to build\use throttles. I know that MODEL RAILROADER has simple throttle plans in it every now and then. Look in the past yearly index for MODEL RAILROADER to find out what issues have plans in them. I would NOT build the HO version for use with N-Scale. The throttle would put out too much power for N-Scale.
Clifton I sure wouldn't use that throttle design if it from 1974. Check around for a more up to date design. Look in the NTRAK throttle book for some simple to build\use throttles. I know that MODEL RAILROADER has simple throttle plans in it every now and then. Look in the past yearly index for MODEL RAILROADER to find out what issues have plans in them. I would NOT build the HO version for use with N-Scale. The throttle would put out too much power for N-Scale.
Hi,all. Clifton, I have a copy of that book copyrighted 1988 and it has an updated design in it.(translate more complicated). I'll let you borrow it if you give it back. Alternatively I have an old MRC 500N Throttlepack that worked last time I tried it (a few years ago). It could go away cheap. Sadly I'm not real strong on electronics so can't be of more help. e-mail at fallenanjlz@home.net Good Luck Bobby
For updated throttle designs, check out Fred Horne's Armadillo & Western web site. He has a lot of good DC throttle designs. I plan to build his design named "The Throttle". Here is the link. Armadillo & Western [ 19 March 2001: Message edited by: mdrzycimski ]
Tractronics CoolerCrawler is one of the simplest throttles I was able to find on the internet. I built two (from scrounged parts, not from kits) and they work great. Go to the CoolerCrawler page to see the diagram. Here is a picture of the hand pieces I made. [ 19 March 2001: Message edited by: sajay ]
