VHF R/C Transistor
06-19-2003, 04:34 AM
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VHF R/C Transistor
What frequency are we talking about? 75 MHz modeling?
Heres a datasheet for anyone interested
http://service.semic.sanyo.co.jp/sem..._e/2SC4910.pdf
I'm sure there's a suitable replacement available, but right now I don't have the time to do a search. Since it shows up on sanyo's website as a datasheet, you might try contacting them to see if its still available and where to get it. Might even convince them to send you a free sample.
Heres a datasheet for anyone interested
http://service.semic.sanyo.co.jp/sem..._e/2SC4910.pdf
I'm sure there's a suitable replacement available, but right now I don't have the time to do a search. Since it shows up on sanyo's website as a datasheet, you might try contacting them to see if its still available and where to get it. Might even convince them to send you a free sample.
06-19-2003, 11:45 AM
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VHF R/C Transistor
OK fellow, that transistor is used in many RC (Futaba,JR, Airtonics) therefore it is 72 MHz. I know the.PDF and his characteristics but I don't find an appropriate substitute. So, I try contact the Sanyo.
John
John
06-19-2003, 05:54 PM
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VHF R/C Transistor
Philips, Motorola, Texas Instruments, National Semiconductor, Matsu****a all manufacture a wide range of discrete transistors. You should be able to find something in their online catalogues.
Look for something with about the same max. collector current and max. Vce. Similar capacitance from collector to base and base to emitter and collector to emitter (within 30%) would help. If the transistor is too different you will have to retune.
Retuning may be necessary anyway, as there can be large variations between transistors, even if they all have the same part number. This is why radios are made with adjustable tuning. If transmitters could be made to all work perfectly without tuning it would be done, since that will save a manufacturing step (and cost).
I've used audio transistors like the BC338 in that application, but at 50 MHz. They should be OK at 72 MHz, but down a little in power. You would not get away with an audio transistor above 100 MHz or so.
Look for something with about the same max. collector current and max. Vce. Similar capacitance from collector to base and base to emitter and collector to emitter (within 30%) would help. If the transistor is too different you will have to retune.
Retuning may be necessary anyway, as there can be large variations between transistors, even if they all have the same part number. This is why radios are made with adjustable tuning. If transmitters could be made to all work perfectly without tuning it would be done, since that will save a manufacturing step (and cost).
I've used audio transistors like the BC338 in that application, but at 50 MHz. They should be OK at 72 MHz, but down a little in power. You would not get away with an audio transistor above 100 MHz or so.
06-19-2003, 06:42 PM
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VHF R/C Transistor
The problem is this transistor 2SC4910 works with low exitation. Any other transistor needs a circuit driver to supply the correct power (750mW) and will be necessary rebuild the circuit
John
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06-20-2003, 12:02 AM
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VHF R/C Transistor
The 2SC4910 (C4910) is used in several current R/C Tx's. For example, the Hitec Flash5 and Lazer use it. JR's Quattro, XF421, and XF662 use it as well. There are many others.
My point? Why not just order it from the JR, Futaba, or Hitec service centers? Or one of the independant shops? Perhaps Radio South would help you out. Yes I understand -- Given that you are in Brazil, availability is a bit complicated. But these sources may still be able to help.
FWIW, the 2SC4272 is another popular RF PA used in R/C apps. Some Tx's use the 2SC4735. I have not looked closely at them to see if they will help you. Here is a data sheet with specs: http://www.bdent.com/pdf/High_Frequency_Tr.pdf
My point? Why not just order it from the JR, Futaba, or Hitec service centers? Or one of the independant shops? Perhaps Radio South would help you out. Yes I understand -- Given that you are in Brazil, availability is a bit complicated. But these sources may still be able to help.
FWIW, the 2SC4272 is another popular RF PA used in R/C apps. Some Tx's use the 2SC4735. I have not looked closely at them to see if they will help you. Here is a data sheet with specs: http://www.bdent.com/pdf/High_Frequency_Tr.pdf
06-20-2003, 12:23 AM
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VHF R/C Transistor
Thank you for the answer friend. I have a small shop of repairs of R/C in the south of Brazil and the difficulty of getting components it is very big. I have been getting some components with Tony (Radio South), but the import brazilian rates is very high. So I seek some transistor substitute - Motorola - Texas - Fairchild ( friendly brands) .Iīll be try C4272 and C4735.
Take a look in my HP www.manoaerorc.hpg.com.br
Regards
Take a look in my HP www.manoaerorc.hpg.com.br
Regards
