Transistor replacements
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Hi there,
I am sourcing the components for the Z80MC, which have brought me to a halt trying to find the pre-biased transistors Q1-Q5 used on the front panel (FJN3303R, FJN4303R) and even their equivalents (NTE2358, NTE2357).? The TO92 versions all seem to be out of production... Are there any other equivalents that could be used instead? Glad if anybody could point me in the right direction. Cheers |
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Hi Josh, Unfortunately at least in their UK branches they are both not available and marked as obsolete. I've also looked at Farnell with the same result. gives a list of equivalents but I am not sure which would be better suited. Curiously enough, Amazon has it but it's a super inflated price, and I would rather pay ?0.50 than ?4.50 Flavio On Mon, 26 Apr 2021, 14:11 joshbensadon via , <joshbensadon=[email protected]> wrote:
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flavio@... wrote:
I am sourcing the components for the Z80MC, which have brought me to a halt trying to find the pre-biased transistors Q1-Q5 used on the front panel (FJN3303R, FJN4303R) and even their equivalents (NTE2358, NTE2357).? The TO92 versions all seem to be out of production... Are there any other equivalents that could be used instead? Glad if anybody could point me in the right direction.These "pre-biased" transistors with internal resistors have been around for decades, and there are hundreds of part numbers. When I designed them into the Z80MC, all the major distributors stocked them for a few cents each. I buy my PC boards and parts to go on them in batches; so I still have enough of the FJN3303R and FJN4303R transistors for kits, and to supply customers who bought the bare boards from me. If that's the case, let me know. :-) But the age of through-hole parts is coming to an end. Surface-mount parts are everywhere; but through-hole versions of the same parts are disappearing. Digikey and Mouser sold their remaining inventories to Rochester Electronics. Rochester is a good outfit; but they have a $250 minimum order. For a 3-cent part, that means buying >10,000! I added the NTE equivalents to my manual. NTE has long been a supplier of replacement parts for service and repair. They buy a standard part, add their own part#, and jack up the price. They maintain inventory, which costs money. So if you only need one, and don't care what it costs, they've got it! It doesn't help that manufacturers don't use generic 2Nxxx or 2SBxxx numbers any more; they hide them with their own "house" numbers, so you can't easily cross-reference them to other parts. When searching, use the term "pre-biased transistors" to find them. There are *lots* of equivalents (especially surface-mount); but they've made them hard to find. Octopart.com is a free search engine for electronic components. They'll show who has (or says they have) stock on parts such as these. At the moment, they list: NTE2357 NPN $1.20 each NTE2358 PNP $0.78 each -- A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. -- Antoine de Saint Exupery -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com -- This email has been checked for viruses by Avast antivirus software. |
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Lee, Many thanks for the reply. I'm absolutely sure that you and the community created the best design with what was available at the time. Once again I am out of luck. TME, being in Poland, and thanks to Brexit, doesn't ship to the UK for the time being. So I will take the risk and order the SMD equivalents (MMUN2212LT1G , NSVMMUN2112LT1G),? with a bit of effort I think I can fit them on the board. Flavio On Mon, 26 Apr 2021, 17:46 Lee Hart, <leeahart@...> wrote: flavio@... wrote: |
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Flavio Vinicius Spalato Zanchi wrote:
Lee,These pre-biased transistors are handy parts. They save parts, and thus save space on the PCB. They are bipolar, and so are not susceptible to static damage, and don't have parasitic "protection diodes" (which was useful for the RS-232 interface). It's unfortunate that you're in the UK. I have the transistors; but postage for a 1-ounce letter to the UK is over $5, and the minimum package postage is over $15. They also insist that envelopes be "flat". I tried to mail an LED in an envelope, and it arrived with chips knocked out of it! Lee Hart -- A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. -- Antoine de Saint Exupery -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com -- This email has been checked for viruses by Avast antivirus software. |
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Frank Palazzolo wrote:
I built my kit to do TTL-serial only, and I don't plan to use real RS-232 voltage levels.Q1 and Q4 (on the Z80MC Front Panel) are only needed for RS-232 serial. So they can be left out. :-) Another alternative would be to find a compatible N-channel andAn N-channel MOSFET (like a 2N7000 or BS170) might work for Q2 and Q3. Their base (gate) is pulled either high or low (so never left floating). The base of Q5 is driven by capacitor C5; so you need the base resistors to work. A P-channel MOSFET (BS250) might work if you added a gate-source resistor to insure that it turned it off. Or, you could leave it off -- without it, you can't reset the Z80 with the DTR line from the serial port. For an active part, it seems like you could find a match in a surface mount package, if you're willing to solder that to the top (or bottom, depending on the pinout).Right; there are lots of surface-mount alternatives. But watch the pinouts! Lee Hart -- A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. -- Antoine de Saint Exupery -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com -- This email has been checked for viruses by Avast antivirus software. |
Zanchius
Lee Hart