Substitute for MV2112,MPS3866 and MRF559

[zxcsemaj]

Hi! Everyone, I'm planning to build a TV Transmitter and can't find the replacement part for this component, does anyone know the Substitute for MV2112, MPS3866 and MRF559? Can't find any substitute on google. Thanks in advance!

 

[zxcsemaj]

Hi! Everyone, I'm planning to build a TV Transmitter and can't find the replacement part for this component, does anyone know the Substitute for MV2112, MPS3866 and MRF559? Can't find any substitute on google. Thanks in advance!

 

[FvM]

If you feel that your question doesn't achieve the desired attention, you are free to explain the problem more detailed. Simple thread bumping and cross posting aren't allowed by forum rules.

--- Updated Jan 9, 2023 ---

The parts are out-of-production but still available at some DIY shops. For replacement with similar parts, we need to know the circuit context which wasn't mentioned unfortunately. Attentive Edaboard users watched https://www.edaboard.com/threads/tv-transmitter.405269 and know that you are trying to reproduce a TV transmitter circuit from a book. I presume the book is discussing required component specifications.

 

[zxcsemaj]

This is the circuit I'm planning to build, since the last time I post they said that the circuit is too complicated to build that's why came up to this circuit of TV Transmitter but the problem is the components that is obsolete. Also, what is this crystal oscillator that has a value of 54.90625MHz. Sorry for reposting the same questions.

 

[FvM]

The crystal has been selected for a specific cable TV (Hyperband) channel 439.25 MHz. You can choose a different channel frequency, or even an arbitrary frequency and tune the TV to it. According to availibility of crystals at your side.

 

[zxcsemaj]

The crystal has been selected for a specific cable TV (Hyperband) channel 439.25 MHz. You can choose a different channel frequency, or even an arbitrary frequency and tune the TV to it. According to availibility of crystals at your side.

Thank you so much, Sir! If I want to have a frequency of 600MHz (UHF) above, should I increase the oscillator or lower it?

 

[FvM]

Hope you understand that the circuit is designed for threefold frequency doubling, fout = 8*fosc. 600 MHz output would require 75 MHz crystal. Intermediate stages have to be tuned respectively.

 

[zxcsemaj]

Hope you understand that the circuit is designed for threefold frequency doubling, fout = 8*fosc. 600 MHz output would require 75 MHz crystal. Intermediate stages have to be tuned respectively.

Thank you so much, Sir! Last question Sir, can I substitute MV2112 Varicap to BB139 Varicap?

 

[lw1ecp]

The MV2112 has typ 56pF @ 4V. The BB139, typ 29pF @ 3V. The voltages for measurement are different but I guess the BB136 will be around 24pF @ 4V. Quite lower than the MV2112, and I don't have the curves to see the capacitances ratios, but I think two BB139s in parallel will serve your needs.
BTW, the BB139 and similar diodes can be scavenged from TV tuners.

 

[dick_freebird]

"NTE" used to be a big replacement-parts vendor with
a good interchange reference book. The old ham / TV
repair shop I used to hit had a peg-wall full of little zip
bags of transistors. I'd bet Digi-Key has killed that guy
off, if the chain smoking didn't.

You might find selection guides at major vendirs, still.
If you picked one with roughly-similar device types
(like, don't go to Semicoa looking for a 50GHz GaN
HEMT).

I turned Mr. Googlez loose on the simple P/N and the
first thing that comes up is multiple eBay vendors selling
onesy-twosey (though you may not like the price, it's
not like you need that many for a one-off project, right?).
If you're patient you can snag a good deal, maybe. Or
pay the "urgency tax".

You could of course drill into detailed attributes and
design care-abouts, and try selection guides with that
kind of search criteria.

The obsoleting of a Motorola part by Microsemi probably
is from them gutting one of their operations that used to
be in the "buy and hold inventory for someday" business.
Microsemi has been a "thatch rake" in the semiconductor
segment, buying up, breaking up, selling off pieces of
companies they've been buying up for decades (before
being themselves bought my Microchip, who cares not
for the trailing edge once its "contribution margin" falls
below threshold-of-caring.

You might look at outfits that are still in the "crusty parts
for high prices" segment, like Rochester, if eBay fails you.

RF-focused stocking distributors' applications engineering
might be convinced to help you out if you lie about the
quantity you'll be ordering and how soon.

 

[zxcsemaj]

The MV2112 has typ 56pF @ 4V. The BB139, typ 29pF @ 3V. The voltages for measurement are different but I guess the BB136 will be around 24pF @ 4V. Quite lower than the MV2112, and I don't have the curves to see the capacitances ratios, but I think two BB139s in parallel will serve your needs.
BTW, the BB139 and similar diodes can be scavenged from TV tuners.

Thank you, Sir!

--- Updated Jan 15, 2023 ---

The MV2112 has typ 56pF @ 4V. The BB139, typ 29pF @ 3V. The voltages for measurement are different but I guess the BB136 will be around 24pF @ 4V. Quite lower than the MV2112, and I don't have the curves to see the capacitances ratios, but I think two BB139s in parallel will serve your needs.
BTW, the BB139 and similar diodes can be scavenged from TV tuners.

Also, is it okay to replace mps3866 with 2n3866?