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Discussion in 'CB and Export Equipment and Accessories' started by spuds619, Jun 26, 2010.
you can look for the NTE sub which is an NTE1271.
they are getting about as expensive as the MB3756.
you can eliminate the chip altogether by replacing it with a 7808 regulator and a relay, or a couple of transistors.
here is a link to one way to do it:
(it is in portuguese so you'll have to use google translate if you want to read the text, not really needed though)
PY2BBS - Hamradio Page
here is another method:
1) remove the MB3756 chip and save the plastic screw and nut.
2) get a T0-220 mica , 7808 regulator , 10uF 10-50v lectro , 0.01uF
3) twist on the 10uF to the ground and output
legs and the 0.01uF to the ground and input leads then solder on three
lengths of wire to each leg and grease / bolt it to the existing hole
on the wall just above the empty 3756 slot.
4) wire the ground lead to the ground foil , input lead to pin 2
location on board , output lead to pin 1 location on board.
5) 12V coil SPDT relay double sided taped to a wall , put spike diode
across coil (1n4004) , wire common switch contact to pin 1 location on
board , NC switch contact to pin 6 location on board and wire NO switch
contact to pin 8 location on board.
6) wire cathode side of coil to +12V on the radio power switch .
7) disconnect the receive wire from the mike jack and tape up.
8) wire mike jack receive (at jack) to the anode side of the relay coil.
just so you know, i have not tried either of these mods personally, but the first one looks logical, and the second one comes from a source that i have trusted for years, and has never let me down.
Thanks for the replies
Thank you for the info and replies. I am not much of an ebay fan as far as buying things of this nature,too much like playing roulette as far as I am concerned.I do go on ebay but not generally for this type of item. Also thanks for the link and the replacement circuit info. That might be an interesting possibility to switch it over to relay operated,i'll have to research it somemore,andas far as it being in portugese,not a problem,It so happens that I am portugese so a translation is not a problem.As far as NTE,that was one of my first choices,but the price on them from the supplier I get my supplies from that I have been using for over 25 years tell me that they are now up to 22 and change each for something I have bought before many times for a 1/4 of the price.Well,off to check the relay option and see its feasability. If we could only go back to the 1960's when you could buy it by the dozens,and buy cheap.Thank you again for the replies and suggestions.
This part you want is nothing more than an LDO, otherwise known as a linear regulator.
Its the drop-in package which is obsolete, but not the function of providing 8.2v at 200mA with enable.
Seems like two of the outputs are controlled by enable pin, but one is always on.
Searching various IC vendors, its not hard to find an adjustable regulator that can take at least 18v, and has enable input pin, and is adjustable with resistors to give you ~8v out.
I search maxim for example and find MAX5087 among others. maybe you dont like that package, so there is MAX16910 in so-8. You cant do it with a single IC, but you can build a little board and hand-wire it in. Perhaps there are more options from linear tech or national semi.