Beta 87 Pre amp help ..FET transistor Info needed.

[gary o]

Cant seem to locate on web or buy the schematic for my Beta 87 its actually a LX2 Radio system but the part that needs fixing is the capsule amp.

The mic head got ripped off sadly I have reconstructed it as best I can.....but

The capsule has 2 legs one is soldered directly to the board the other pokes thru a hole in the board doesnt even touch the board so something must have connected to it ?.....nearbly there seems to be 2 solder blobs on the board....intrueging...

I wondered if a FET transtor connected the three points....I have a wired Beta 87 ,I had a peak inside & there seems to be a transistor connected directly to one leg of the capsule via its middle leg {base ?? is it ?}again not touching the board at all{Is this to do with hi impeadance?} the other 2 legs of the transistor are on the board.

The transistor in the wired Beta 87 has 156K70 on it, anyone no what this is & if I can get one somewhere ??

Im told I cant buy the tiny amp board as spare part or transistor & would have to buy the complete 87 head for 270 pounds a lot of money for the sake of tiny amp..if I cant fix amp im wondering if I can build my own tiny pre amp instead, I remember seeing really simple 1 transistor design here from a neuman mic.. dont no if this is feasable

 

[gary o]

Update I have found the missing transistor sadly with broken legs will try to repair as am deperate.

The number on the transistor is we think K377 J20 anyone no of this or equivilant

Thanks for reading

Gary O.

 

[bcarso]

Check out:

http://www.alldatasheet.co.kr/datasheet-pdf/pdf_kor/126056/SANYO/2SK377.html

 

[gary o]

Hey thanks Bcarso thats way helpful cant find anywherethat sells them yet but have got a much better chance of finding one now...many thanks

.............Gary O.

 

[gary o]

Woo hoo !!!! havent found transistor at a supplier yet...but looking thru my electronic junk bits & bob I found some little condenser mics i had taken out of old cassette players & such they have there own little built in amps, I took a transistor off of one of those soldered it into the Beta 87 & it works seems to sound exactly the same as it did before I have been comparing it to my wired Beta 87, im well pleased ! the transistor had no markings on it so dont no if its the exact one.

If anyone else has a broke 87 Shure will just tell you its not a servicable part & ask you to part with 250 pounds or more so its well worth a try


Cheers...........................Gary O.

 

[bcarso]

Probably equally scarce are two old Toshiba parts that look like rough substitutes: 2SK266 and 2SK645. Neither comes up on the Toshiba Semi Japan website.