searchnig for schematic Threshold Fet one

[doum]

Hello

Is it possible to find all the schematic for the Fet one?

Thank you

 

[jacco vermeulen]

Maybe if you tie up the Pass Master or Eric Lauchli and tickle their feet with a feather for a few hours.

(or ask Steve Jensen Eddy if he managed to borrow it from Lauchli)

 

[SL10User]

Got a Fet One today. Seems to have a defective Power Supply.
(A Lot of Transistors MPSA92, MPSA42, MPS6571, FPN4250A, FT317).

Output signal is not symmetric, same on both channels.

Has anybody the schematic?



Thanks,
Gerhard

 

[Zen Mod]

just Fet2

buzz if you need that

 

[SL10User]

BUZZ!

Maybe it is similar or the same....

(hopefully), Gerhard

 

[Zen Mod]

......

 

[SL10User]

Thanks.

But what I need is the Power Supply....

 

[Zen Mod]

in fact - its certainly simple enough , so you can replace everything for few greenies

 

[SL10User]

Replace everything......

Thought to be in diyAUDIO forum. Not in an ordinary workshop....

 

[Zen Mod]

if that drek is in my workshop , I would find what's the culprit - without asking and replacing everything .....

that's just plain and simple preamp .......



edit:

with "everything" I meant on everything in PS section ; it certainly needs recap after all those years ....... and you have - what - few more parts , except caps ...

 

[SL10User]

As I said, a lot of transistors (13).
The Caps are all ok. Resistors too.

 

[Zen Mod]

exactly right time to find how to test transistor

 

[SL10User]

Did that already.
Found 4 completely shortened and one partial shortened.
Want to understand what happened and to avoid it happen again.

And of course what's the sense of it at all......

Is it sooo hard to understand, why I'm trying t reach a schematic?

 

[Zen Mod]

happy hunting ;

I hope someone will chime in with needed schmtc , so we can help you in easier way

 

[SL10User]

Going to order the defective parts (or replacements).
When replacing these I try to draw the schematic (have to pull the pcb out, didn' that already...).
And hope they will not blow up again....

 

[Zen Mod]

you can replace those electrolytics too ;
they're old as Bible

 

[SL10User]

Why?

Nominal capacitance 1.5 mF, measured 1.9/2.0 mF.
Typical ESR 170 mOhm, measured 120/130 mOhm.

Same advice as "change everything"?

 

[SL10User]

BTW:

Pulled out the pcb an found shortened B-E on several transistors by the soldering side layout.
So they are not defective. Only three were gone....

 

[Zen Mod]

Why?

Nominal capacitance 1.5 mF, measured 1.9/2.0 mF.
Typical ESR 170 mOhm, measured 120/130 mOhm.

Same advice as "change everything"?

well - you must confess that novice ( who is asking for schm of simple preamp ) isn't supposed to have ESR meter .... and I couldn't know in which condition they are .....

so - to rephrase my self - for proper repair of preamp - replace all broken parts .....

 

[digits]

riadial caps tend to have significantly longer life rateings in general, I just hate the way they go when they do decide to blow, as there are no venting grooves.