Threshold Stasis 3 biasing for dummies

Audioman12

Member
2016-01-18 10:58 pm
Kzn
Hi all you knowledgable people

I am trying to set bias on the Stasis 3, I have the schematics and biasing data but it is confusing for the novice.

I have some questions which will probably sound silly but I need to know...

Please help......

When biasing do you short the inputs ?
(connect the 2 terminals of the input RCA plus and minus on the R channel and do the same on the L channel)

When biasing do you connect a source to the input RCA ?

When biasing does one connect speakers ?

When biasing where does one measure the voltage ?
( across the negative ground fuse terminals with the fuse removed or across one of the 0.68ohm resistors )

I will be grateful for the info :wave2::wave2::wave2:

Audioman12
 

Nelson Pass

The one and only
Paid Member
2001-03-29 12:38 am
>When biasing do you short the inputs ?

>When biasing do you connect a source to the input RCA ?

>When biasing does one connect speakers ?

Not necessary for all three questions.


>When biasing where does one measure the voltage ?

I measure across a sampling of the Emitter resistors on the output stage
for each channel. Do this in the middle, front to back, as this avoids
measuring the driver transistors which have a different reading.

Overall, you want the amplifier to settle in at a nice temperature of about
50 deg C on top of the sinks after running for an hour with the top on.

This temperature is the 10 second hand on the sink rule. If you can just
hold your hand on the top of the sink without pain for 10 sec, you're good.

Be careful, it's easy to over-bias. Better to start out low than high.

:cool:
 
Thank you for the additional info

As per title.

I do know were the Transistors are both the little black and big silver ones

Don't really know where the driver transistors are and where (or as opposed to)the output transistors are. (I know you are probably thinking that I should not be doing this if that is the case):confused::confused:
Do know where the emitter resistors are though.
I do know how to read the circuit diagram and correlate this to the circuit board.

Can someone please point out on the Stasis 2/3 circuit diagram where the actual bias measurements must be done. Sort of an annotated diagram.

This would be highly appreciated and welcomed
Hope I am not asking too much.....:D:D:D
 
all you need to know is where emiter resistors (of output transistors) are , and to measure across them as secondary information

what is of primary importance is - temperature on heatsinks

meaning - voltage across emiter resistor(s) is giving you info about increments during setting procedure

re-read Papa's post

emiter resistors are those fat ones on heatsinks ...... blue=yellow=gold=gold
 

Audioman12

Member
2016-01-18 10:58 pm
Kzn
So if I am getting all this correctly then the temperature should be set and the bias voltage measured thereafter just chech what it is

I was under the impression that the voltage is the more important measure and the temperature secondary.

I was obviously wrong

Thank you for clearing that for me :p:p:p
 
voltage across emiter resistors is there to give you something to lay eyes on , and tell yar brain how fast you're going

temperature is primary , but changes are slow

so - observing voltages , make small increment , put lid on , wait new temp. equilibrium

if needed repeat , in so many increments as needed to arrive at proper heatsink temperature

in the end - voltage drop across each emiter resistors must be in same bracket (say percentage of resistor tolerance) , and mid value same on both channels
 
Biasing gone wrong. An explosion later

Do not know if I should start a new thread or continue here.

Something went wrong last night, there was a short and a spark and something flew out. (Half of the resistor covering on the second emitter resistor flew out.) Due to pulling, the leads to which I attached crocodile clips touched each other or one of them touched the chassis whilst attached across the second emitter resistor. The pictures attached will illustrate this. Don't know what else has gone wrong( not much I hope)

Too afraid to switch on after this happened.

Much self loathing thereafter. Could not sleep as made a cardinal error

image_zpsvamy93sb.jpeg Photo by Audiomann | Photobucket

there are 3 pictures there
 
Last edited:
Ok don't know if I have the technical expertise for that. But will try

None of the fuses went. The resistor is 0.68ohm but what wattage are they ?

Does anyone have pictures of stripped down stasis 3 boards and plates with transistors removed. Would appreciate them. Any pics as I can't seem to find them.
:hohoho::hohoho::hohoho::hohoho: thank you for the info Zen Mod

Feel like have Father Christmas on my side
 
Resistor type

It has been mentioned that the resistors are Carbon Composition types but when the one blew off its cover, there is definitely a coil on the inside as per picture

The outside look of the resistor is definitely closest to the Carbon Composition type hence the assumption.

picture distinctly showing the coil

image_zpspvsroafn.jpeg
 
Eternal optimism

Got the appropriate resistor removed the blown one and installed it hoping that all will be well.
Not so. :mad::mad::mad:

The replaced resistor has no voltage drop across the two poles whilst all the others do. Does this mean anything specific or does this not delineate the problem any further ? It is definitely correctly installed.

Anyone suggest anything else to try ?
 
that means that associated transistor is blown , but not in short (which is your enormous luck! )

that also means that you probably powered up the beast without proper checking of all what was mentioned before

there is a slight possibility that base resistor of that transistor is blown , eaving faint possibility that transistor itself is good

however - you need to check it ( and all others , if you ask me ) at least with diode test

if blown - replace it - Papa gave type recipe somewhere in most recent Treshold threads
 

rogerh113

Member
2014-10-08 9:35 pm
Hi,



Old thread, but perhaps someone can help. Looking for a multiturn trim pot for my Stasis 3, but not having any luck finding something that will fit and allow adjustment from the back as the current pot does.



Any pointers would be appreciated. The current pot is hugely jumpy, and I am assuming is well past its use-by date.....


regards -- Roger