help to set dc offset to threshold s450

[alfalf1]

hi to all forum member i need our help to set the dc ofset of treshold s450.

i have purchased it used but in a right channel i read 1,2v dc and left channer i read -1,3 volts dc.

i nned also the schema or servece manual to teterminare the trimmer that regulate it.

i wait soon our help

thanks at all in advance and exluce me to my little english

i am italian

alfonso

 

[Zen Mod]

well , put some Italian pictures here first ......

 

[alfalf1]

same pcture

hi i see in the driver card only a blu trimmer

but i have tried to regulate it bat the cd remail aroundo 1.1 volts dc

 

[alfalf1]

pictures

following pictures

 

[alfalf1]

pictures

well , put some Italian pictures here first ......

 

[Zen Mod]

to help me to determine which iteration of front end you have in that amp,read to me type of that 6-legged small metal transistor (on first pic)

then I can try to find schematic to point you in right direction

however , what you'll certainly need is to do some maintenance - for what you need to make front end pcb accesible

when you make that ,take few frontal pictures of pcbs and post them - so we can see is there need for changing small electrolytics and anything else

btw. pot you have on pcb is for setting Iq - standing current

you have appropriate info (pdf file) for that here : Treshold Treasure ?? while Papa was there : 400A | Zen Mod Blog

but , prior to that , you need to solve offset issues

 

[alfalf1]

the digit on transistor and foto

hi Zen the digit on metallic transistor si d8924

i dismount the left drive card following picture:

i wait your news

 

[alfalf1]

right driver card

folloguing right driver card

 

[alfalf1]

another information i dont know if is it possible to be usell about the problems

i have disconnect the power supplay 24 hors before, and when dismount the card on the 6 big power cap (33.000 UF) 5 was discharge and only one was still full chargeed.

 

[Zen Mod]

isn't that small transistor 2N5566 ?

however , while you're at it - replace those 2 electrolytics (1 per pcb)

take a gooooood look at solder side , re-flow any suspicious solder point

I'll dig adequate FE schematic later , maybe no before tonight

 

[Zen Mod]

here it is , adequate

'll be back later

 

[alfalf1]

yes confirm is 2n5566 and after there is write d 8924

the electrolytics is that one orange (1 per pcb)?

 

[Zen Mod]

yup

and - replace that Tantalum cap - biggest yellow blob, right below CNY optocoupler , bellow trimpot

put any decent electrolytic there ,with same capacitance/voltage

 

[alfalf1]

10v 220uf

 

[alfalf1]

ok tanks and after remonting and test ?

 

[Zen Mod]

yes , try

test conditions - no load at output , all inputs shorted (XLR pins 2 and 3 to pin1/gnd )

edit:

it'll be good to confirm voltages noted on schematic

 

[alfalf1]

hi the Tantalum cap whic valus is v and uf

no there is write anything.

 

[alfalf1]

i can substitute the 10v 220uf with 35v 220uF (i have this new at home) or have to purchase it.

should be the same.

i wait your confirm

 

[Zen Mod]

35V is better than 25V and better than 10V



that tantalum cap - no markings on both channels ?

 

[alfalf1]

hi the Tantalum cap whic valus is v and uf

no there is write anything.