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Per-Anders Sjöström

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QRV-02 support JIN

Started by peranders, January 19, 2006, 09:10:51 AM

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Check first the supply voltage. If you have only 2 separate AC sources you must connect the other channel in parallel.

12 VAC is a bit little so check the raw voltage. It must be 20 volts at least if you want 15 volts out. If the voltage is under that you can change the regulators down to 12 volts. 33 k in parallel over the 3k3 (or 3k0) at the regulators.

AC source 1 connect it to X1, pin 1 and 2
AC source 2 connect it to X1, pin 3 and 4
Mount B1 and B2

Check then that you'll have 15 volts and -15 volts in the both channels.

I'm not sure how your adapter looks like. Have you 3 or 4 wires?

The possibly fried opamp might be alive, not risky to mount it correctly and test.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff



i dind't try anything yet, dind't have time
( putting time on the working and amazain 07 )

The ac adapter ( transformer ) as 3 wires out!
2 wires give +12ac
and 1 wire is ground i guess

cna this work ? or i have to connect it in paralell and bridge the B1-B2?

Please instruct me on where exactly to take measurements!
i do not quite understand what to look for

i soldered the chip back on the correct side,
let's hope that i dind't fry the 40$ OPA chip under it :p

let me know what to test exaclty with # and pins :)


If you AC adapter has a centertap, connect this to ground, pin 2 or 3. The other wires to 1 and 4.

Notice though that 12 VAC is good for 12 VDC stabilized.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff


is that enough to make the amplifier run normally ?

this is only a temporary transformer
i'll get audio toroidal tranfos once everything is setup !

what do you think ?

the connection seems ok from what you say

what to check then ?

not all the leds are lit! :(

is there a place where i can check for correct voltage ?


Study the schematics carefully. You have a net called 15V_L and -15V_L (left channel). Those points can be reached in many places but pin 4 and 7 of the opamp may be the easiest to reach.

I'll it's possible to have a bit low voltage but be aware of some hum due to partly stabilized voltage.

About the LED's: (have you read this?)
QuoteIf you don't want to trim the idle current you can omit P1, R15, R16 and T4. The LED's creates sufficient idle current of T5 and T6. If you want more current in an easy way, change colour of the LED's! If you have T4 mounted you can either have or loose the LED's. If you do have the LED's you will get a limitation of max bias current
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff


ok i'll have a look at the schematics later on at home

but i don't quite understand the "LED" thing and the trimmers?
i never read that passage you quoted...where is it from ?

i know that i installed 2 trim pots
but i'll check tonight wich one

i didn't adjust it at all though


The text is from the building description. I'll recommend that you read the text I have written.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff



well i had read it a few times, while assembling the unit

but as i told you previously in emails,
i am a total NOOB

so i can't just look at schematics and see what does what and where it goes to

i have a basic idea of how electronic works, and i can isolate different parts of a schematic ( PS, output stage, input stage ) and that's about it!

let me know if you can be of more help regarding the power supply
i need to take measurements to see if i have a problem somewhere
( i think )
meanwhile i'll reread the building description a few times :)


PerAnders i need help!

i tried to check out voltages, i don't even know where to start!

Please i need guidance to complete this amplifier!


ok i checked for power supply voltage

i got +13.82V on both side measuring at C30/G30 postisive side

what can i verify next??


i also checked voltage between R17 and R18

not too sure if i took the measurement the correct way

but i get 0.12v on each side

with my + and - from the voltmeter on R17 and R18

what do you think ?


First of all you must check your supply voltage. 13.7 V is probably OK (a bit low according calculations), how about the negative? How much voltage do you have in, the voltage before the regulators?

0.12 volts across R17 means 5.5 mA which is a bit low. Should be more than 20 mA. Do you use only LED's or do you have P1, R15, R16 and T4 mounted? You should not have both LED's and the transistor.

I know you say you can't read the schematic but try to indentify for example R1 and then check where it is on the pcb. Each part in the schematic corresponds to a real part on the pcb. If you are going to troubleshoot you must be able to read the schematic.

Sorry for my late response. The email notification did not work of some reason. It usually does.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff


hi PER :)

well i have them ALL mounted :p
that could be the problem ?

i have installed all the LEDS
then P1, R15 R16 and T4

what do i need to remove ?

let me know :)


It's no harm to have them all mounted but this wasn't the idea. The drawback you'll get (not sure it is for you) is that the max idle current is determined by the LED's.

The LED's serves as a fixed voltage source of 1.5-1.6 volts each. The other circuitry is a variable voltage which also senses the temperature.

If you have the LED's, they should also be lit.

Please do read the text I have written.  :idea:
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff


ok per,
i have read, reread, and rere re read it all over again
building, description, schematics ...
i can't find where to start at!!!

What to do next ?
please let me know in clear steps ,
i seriously don't know what to do!
i want this amp to work!

would it be a good idea for me to post a photo of the board?