Sony STR-V4 receiver outputs

[Mico]

Well, thanks for the block diagram - that always helps! So, given what we now know, if the bass and treble controls affect how the noise sounds, that is, you can affect the sound of the noise, the source would be IC401 - assuming the V4 uses the same device.
The V3, however, is different because it has 2 discrete transistors in what Sony calls the Flat Amp instead of an IC. So, now it is time to open the V4 up and see what the real answer is.
Cheers,David

If we take for granted that V4 and V4L are same in that department, and I do not see why they would not be, there is no IC410 in the Flat Amp, same discrete transistors as in V3. For whatever it is worth, I still can not figure out from the block diagram why Tape inputs are not affected by noise. Another weird thing I have just discovered is that AM input is also totally quiet...so just FM and Phono .

 

[Mico]

I was about to sneak under the hood and check few components, those two transistors in the FlatAmp, maybe few caps etc. And than DANG - typical Sony double bottom chassis!
Simply hate this, once gave up on beautiful STR -7065 which needed recap as it had completely closed bottom. I had to take out EVERYTHING from the top to get access to PCB boards.
And 7065 was a rat`s nest, a lot more wiring than in the following models.
Do not understand why they made it like this as this was PITA even for Sony to service the units. V4 has accessible tuner board on the left but all the rest is "undercover".
Will see if I am ready to sacrifice so much time - or just let it be as-is. BUT it sounds simply beautiful, I could not believe something in this class would challenge my Onkyo TX 8500.

 

[Mico]

I am bumping my own two years thread...sold this STR-V4 from 2016 - but could not forget how good it sounded and got another one!
Still no Service Manual or schematics anywhere on this planet - except on that dreadful site where some $@&%*# sells it for 125$ US plus generous shipping of 15$!
Anyhow, does anyone know at least how to adjust Bias on this Sony? STR-V4L SM calls for 50mV (quite high) and Bias pots have exactly the same designation on the PCB, but I do not see the test points on my plain V4. 4VL amp board is also upright as opposed to mine which is laying flat. I see those two test pins close to bias pots, but just one per channel, could it be that other probe goes on the chassis? Big time guess without schematics and quite unlikely, not keen in experimenting.

If I ever lay my hands on SM for this one, copies will cover all light posts in my neighborhood .

 

[Mico]

UPDATE(2): I posted different STR-V4 bias adjustment procedure here but it got edited (e.g deleted) as I figured out few things. There was a Service Bulletin specifically for STR-V3`s bias adjustment (to which I was referring) and that cleared out a few things . So, bias for STR-V4 should be adjusted across ONE output resistor to 25mV. And that was it, 50mV in STR-V4L SM was current across TWO output resistors. The original measuring points from STR-V3 SM still apply on V4 - but this should be much easier. The attached images are from SM, not Service Bulletin.

 

[jmhanna]

Hi, reviving this post to (re)ask a question regarding setting bias on the STR-V4 receiver. I've seen other manufacturers be really specific in their service manuals regarding taking the bias measurements (warmed up, no source input, volume down, speakers switched out) but the SM for the Sony units leaves a lot of these details out. When looking at the Sony SM it shows the (-) mv meter lead on the (+) speaker A terminal, and mv meter (+) goes to the test point on the amp board. If we are using the speaker A terminals, one would think that speaker A should be selected ON when taking the readings, right? I think so also, but am not sure and wonder what the experts think? I'm seeing this: set the bias to spec per the SM with speakers A ON looks perfect, but switching speakers OFF makes the reading more than double (in a positive direction) and then disconnecting the speakers gives yet another reading, with speakers A ON and OFF.

To convolute things even further, if I use my 8 ohm 100Watt dummy resistors, I get readings that are even more different than with the test speakers connected to set A (a pair of Advent /3s).

My instinct is to just take these readings with NO SPEAKERS connected, with speaker switch to the A set. Can anyone confirm this? Am I just thinking way too far into this?

I truly appreciate all of the advice from the discussions here, this is an invaluable resource!

 

[jackpate]

I hate zombie threads, but it seems appropriate to update here. I was able to successfully adjust the bias on my mint STR-V4 using the diagram provided. Connecting speakers made no difference (I tested after I adjusted). One note: Holy fine hairs, Batman! Those adjusters are VERY sensitive. I ended up doing basically quantum adjustments to achieve the 22mv spec. I got there, tho, with patience. Mine were WAY out of spec, like 90 & 110. I should add here that my unit, purchased from the original owners, included the user manual with circuit diagrams. I uploaded it to hifiengine here. To my knowledge, this is the ONLY copy on the Internet (most everything refers to the 4L).

Results: Much improved sound. I noticed right away that the loudness switched needed to be OFF except in very quiet listening. Way more balanced. Before, it sounded "compressed," for lack of a better term. I am running Sony SSCS3 towers, because they were on a huge sale.

EDIT: One other positive change: Before, when I powered the receiver off, there would be a short fart-y noise from the speakers. With the adjustment, that noise is gone.