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Sony STR-V4 receiver outputs

Mico

Mico

Well-Known Member
Have a chance to pick minty Sony STR-V4 receiver for around 80$ - so not quite a thrift find.
I always wanted to give this line a try but never came across decent sample. My question would be what are the outputs on those, TO-3 or Power packs (STK) ? Could not find one single image of nudies for STR-V4 , I think previous generation, STR 5800SD and STR 6800SD had Darlington packs, not sure for the later ones.
Not crazy to go after one if blowing one of those outputs could turn it instantly into doorstep.
 
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Thanks, that sounds promising. I have heard nice comments on V4 sonic performance, even more favorable than bigger toriodal models.
Will lay my hands on it soon....
 
Count me in as a fan. Mine is smooth, detailed, and mellow. At some point I will recap it, but it is part of a system where I really don't think much about the gear, but just enjoy it.

It also has the best loudness button I have ever used (used as intended when listening at very low levels, that is).

If I did not have one yet but knew how good it is, I would pay $80 with a smile on my face.
 
So got it along with a half dozen other things I did not plan to take but it was real bargain, so other stuff will pay off for Sony :naughty:.
Everything looks fine and first impression is it really sounds good. The only problem seems to be nasty crackling and static from Phono/FM/AM selector switch, only on the right channel.
Despite heavy Deoxit treatment it is still there, sometimes it acts up on its own, not as bad as when I move selector but bad enough. I am wondering if it might have cold solder somewhere on that switch - but it does not cut out completely ?
Also, does anyone has SM for "straight" STR-V4, Hifi engine has only for V4L and amp section looks different, I am not sure where to check for amp bias and if recommended value (50mA) is correct.
 
After all it seems that crackling and static has nothing to do with any switches,I have a bad cap somewhere. I do plan to recap this thing but for now would like to be able to listen to it without blowing my right ear drum.
Static and crackling in R channel starts minutes after turn on, it does depend on the volume level (unlike some other units when I could hear it even with volume at zero) and affects all inputs.
Unfortunately no jumpers on this receiver and I can not separate amp and pre-amp to roughly locate the troubling section, any ideas whee to look first?
Nothing seems to be leaky on the boards but I have had quite few bad ones in the past that did not show any visible problems.
 
Noise on one channel indicates that channel and if heard on the AUX input, its likely a noisy transistor or, more likely, an chip. Unfortunately Sony, like many other vendors back then were moving quickly to reduce parts counts with op-amp-based chips. In the V series, some of these were prorietary and may be hard to find.

Other symptoms to check for:

- Does the DC offset on the offending channel tend to start jumping around with the onset of the noise?

- Can you press the board anywhere and cause the noise to come and go or get worse/better? Use a bamboo skewer - nothing metal to do this.

- Once located, can you use a soldering iron to heat up the chips and/or transistors in the area and hear a change?

You'll have to chase the signal back toward the input to determine where it starts otherwise.

Cheers,

David
 
dshoaf said:
Noise on one channel indicates that channel and if heard on the AUX input, its likely a noisy transistor or, more likely, an chip. Unfortunately Sony, like many other vendors back then were moving quickly to reduce parts counts with op-amp-based chips. In the V series, some of these were proprietary and may be hard to find.
Other symptoms to check for:
- Does the DC offset on the offending channel tend to start jumping around with the onset of the noise?
- Can you press the board anywhere and cause the noise to come and go or get worse/better? Use a bamboo skewer - nothing metal to do this.
- Once located, can you use a soldering iron to heat up the chips and/or transistors in the area and hear a change?
Cheers,
David
Click to expand...

I really hope it is not a chip, otherwise I am cooked., there are one or two Sony chips on each power amp board. I can hear damn crackling on all inputs including AUX and moving any switch makes it worse, that is why I got fooled at the beginning.
I was betting on the bad cap, tracing back on the bad channel path will be challenge for me. DC offset was stable regardless of the noise but will check again, just in case.
 
David , there is something with DC offset it just took me some time to play with it. So, when Tape selector is set on source and Phono, FM or AM selected (no AUX on this one...) and I am turning Volume selector back and forth between 9 and 12 o`clock
DC offset on bad channel goes wild. It reacts on the Volume level and occasionally jumps over 1V. Also, turning On/Off Loudness switch creates crackling click which sends DC offset into stratosphere, anywhere between 150-1700mV !!
Same exercise does not affect the good channel at all, no crackling from Loudness switch, no noise when Volume is rotating at very high value and no shifting in DC offset. Hope this is not a bad news, very curious to hear if this gives any hints what might be going wrong.
 
The noise problem is being masked by poor switch contacts (fix with DeOxit) and the volume pot (FaderLube). All the controls should be cleaned first then re-evaluate the problem.

If you allow the unit just to sit - not messing with the controls - and monitor DC offset, what happens as you listen for the noise? You can use headphones to minimize the impact of a sudden rash of noise, too.

Cheers,

David
 
I cleaned everything with DeOxit two times, noise (both from switching and spontaneous) was much worse before. The static on Volume pot, Loudness and Phono/FM/AM switch are only on the bad channel - just coincidence?
When I do not touch controls and listen to noise, DC offset is stable and same on left and right channels (40mV) even at the sudden rush. Yes I am using cheapo headphones to monitor the whole thing, too risky to use speakers.
 
Yep, you've got a noisy device - most likely a transistor in the signal chain. Next step is to 'divide and conquer'. That is, you'll need to find a way to tap into the signal chain somewhere in the middle between the preamp section and the power amp section.

A schematic (or link) will help be more definitive.

Cheers,

David
 
If your STR-V4 does not have the same control layout as the V4L, they'll be different receivers inside most likely. To remain competitive, Sony was fast to turn over their product line models back then.

I see Service Manuals have been sold on ebay for the V4. Sony service manuals were always the best for a tech to use - well documented with color overlays - awesome.

Cheers,

David
 
dshoaf said:
If your STR-V4 does not have the same control layout as the V4L, they'll be different receivers inside most likely. To remain competitive, Sony was fast to turn over their product line models back then.
I see Service Manuals have been sold on ebay for the V4. Sony service manuals were always the best for a tech to use - well documented with color overlays - awesome.Cheers,David
Click to expand...

STR V4L has all the controls of V4 plus AFC switch, also Monitor and Function switches have inverted positions. According to google images, amplifier section has different layout too....very strange.
I think that is more than enough to consider them different so I have to find V4`s Service manual-dang . Update: there is one on epray for 50CAD with shipping :eek:!! That is daylight skinning....
 
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Allright, I made a major omission: when I listen through Tape 1 & 2 inputs amp is quiet like a mouse! Yesterday I connected CD on Tape 1 and tuner on Tape 2 and there was absolutely no noise?!
As soon as I move selector from Tape back to Source (Phono/FM/AM) static is back, full time. Now I am confused, that should exclude noisy component in the signal path - but what the heck it is?
I was thinking that Function switch might have cold solder joint, it that makes any sense.
 
Nope, Mico, the Tape inputs are switched in down stream in the signal chain from where the problem is. This is what I meant by divide and conquer. From that one test, we know the problem is in the preamp section. Generally this is the area around the tone, balance and volume controls. You cannot open the unit and see the problem but someone with some experience can take what you've figured out so far and run with it.

What we know now is there are component(s) that need replacing somewhere in the preamp.

Cheers,

David
 
Nope David, Tape inputs are switched before the tone, balance and volume.. Strictly a switching problem. The STR-V5 service manual is available on HiFi engine, and should have a similar circuit to the V4. Clearly shows all Tape/Source switching prior to any active components.



hfe_sony_str-v5_service.pdf (SECURED) - Adobe Acrobat Reader DC 11182016 71551 AM.jpg
 
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TPettenati said:
Nope David, Tape inputs are switched before the tone, balance and volume.. Strictly a switching problem. The STR-V5 service manual is available on HiFi engine, and should have a similar circuit to the V4. Clearly shows all Tape/Source switching prior to any active components.
View attachment 821523
Click to expand...

STR-V3 has identical Function / Monitor switch layout as V4 and SM is available on Hi-Fi engine, I will take a look if it is similar to V5. That would be good news for sure.
Update: V3`s block diagram seems to be very similar
 

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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
 
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