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Odd diode in Sony str-v3

Chriswashere

Chriswashere

Active Member
Hi all, I have a quick question about replacing a diode in my Sony str-v3. The diode is a Sv04S and I can't find a replacement anywhere for it. Does anyone know what to replace it with?

I'm going to be honest here, I'm a college student that doesn't have a lot of cash so I'm always looking for the best, but lowest cost option. This unit is in "barn find" condition, so there's no guarantee it can be saved anyways, so it's best to not start pouring cash into it. At the moment this diode is the last major obstacle besides trying find an affordable replacement for the 2sc1986c output transistor.
 
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Using google I found this post. Looks like there was a sony bulletin on building a circuit to replace the diode. Look it over but I would wait for someone else to chime in as well.

http://electronics.stackexchange.com/questions/243654/what-can-i-use-to-replace-an-sv-04f-bias-diode

kxlC8.jpg



There is more to the post there.

Nashou
 
That's an interesting route to take, but it is a possibility. There was also talk about using 4 1N4148 diodes in series as a replacement as well.
 
Four 1N4148's will have way too high a voltage and idle current will be crazy. Four 1N4004's (or four UF4004's) will be fairly close to the original diode.
 
There is someone on ebay selling a pair of the SVO4 diodes for ~ $10 shipping included. (SV-04 / SV04 / DIODE / COMPARABLE TO ECG607, NTE607 / 2 PIECES ). These are the style without the mounting hole. And TIP41C's are a decent replacement for the 2SC1986C TO220 outputs. They can be found on the bay as well for $3.75 for 10, shipping included (10PCS TIP41C TIP41 TIP POWER TRANSISTOR NPN 100V 6A USA Seller Free Shipping)
 
Thank you both for your replies on this.

Do you think I could use some1N4002 diodes instead of the 1N4004? I only ask this because last night when sorting through some estate sale parts, I found a bag of them.

Thanks Tom for finding those parts. The transistors are an excellent deal and they're already on the way. Unfortuntly those diodes are still a bit much. If this unit wasnt a barn find $10 wouldn't be too bad, but I don't want to get too invested just yet.
 
The problem is that the diode that has died is unobtainable now, it also performed a very specific and important function, so any replacement needs to be exact. I would exactly with what Echowars has recommended if you want to replace this part.
 
Chriswashere said:
Do you think I could use some1N4002 diodes instead of the 1N4004?
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Sure. But power up after the replacement with a DBT to prevent any disasters. While on the DBT, adjust the bias trimpot to confirm you can do so, then turn it down to minimum bias before attempting to power straight from the AC line.

RE: The diodes. The larger silicon area of the 1N400x series is what results in the lower Vf that makes these diodes usable. The tiny silicon area of the 1N4148 results in a higher Vf and makes them unsuitable for this.
 
Sorry for my late reply on this, I really haven't had much time for audio lately. Today some of the Sony parts came in, so I decided to recheck those diodes before messing with much. Now I can't get a reading out of either one, which is odd. Theyre both out circuit as well. I guess that means the right channel has issues as well, which wasn't expected. I even set the meter to the highest resistance setting and nothing.

Anyways, here are some pictures of the diode creation. I guess another one will have to be made :thumbsdown:.
 

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Are you sure? Those diodes are not that easy to kill.

Get a 9V battery and a 1K resistor and make a little circuit with your diode assembly. Now measure the voltage across the diodes.
 
At this point i'm not sure of anything. I made the circuit you suggested, and both of the old diodes get a voltage reading, so maybe they're good? I've never come across a situation like this. Usually parts are obviously dead, and that's that.

I think I might just put these back in, and power up the unit on my Variac. The output transistors came in today, so now I'll put in a 47k trim pot to replace the destroyed 22k, and then find (or order) a 24k 1/2 watt resistor. Then we can see what the issue is, judging that the power supply and everything else is alive.
 
Well, I guess the real question was never asked: why do you think the original diode needed replacing? If it is because it failed a meter diode test, know that a lot of meters do not supply enough voltage to forward-bias the diode and will make the part look as if it has failed.
 
Well, the reason for that was because of the condition of the channel itself. All the surrounding components were dead due to either blowing, or being roasted.

Here is a list of dead components: R707,R710,R712,R713,R714,R720,Q711,Q712,Q713, and RV701. I believe that's it, but there may be more.

Before testing, all it seemingly needs is R707.
 
Been meaning to ask....whose 1N4150's are we talking about? Vishay? Microsemi? Fairchild?
 
EchoWars said:
Been meaning to ask....whose 1N4150's are we talking about? Vishay? Microsemi? Fairchild?
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EW, didn't try all brands; it didn't seem to matter much during my testing with the couple I ahd, but let me know if you find different and I will order in a few of each well known brand and plot the results. Vishay is what I used for the presented results though
 
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Well, the only ones that make any sense to purchase are the Vishay. The Micro devices are going for $1+ each! F^$# that!
 
EchoWars said:
Well, the only ones that make any sense to purchase are the Vishay. The Micro devices are going for $1+ each! F^$# that!
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Yeah, I saw $2-5 on Mouser for the Micro... what's that about?! So I ended up ordering 100x of the vishay as the quantity cut gives you 7cents/piece and it's nice to have a bunch to get the total Vf just right. I did also try some smd 1N4150 too, which I thought might yield a neat/compact replacement for the SV04, but it just wasn't happy with the mechanical stability of the joints (I thought about enclosing the entire thing in thermal epoxy though...will post on that over in AU-X11 thread. The SMD had very little variation in Vf)
 
Well, got back on this project. Right now I'm getting output from both channels at low power (20vac), but there is a hum in the background. When the voltage is turned up, the audio keeps spiking, as if a machine gun is rapidly firing. Just "pop pop pop pop" rapidly over and over. Ideas?
 
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