Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

[JDC]

Got a Sony STR-DE697 with a bad power transformer (1-435-281-11). This will be my second receiver with a bad transformer; the first I was able to find a direct replacement off ebay. With this one, nothing has been found except for an old ebay listing for the sub board itself.

Tried to find a service manual to determine the transformer's specs but to no avail. Tried similar models with the same model transformer but no go.

So....

1) How does one determine a transformer's specs (input, output) if there is no information about it available? Are there clues on the board itself?

2) Is this one of those "Don't waste your time, kid." moments?

I appreciate any and all responses.

[petehall347]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

standby transfor is it ?
9v after rectification ... i am not very good at working out the AC. will be less than 9v is all i know .

[R_J]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

2 seconds on google & I have the service manual, A transformer with 6.3vac will give you the 9vdc you need. It is likely there is a primary thermal fuse that is open.

[JDC]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

2 seconds on google & I have the service manual, A transformer with 6.3vac will give you the 9vdc you need. It is likely there is a primary thermal fuse that is open.

I must have mixed up this model with another one I'm fooling around with. No wonder I couldn't find the manual. Thanks.

Can you (or anyone else) recommend a replacement transformer? Would this be appropriate?

https://www.ebay.com/itm/PHILMORE-TR...MAAOSwjrFb-Yzg

[Khron]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

How did you determine the transformer is bad, though?

[JDC]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

How did you determine the transformer is bad, though?

No relay click or standby light was my first clue. Relay tested fine.

Primary side of transformer has 3 poles, measured OL on all of them. I know this isn't the best way to test these things but it's good enough for me.

Even if I'm wrong, I'd like to learn how to tell what is needed for a replacement if a direct replacement isn't available. I'm missing something simple, I just know it.

For those of you following along at home, attached is the schematic for this stereo.

[momaka]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

Primary side of transformer has 3 poles, measured OL on all of them. I know this isn't the best way to test these things but it's good enough for me.

Even if I'm wrong, I'd like to learn how to tell what is needed for a replacement if a direct replacement isn't available. I'm missing something simple, I just know it.

Well, given that it is used for standby function, it probably doesn't have to output a whole lot of power. So likely you'll just have to find a 6.5V VAC transformer (since you want to get 9V DC) capable of probably at least 200-300 mA to be on the safe side. If space allows, maybe get one capable of at least 500 mA to be safer. Actually, on that note, the output current on the new transformer may not always be mentioned. Instead, you may just see a voltage and VA (Volt-Amps) rating. For the volts, make sure to get one that also matches your primary-side requirements - i.e. 115V if you're in North America or any place with 115V AC lines, and 230V if you're in Europe and most of Asia and Africa. As for the VA rating: that's basically a power rating. In simple terms, it's similar to Watts, but basically a bit more "inflated". So if the transformer is rated for let's say 6V output and 9 VA, the expected maximum output current possible should be somewhat less than 9 VA / 6V = 1.5 Amps (it can vary, based on how inductive or capacitative the load is.)

All that aside, before you even go looking for a replacement original transformer, try seeing if you can fix the old one. Sometimes, these line AC transformers will have a thermal fuse inside. If you remove/break away some of the plastic tape and cover over the blue side, you may find a square box fuse in there. If you do, check it. If it's open, try replacing it with same or slightly lower-rated fuse and see if traffo works again.

[stj]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

also look where the windings are wrapped and soldered to the pins - they can break there because it's a weakpoint.

[JDC]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

Well, given that it is used for standby function, it probably doesn't have to output a whole lot of power. So likely you'll just have to find a 6.5V VAC transformer (since you want to get 9V DC) capable of probably at least 200-300 mA to be on the safe side. If space allows, maybe get one capable of at least 500 mA to be safer. Actually, on that note, the output current on the new transformer may not always be mentioned. Instead, you may just see a voltage and VA (Volt-Amps) rating. For the volts, make sure to get one that also matches your primary-side requirements - i.e. 115V if you're in North America or any place with 115V AC lines, and 230V if you're in Europe and most of Asia and Africa. As for the VA rating: that's basically a power rating. In simple terms, it's similar to Watts, but basically a bit more "inflated". So if the transformer is rated for let's say 6V output and 9 VA, the expected maximum output current possible should be somewhat less than 9 VA / 6V = 1.5 Amps (it can vary, based on how inductive or capacitative the load is.)

All that aside, before you even go looking for a replacement original transformer, try seeing if you can fix the old one. Sometimes, these line AC transformers will have a thermal fuse inside. If you remove/break away some of the plastic tape and cover over the blue side, you may find a square box fuse in there. If you do, check it. If it's open, try replacing it with same or slightly lower-rated fuse and see if traffo works again.

Thank you for this info. It helps.

I ended up buying this: https://www.ebay.com/itm/PHILMORE-TR...72.m2749.l2649

Attached is a picture of it. Used the two black for the primary, one red and one green for the secondary. Did I do that right? Tested by itself, output is around 8VAC. Too high? I can see why this should have worked but it didn't!

On a related note, I'm willing pay someone what I can to help me with this. I realize this is a public forum and posts are for everyone's benefit, but if I have to sweeten to pot (so to speak) to increase motivation, I'm willing to. I don't care to sell this thing nor keep it. I just want to learn. If interested, PM me.

I'm thankful for everyone's help so far.

[R_J]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

Yes you did it right, the a/c voltage may read a bit higher without any load, once installed it should be ok and the dc voltage should be close to the 9v required.

[JDC]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

I'm still not getting 9V standby though. Obviously I missed something. I'll keep digging. Thanks for the confirmation, RJ!

[Khron]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

Is C950 (3300u / 16v) ok? Still no 9V standby even with the digital board disconnected?

[R_J]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

Like khron said, disconnect CNP903 going to the digital board, If C950 is bad as in open, you should still get some standby voltage, check that there is not a short across C950.

[JDC]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

SUCCESS! The cap was fine. Apparently a ribbon cable worked itself loose from the a board (digital board?). I started at the power button and worked my way back and there it was. She turns on now. Man, that was fun! Thank you all for the help!

But i'm still in the dark about how 9VDC can come from 6.3VAC. If there is a link I can read, please post it. I realize I don't know everything I should but I learned a lot about transformers with this one.

[stj]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

6.3v is the average of the sinewave,
when you convert it to dc and use a capacitor to hold the voltage up during the low points in the wave, you get peak voltage.

peak voltage is roughly the ac voltage x1.4
keep that in mind if you work on rectified mains!!

[stj]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

https://www.youtube.com/watch?v=n2iPFZWe7uk
the Iranian master will explain

[momaka]

Re: Sony STR-DE697 - Bad Transformer. Replacement? Unknown Value!

Congrats on the repair!