Sym proceed - zero cross switch repair (help needed)

[rena]

Hello, I recently bought a second hand zero crossing power distributor that doesn't work.
I traced the schematic but I don't know much about alternating voltage (except for audio and PSU) so I can't make sense of it.
It is centred around a solid state relay and two transistors.
As far as I understand, when switched ON, one transistor turns ON an LED and the other one is supposed to close a relay.
The solid state relay is in charge of the zero crossing.
The LED do turns ON but the relay is no closed.
I tested the relay off circuit and it is working.
I first suspected the transistor so I changed it with a new one but it didn't fix the problem.
At some point (before I receive the new part) I tried with a totally random part number (D2012) and of course it didn't fix the problem but it continuously switched the relay ON and OFF so something was happening at lease.
From my understanding the full circuit is AC powered (?). Doesn't it need some DC at any point ?
I don't want to bother anybody but I would greatly appreciate if someone could explain me this circuit and potentially help me fix it.

*(+),(-),(~) and the solid state relay's terminals.
N = Neutral at input
L = Live at input
N' and L' are the output

[rena]

Pictures of the inside and the circuit itself.

[squadchannel]

maybe this product.
https://ameblo.jp/kawamura-tokei-megane/entry-12468662543.html
https://web.archive.org/web/20150628122842/https://www.symproceed.com/powerconditioner/sp-pz8b.php
Looking at the photos posted on the mentioned blog, there are areas that have been modified in the past.
I think it would be a good idea to restore them to their original state.

You could repair it, but as a last resort, there are products that have a zero-cross circuit built into the SSR. It may be a good idea to replace it.

As an aside, TE is of the opinion that zero-cross switches shorten relay life and generate EMI and RFI. If I were you, I would not consider using them.
https://www.te.com/en/products/relays-and-contactors/relays/intersection/zero-crossover-switching-transformers.html?tab=pgp-story
japanese:
https://www.te.com/ja/products/relays-and-contactors/relays/intersection/zero-crossover-switching-transformers.html?tab=pgp-story

[rena]

Thank you for your message.
Actually everything is in its original state and no parts have been changed.
Any idea what could be the origin of the problem ? The SSR itself ?

[squadchannel]

I have no idea about the circuitry, but the parts used are simple components and I can't see why they don't work. If I had to guess, it would be the SSR, but have you checked its operation by itself? 
In practice, a zero-crossing switch could be achieved by using a diode, a resistor and a capacitor to step down and rectify the voltage, and then inputting the voltage to an SSR.
because the SSR used is a relay that operates at zero crossing.

But after the SSR operates, the circuit has a common mechanical relay operating to bypass the SSR contacts. I don't understand why they are doing this.

Presumably, this product is for audiophiles and was made with a focus on "sound quality".

check to see if the SSR is working properly.

[perieanuo]

datasheet says http://www.solidlink.pl/files_mce/produkty/Przekazniki_plprzewodnikowe/S5_225.pdf the C doesn't have 0-cross.
if 0-cross is the issue, dig into this check ssr directly by opening him with DC 18-28V on +- inputs, you need scope to clarify if opening is synchronic with 0 pass.
br, ovidiu

[fzabkar]

Same datasheet from manufacturer's web site:

https://www.jelsystem.co.jp/en/pdf/s5_e.pdf

ISTM that the circuit is very ugly. It relies on the SSR's 1500 ohm input impedance to generate the required input/control voltage (28V) from the rectified mains via a high-wattage potential divider. Yuk!

  120V x sqrt(2) x 1500 / (2200 + 1500 + 6200 + 200) = 25.2V

Then the same philosophy is applied to derive the correct voltage for the relay coil. Again, Yuk.

BTW, the power LED is drawn with the wrong polarity, as is the 2.2uF 160V capacitor.

The coil resistance for the 24V version of Omron's G4A-1A-E relay is 640 ohms.

https://www.mouser.com/catalog/catalogusd/648/1959.pdf

The voltage appearing across the coil in that circuit, assuming a mains supply of 120Vrms, is given by ...

  Vcoil = 120V x sqrt(2) x 640 / (640 + 15000 / 4) = 24.7V.


I would measure the voltages across the 15K resistors and the relay coil.

[rena]

Thank you everyone !

fzabkar, in  120V x sqrt(2) x 1500 / (2200 + 1500 + 6200 + 200) = 25.2V could you tell me where you find the 2200, 6200 and 200 please ?
I guess it's the 5W resistors for 2200 and 6200 but what about the 200 ?
I'd like to be sure to understand.
Something that I absolutely don't understand is if I'm supposed to find DC or AC voltage. At which point in the circuit is the AC rectified to DC ?

I realized I forgot to check the polarity of the LED when drawing the schematic ! Thank you !

I will check those voltages. I'm supposed to find DC or AC at those points ?

[fzabkar]

Sorry, that should have been 220 ohms, not 200.

AC is rectified to DC by diode D1 and the 33uF capacitor. Those test points are DC.

D1 can't be a 1N5401. That is only rated for 100V.

Also, Q2 is a 2SC2911 which is rated for 160V. That's right on the limit for this application.

[rena]

Thank you !

On D1 and D3 it is written DD401F.
On D2 DD405E.
I assumed it was 1N5401 and 405.

I check those points and found 11.9V across the resistors and 3.2V across the winding.

[fzabkar]

What is the voltage across the 33uF capacitor?

[rena]

I find 46.5V DC

[fzabkar]

I find 46.5V DC

You should be measuring 160V - 170V DC. Perhaps the 33uF capacitor has dried out? That's assuming that the AC input is indeed 120VAC. In fact, 160V is a marginal rating for that capacitor.

It could also be that D1 has become leaky, although that would make the capacitor look like a short.

[rena]

That was it !
Thank you, it is working now.
I feel so silly because I was pretty sure I checked the cap, but it seems I didn't...
I learned a lot and I will read a few things about "high-wattage potential divider".

Thank you all again!