Battery charger, no output

[Simon_a_s]

Repairing a 60V battery charger for an electric scooter[/img]. Circuit board is called "JYHK 34" and "JY-PCB-0012 v1.10". Found that a SCR (BT151) was blown. It measures ~100 ohms between gate and cathode. Anode, cathode junction is open. Measured 62 volts at the capacitor connected to the positive leg of the output so it appears to function ok till that point. The SCR is connected between the negative lead at the capacitor and the negative output lead.

Replaced the SCR with a new one but it's still dead. There doesn't seem to be a trigger signal at the SCR gate. The Q6 PNP is fine. Traced the gate lead to a component I can't identify. There's no diode junction, infinite resistance if you measure over it with a DMM. I first thought it was a zener but it doesn't got a polarity marking. The markings on the PCB are "DZ1" and a there's a TVS diode (?) symbol. The presumed diode is marked "BP 3 D" - unknown in which order.

Made a simplified circuit diagram (see attachment). What's this diode? What can I replace it with. I'm by no means an electronics expert and I don't understand fully what this <diode> is supposed to do.

[RoGeorge]

Most probably it's a diac, often used to open a thyristor or a triac.
https://en.wikipedia.org/wiki/DIAC

[Simon_a_s]

Thanks! Found a DIAC called DB3. Might be the correct component.