Issue with power supply (intermittent)

Hello,
I'm wondering if anyone can assist. My power supply is a 16vac 1250ma 'wall wart' / 'power pack'.
After completing the Power Supply section of the instructions and testing the voltage pads with my multimeter, all values were correct (+5v, +15v, -15v) I moved on to the noise section and all was fine when measuring the IC voltage before soldering it in.

When the time came to measure the voltage before soldering in the IC on the Accent section, I noticed the voltage readings were all over the place bouncing from low 0.x values through to Overload. I assumed something went wrong when installing the Accent section, so worked my way backwards, first separating the main board from the power supply and testing the pads again. The voltage issue was still present. So I then went and measured wall wart directly (one pin inside the barrel and the other outside) and it returned a consistent voltage (although, it does read 18V, not 16V.... but it wasn't bouncing all over the place like it was previously)

Then I had the idea that there was possible interference because I had my soldering iron and the wall wart for the yocto plugged in to the same power strip. When I turned off my soldering iron, I got voltage readings again on the pads. I connected the main board again and got voltage readings on the pads for the Accent section, and proceeded to solder in the IC, assuming that somehow my soldering iron had interfered with it.

The next day I worked on the Bassdrum section and once again when the time came to test the voltage on the IC pads, the voltage readings were all over the place again - this time I'd turned off the soldering iron - so it seems I have a bigger issue.

I dont think the wall wart is the issue because every time I measure it with the multimeter it returns 18V (although, that seems a bit high. Is that the issue here? When I test the circuit it shows ~15V, so the power supply circuit board seems to do its job WHEN it works.) I've attempted to reflow the pins on the power jack - this worked and allowed me to get the IC for the Bassdrum soldered in, but after that when I tested again, the problem was back again.

Does anyone have any ideas what the issue could be here? What other components on the Power supply board should I try to test?

Thanks in advance!
W

Just to follow up, I replaced IC5 (7915) and its working again, although the negative voltage reads -17v... seems a bit high but when testing on the mainboard it is +/-15v...

Seamlessly set up your Vizio home entertainment system at vizio.com/setup
Go to vizio.com/setup for quick activation and device registration.
Set up Vizio SmartCast devices easily at vizio.com/setup
Enjoy hassle-free setup for your Vizio TV at vizio.com/setup
Set up your Vizio Smart TV or soundbar easily at vizio.com/setup.

Visit vizio.com/setup to quickly connect your Vizio Smart TV or soundbar. Follow guided instructions to register your device and enjoy endless streaming.
At vizio.com/setup, you can set up, activate, and personalize your Vizio Smart TV or soundbar. Unlock access to apps, streaming services, and smart features.
Easily configure your Vizio entertainment system at vizio.com/setup. From Wi-Fi connection to app activation, complete your setup in just a few clicks.
vizio.com/setup helps you get your Smart TV or soundbar ready for use. Start enjoying your favorite shows, apps, and movies with a seamless setup process.
Go to vizio.com/setup to register and activate your device. Whether it’s a TV or soundbar, enjoy fast setup and premium entertainment at home.

Set up your Vizio SmartCast TV or soundbar online at vizio.com/setup. Connect, register, and begin streaming with smart features designed for you.
Activate and enjoy your Vizio Smart TV at vizio.com/setup.
vizio.com/setup – the easiest way to connect your Smart TV or soundbar.
Start streaming in minutes by setting up your Vizio device at vizio.com/setup.
Visit vizio.com/setup to unlock apps and features on your Vizio TV.

Step-by-step guide to restore your Vizio TV at vizio.com/setup to factory defaults for smooth performance.
Troubleshoot at vizio.com/setup why your Vizio Smart TV won’t turn on with quick fixes, expert tips, and simple steps to get it working again.
Easily activate your Vizio Smart TV with vizio.com/setup. Connect to Wi-Fi, register your device, and start enjoying smart apps and entertainment instantly.
Visit vizio.com/setup to personalize and configure your Vizio device. Whether it’s a Smart TV or soundbar, you’ll be ready to stream in just minutes.
Make your Vizio setup simple at vizio.com/setup. Whether connecting a TV or soundbar, follow the quick guide to start streaming right away.

vizio.com/setup provides a quick way to set up and register your device. Activate your SmartCast TV or soundbar and access built-in apps, movies, and shows.
Go to vizio.com/setup to easily connect and activate your Vizio Smart TV or soundbar. Complete setup in just a few steps and enjoy unlimited streaming.
Set up your Vizio entertainment system online at vizio.com/setup. From Wi-Fi connection to SmartCast activation, everything is made simple and hassle-free.
vizio.com/setup helps you link your TV to Wi-Fi and streaming apps instantly.
Visit vizio.com/setup to unlock apps and features on your Vizio TV.

bitdefender central is your all-in-one platform to manage devices, activate subscriptions, and ensure complete online protection with ease.
Secure your digital life with bitdefender central – manage security, track devices, and protect your data anytime, anywhere.
bitdefender central helps you control your cybersecurity, monitor threats, and safeguard your devices in one simple dashboard.
Easily manage your Bitdefender account, protect your devices, and keep your family safe online with bitdefender central.
Stay in control of your online safety – bitdefender central lets you manage licenses, monitor security, and track your devices.

Access, monitor, and secure all your devices from one place with bitdefender central advanced security dashboard.
With bitdefender central, you can manage subscriptions, track lost devices, and ensure your family stays protected online.
bitdefender central is a secure hub to update, control, and protect your devices against cyber threats in real time.
Simplify your digital safety—bitdefender central lets you manage security settings and monitor threats from anywhere.
Protect what matters most with bitdefender central centralized dashboard for device safety, account management, and parental control.

bitdefender central helps you stay ahead of cyber threats with easy-to-use tools for monitoring, control, and online safety.
bitdefender central is your secure portal to manage antivirus protection, monitor devices, and keep your data safe.
Stay protected with bitdefender central, the hub for all your security updates, alerts, and account management.
bitdefender central allows you to activate licenses, control devices, and safeguard your digital world in one place.
Manage your online security with bitdefender central intuitive dashboard and advanced protection features.