Affordable, Quality Audio Repairs & Restorations

Phone: 519-513-1084

Email: repairs@dnaelectronics.ca

Address: 15 Shaftsbury Dr. Kitchener, ON, Canada

Quality, Reliable Restorations by Experienced Father & Son Technicians. We Take Pride in our Workmanship.

Receivers | Power Amplifiers | Integrated Amplifiers | Preamplifiers | Tuners

D 'n A Topics & Resources

Restoration Information

General information about our restoration work, and pricing information for various models.

Audio Specifications Database

We are compiling a database of audio equipment specifications gleaned from our annual equipment directory magazines, owner's manuals, service manuals, etc.

Audio Picture Gallery

Pictures of some of the equipment we've worked on, with occasional commentary.

Our Testing Procedures

We test the audio components we restore to ensure they perform at least as well as expected. This is both an overview of our measuring procedures, and an attempt to make clear exactly what is being measured.

FAQ

Answers to some frequently asked questions.

Philips 578 Gallery

Pictures of a Philips 578 power amp (sometimes listed as an AH578 or 22AH578). You can check out the specs here.

When vintage audio equipment is being discussed, Philips is not a name that comes up often. However, the 578 is a pretty decent amp.

If you have a Philps 578 amplifier that is in need of repair, call us at (519)513-1084, or email your enquiry to repairs@dnaelectronics.ca.

The Philips 578 has a rather heavy power transformer. Each channel has separate bridge rectifiers and two 15000 uF main filter cans, but there is only a single main winding shared by both channels. That's okay, though; Given the weight of the transformer, I'm guessing the secondary is pretty stiff. The rails are ±78 volts.

This amp has a soft-start circuit. It is the usual setup: A power resistor that is shunted out of the circuit by a relay. It also has a main power relay that trips when you touch the power switch on the front panel. And speaker protection relays (there is no delay). An amusing amount of clicking occurs immediately after you touch the power switch.

This capacitor was never soldered before the amp left the factory (inside red circle).

An unrestored driver board. There are two of these boards.

Testing a driver board before installing it in the amp. In the picture is our trusty Heathkit 'scope. A vintage relic in it's own right, it is more than adequate for diagnostic purposes.

There are 8 output transistors per channel in a quasi-complementary arrangement (all output transistors are NPN).

The Philips 578 has soft-touch controls. I'm not a fan of these, but they worked flawlessly. There is a manual power switch on the back panel that disconnects the AC. The soft-touch power switch on the front panel requires a standby power supply that is always on, so long as the manual switch on the back panel is closed.

The 578 has power, meter sensitivity, subsonic filter, and speaker selector switches on the front panel, as well as level controls.