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Proton AM-300

Stereo Integrated Amplifier (1987)

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Proton AM-300


Power output: 30 watts per channel into 8Ω (stereo)

Frequency response: 20Hz to 20kHz

Total harmonic distortion: 0.02%

Damping factor: 90

Input sensitivity: 0.2mV (MC), 2.5mV (MM), 150mV (line)

Signal to noise ratio: 75dB (MC), 90dB (MM), 100dB (line)

Output: 150mV (line)

Speaker load impedance: 4Ω to 16Ω

Dimensions: 420 x 75 x 288mm

Weight: 7kg

Year: 1987



haraldduell's picture

re: AM-300

Yes, I found the two small bulbs, now to figure their value to find replacements. Can anyone read the schematic?
Cheers, Harald

re: AM-300

Have you figured what size bulbs they are? I have one bulb working, but it is very dim. If I shine a flashlight in the holes where the bulbs go, you can see the display. It seems to work as far as selection of components, and increasing, and decreasing volume. I wonder if it would be possible to replace the bulbs with LEDs. Anyone have any ideas?

I guess you could clip the bulbs, and get a voltage reading on the circuit to determine the amount of voltage to the circuit. The schematic only shows 3 bulbs, but we need a parts list to determine size.

Anyone have any ideas?

re: AM-300

Has anyone replaced the LCD display light in a Proton AM300?

re: AM-300

I did it twice on my unit years ago. Pulling my HiFi out of storage with renewed interest and will have to do this a third time.
I will take a VoltMeter reading and use LEDs this time.
Originally I had clipped a bulb out and went to an electronics store to pick a similar one.

Late evening edit:
Just measured the voltage to the power-ON bulb to ~8.5V. It is the same for the two LCD backlight bulbs: all 8V each.

For kicks, I tried using a 3V tiny LED I had, just to see if it would drive it and yes, it did, but for a short period until it burnt. One could use a resistor in line with the LED but I'm not a fan of resistor heat dissipation.

These will be a suitable replacement:

Second edit
I'm confirming LED swaps work fine. beware though: in their wisdom and because it doesn't really matter for the original incandescent lights, Proton didn't observe the normal polarity colour coding. It's totally random: the AMP LCD backlights were different from one another and the AD-300 tapedeck were both reversed. So, check polarity before soldering!

I replaced the AMP's power and backlights and only the tapedeck backlights, leaving it's working power-ON lamp intact (until next time).

After 20 years, this thing still sounds as awesome as it did back then.

haraldduell's picture

re: AM-300

Sorry to say I have not, but mine does not light up. Any idea where to look for the problem? Kind regards, Harald

re: AM-300

I've read there are 2 bulbs behind screen, so you should access them by opening the unit and removing face plate.
BTW, I have one too and think it's a really good sounding unit w/ a full bodied sound and powerful bass.

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