Marantz 2225 Repair Part 2 - Intermittent Sound Cutoff

This is a common issue for an amplifier/receiver with a differential front circuit. Based on my past experiences, the intermittent sound cutoff mainly caused by the unmatched differential transistors. It occurs when the aging transistors develop flaws over time as they are used. These unmatched transistors cause the DC offset drifting and activate the speaker relay due to the undesirable condition of amplifier operation. I hope this video will be helpful to other DIY fans dealing with this type of intermittent sound cutoff issue.

[@lawchoongseng789]

Great to have amplifier schematics. To make troubleshooting easier.
Some brands don’t publish.
Making repair more challenging.

[@VintageAudioFan]

I fully agree with your comments. Also there were some products had made with several versions. Same model name/number but have different parts and configurations on PCB (i.e. HK 330, Hafler's DH-500..etc.). I have dealt with this type of problem (Accuphase P-300L) before. Fortunately, I used other similar products to figure it out the schematics and got it fixed.

[@josegil8395]

Soy fanático a estos aparatos hermosos. Pero soy muy pobre quisiera tener uno de esos. Donado por alguien de buen corazón.. Para cuidarlo y mimar lo como un bebe.. Me fascina mucho la música... Tengo 60 años.. Vivo en una vereda de Pereira... 🙏

[@3lullabies]

I inherited my dad's 2225 and I remember back when I was a kid, it would cut off if it was turned up too loud. Is that
by design I wonder?

[@VintageAudioFan]

There is a protection circuit designed to protect the speakers in Marantz 2225. It will cut off the speaker connections when it is overloaded at output of the amplifier section.