Inter-M PA-9324

I first heard about Inter-M in early 2000. Inter-M is a South Korean corporation. They are well known in the Pro Audio domain. I think I've serviced some Inter-M from MPSI in 09. I cannot recall what they were nevertheless I'm going treat this Inter-M as my first encounter. I expect to see good internal layout and tech friendly connection.

This PA9324 is a mono amp or to be precise, a Public Address amplifier. I noticed how a Public Address (PA) differs to the common Power Amp (PA). If we look at the rear, we see a set of Banana plug meant NOT for a speaker but for external power supply. The speaker(s) is instead plug to the power supply like crimp socket. It indicates voltage between 41V, 70V and 100V. Is this touch safe? Will it shock if I touch? I think I'll pass. Then there's the speaker thing. The speaker isn't like the one we all know. This writer was provided a horn speaker for testing (if it's repaired). The speaker has a rotary switch for the desired option. That's all I know so far. It would be hard to recall those info again when the next PA comes in. Whenever that will be. Hehe. Anyhow,

I can say this PA9324 is also a gymtronics. It weighs like a boulder and a potential back breaker. I felt like I'm carrying teenager yustech up the steps. Most of the weight is from the power transformer. Beefy as it so and there's two of them. One is for mains and the other is an output transformer. Like a tube amp to a limited degree. There's another a small input transformer on the main board. It does differs inside too as much as it is outside.

The unit do not looks not too dirty inside. There's a small amount dry dust at the obvious spot e.g. the fan, the full bridge rectifier and heat sink fins. The user had store it correctly in a cool and dry spot.

The inside layout is modular. Well-spaced for ventilation or to probe around. All wire connection are detachable enabling the power amp block to be pulled out for cleaning. That's good because on top the weight, you don't want to piss the person who is fixing it. Thumbs up Inter-M board engineers for putting much thought about us small time techs outside of your tranquil air-conditioned lab.

The main problem was no power. It blew a fuse. Let me rephrase that. It ruptures and melted the fuse with the fuse holder. There's no way of pulling out the carnage left in there. Dangerous too so both was replaced.

The main filter cap has signs of wear. It was high on my suspect list. In circuit its link to the departed 20A fuse. The cap had an internal short. I never seen a 15000uF capacitor worked to death before. It was replaced together with a semi's.

Before I close the lid, I noticed some test points and trimmer pots. I know it's for some sort of offset bias/idle calibration. The schematic didn't have any notes for that hence I need to search or ask around in forum. Whether I get it or not this amp will exit my door when the time come.

Thank you

yustech