So, following the death of my ancient FAL Phase 44 amplifier, I found a series of very cheap amplifiers on eBay. They’re all based around something called a “Class-T” amplifier IC which seems to be an all in one IC that just needs hooking up to some inputs, speakers and electricity to work.
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Sometime last year my old Kenwood hifi amp stopped working due to the speaker cutout relays not working. The speakers would never switch on, making for a fairly useless amplifier.
While my cousin was sorting out his mess before moving to the US he found this old “FAL” brand amplifier. A spot of Googling reveals this was made by a company called “Futuristic Audio Limited” who also seem to make guitar amps. He didn’t want it, I needed an amp, so it came home with me.
Due to its age I noticed quite a lot of noise when trying to adjust the volume so decided today to take it apart and attempt to clean the insides out. I also bought some switch cleaner to spray in the potentiometers.
Unfortunately I think cleaning the contacts on the potentiometers and switches might have messed the electrical characteristics of the amp up. Since this isn’t an IC based amp, I have a feeling there’s a fine balance between the components that makes the thing work, and squirting a load of switch cleaner into things has altered this. When I power the amp up, only the left channel works and the volume goes really loud then distorts – all by itself, without me moving the volume knob. I’ll leave it for a few hours to see if the cleaner evaporates off. It’s no great loss if it is broken, the reason I took it apart was because the sound wasn’t correct and the volume kept wandering between left and right speakers, so maybe it’s finally packed in.
Looking at the electronics inside, part of me wonders if it’s repairable.
I’ve an old Kenwood amplifier that used to be in my front room, doing sound for my (now missing) Xbox 360 and other consoles, etc. After coming home from a trip out over New Year I discovered the amp wasn’t working.
I proceeded to take out the relays that isolate the speakers and dismantle them to see if anything was burnt out or corroded. They worked fine so I abandoned the project out of boredom.
Tonight I put the whole lot back together, soldering in the relays and… it all works! I have no idea what I’ve done, but it seems taking everything apart and resoldering the relays has repaired the fault. This is good, I can now play music with decent speakers in my office 🙂
Oh yeah, and if you’re now the proud owner of a stolen Packard Bell laptop, I hope you enjoy it. It overheats, is slow as crap and contains no battery. As to the work laptop it’s totally unsellable due to being security marked, and you won’t be able to use it without re-installing something. And you left my car despite obviously seeing my car keys, you dozy bastards.
After many years of faithful service, my Kenwood A/V amp has ceased to function. When turned on the display lights up, the inputs can be selected, the remote control works and that’s about it, it doesn’t make any sound. This is a fairly important feature for an amplifier.
I noticed that usually there’s a click from a relay when the system is fully powered up. This doesn’t happen any more.
Being of a technical and slightly curious mind I set about seeing what was wrong. I took the lid off and immediately realised a major thing; the amp is not designed to be dismantled without a fight as a tin full of 30 screws is evidence of. It also contains some irritating ribbon cable that seems soldered rather than in a neat plug.
Using a combination of a hot soldering iron, desoldering braid, a bit of brute force and a screwdriver I successfully removed the two relays. They’re 24vdc/120vac components with removable plastic lids. It took two PP3 batteries clipped together with a 4xAA battery case for some extra voltage to make the relays energise. This proves they’re not faulty.
Hmm… maybe the burnt looking bits of circuit board are important then. Why do I have a nasty feeling one of the high power transistors has died taking out a few other components with it?
Everything is nicely removable and there’s no surface mount stuff on this part of the board at all. It’s repairable, if someone could install the service manual in my brain.
Well at least if I can’t fix it I have a source of interesting parts to use in something else.