Anyone know what this likely to be it hums quiet loudly it gets louder as you turn it up . Guessing it maybe capacitors but hoping to get some advice from someone that knows this boombox as I know it has a reputation for being difficult to work on .Thanks
Hi, audionut . Welcome to Stereo2Go. From your “North Yorkshire” location, I assume you’re living somewhere in the UK. No, I’ve never handled, much less owned a Sanyo M-9998, whatever the version (“-K” or otherwise). And, no, I’m no repairer either. (I had “lead balloon” success trying to fix the completely jammed, non-functioning cassette-deck mechanism of my Aiwa CS-600U, a smaller, decidedly less fancy, presumably less coveted portable stereo than a Sanyo M-9998.) Fear not, though: someone here with experience in handling (and even fixing) a Sanyo system a lot bigger and fancier than my M-1770K should weigh in on how to open up, troubleshoot and repair the audio circuitry of your sizeable, doubtlessly complex sound system. Those experienced ones should reply to you before too long. (Incidentally, my recently purchased Sansui CP-99W also has a noticeable hum for several seconds when it’s turned on, perhaps for the first time in a while. It more unhappily has no audio at all in any mode – TAPE, TUNER, LINE IN, etc. – and its cassette decks have PLAYBACK that’s way too fast. I sent it off to a repair firm a ways away from here. Hope they’re good with my most powerful unit …) I hope I haven’t bored or bugged anyone with my “two cents” input that doesn’t directly address your problem. I do hope that you succeed in fixing the “loud hum” issue with your Sanyo. That late-Seventies sound system was – or almost was – the pinnacle of portable audio refinement. Have a good day.
Well this is Walkman land these days to be honest. Humming can be as simple as it needing the switches cleaned so that’s always the best place to start
Notoriously hard to work on these units are as they're filled to the brim with their components. Any luck with the fix?
I'm not going to be much help since I've been struggling with my own M9998. I can only offer some ideas. Hopefully the real experts will offer their expertise. Have you had it apart yet? If not, you have to be extremely organized when working on this model. The case is just crammed with stuff, and in an apparently somewhat ad-hoc fashion. Take lots of photos, label things, keep detailed notes. Read through my recent thread about mine. When reassembling, note the tricky lever that will prevent Record from engaging, and note the Record lever will not fully depress unless there is a writable cassette loaded. There are also some tricky spring-loaded levers on the AMSS board. Consider buying a service manual if you get bogged down. Do a search for repair stories here and in Stereo2go. Does the hum show up in all of the AM, FM and tape modes? And do you get any sound besides the hum? How about with earphones or through the external speaker connections?
