Sony Microcassette M330 overheating - UK Vintage Radio Repair and Restoration Discussion Forum

IanNVJ35 · 17th Jan 2023, 6:39 pm

I am having a go at fixing this little machine for an older lady who wishes to play her old micro-cassette collection.

I somehow feel it's a bit beyond me as it's all surface mount and no manual but I have the fault of seemingly no operation, so I tried on my bench PSU. I see that the Voltage (3) is dragged down to around 2 at 500mA limit with the power amp IC getting hot.

Nothing operates nor does the motor turn.

It's this one. https://www.nisshinbo-microdevices.c.../NJM2073_E.pdf

I checked if it was short internally - it isn't. I checked if the output was shorted - again, it isn't. There was some heavy brown flux on the trace side of the PCB around many of the solder joints which I cleaned off leaving an odd remnant of white gummy stains. I'm wondering if components may have been damaged by this.

Thanks for any ideas. If I can't fix it I will just return to her but I want to try.

ben · 21st Jan 2023, 12:42 am

The problem is likely very near the power input. Short in a dc socket? Probably simpler to pick up another one online, they're cheap enough.

knobtwiddler · 21st Jan 2023, 12:02 pm

Does it contain tants or types of caps that can fail short circuit?

MLCCs, especially SMT types, can fail this way.

G6ONEDave · 21st Jan 2023, 12:26 pm

I have the paper service manual for this model that I could scan and email to you. If it's of any help PM me with your email and I'll get it scanned in the next couple of days.

Dave

IanNVJ35 · 21st Jan 2023, 1:10 pm

Thanks for the input. I checked for tants but only a few electrolytic ones which read OK.

I'm actually running from the battery supply with flying leads. This evening I will lift the DC input leg on the amp - see if that helps.

Dave, the service manual would be appreciated. I'll pm you.

Yes I thought straight away of suggesting a working replacement but I'd at least like to try. I'm interested in what could be wrong.

17th Jan 2023, 6:39 pm	#1
IanNVJ35 Heptode Join Date: Mar 2010 Location: Hemel Hempstead, Hertfordshire, UK. Posts: 813	Sony Microcassette M330 overheating I am having a go at fixing this little machine for an older lady who wishes to play her old micro-cassette collection. I somehow feel it's a bit beyond me as it's all surface mount and no manual but I have the fault of seemingly no operation, so I tried on my bench PSU. I see that the Voltage (3) is dragged down to around 2 at 500mA limit with the power amp IC getting hot. Nothing operates nor does the motor turn. It's this one. https://www.nisshinbo-microdevices.c.../NJM2073_E.pdf I checked if it was short internally - it isn't. I checked if the output was shorted - again, it isn't. There was some heavy brown flux on the trace side of the PCB around many of the solder joints which I cleaned off leaving an odd remnant of white gummy stains. I'm wondering if components may have been damaged by this. Thanks for any ideas. If I can't fix it I will just return to her but I want to try.

21st Jan 2023, 12:42 am	#2
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,095	Re: Sony Microcassette M330 overheating The problem is likely very near the power input. Short in a dc socket? Probably simpler to pick up another one online, they're cheap enough. __________________ Regards, Ben.

21st Jan 2023, 12:02 pm	#3
knobtwiddler Heptode Join Date: Mar 2016 Location: London, UK. Posts: 690	Re: Sony Microcassette M330 overheating Does it contain tants or types of caps that can fail short circuit? MLCCs, especially SMT types, can fail this way.

21st Jan 2023, 12:26 pm	#4
G6ONEDave Octode Join Date: Dec 2019 Location: Owston Ferry, North Lincolnshire, UK. Posts: 1,396	Re: Sony Microcassette M330 overheating I have the paper service manual for this model that I could scan and email to you. If it's of any help PM me with your email and I'll get it scanned in the next couple of days. Dave __________________ Quote "All is hyperthetical, until it isn't!" (President Laura Roslin, Battlestar Galactica)

21st Jan 2023, 1:10 pm	#5
IanNVJ35 Heptode Join Date: Mar 2010 Location: Hemel Hempstead, Hertfordshire, UK. Posts: 813	Re: Sony Microcassette M330 overheating Thanks for the input. I checked for tants but only a few electrolytic ones which read OK. I'm actually running from the battery supply with flying leads. This evening I will lift the DC input leg on the amp - see if that helps. Dave, the service manual would be appreciated. I'll pm you. Yes I thought straight away of suggesting a working replacement but I'd at least like to try. I'm interested in what could be wrong.