The controls are clean, the sound quality is good.........but after 15 minutes the left channel starts making a light background hum that stays constant regardless of the music source. It always starts about 15 minutes after I power it on. Could it be bad caps, or a bad transformer?
Left channel hum on Fisher PH-492
- Thread starter Reli
- Start date
Hi Reli, thanks for your contributions on wiki boombox. I sold a PH-490 a few years back and wish I hadn`t. That said , a visual inspection of capacitors : If the top of the capacitor is bulging, it`s bad. No point to point testing required.
Examining the 15 minute time frame, when the hum occurs have you tried placing your finger over various solder connections on the main board? Stay away from the transformer, where the leads are 12 volts and beyond it`s quite safe . Placing your finger will give various tones, left speaker, right, etc. Slight pressure on caps and others may reveal a cold solder joint that needs to be resoldered.
Good luck and report back with your findings.
Examining the 15 minute time frame, when the hum occurs have you tried placing your finger over various solder connections on the main board? Stay away from the transformer, where the leads are 12 volts and beyond it`s quite safe . Placing your finger will give various tones, left speaker, right, etc. Slight pressure on caps and others may reveal a cold solder joint that needs to be resoldered.
Good luck and report back with your findings.
That 15 min time frame also might have to do with some component heating up also. I hope not!
With a laser thermometer check identical components on both channels to see if there is any temperature difference.
Just a thought!
With a laser thermometer check identical components on both channels to see if there is any temperature difference.
Just a thought!
Can you report back your findings? Interesting approach, old school always used fingers to find. Lasonic, and many discolites were notorious for cold solder joints.
Thanks guys, I'll check it out but it's gonna be awhile since I have too many projects going on at the moment
I have to agree on that my cousin has one and it is more crispy and base deeper and louder.