Old Sony MHC 1600 display problems

SDWE61988

Member
2013-03-16 5:50 pm
Hello,

I have an old sony MHC 1600 stereo system that seems to be working fine with the exception of the Display on the main componet assy. Does anyone know where I could find a service manual? I know it is an old obsolete system, but I would like to fix it, if it something simple.

Thanks,
 

SDWE61988

Member
2013-03-16 5:50 pm
Thank you. I will have to open it up this week and see if I can verify the filament. The display does light up faintly after about 15 minutes of operation. I suspected it was the problem. It is probably impossible to find a replacement new. Is there some boneyard somewhere for old audio/video systems (like a junk yard for cars or planes) on-line or otherwise that might have something like that?
 

MarkF

Member
2013-12-04 12:46 pm
I have had with two MHC-1600 this problems with the same cause: The display-IC needs 32V which is made with a Villarde-cascade from 20V AC. C278 - 47u/50V - is the first cap in this cascade. It was defective on both motherboards. Bacuse the voltage across the cap is around 53V a 50V-type is "programmed" to fail, so for replacement a 63V-type is recommended.
 

BarryMa

Member
2022-03-20 2:43 am
I have had with two MHC-1600 this problems with the same cause: The display-IC needs 32V which is made with a Villarde-cascade from 20V AC. C278 - 47u/50V - is the first cap in this cascade. It was defective on both motherboards. Bacuse the voltage across the cap is around 53V a 50V-type is "programmed" to fail, so for replacement a 63V-type is recommended.
I just wanted to say Thank You for posting this so long ago. My MHC1600 also had a failing display and finally got retired in 2019. I finally got around to taking the plunge today and swapped out the two 47 uF caps on the Main Board (c278 and c279) with fresh 60 V versions and it worked!

Despite best efforts, I still managed to rip the circuit board traces for C278 on both sides, so had to resort to a bodge wire to the power source and soldering to the diode on the other side. It might have been better if I had tried clipping the old wires on the component side and soldering to them instead I guess.

The old bad caps showed none of the usual electrolytic problems of leaks or bulges, but my meter confirmed they were useless.