Sony CMT-SPZ90DB HiFi PSU Problem?

[Nevillet]

Hi All,

I'm trying to repair a Sony CMT-SPZ90DB compact HiFi that includes a 3-disk CD, cassette & tuner.

When it's plugged into power the red LED illuminates but when the Standby1/0 button is pressed it briefly starts up with CD & cassette motors starting but then goes back into standby.

The power board shows signs of heat and a picture is included as is the service manual.
I've been doing a quick check of a some componants in the PS board and came across D602 which is open circuit.
Off the board it's still reads o/c.
The diode is marked T2D64.
Can anyone help me identify this diode and find a suitable replacement?
Many thanks.

[R_J]

Re: Sony CMT-SPZ90DB HiFi PSU Problem?

D602 is not your problem, the diode will check open as it is a zener diode and a regular diode junction connected common cathode. Replace C604 and C25 and see if that helps
Then check your standby 4V and see if it stays up or drops when you turn on the unit, if it drops, change C654 if it is ok, check the 16v and 28v If they drop change the output caps like C31,C32

[Nevillet]

Re: Sony CMT-SPZ90DB HiFi PSU Problem?

Thanks so much for your help. I'll get back to it tomorrow and report back.

[Nevillet]

Re: Sony CMT-SPZ90DB HiFi PSU Problem?

I swapped C604, C25 & C654.

Their measurements off the board is below:



The 4V rail measured at CN604 (pin2) is 3.931V an it doesn't change when the power button is pressed.

[R_J]

Re: Sony CMT-SPZ90DB HiFi PSU Problem?

ok, so the standby voltage seems to be ok, what about the 16v and 28v do they come up? It could be that the power supply will not stay powered up OR there could be a heavy load on the 16 or 28v lines, possibly a shorted output ic?

[Nevillet]

Re: Sony CMT-SPZ90DB HiFi PSU Problem?

The 16 & 28V rails are stable and have minimal movement when the power button is pushed.

[R_J]

Re: Sony CMT-SPZ90DB HiFi PSU Problem?

Then the power supply is likely ok and the fault is somewhere else, I would suspect the audio output ic could be shutting things down, Check the voltages on Q701 protect detect.
Did you do the cold reset? have you tried the test modes, (page 10)

[Nevillet]

Re: Sony CMT-SPZ90DB HiFi PSU Problem?

Hi all,

Just to report back on this one.
When the unit is powered up it goes through an initialisation sequence that first checks the CD player for disks in the 3 trays.
It then spins up the cassette deck, moves the heads in and out except they didn't and I noticed that two belts in the cassette deck were very slack so I replaced them.
After that the machine started working correctly...