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|28th July 2019, 07:11 PM||#1|
Join Date: May 2010
SONY HCD-H5900 Fault finding help
Hi friends need a little of help here. I'm lost
Me & my brother own a Sony MHC5900 system, only difference mine was purchased a couple of months later.
One time my brothers CD unit developed a fault in the sled switch which I repaired cleaning it sucessfully.
We've done some improvements in the house (floor and painting) and in my old brother's bedroom I installed an office where I have my computer desk and so I took the opportunity to put my system in use again which was sitting gathering dust connecting it to the computer. Tossed my cheap computer speakers also.
I Cleaned the dust, the acrylic fronts & VFD's also developed a kind if black fume which I also cleaned and fitted new belts and pich rollers on the Cassette mechanisms and lubed all the gears and it works now like new.
My brother saw it and asked me if I could make the same to his system and I took the challenge.
Uppon powering / testing his system I noticed the Tuner / CD unit wasn't working again, only the display was changing according to key presses, so I took the cover off and saw a black stain on the upper side of the PCB.
I cleaned the stain and it seems that some capacitor leaked and corroded some tracks. Measured, cleaned, restored a few open tracks, and got the tuner working. The CD transport seemed dead except it would close the door when opened, but didn't react to the eject button, no laser movement and no spin. Voltages are there but no communication perhaps.
That leaking did some serious damage ...and I can't peek under the IC's.
Now it was a time for changing parts beetween units and found out that the mainboard is faulty since the CD transport works fine on my system as the front display panel and the PSU. By the way the PSU primary winding couples to a secondary winding on the DSP pre-amp. The board says AC on those pins and I was tempted to connect it to the mains when I saw the schematics... So in order for the CD to work, it must be connected to the pre-amp with a 20 or 30cm ribbon cable. Thank You Sony for this long cables and also for the long flatcables !!
Went to the internet and found a greek site which had board for 40 bucks advertised 100% tested and so I ordered it. Before You start to throwing flames at me, I'm aware of the risks...and it is nearly impossible to get it new. Installed the new board connected all together and indead the CD plays, the Tuner tunes, Keys and display are working, but, there is always a but ... I get no audio on the right channel nor for CD nor for the Tuner.
I can confirm it is the right channel by headphones, speakers and touching the pins on the board connector pins unpowered.
So all labelling on the board seem correct. It is indead the right channel.
As there are no components between the system control connector and the switch IC102 and as the control signal is common to both channels and as it also contols the Tuner switching, I'm suspecting of it. I have continuity between the system connector pins and the Switch IC pins. So no broken tracks between IC and connector.
With the board disconnected, on my Fluke DVM measuring resistance between output pin R & Ground I get near 100K reading (there are two 100k resistors connected to ground at the output) and it makes sense, since the switch schould be open without power.
Now the strange thing... measuring resistance between output pin L & Ground I get near 6-7K reading.
First I thought here lies the problem, but wait... this is the correct working channel. I've double-checked !!
I'm aware of the loops between the sides of the IC. Left side controls Tuner, right side controls CD. Switching voltages are there because it switches correct between Tuner & CD... and I can't break the loop on this channel since the track is under the IC.
As the Tuner is working / switching on the original (CD faulty board) I am tempted to transplant the switch IC to the new board but the readings make no sense. On the original board I get 100K readings on both channels, but there is audio on both channels as far as the Tuner concerns, since I can't test the CD part.
I could remove the IC and hardwire pin positions for testing...
So, I'm a bit lost and would like to have some advice how to proceed before destroying both IC's.
|4th August 2019, 06:52 PM||#2|
Join Date: May 2010
As suspected the switch TC9215 IC was faulty.
I ordered two new ones from Liitlediode two weeks ago as I can only find the DIP version, but still waiting.
Today I was tired of waiting and as I will toss the original corroded board anyway I gave it a try and removed the IC from it and transplanted it to the other board which I bought faulty with only one channel working and it came into life. First I've measured the tracks for continuity based on the schematic and I've also took the opportunity to make a new larger and thicker heatsink for the two regulators as the original got a bit hot for my taste. Idling now at 40-45º when cd is playing. Ambient temp is 25º.
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