Audio , no video

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By somacast

Resident (34)

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18-05-2021, 15:50

Pencioner wrote:

looks identical to Sanyo Wavy PHC-70FD - which is not a surprise anyway

yup its based on sanyo afaik

By somacast

Resident (34)

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18-05-2021, 15:52

Alexey wrote:

The problem is most likely in MC1377P encoder or its surrounding elements. The board is so dirty and rusty that I really wonder how it still works. According to my previous experience with Yamaha video boards in similar condition, any through-hole element could rust out and loose connection to the board, for example a transistor's pin could look intact, but when you slightly bend it, it snaps off because it rusted out.

If you plan to sell the broken motherboard, I would be willing to buy it from you.

i knew someone would say something about its clearness, lol , you won't belive how filthy this was sich that I quite alright with how it turns out now

i won't sell it its my main board now Smile , and thnx for the hint , i will remove it and socket it, replace it and c as i tested some caps they read good with low esr ..

By mars2000you

Enlighted (5885)

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18-05-2021, 16:00

Can you also take a picture of the back side of the PCB? The Toshiba T9769(?A) chip is probably hidden there.

By Grauw

Ascended (9824)

Grauw's picture

18-05-2021, 16:21

Hm yeah it looks in pretty bad shape, e.g. next to the RF module there are two resistors that look like they may be rusted off. I would in general check any connections on the board that have rust on them, clean them with a cotton swab and IPA, resolder connections that look dodgy, test them for continuity, add bypass wires where needed and replace components that were too much affected by the rust.

But it’s good news that the RGB works, that means the problem is localised to the part of the circuitry where the composite video is generated (likely near the RF module).

By somacast

Resident (34)

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18-05-2021, 16:59

thanks alot I will check it out

By Alexey

Guardian (3093)

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18-05-2021, 17:05

somacast wrote:

i won't sell it its my main board now Smile , and thnx for the hint , i will remove it and socket it, replace it and c as i tested some caps they read good with low esr ..

I thought you had a defective board, so you bought another one, but video there didn't work. I just wanted to buy the original broken mainboard from you, not the one you are fixing now.

Check all elements surrounding the video encoder chip - it's quite likely that you will find a broken or rusted out pin on one of the elements.

By somacast

Resident (34)

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18-05-2021, 18:52

Alexey wrote:
somacast wrote:

i won't sell it its my main board now Smile , and thnx for the hint , i will remove it and socket it, replace it and c as i tested some caps they read good with low esr ..

I thought you had a defective board, so you bought another one, but video there didn't work. I just wanted to buy the original broken mainboard from you, not the one you are fixing now.

Check all elements surrounding the video encoder chip - it's quite likely that you will find a broken or rusted out pin on one of the elements.

ohh sorry , I misunderstood, thanks for the offer but as you see they tend to break alot it seems so i will just keep it on a shelf just in case, sorry

thnx for the hint too , i will see

By somacast

Resident (34)

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18-05-2021, 18:53

mars2000you wrote:

Can you also take a picture of the back side of the PCB? The Toshiba T9769(?A) chip is probably hidden there.

https://ibb.co/ry9QpWG

dirtier than topside
cleaner , waaaaaaaaaay cleaner what it looked like

i can also say that the mc1377p looks fine, it reads all same voltages similar to the other board

By mars2000you

Enlighted (5885)

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18-05-2021, 19:01

Thank you! We finally know it's the B version of this chip! Smile

By somacast

Resident (34)

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18-05-2021, 20:42

mars2000you wrote:

Thank you! We finally know it's the B version of this chip! Smile

most welcome, but is there anything else to look for here Smile

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