SONY HB900, Help

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Door Gloriou

Expert (122)

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28-03-2019, 08:23

Greetings all,
This week I got the HB900. when I turned it on, the capacitor Vaporized (the biggest one in the PSU).
The unit is 100V the source is also 100V.
Why did that happen? Problem will be solved if the capacitor replaced? the previous owner stated before anything happened, that the unit is working (at that time) even the photos he/she posted showed working condition.

Guys your help is much appreciated. Smile

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Van Jipe

Paragon (1366)

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28-03-2019, 09:43

verify frequency 50 or 60hz on HB900 and on your source

Van rderooy

Hero (548)

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28-03-2019, 10:01

I would probably put it down to bad luck. The HB-F900 came out in 1986, 33 years ago. Capacitors don't last forever. This is the risk of any old electronics.

If you don't have the skills, and since your asking this question, I'm guessing you don't. You should find somebody that knows how to repair such electronics. He should check for any leaking capacitors, both in the PSU and on the mainboard and replace them. Some people go even as far as to completely "re-cap" the board (meaning to replace all old capacitors). Leaking capacitors are a big problem in old electronics as the capacitors contain an acid and will literally slowly eat its way through the traces on the board.

Note that not all capacitors are equal, some brands have stood the test of time better then others. Nichicon capacitors are generally regarded as the best, and normally don't leak.

If your looking for information, have a look here, it contains pretty much all we know about the system:
https://www.msx.org/wiki/Sony_HB-F900
There was also a European version, but I don't know how similar the internals are.
https://www.msx.org/wiki/Sony_HB-G900P

Van rderooy

Hero (548)

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28-03-2019, 10:05

p.s. if you find any leaking capacitors, pour some Vinegar over the effected area. It will neutralise the acid from the capacitor, stopping it eating into the board any further. Afterwards, you can use some Alcohol to clean off the vinegar.

Van Gloriou

Expert (122)

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28-03-2019, 10:17

Jipe wrote:

verify frequency 50 or 60hz on HB900 and on your source

Our frequency in this area is 60Hz, even the HB900 since it is Japanese

Van Gloriou

Expert (122)

afbeelding van Gloriou

28-03-2019, 10:20

rderooy wrote:

p.s. if you find any leaking capacitors, pour some Vinegar over the effected area. It will neutralise the acid from the capacitor, stopping it eating into the board any further. Afterwards, you can use some Alcohol to clean off the vinegar.

Thanks for your detailed info.
indeed there is two leaky small capacitors in the PSU Board (Gummy type leaking)
will these two damaged capacitors affect the other one making it smoke?

Van Nprod

Resident (36)

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28-03-2019, 10:49

Quote:

(Gummy type leaking)

When capacitors leak it's more of a "crusty" substance, perhaps the gummy stuff is just hotglue they put on from the factory sometimes. In any case it's best to replace any suspicious capacitors with good new ones for 30 year old tech like this.

Van Gloriou

Expert (122)

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02-04-2019, 12:36

Nprod wrote:
Quote:

(Gummy type leaking)

When capacitors leak it's more of a "crusty" substance, perhaps the gummy stuff is just hotglue they put on from the factory sometimes. In any case it's best to replace any suspicious capacitors with good new ones for 30 year old tech like this.

Yes,
I noticed that on the NiCd Battery on the main board of the same computer.
You are right, the gummy was to make them glued to the board

Van Gloriou

Expert (122)

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02-04-2019, 12:49

I got that capacitor replaced.
and checked the board with very slight load, and it was OK
However when I gave it another go while connected in the computer, sparks came out from one area of the board and the fuse gone bad.

So any ideas what could be wrong?

Van RetroTechie

Paragon (1563)

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03-04-2019, 06:27

Electrolytic capacitors sometimes go poof if they haven't been powered for a long time (say, several months or more), and then (suddenly) see full working voltage again. Common for example with old TV's that sat in the attic for a couple of years.

Possibly this capacitor took some other component(s?) with it. But first things first:
-This power supply is a switch-mode type, roughly half the board carries mains voltage! If you're not 100% sure you understand the safety implications of that, then don't even ATTEMPT to repair it! A mistake is easily made (like, power cord still plugged in while you thought it wasn't, some parts live while you thought a switch would cut that off etc), and can potentially KILL you. Evil
-You 100% sure that replacement capacitor went in with correct polarity?
-Do an optical check of the board. Usually when sparks fly, that leaves marks. Components that look melted (apart from the fuse Wink ), cracked or otherwise out of shape, soot patches, damaged pcb traces, whatever.
-Replacing the power supply as a whole with a modern one, may be your easiest bet.

Van Gloriou

Expert (122)

afbeelding van Gloriou

03-04-2019, 09:41

RetroTechie wrote:

Electrolytic capacitors sometimes go poof if they haven't been powered for a long time (say, several months or more), and then (suddenly) see full working voltage again. Common for example with old TV's that sat in the attic for a couple of years.

Possibly this capacitor took some other component(s?) with it. But first things first:
-This power supply is a switch-mode type, roughly half the board carries mains voltage! If you're not 100% sure you understand the safety implications of that, then don't even ATTEMPT to repair it! A mistake is easily made (like, power cord still plugged in while you thought it wasn't, some parts live while you thought a switch would cut that off etc), and can potentially KILL you. Evil
-You 100% sure that replacement capacitor went in with correct polarity?
-Do an optical check of the board. Usually when sparks fly, that leaves marks. Components that look melted (apart from the fuse Wink ), cracked or otherwise out of shape, soot patches, damaged pcb traces, whatever.
-Replacing the power supply as a whole with a modern one, may be your easiest bet.

You are absolutely right. (SAFETY FIRST) Smile
yes the capacitor's polarity was right. also the PSU was tested with slight load and confirmed was working fine. PCB checked previously and even after the spark (nothing can be seen visually).
however yet to be confirmed that the fault is coming from the load (while connected to the mainboard and floppy drives).

My last resort will be swapping it with a modern one Big smile (hopefully the motherboard is still alive) Question

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