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Electronics => Repair => Topic started by: BlueApple on August 30, 2022, 09:43:56 pm

Title: Amstrad PCW let out the magic smoke! (CRT Board Repair)
Post by: BlueApple on August 30, 2022, 09:43:56 pm
I found an Amstrad PCW 8256 at an estate sale. When I got it home and powered it on smoke came out. Looking at the board one capacitor is bulging. There also is no power on the 12v rail.

Can capacitors let out smoke without it being visible?
Title: Re: Amstrad PCW let out the magic smoke! (CRT Board Repair)
Post by: Rasz on September 02, 2022, 05:31:07 pm
to amateur eye? definitely
Title: Re: Amstrad PCW let out the magic smoke! (CRT Board Repair)
Post by: BlueApple on September 02, 2022, 06:55:36 pm
Quote from: Rasz on September 02, 2022, 05:31:07 pm
to amateur eye? definitely
Ok. I'm gonna go ahead and buy a new cap.
Title: Re: Amstrad PCW let out the magic smoke! (CRT Board Repair)
Post by: Rasz on September 02, 2022, 07:32:17 pm
singular cap? so you did find the culprit? afaik there are a couple of electrolytics on pcw
Title: Re: Amstrad PCW let out the magic smoke! (CRT Board Repair)
Post by: BlueApple on September 02, 2022, 07:38:42 pm
Only the one cap is bulging and tests bad with my multimeter. I just desoldered it to test it out of circuit and it still tests bad. It was leaking too.
Title: Re: Amstrad PCW let out the magic smoke! (CRT Board Repair)
Post by: BlueApple on October 08, 2022, 07:08:17 pm
I replaced that cap, turned it on, and a few transistors blew up.  :-BROKE
Title: Re: Amstrad PCW let out the magic smoke! (CRT Board Repair)
Post by: Rasz on October 08, 2022, 08:37:46 pm
haha thats awesome!
looking at https://www.cpcwiki.eu/index.php/PCW_Mainboard_Versions#PCW_8256.2F8512 (https://www.cpcwiki.eu/index.php/PCW_Mainboard_Versions#PCW_8256.2F8512) I dont see any transistors
is there a rifa capacitor in the power supply?
Title: Re: Amstrad PCW let out the magic smoke! (CRT Board Repair)
Post by: Audiorepair on October 08, 2022, 08:38:34 pm
I think prisoners should be given such tasks whilst incarcerated.
Title: Re: Amstrad PCW let out the magic smoke! (CRT Board Repair)
Post by: T3sl4co1l on October 08, 2022, 11:51:51 pm
Quote from: Audiorepair on October 08, 2022, 08:38:34 pm
I think prisoners should be given such tasks whilst incarcerated.

What?  Vaping electrolytics?

Tim
Title: Re: Amstrad PCW let out the magic smoke! (CRT Board Repair)
Post by: Gyro on October 09, 2022, 01:26:42 pm
Quote from: BlueApple on October 08, 2022, 07:08:17 pm
I replaced that cap, turned it on, and a few transistors blew up.  :-BROKE

Quote from: Rasz on October 08, 2022, 08:37:46 pm
haha thats awesome!
looking at https://www.cpcwiki.eu/index.php/PCW_Mainboard_Versions#PCW_8256.2F8512 (https://www.cpcwiki.eu/index.php/PCW_Mainboard_Versions#PCW_8256.2F8512) I dont see any transistors
...

It seems likely that the 'transistors' may actually be Tantalum bead capacitors. Those are what I would expect to blow up in a noticable fashion on something that old that has been stored in unknown conditions.
Title: Re: Amstrad PCW let out the magic smoke! (CRT Board Repair)
Post by: BlueApple on October 10, 2022, 02:48:06 pm
Quote from: Gyro on October 09, 2022, 01:26:42 pm
Quote from: BlueApple on October 08, 2022, 07:08:17 pm
I replaced that cap, turned it on, and a few transistors blew up.  :-BROKE

Quote from: Rasz on October 08, 2022, 08:37:46 pm
haha thats awesome!
looking at https://www.cpcwiki.eu/index.php/PCW_Mainboard_Versions#PCW_8256.2F8512 (https://www.cpcwiki.eu/index.php/PCW_Mainboard_Versions#PCW_8256.2F8512) I dont see any transistors
...

It seems likely that the 'transistors' may actually be Tantalum bead capacitors. Those are what I would expect to blow up in a noticable fashion on something that old that has been stored in unknown conditions.
Do they have 3 legs? And also they are on the power board not the computer board.
Title: Re: Amstrad PCW let out the magic smoke! (CRT Board Repair)
Post by: BlueApple on November 16, 2022, 07:38:34 pm
I figured out why the transistors blew up, I forgot to connect the power to the motherboard and they must've overloaded.  :palm: