SM 124 works but long delay in switching on..why?

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Chandler
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SM 124 works but long delay in switching on..why?

Postby Chandler » Sat Jul 02, 2011 6:45 pm

i have a fully working SM 124 monitor but when i first switch it on it can take upto 5-10 seconds for the green led to illuninate after power on

if it's been on and i switch it off... then on again it will power up immediately

so just this cold start delay

i have changed all electrolytic caps and checked all solders

can anyone advise to a possible cause of this?

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nativ
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Re: SM 124 works but long delay in switching on..why?

Postby nativ » Sat Jul 02, 2011 8:21 pm

Timeslip?

Perhaps the is a tear in space time fabric.... get out your needle and thread!
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Dal
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Re: SM 124 works but long delay in switching on..why?

Postby Dal » Sat Jul 02, 2011 10:30 pm

Hmmm electrolytics would have been my guess too - Especially with warm starts being ok.

Maybe Hippy Dave or 1024Mak might have some enlightening suggestions on this one?
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Re: SM 124 works but long delay in switching on..why?

Postby Hippy Dave » Sun Jul 03, 2011 2:59 am

Check out pages 17 and 30 of the following file:
http://dev-docs.atariforge.org/files/SM ... Manual.pdf
Note the comments related to Q901, IC901 and P901.

Hope that helps.

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Re: SM 124 works but long delay in switching on..why?

Postby 1024MAK » Tue Jul 05, 2011 12:39 am

Yes as Dave says have a look in this area - do you have a meter?
If yes see what voltage you get across C905 (it should be at least 18V to 22V dc)
Also what voltage you get across C907 or C908? (this should be 12V dc)
You should also get 12V dc on pins 2 and 1 and on pins 3 and 4 of P901 on the main PCB.
Do keep your fingers etc away from the high voltage parts...

If problems continue (and it's not poor connections on P901 etc) renew IC901 AND Q901 with the same types. Also check R902 and R903 (if Q901 is connected, desolder one leg of each resistor to test it).

If the monitor is one of the other chassis (designs) you will have to give a little more detail (include pics of the circuit board inside).
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Re: SM 124 works but long delay in switching on..why?

Postby Dal » Tue Jul 05, 2011 9:22 am

1024MAK wrote:Do keep your fingers etc away from the high voltage parts...
"etc"?? The mind boggles... :lol:
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Re: SM 124 works but long delay in switching on..why?

Postby Shredder11 » Tue Jul 05, 2011 12:21 pm

She was electric that night....blew my mind and my testicles away! :lol:


Or do you mean something else? :wink:

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Re: SM 124 works but long delay in switching on..why?

Postby MRAtari » Tue Jul 05, 2011 4:39 pm

which type is it? there were 2

the early type has the big transformer and PSU mounted on the side

the later type has the psu incorporated inthe main pcb
Last edited by MRAtari on Tue Jul 05, 2011 4:42 pm, edited 1 time in total.

Chandler
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Re: SM 124 works but long delay in switching on..why?

Postby Chandler » Tue Jul 05, 2011 4:40 pm

it's the later type SM 124 which has the PSU incorporated into the main PCB (not mounted on the side)

have so far changed IC901 but still the same

could the delay be anthing to do with the LOPT?

Chandler
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Re: SM 124 works but long delay in switching on..why?

Postby Chandler » Wed Jul 06, 2011 8:27 pm

sorted it! seems it was a dodgy (new) main cap, replaced it and now it powers on quick

nice one! :D

but staying on the same note! :wink:

i have another non working board which doesn't power up (no power LED)

originally i found BU806 was dead (3 legged transistor fitted to metal shield outside of L.O.P.T)

replaced that / no change

when switched off i hear a high pitch wining sound which dies down after a few seconds...

so far:

changed all caps

checked the following ok: D901 / IC901 / R901 / R902 / R903 / R904 / R914


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