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Hi, been repairing an Spectrum +3, so far i've managed to get memory replaced and socketed, floppy cleaned and new belt in place both reading and writing ok. I've also replace all electrolitic capacitors.
The only issue i'm getting now is the sound outputing slightly louder than normal and this causes slight distortion. My firt thougt was the caps but nothing changed after replacement.
Any ideas were to look? Thanks.
There was a problem with the +3 sound (at least with the issue 1 +3)
there is an explanation (and fix) here http://www.secarica.ro/html/plus3_hardware.html
I haven't got around to doing it myself though (I have 1 +3 that sounds OK and another that is totally distorted)
Mine is an issue 2, my mistake for not mention it on 1st post :oops:.
@JLPedro
My friend, I will need to confirm the schematics, but its might be that your -12v is not being supplied properly.
what is the -12v and +12v voltage readings with a multimeter?
I've used to test more than one psu (one +3 psu and at least two +2a psu) so i'm guessing power source isn't the issue (it would be very unlikelly all of them are faulty, plus they work 100% on other +3 and +2a).
Can I get sound directly from the AY chip? Mixing the A, B and C to one wire and gnd and connecting to external amp is my next trie to see if the sound is 100% clean.
@JLP
yes you can combine all the output channels on the AY synth, you must also connect all the grounds together as well.
Time for update on work done.
Sound tested directly from the AY chip, it sounds better but spekers are better than the tv anyway, small distortion on sound remains.
AY chip desolded and socket put in place, tested with known working AY chip and result is same, original AY chip also works fine on other +2A.
Some pics attached of work done.
Time to check schematics again to see were power to the ay chip comes.
Can this be related to the ram being socketed (diferent chips were used but same timming)?
-12v get in by the MC 1488, i read -12,21 on pin 1 (gnd) and 7 (-12v), also -12,21 from the psu.
-12.12V is normal. I mind to replace the decoupling capacitors or even do a stereo output from original Spectrum mono.
Do you mean C1 to C7 and C9 to C12 ceramic ones and C8 right?Quote:
Originally Posted by rkauer