Sinclair 128K problem

Here's one for the Speccy techs out here:

Got a Sinclair 128K Heat-sink UK version with the following problem, all works 100% except no AY sound output, nothing, plays 48k sound and i can ear the key strokes with speakers connected to the EAR socket (TV output sound is only noise on both beeper or AY sound, image is fine).
I'm using an +2 psu (9v 2,1 amps) and it reads perfect values. Other things i checked were the IC 7805cs and it reads 5,05v and 11,50v (strange as the psu outputs 12v and on the ic only gets 11,50v...), also checked the AY-3-812A 5v pin and it reads 5,02v (+5v pin 3 and GND pin 6).

Any ideas??

Replace the audio chip.

Is there a way to really be sure is the Ay chip at fault, as it is very difficult for me do desolder that kind of ic (only have a basic solder sucker).
And can I use the AY chip from a +2 Grey spectrum?

Hi JLPedro

First of all, TV output sound is only noise because UK PAL and European PAL are slight different in modulation sound. Second, I agree with rkauer, try to replace the audio chip, is the same as you can found in the Speccy +2 grey model, and in other home computers.

Regards

Will do that then, going to post an wanted for a AY-3-8912A chip.

Thanks for all the help :thumbsup:.

Remember to use a socket for the replacement instead direct soldering.

Oh, socket strips are perfect for this.

Litle update on this, conecting the mic socket to my creative speaker amplifier i get a loud amp sound and if listening carefuly you can ear the AY sound of the game very low.

So this means the AY chip is ok and the problem is or the socket or some component between the ay chip and the mic socket.
Is the mic socket amplified on the 128K+ ?

AFAIK, on all original Spectrums, 'ear' plug is output, 'mic' is input.
So you need to connect to 'ear'.

In any case, its just a standard line-level output.

Same result pluging on the ear socket.

In ay chip pin 1,4,5 is audio output, try connect speaker to this point.and ground. If sound back something is wrong beetwen chip and mic output , propably capacitor is broken.