ZX Spectrum 48K - no sound from speaker

[quark]

Hi,

I have issue 6A which works fine in general, but there's no sound from the speaker.
As there's sound from the EAR socket I'm guessing that the speaker is dead.
Is there anything else to check and can I somehow check if the speaker works?

Regards,
Jesper

[1024MAK]

Hello Jesper

Check/test diodes D9 and D13, and transistor TR7.

The diodes can be tested on the diode test range of a digital multimeter. The loud speaker can be tested using the 200Ω resistance range on a digital multimeter.

Mark

[quark]

Hi Mark,

thanks for the information.

I've checked D9 and D13 which are fine. I can't check TR7 but can try to replace it.
Checking the resistance of the speaker shows nothing on the multimeter, as if there's no connection.
I assume this points to a dead speaker?

Regards,
Jesper

[1024MAK]

What do you mean by nothing?
Do you mean zero ohms, or ‘O.L’ or another indication of over-range that indicates an open circuit?

The resistance of the speaker should be around 40Ω

Mark

[quark]

As in no difference if the probes are connected or not.
It's not 0 as in shorted.

[1024MAK]

So open circuit then. Therefore you need a new speaker.

Mark

[quark]

OK, thanks for the confirmation

[1024MAK]

It would also be a good idea to desolder the transistor from the circuit, then test using the resistance range between collector and emitter (positive lead to collector). Then test it on the diode test range (it should test as two diode junctions, with base being the ‘common anode’ and the collector and emitter terminals being the ‘cathodes’). Also if you have a transistor tester, test it on this. If there is any doubt, renew it.

Mark