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SiriusHardware · 29th Jan 2020, 7:07 pm

The purpose of L4 is to prevent interference from travelling from the supply rail into the audio sub-carrier circuit and also to prevent interference from travelling out from that part of the circuit and onto the supply rail.

For diagnostic / testing purposes you can replace it with a wire link or very low value, low wattage resistor and then once you have the machine essentially working again, seek out a replacement for L4. If you do that, however, you first need to be sure that there is no longer a short between the 'bottom' end of L4 and 0V.

Probably the easiest place to measure for a short would be between pin 8 (+5V) and pin 1(0V) of the MC1376 IC. If you find a short there, find the cause of that short and then replace L4 (temporarily) with a wire link or very low value resistor.

The audio socket modification you did, was that of your own devising or was it from an online how-to somewhere? If the former, can you post details, if the latter, please post a link to the modification guide you followed.

29th Jan 2020, 7:07 pm	#13
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,556	Re: ZX spectrum +2 The purpose of L4 is to prevent interference from travelling from the supply rail into the audio sub-carrier circuit and also to prevent interference from travelling out from that part of the circuit and onto the supply rail. For diagnostic / testing purposes you can replace it with a wire link or very low value, low wattage resistor and then once you have the machine essentially working again, seek out a replacement for L4. If you do that, however, you first need to be sure that there is no longer a short between the 'bottom' end of L4 and 0V. Probably the easiest place to measure for a short would be between pin 8 (+5V) and pin 1(0V) of the MC1376 IC. If you find a short there, find the cause of that short and then replace L4 (temporarily) with a wire link or very low value resistor. The audio socket modification you did, was that of your own devising or was it from an online how-to somewhere? If the former, can you post details, if the latter, please post a link to the modification guide you followed.