Hello Friend. According to data, that transistor tz1148 has a damper diode and internal resistance and its replacements are d1439, - d1555, - d2499, - d1650, - d1651, - d2586, - tt2140, - tt2024, - d1556, --d1878. and there are more all these are with damper. and this I indicate in case you want the replacements of that tz1148. Cheers