Crown D-150

rick1949

Member
2016-01-31 6:49 pm
I have a Crown D-150 with a good channel and a distorted channel. In reading a previous thread by "djk", the problem appears to be the same asw noted for a Crown D-150A amplifier.

My question is that transistors noted as Q102 and Q202 are for the D-150A schematic. For the D-150 are these transistors the same as Q2? The parts list has the part listed as "PNP transistor" with no part number. Would someone be able to suggest a transistor number?

Thanks
 
I hope you are new to the repair hobby.
Defective transistors are usually sonically dead, or make popping noises, hiss or crackling.Sonically dead defective transistors usually produce improbably values of DC voltage, like the base and emitter are not 0.6 v apart or collector DC not between 1/4 and 3/4 of the power supply voltage.
distortion in amps over 20 years old is usually dried up electrolytic caps or dirty oxidized connections. The connections can be removed and replaced to scrape the oxide off. The electrolytic caps are the ones with a plus on one end or a minus pointing to one lead. (Although since 2011 nichicon is leaving the polarity label off small ones). Rather than buying a $100 Peak e-capacitor cap/esr meter to sort cracking rubber caps by water content, on amps over 15 years old that sound funny, I reseat connectors, then replace all the e-caps based on the production date. They now make some with 10000 hours service life e=caps that might have better sealant to keep the water in longer than original. Although Crown didn't install many 500 hour rated **** e-caps.
Distortion can also be cold solder joints, although crown doesn't have a reputation of making many of those either.
I replace BJT transistors based mainly on package size, keeping some 100 v or higher Vceo ones around. MPSA06/56 , 2n5401/5551, TIP41C/42C, MJE15032/33, MJ21183/4 will cover most needs. Paralleled and complementary (like Output) transistors have to changed in sets. Don't forget to order heat sink grease and washers if you have to change any transistors having them. The stuff is poisonous, don't lick it.
See this thread especially about checking output idle current is proper before buttoning a BJT amp up. http://www.diyaudio.com/forums/solid-state/136261-vintage-amplifier-repair-upgrade-manual.html
Good luck.
 
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