Help with these? DC300A schematic anyone? Parts

[DogStone]

Hey all, here's the pic, I went through the unit with my tester and I can't get a reading from either of these. Anyone know off hand what they are, or what they do? Were could I get them? Thanks in advance.
Anthony

[llwhtt]

You can download the service manuals for all 3 versions of the DC300 from the Crown site, they're under discontinued products. As for those parts they are just signal diodes, 1N4148.

Craig

[powerflux]

excuse me for saying this but if you don't even recognise diodes (i doubt that they are defective) the DC300, or any slightly complex amplifier is too complicated to begin with.

besides: the voltages in that amplifier could be lethal if handled wrong.

i can recommend the book Electronic Devices (Conventional Current Version) by Thomas L. Floyd, it's very practical with a lot of theory. but any network theory book would also be of great help in your experimenting

[DogStone]

Originally Posted by llwhtt

You can download the service manuals for all 3 versions of the DC300 from the Crown site, they're under discontinued products. As for those parts they are just signal diodes, 1N4148.

Craig

Yup, 4148 thanks, these run in paralell so makes sense, also one of the output transistors is on it's last leg do you suggest replacing them all?

Using the analogy of mules and a wagon, would'nt you want all your mules to pull equally. I'm thinking some may have been carring the load so to speak.

Lemme know what you think.
Anthony

[llwhtt]

Replacing all of them in the bad channel is your best bet, Crown still has their tested and graded parts last time I checked, they are expensive though. I just ordered two channels worth of 2N3773s from Digikey. Mouser has them now also. There were several types of outputs used in the DC300 so check to see what yours has. The drivers are a different matter, mine were a discontinued type so gathered up a few used 2SD555s as those were used in some of the DC300s. If you downloaded or looked at the service manuals you know what I'm talking about. It's been awhile since I've even looked at mine but my last plan was to update to the latest version to have a greater chance of available xsistors.

Craig

[donaldduck]

Originally Posted by DogStone

Hey all, here's the pic, I went through the unit with my tester and I can't get a reading from either of these. Anyone know off hand what they are, or what they do? Were could I get them? Thanks in advance.
Anthony

I have two of them. I have repaired them for 20 years. use them on my home equipment what a nice amp. we used them for running motors for a olh EMI head CAT scanner we had to repair them in the field what you need to know I know.......

you can call me at 561 441 4714
Craig