My first Crown DC150A with IOC lights on. Never worked on one ever. Has been worked on before and sports Hitachi 2N3773's for outputs and a ECG op amp on the main board.
One channel .250mV on output other channel #2 has -44 on output. Can someone suggest replacement transistors?
Looking for service manual to find a schematic of it. So far not finding a manual of amp with IOC lights.
One channel .250mV on output other channel #2 has -44 on output. Can someone suggest replacement transistors?
Looking for service manual to find a schematic of it. So far not finding a manual of amp with IOC lights.
All you need to know is here; D-Series | Crown Audio - Professional Power Amplifiers
Check input/output off set measurements first.
Don't replace the transistors without checking they are damaged first!
2N3773 are still about the best replacement output pairs.
Check input/output off set measurements first.
Don't replace the transistors without checking they are damaged first!
2N3773 are still about the best replacement output pairs.
Results
One trashed output transistor. Other transistors test fine on the transistor tester. Can't seem to find Hitachi 2n3773's. I would like to replace the pair.
Otherwise....MJ15022's? on semi?
The other channel will not zero out the DC offset. Maybe this is due to the ECG725 opamp not being a good replacement?
One trashed output transistor. Other transistors test fine on the transistor tester. Can't seem to find Hitachi 2n3773's. I would like to replace the pair.
Otherwise....MJ15022's? on semi?
The other channel will not zero out the DC offset. Maybe this is due to the ECG725 opamp not being a good replacement?
2N3773s are available from almost everywhere, make doesn't matter.
739UPC dual op amp in my experience, they never fail, just as well as they are obsolete.
If you first set the input offset to its centre position, adjust the output offset to null the output then fine adjust the input offset for as close to null as practical. +- 50mV or better is your aim.
739UPC dual op amp in my experience, they never fail, just as well as they are obsolete.
If you first set the input offset to its centre position, adjust the output offset to null the output then fine adjust the input offset for as close to null as practical. +- 50mV or better is your aim.
I can find 3 or 4 different 2N3773's but no Hitachi. Unfortunately the original ua739 op amp is missing and a ECG is in its place. Here is where I insert I don't like ECG or NTE parts.
As for the make of the transistor......
I've used a number of different transistor brands. I've had some of which will not work correctly even if they are the same number. So, in my opinion all the brands are not equal.
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Hitachi and Toshiba 2N3773's are (were, they are NLA) less like the original RCA units than the ON Semi ones are.
Be careful choosing different types, (not makes) of transistor. The Vbe can be different and give you serious issues with bias problems, plus if the HF tolerance is too high, the amplifier may 'take off' at RF.
I've gotten epitaxial and homotaxial 2n3773 transistors before so that is why I want to make sure I get the right ones.
Can't get hometaxials anymore. Unless you find NOS RCA's. Every one made today is epitaxial. The Jap versions were often triple diffused, but meeting the original Motorola spec. Including the second breakdown. The American makers never figured out how to do that but the Japs did. Vbe, however, could be quite different - but since they only spec a maximum at one or two current levels it could still be "in spec".
A brief trip to ebay had me laughing. About everything was from China. They had "ON" semiconductors with the writing on the transistor 90 degrees off what it should have been.
Still looking for a pair of Hitachi 2n3773's.
Still looking for a pair of Hitachi 2n3773's.
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