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Old 1st November 2009, 07:08 AM   #1
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Post Crown DC300a Repair Questions

HI all, first forum, hope all is well. Hope i'm in the right place.
I just recieved an dc300a from a neighbor cleaning out his garage, (free by the way) yup score well see maybe someone here can help me out here's the thing he said it he remembers it working 20 years ago when he put it up at least 1 channel for sure plugged it in and it powered for about 20 secs. Red light on one channel (R) solid then just fadded out. Replaced fuse PoP! what can it hurt one more PoP! Realy old in bad shape power cord with no ground pin pulled so resoldered a new cord (grounded) rubbing my hand together Oh boy! Oh boy! here we go............. yup you guessed it POP! Blown fuse now what? anyone who can help it would be much appreciated! SeeYA!
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Old 1st November 2009, 03:58 PM   #2
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this is a question that is skill depented ....advice ther is plenty .... you need to have the skills time litle money and acces to instrunmments if you are looking for precise repair and upgrade of an old amp

here is a link with some usefull info it can be used a s a base for a very good repair ..

vintage amplifier repair/upgrade manual
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Old 1st November 2009, 04:54 PM   #3
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TomWaits did an exellent job with a DC300A here:
Resurrecting a Crown DC300A
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Old 2nd November 2009, 04:21 AM   #4
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Default CRown dc300a

Thank you for the quick responses. Sakis, very greatfull for the article, however a solderer and a volt meter is about all i have at this point. I was hoping it was a quick fix since it did power up for for a few.

Dont want a complete upgrade planned on using it initially for a PA or bass cab. just wanted to get it going. Everything inside apears to be perfect and the guy who gave me the dc300a bought it new and never opened the unit to work on it. Can"t seem to locate the protection switch in this unit for "normal or Hysteresis". It's factory wired for 120V.

Why would it power up initially, then die, and now blow fuses, dried out caps? weak ground? Large barrel type connections on the rear heatsink? To much voltage? bear with me I'm F>O>B when it comes to this old equipment but have ability and it's no fun at all having someone else repair it for me i'm a hands on guy and just built a tube amp for my guitar out of an old Sears Silvertone organ that I ripped apart.........What a ******* beatiful tone I have now! Any quick checks for me to think about? Thank again.
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Old 2nd November 2009, 04:59 AM   #5
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Quote:
he remembers it working 20 years ago when he put it up at least 1 channel for sure plugged it in and it powered for about 20 secs. Red light on one channel (R) solid then just fadded out. Replaced fuse PoP!
Could be due to oscillation caused by dry/bad small caps or a bad solder or....
You can repair an amp just using a volt meter, but it's not an easy task though.

Put a light bulb (60W) in series with the AC MAINS to the amp. This may give you time to do some measurings around the circuits.
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Old 2nd November 2009, 05:04 AM   #6
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Default Pics dc300 a

Crown inside view
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Old 2nd November 2009, 05:11 AM   #7
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Default Thanks Jan!

This will work with no power! or turn it on since the fusses have blown then check? with light bulb (60W) in series with the AC MAINS to the amp.
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Old 2nd November 2009, 08:10 AM   #8
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Default Light bulb (60W) in series with the AC MAINS to the amp?

This will not work with no power! or turn on, since the fusses have blown then how to check?
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Old 23rd November 2009, 04:41 AM   #9
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Default dc300a

Quote:
Originally Posted by DogStone View Post
HI all, first forum, hope all is well. Hope i'm in the right place.
I just recieved an dc300a from a neighbor cleaning out his garage, (free by the way) yup score well see maybe someone here can help me out here's the thing he said it he remembers it working 20 years ago when he put it up at least 1 channel for sure plugged it in and it powered for about 20 secs. Red light on one channel (R) solid then just fadded out. Replaced fuse PoP! what can it hurt one more PoP! Realy old in bad shape power cord with no ground pin pulled so resoldered a new cord (grounded) rubbing my hand together Oh boy! Oh boy! here we go............. yup you guessed it POP! Blown fuse now what? anyone who can help it would be much appreciated! SeeYA!
most of the time the big Bridge rect is shorted replace it with a 25 amp type bridge rect this is what we did in the 80 s
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