| Jimmy D. |
Can anyone tell me the picture on page 20 of Brian's manual does not match the labels on the rectifier and chip boards, e.g. if you trace the wires in the pic the labels on the each card do not match.
Regards,
Jimmy D. |
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| x. onasis |
3875 or 4780 kit? Brian's manual is for the first edition of the 3875 kit. He's a busy guy lately, and hasn't updated it for us compleat idiots.
But this post should sort it out for you.
http://www.diyaudio.com/forums/show...9747#post369747
If not, keep asking. |
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| Jimmy D. |
I have the 3875. Thanks for the link to the old post. I corrected my wiring error and I still get a violent fuse blow. Luckily I think it's saving the rest of the amp. It acts like a dead short. I plan to disconnect the PS board from the chip boards and first see if the trannie is ok. I bought the one Brian uses from Victoria, nice iron so I doubt that's the problem.
Thank you again for your help.
Jim D. |
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| jtsjf |
Are the diodes in the correct orientation?
you might try removing the secondaries from the transformer, and measure the voltage output from them. Then measure resistance across the diode bridge- it should be 'one-way' only. Good luck with it.
J |
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| Peter Daniel |
| How big is your transformer and what fuse value are you using (also fast blow or slow blow?) |
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| wyomitch |
Brian also has a lot of photos in his completed amp gallery to refer to that I found very useful in wiring up my amp.
Mitch |
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| Jimmy D. |
Yes, the diodes are in the correct orientation.
The transformer is 320VA, 2x24V from Victoria. The fuse blew violently using 2 amp and 3 amp fast blow.
I'll do some more checking later tonight.
Thanks for all the help!
Jimmy D. |
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| Jimmy D. |
Well I lifted both power transforer secondaries from the PS board and the secondary voltages measure fine at around 25v..... no problem. I then reconnected the PS board and lifted all the ouput DC leads. Fuse blew when powered up. So problem is narrowed down to PS board when powering up. Could it be that the in-rush current is too much for the 3 amp fast blow? I don't see anything obvious wrong with the PS board.
I hope it's something this simple.
Jimmy D. |
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| pinkmouse |
| Surge is most likely the cause, fast blow fuses aren't really suitable for toriodals. Depending on your line voltage you might be able to get away with a 1 amp slowblow, I like sand filled ceramic types personally! ;) |
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| Jimmy D. |
Problem is solved. A 3 amp slo blow fuse did the trick. I did not have a wiring problem afterall. All the tube amps/linestages I've built in the last 5 years have not taken more than a standard 2 amp fuse.
Thanks for all the help!
And first listen tells me this amp will not additional gain on the front end.:) |
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