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Old 20th March 2014, 04:15 AM   #1
Jonnova is offline Jonnova  United States
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Default Amber Series 70 Fuses

My first post here, and the reason for my post is, I have an Amber Electronics Series 70 amplifier that I am in the process of overhauling, it came to me with a shorted diode and a dead lm391n-100 for those of you familiar with the amp. I am nearing completion of the rebuild and since I received the amplifier second hand it has 4 different values of fuses in the power supply for the right and left channel. I was hoping someone out there has this amp or a manual for it and can tell me the correct value for these fuses. I do enjoy this site and the vast amount of information available here.

Thank you for your time,
Jon
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Old 20th March 2014, 06:00 PM   #2
Orit is offline Orit  Italy
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In order to answer you for the fuses, I need to give a look at the basic diagram I've got at home.
One BIG warning for this power amp: it's totally DC, without ANY DC protection circuit for the speakers, it's a real woofer killer ! I strongly suggest you to modify the input circuit and add 1uF, non-electrolytic capacitor in series for each channel.
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Old 20th March 2014, 08:01 PM   #3
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Be careful of the replacement IC's. A lot of these were counterfeited (rebranded smaller versions). I always ran that unit at full power into a load box after repairing it. If the chip is a counterfeit, it'll blow before full power. The pain in that is it takes the expensive outputs with it!
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Old 22nd March 2014, 05:41 AM   #4
Jonnova is offline Jonnova  United States
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First of all thank you both for the input. I will be looking into both of your suggestions.
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Old 22nd March 2014, 09:45 PM   #5
Orit is offline Orit  Italy
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To answer your question, if the schematic is right:
F1 is on the PS primary, slo blo
F2 = +40V, right channel
F4 = -40V, right channel
F3 = speaker output, R
F5 = speaker output, L
F6 and F7 are not shown, should be +40 and -40, left channel.
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Old 11th February 2015, 11:19 AM   #6
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found this thread that might rescue my Amber 50c. I got the amp as a gift from a friend. He explained that only the left channel worked. After opening the amp, I found the cause of the channel failure: a blown resistor near MJE250 transistor, I think it was 68ohm. I replaced it and bingo! both channels worked fine, until I increased the volume for testing. As soon as it hit certain level, the same resistor blew up big time.
Long story short, I was wondering if any of you guys can help me to obtain an schematic so I can troubleshoot the problem. Or if you happen to have suggestions...I will appreciate any input.
Thanks!
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Old 11th February 2015, 05:27 PM   #7
AVWERK is offline AVWERK  United States
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I,ll check the original box to see if it has the manual since I have one these in a closet somewhere .
You will want to change the feedback cap to a polypropylene. I was down at the factory when these were popular and this was suggested.
Completely changed the sound for better in comparison in this amp.
These amps would blow fuses quite easily for what ever reason unrelated to loads.
Probably line fluctuations.

Regards
David
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Old 11th February 2015, 07:47 PM   #8
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Thanks David. I could replace the feedback cap as you suggested but since I am quite new with this, I simply don't know which one is. I am ok with electronics but I tend to feel blind and my confidence drops when I don't have schematics. So I really hope you are able to find any document that could help me to understand better the 50c. I am determined to rescue it because it would be a shame to discard it when I am sure it's a great piece of equipment. Thanks again!
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