CHAMP ELECTRONICS -" THE VINTAGE VALVE AMP HOSPITAL"

NOTTINGHAM, ENGLAND

SERVICING A CARLSBRO 100 TOP AMPLIFIER HEAD







The "100 Top" (and its younger brother the "50 Top"), these were supposedly Carlsbro's budget range. However to be honest, they were just as good as any of the others. They used the same components, boards, tube bases, chassis, transformers and well...everything really! The only thing they didn't have was the choke (replaced with a 100 ohm 5 watt wire-wound resistor which makes little or no difference in performance) and they featured just one channel with high/low gain inputs and a three band EQ......eliminating the presence control. They sound bloody great!






This actual amp was brought to me by a very nice guy named Ron. Ron had spent much time replacing many components and, although he had a fair bit of knowledge on electronics, he was pulling his hair out by the fact that at lower volume levels the amp sounded great & perfect but, at higher levels it was going into spurious oscillations! He had contacted me to see if I could shed some light on the problem.






The job quite neatly done by Ron.





And here too. I did blob on a replacement 82k splitter anode resistor, as it was a bit too much out of spec....as can be seen here. Nevertheless it didn't cure the problem.





After further diagnostic tests on my wonderful, reliable test-gear, it didn't take long before I told Ron the bad news. The output transformer was the problem with an arcing primary.....but only under harder conditions.





It was a Partridge transformer but......once in a blue-moon a faulty one does come-up.





I did a rewind of the output trany (though not shown in any of these photos), and apart from a "thank you, the amp is fine" phone call from Ron, he has never been back. Yet another satisfied customer and another great amp!







 

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