CHAMP ELECTRONICS -" THE VINTAGE VALVE
AMP HOSPITAL"
NOTTINGHAM, ENGLAND
SERVICING OF AN ORANGE ROCKERVERB 50
COMBO
AMPLIFIER
Originally brought to me by a guy
named Craig. It appeared that this amp was intermittently dropping in
volume and basically being “a pain in the
arse!”
I would prefer an amp to be
completely dead instead of looking for that “proverbial needle
in a haystack”.
After a good few hours on test, I
did indeed see this volume dropping problem happen on the test gear. I
spent a fair amount of time looking for this and, after
re-soldering many joints, I felt I may have cracked the problem!
Back in the case and
showing all the in/out sockets. I told Craig that I thought I had found
the problem as it wasn’t dipping in volume anymore. However,
I couldn’t be 100% sure. He collected the amp and in-fact his
testimonial e-mail is at the end of the article.
Some
months later Craig e-mailed me again saying that the amp had been fine
but, one night at a gig it suddenly did it again! This time he took it
back directly to Orange. Adrian Emsley (the designer of these) actually
took it in personally and, whilst Craig was present, he tried to source
the problem too. Apparently with no luck, so he simply replaced the
whole pre-amp board for Craig…..good man! That's what I call
good service from Orange.
The
50 watt power rating on these Rockerverb’s is a little on the
low-side. It uses a quad of 6V6’s to achieve this, which is
asking a little bit too much of them in my opinion. Even with the JJ
6V6’s, which are pretty much the best, the amp still
struggles to make the 50 watts. Having spoken to Adrian about this, he
recommended using just a pair of EL34’s…..in-fact
he had done this to Craig’s amp at the time of changing the
pre-amp board.
However, a few moths
later again, Craig was back on the phone to me with the story of how
the amp had gone down again, and this time was sounding really funny
& strange. We arranged for him to bring it round to me again
and this time it looked dreadful on the test gear! It simply turned out
that one of the pair of EL34’s that Adrian had put in for
Craig had gone completely kaput! No wonder it sounded crap! Craig also
explained that, since Adrian had put the pair of EL34’s into
it rather than the original quad of 6V6’s, he had never
really liked the sound of it.
Simple solution here:
1. Solder a small resistor across
the bias feed resistor to increase the bias swing on the adjusting pot.
2.
Fit a quad of 6L6’s (these are still beam-Tetrodes, like the
6V6 but a bit beefier…..whereas EL34’s are a
Pentode & do tend to sound “more harsh”).
3.
Set to the correct bias (about 52 volts) and...... away you go!
Craig has since rung me and says how much he loves it with these
tubes…..and still with good power too!
Craig's
Email:
"Hi John,
hope you're well? Thanks for the work you did on my Orange amp. It's
been running flat out for the past week with no recurrence of the
original fault!
I
just wanted to say thanks again for your expert work, and if I have any
other urgent problems with any of our bands' gear you will be the first
person to call.
All
the best, Craig."
