CHAMP ELECTRONICS -" THE VINTAGE VALVE AMP HOSPITAL"
NOTTINGHAM, ENGLAND
REPAIR OF A BIRD 4/25 GOLDEN EAGLE COMBO AMPLIFIER
Hi Folks,
This amp was brought to me a while ago by a guy I would now
class as a friend…..Justin.
Justin explained to me that he had taken
this Bird 4/25 (meaning 4 inputs and 25 watts) to a music shop in Nottingham
(this was before he knew me), and not only did they have it for about two years
but also, when he asked about it (after asking a few times before), they told
him it couldn’t be done! On collecting the amp back from this shop he found
that they had left everything loose and hanging out. About half the hardware
(screws nuts etc) was missing, as too was the Bird badge from the front!
Fortunately he contacted the shop and they have since found it. Justin is going
to take a photo of the front with the badge re-attached to feature here on my
website soon.
When Justin first brought me the amp I warned
him this one was going to be a mammoth task as undoubtedly virtually all the
components would have died. All the Hunts caps would have to go, as well as
virtually all the stupid metal end-capped resistors which normally fall apart
whilst one is just looking at them!
The rear of the pre-amp section before the commencement of any work.
As above, but this time the main power-amp
board. (Actually I had changed a couple of caps before I realised I hadn’t
taken this “before” photo. Whoops!)
Underside of the power-amp PCB and, even
though this is from the sixties, the print is quite strong and doesn’t come
off as easily as with some other brands!
The pre-amp control panel. Just note the top
right-hand control marked ‘repetitive echo’. I’ll tell you about this
later in the article.
Everything changed on the main power-amp board except for three resistors which were of good quality, fine,
and therefore retained!
Same again…..everything this time on the
pre-amp board. My Australian friend Mervin [Doctor Valve] was staying with me for
seven weeks
at the time and we did this repair between us. We actually struck a deal. Mervin said
“I’ll do the power section and you can do the pre-amp”. I wonder why?
Seriously though, the pre-amps are usually more fiddly, but I didn’t mind!
Both completely finished and on a bench
test. Everything looking a lot
better now!
The original spring reverb unit which utilizes
2 x Acos GP91 pick-up (as in record player) ceramic cartridges for the send and return. These cartridges simply die over time, as the Ceramic disintegrates! Even
when new they never really performed that well; always very noisy and subject
to vibration. Although the famous Hammond organ American reverb unit (Accutronics)
was available back in the sixties when this amp was designed and made, my
guess is that the Bird company didn’t opt to using the Accutronics tank in
order to keep the whole thing British.
Empty cabinet, but with the original Wharfedale 15" speaker still in place.
Piecing everything back together.
As above, but also showing the replaced
Accutronics reverb tank.
As above.
Close-up of the second-hand reverb tank that I have fitted,
along with the black reverb drive transformer on the right. I also had to
re-design the drive stage for the reverb to be able to use a drive transformer.
The original Bird Company plate & serial
number.
All done, with new hardware throughout & velcro cable-tidies supplied.
Finished……phew!
Off the bench at long last! Unfortunately I
couldn’t replace the four missing push-button knobs. My stock of these ran out
years ago!
And finally about that ‘repetitive echo
control’. It’s not really an echo but is slightly ingenious. What this
control really does is it uses the tremolo function to modulate the return of the
reverb only, not the straight through signal, and so it gives the impression of
a kind-of echo! Nobody else ever did this to the best of my knowledge so you
could say if someone records with this effect in this day and age….it could
be classed as quite original!
…..And as a final point here: again to the best of my knowledge, and apart from
James
Payze's amp which is on the
Vintage Hofner website, I think that you would be hard-pressed to find another one of these on
any website in the world, particularly one showing all its guts and a full service/repair from
start to finish!
Hope you enjoyed the
article. Peace & good health to you all.
Thanks for dropping by, cheers, John.