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.


 

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