Going well there Alan. The bracing angles were a good idea. I'm looking forward to seeing how this turns out.
Going well there Alan. The bracing angles were a good idea. I'm looking forward to seeing how this turns out.
... well it has taken a while.
I started this back in 2017 and have had several more 'false' starts to get it completed. So having cleared everything else it was time to concentrate on finishing the old Radford.
It is an STA12 which is a very close relative to the original STA15 (EF86, ECC83 and EL34 etc.)
Recapping a little (Tinypic is closing soon so the original pictures might vanish soon...), the first problem was someone had modified this amplifier in a very unsympathetic manner, then the chassis was distorted due to the much flimsier metal used on these models. This distortion then leads to the component boards also bending and so on.
Excellent work here, not.
I previously reinforced the chassis plate and 'reverse engineered' the component boards from an original STA15 diagram and a couple of rare STA12 photos on the net. That and a few obvious, and some less obvious, differences in the circuit / layout.
Then my next problem were the output transformers. The new replacements are for the Series 3 STA15 having different output taps to the originals, so required different impedance switching etc. But they fit very well.
And that is where I had to halt for some time, until last week in fact. So to start with I had to meld the earlier and later impedance switching using the Series 3 as my template.
Then wire up one of the circuit boards switch on and hope... for the best.
I was greeted with a low 'far*ing' on initial power up, but reversing the primaries fixed that. Then music at last if only in mono.
I left it running for an hour or so and all was good. Happy everything was well - on to the other channel asap.
So there we are, it has been running for a couple of days now and it is an astonishing amplifier. It really does the Radford thing very, very well. So much detail and control all through the volume range and no noise. Not bad for an amplifier made in 1960. Even the mains transformer is much quieter than my STA15 III. It has become my instant favourite.
Still a few of things to do though.
First is thank Will at Radford Revival, it could not have happened without him.
Then it needs a base plate, it came without one and it's on 4 rubber feet at the moment.
Alan
Last edited by snowman_al; 26-08-2019 at 06:03.
Beautiful work done there Alan. Well done!![]()
Barry
Bravo... Top Job
Regards,
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Oh my god! There's nothing wrong with the bidet is there?
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Great job, glad to be of assistance with the OPTs and happy it all worked out![]()
Radford Revival
www.radfordrevival.co.uk
Superb job Alan, that must have taken a good few hours (weeks?).
Another thumbs up for WillGreat to have such committed engineers on AoS.
Location: Hampshire
Posts: 306
I'm Mel.
Another well documented rebuild Alan.
Your care and attention to detail is amazing - most would be rushing to get the job done rather than doing it properly.
I'm still enjoying the World Designs KEL 84 you rebuilt and documented in the same manner as this.
Mel
Great to see another of these superb amplifiers resurrected and good for years to come. The Radfords really do seem to be an amp for life as they are so serviceable especially with Radford Revival on hand. Really good stuff![]()
Location: Nottingham
Posts: 575
I'm Ian.
No sorry I did not. I decided to leave it 'as is' to show some of its age...
I have a metal plate for the bottom now so will give that a coat of something close from Halfords or the motor factors. It does not need to be perfect, it will be underneath.
The other thing is that it is totally different in colour to my STA15 III (which is two tone and I guess will be similar to your 25). The closest picture to the real STA12 colour is the 'rear view' (one from last) the white balance on my camera is not the best.
I have found that the Humbrol (or Airfix) enamel actually can be mixed to match lots of things with a bit of time so that might be the way to go if the areas are not too large or obvious?
Alan
PS thanks for the comments everyone.