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Radford STA15 Restoration.

Discussion in 'classic' started by snowman_al, Jun 22, 2021.

  1. Mike P

    Mike P Trade: Pickwell Audio

    +1 on the F&T dual section caps.
     
  2. snowman_al

    snowman_al pfm Member

    A quick update on progress.
    Removed the rust and dirt from the transformers and choke. Cleaned out the solder tags for re-assembly.

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    Cleaned most of the rust off the chassis and cage. I'm going to try a couple of old BMC colours for the paint, 'Farina Grey' for the chassis and 'Old English White' for the cage.
    Modded the speaker terminal holes to take slightly larger sockets.

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    Freed up the rusted up mains switch and cleaned the rust off the voltage selector assembly.

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    Cleaned and polished the chassis top.

    [​IMG]
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    Re-assembled the boards. I've slightly modified the board with the two 'double' caps.
    I did not want the twisted together look mentioned before, and I may just want to power the pre-amp from the amp in the future, so I have drilled two mounting holes in the ground track and mounted one cap on top to match the other board and mounted the pre-amp smoother cap under the board. There is plenty of clearance.

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    There you are to date. Alan

    There are a few more pictures here if you care to look: https://photos.app.goo.gl/VpUCFZjwhYME1N6K8
     
    torstoi, Craig B, Raoul Duke and 3 others like this.
  3. Tony L

    Tony L Administrator

    Neat, I’m surprised that switch came back! Preamp supply is odd, it would trigger me being different right/left!
     
  4. Yank

    Yank Bulbous Also Tapered

    I'm still triggered by the diff amp with a triode on one side and pentode on the other.
     
    Raoul Duke and Tony L like this.
  5. snowman_al

    snowman_al pfm Member

    Moving on well with the STA15.

    Chassis and bottom cover have had the rust removed (Hammerite Rust Remover Gel is remarkable stuff), rubbed down, primed and given 3 coats of 'Farina Grey'. It is not quite the original colour, but every piece of Radford I have is a slightly different colour...

    [​IMG][​IMG][​IMG]
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    Left it for 3 days for the paint to harden and have started re-assembly this morning.
    Rear panel completed, top of the chassis refitted and output transformers and smoothing cap fitted.
    Just a few earth / ground wires installed so far.

    Interestingly, I've found 2 un-soldered joints so far. One of the screen grid 1kΩ resistors was only soldered at one end and tightly squeezed round the tag at the other and the smoothing cap ground was just wrapped round the tag! In fact some of the soldering is very sparse (poor).

    [​IMG]

    The other thing is that several of the smaller wires have a green growth especially at the solder point, but even through the insulation as well. Several strands have been broken in a good number of wires from the board to the valve holders. And any disturbance breaks more...

    Valve runners and trims have been ordered from Will, I've prepped the B9A holders and got the hardware sorted. Old English White paint for the cage has been ordered too, watch this space.

    More pictures here if you want to scroll down them. https://photos.app.goo.gl/VpUCFZjwhYME1N6K8
    Alan
     
    torstoi, Johnjo, Mike P and 3 others like this.
  6. Tony L

    Tony L Administrator

    Great work, that is going to be a stunning amp!
     
  7. snowman_al

    snowman_al pfm Member

    Looks like some of the Imgbb pictures dropped off the previous post?
    Here they are
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  8. Mike P

    Mike P Trade: Pickwell Audio

    Excellent work as usual :)
     
  9. Radford Revival

    Radford Revival Trade: Radford Revival

    Looking good! It'll look a treat with fresh runners too!
     
  10. snowman_al

    snowman_al pfm Member

    Spent some time listening to the mains transformer 'buzz'. Found that off the chassis there was nil noise from the transformer, but as soon as it was mounted on the chassis a very slight buzz could be heard, and felt, even with no load. Tried various torque settings for the mounting bolts, but it was still noticeable. As my STA12 has thin rubber washers under its transformer and is very quiet, I tried various rubber and felt washers and found the 2mm felt ones all but eliminated the buzz. So I've mounted the transformer on them.

    [​IMG][/url[​IMG]

    I've wired up the output transformers.

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    Then Will's valve runners and trims arrived so a quick dry run, very nice.

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    Mounted the hardware.

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    The cage has had 3 coats of Old English White paint, but is still very soft, but a quick look at the final colours...

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    More pictures here: https://photos.app.goo.gl/VpUCFZjwhYME1N6K8
    Alan
     
  11. sideshowbob

    sideshowbob Champagne fascia aficionado

    Beautiful
     
  12. Tony L

    Tony L Administrator

    Amazing progress, it really looks superb. Have you a solution for the now missing front badge/logo?
     
  13. snowman_al

    snowman_al pfm Member

    Tony,
    Will does replica 'badges' and I've ordered a pair. I still have the originals, though they are worse for their removal, that I will keep inside the chassis once complete.

    Thanks for the comments everyone.
    It looks even better with the handles and new trims bolted in place...

    [​IMG][​IMG][​IMG]
     
    chiily, calorgas, Craig B and 8 others like this.
  14. Radford Revival

    Radford Revival Trade: Radford Revival

    I might be out of a job :D
     
    chiily, lordsummit, twotone and 5 others like this.
  15. Raoul Duke

    Raoul Duke pfm Member

    Great progress! And the colours look very close to original to me. I noticed some sticky green original wires on my amp as well. Can I ask what hookup wire you used to replace the orginal? I recall I was struggling to find good quality solid core wire the of the right gauge when I was doing my restoration. The new valve runners from Will really look the biz and I'm regretting not grabbing a set of those myself.
     
  16. torstoi

    torstoi pfm Member

    Thanks for the hint..one of my preamps came back from restauration buzzing like crazy,
    which it did not before.
    It may have been taken out and put in again with not the same or unsufficient torque perhaps,
    now I know what I can try to solve it,,,thx a lot !

    Very nice work you do there btw..I enjoy watching it.
     
  17. snowman_al

    snowman_al pfm Member

    Hi Jonathan,
    I've used stranded wire mostly, being in the UK a combination of 7/0.2, 16/0.2 and 24/0.2, not sure what standard is used in RSA. I think 7/0.2 = 24AWG.
    It is the original 7/0.2 stranded that have rotted out on this one. I read other people have the same problem with bad connections and it turns out to be rotted wires where they are soldered to the board or valve holder... The picture is of one of the stranded black wires I stripped back about 3 inches...
    Fortunately the single core white used on the heaters and black chassis connections were all fine and have gone back on. Yes I'm pleased I replaced the runners.
    [​IMG]


    Progress to date, the valve runners have been re-wired. Those are the original black and white wires and resistors.

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    They've been re-installed and the chassis wiring (output transformers and mains transformer etc.) nearly done.

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    Whole sequence here: https://photos.app.goo.gl/VpUCFZjwhYME1N6K8

    And thanks again for the kind words everyone, Alan
     
    Raoul Duke, booja30, torstoi and 3 others like this.
  18. Bad Parameter

    Bad Parameter pfm Member

    Are these active production resistors? If so what type or Mouser, Digikey, Farnell etc link? They look nice in vintage gear. Very nice work, though for myself I'd have gone for a do no harm shabby chic restoration as mention in post #9.

    [​IMG]
     
  19. booja30

    booja30 pfm Member

    Were these only available in the UK or Europe? It looks like a really fun project and I was poking around on eBay and other sites and only see results in the UK. It’s a really nice looking amp.
     
  20. Bad Parameter

    Bad Parameter pfm Member

    USA back then was a hifi power house, we didn't need no twee little British amps o_O The few that made it over will likely cost you 3X what they cost in UK, could be worse you could be in Japan. Get a UK PFMer to grab you one, box it proper, and ship it over, but it's so hard at this point to find anything of any sort vintage that hasn't already been restored, often badly and too expensive, or been through too many hands and dubious. The mint stuff goes to Sotheby''s now.

    That's why if you find something even if well worn but intact it's best to leave it as is, other than dead mint untouched honest wear and original patina commands the highest price these days. Motorcycles, cars, guitars and amps, bicycles, furniture, restored is a tier below worn and untouched now. It's not really a shabby chic, distressed, old-timey-trust-funder, fad either, it's just the rarity at this point. No more barn finds as there are no more barns, it's all been turned into condos and malls. This is maybe the last decade were something old of quality shows up untouched.

    Old geezer in town has a Moto Guzzi V7 Special, one of the earliest ones, that he's been Sunday driving since he bought it new 50 years ago, perfectly intact and maintained, every part well worn but undamaged in any way. If I had any money I'd offer him whatever he asked for it and continue riding it just as is. I bet someone stops him three times a day to ask if he's willing to sell it. If it was restored people would say super nice, but they wouldn't gush over it.
     
    Yank, booja30 and torstoi like this.

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