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Radford STA15 Restoration

chiily

chiily

PFM Special Builder
Today was the day that this package arrived...



Containing an STA15
PXL_20220511_192628887 by Garf Arf, on Flickr

PXL_20220511_192441396 by Garf Arf, on Flickr

Overall it doesn't look to be in too bad a shape.
PXL_20220511_192355413 by Garf Arf, on Flickr
PXL_20220511_192400164 by Garf Arf, on Flickr
PXL_20220511_192427280 by Garf Arf, on Flickr

HT cap is not in the best, having had a little vent.
PXL_20220511_162408127 1 by Garf Arf, on Flickr

Left and right boards looking untouched apart from the 470R resistors, which look to have been replaced at some time based on their pristine looks and the board being black from heat.
PXL_20220511_162424785 1 by Garf Arf, on Flickr

...and the right board has more heat blackening, plus the resistors are a different type.
PXL_20220511_162354140 1 by Garf Arf, on Flickr

Resting, in fact quite well stuck, on the RHD boards resistor is a chunk of glass, I assume from a valve, but who knows.
PXL_20220511_162403530 1 by Garf Arf, on Flickr

Valve-wise it has four Blackburn Mullard EL34s in two pairs, one from 1966 and the other pair from 1969. Both 82s are Blackburn Mullards from 1965. One EF86 is a BRIMAR and the other I think a, well I'm not sure, here is a picture.
PXL_20220511_160408294 1 by Garf Arf, on Flickr

The rectifier was a GZ32, very strange, again a Blackburn 1966 Mullard. I will do the diode mod to the amp in due course and add a modern, quality GZ34. I have a Harma Retro from Watford valves on the shelf.

I've checked the continuity of the transformers and all looks well. The seller did tell me that he had been using the amp up until a few days ago.

It does have a pair of chrome handles, sadly both are bent, one more than the other. Once I have then straightened out I'll take a couple of pics and post. The chrome on then is in good shape.

Be prepared for lots of questions...

First one, would it be heresy to drill out the rivets holding the phono connector and replace with 3M machine bolts? I would like to fit the same phono connectors I did to the Leak.
PXL_20220410_143746981 by Garf Arf, on Flickr
PXL_20220402_152219712 by Garf Arf, on Flickr
 
257 after mine, which is playing Mingus right now! Mine doesn’t have 48 at the front though. Wonder what that signifies?
 
Marchbanks said:
257 after mine, which is playing Mingus right now! Mine doesn’t have 48 at the front though. Wonder what that signifies?
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I was trying to decode the number on the front earlier..

48 BO 748

748 is the production serial number, I'm guessing from your post.

48? No idea either.

BO? Body Odour, Beautifully Ordained
 
If you re-cap the electrolytics,F&T do dual section types which ,to me look a lot more pro' than 2 separate caps hooked together.Can recommend them as being v good. The green 470ohm may have been changed from 390ohm to give the EL34's an easier life (check with the other channel),some were originally fitted with 390 in the factory ,as was mine.The EF86 is rebranded as a Tungsram ,not an original.The serial no on mine starts with 48 and is no 729.ISTR I read somewhere some were supplied as kits ,maybe this is why some have 48 as a prefix - If incorrect , stand to be corrected etc
cheers
Mick
 
I would probably go for new boards by the looks of it - I can supply new handles too if need be. I actually have a set of made up boards on the shelf ready to go if necessary.
 
mik_rik said:
If you re-cap the electrolytics,F&T do dual section types which ,to me look a lot more pro' than 2 separate caps hooked together.Can recommend them as being v good. The green 470ohm may have been changed from 390ohm to give the EL34's an easier life (check with the other channel),some were originally fitted with 390 in the factory ,as was mine.The EF86 is rebranded as a Tungsram ,not an original.The serial no on mine starts with 48 and is no 729.ISTR I read somewhere some were supplied as kits ,maybe this is why some have 48 as a prefix - If incorrect , stand to be corrected etc
cheers
Mick
Click to expand...


To the best of my knowledge, Radford only made kits available for a brief period circa 1962 / 1963 following on from a series of articles published in Hi-FI News. I have the original flyers for these D.I.Y. factory issued kits. The prefix 'C' for constructor was used to identify these versions.
 
brecklandboy said:
To the best of my knowledge, Radford only made kits available for a brief period circa 1962 / 1963 following on from a series of articles published in Hi-FI News. I have the original flyers for these D.I.Y. factory issued kits. The prefix 'C' for constructor was used to identify these versions.
Click to expand...
Would it be possible to scan those flyers and post them here please? I would be very interested.
 
brecklandboy said:
To the best of my knowledge, Radford only made kits available for a brief period circa 1962 / 1963 following on from a series of articles published in Hi-FI News. I have the original flyers for these D.I.Y. factory issued kits. The prefix 'C' for constructor was used to identify these versions.
Click to expand...

Thanks for this,it was something I had a vague recollection of (long before t'internet) and thought might have been a possibility
Mick
 
chilly, if you can send me your email address via the messaging system, I can attach a couple of half- decent images of the original double sided A5 size leaflet which you can then post on this thread for general information.
 
brecklandboy said:
To the best of my knowledge, Radford only made kits available for a brief period circa 1962 / 1963 following on from a series of articles published in Hi-FI News. I have the original flyers for these D.I.Y. factory issued kits. The prefix 'C' for constructor was used to identify these versions.
Click to expand...

That is my understanding too. That was the Series 2 with the 6U8 phase splitter. I think the 'C' was positioned just before the STA15 so 'C'STA15 then a long serial number without letters?
No idea re the '48' pre-fix on a Series 3.

chiily said:
First one, would it be heresy to drill out the rivets holding the phono connector and replace with 3M machine bolts? I would like to fit the same phono connectors I did to the Leak.
Click to expand...
Why heresy? I had to do that on my STA12.


IMG-7992.jpg
IMG-7992.jpg
 
snowman_al said:
Why heresy? I had to do that on my STA12.


IMG-7992.jpg
IMG-7992.jpg
Click to expand...

That looks really good.

Heresy, because of a number of people who complained when I dared to suggest that I change a capacitor or a resistor in a Quad II, regardless of whether it would have made the amp usable. :) It is that balance of restoring something that one wants to enjoy by using it for the purpose it was designed and built for, against shrink wrapping and popping it in a display case. I'm more of the bent to make the device useful without generating some Dr Frankenstein monster. :)

I do love the way that all the slots are aligned Al :)
 
I think you'll find this Tungsram branded valve was in fact manufactured by Philips / Mullard at one of their factories in either Holland or Belgium in the 1960s. The internal factory designation for this version of the EF86 etched on the glass near the base is usually '8Y6' or possibly '8Y7'.
 
brecklandboy said:
I think you'll find this Tungsram branded valve was in fact manufactured by Philips / Mullard at one of their factories in either Holland or Belgium in the 1960s. The internal factory designation for this version of the EF86 etched on the glass near the base is usually '8Y6' or possibly '8Y7'.
Click to expand...

I thought the ones with "FOREIGN MADE" printed on them were usually for the US market, no?
 
I don't think that's the case as they are quite common in the U.K. These are very good valves - as good as the British manufactured ones ( excluding the rare M8195 version) in quality terms.
 
Nuts and bolts , lots of stuff got cadmium plated back in the day, as it ages it oxidises and forms a white powder, this is really dangerous stuff.

if you’re working on old gear I’d recommend you read up and make sure you know what the potential dangers are.
 
brecklandboy said:
I think you'll find this Tungsram branded valve was in fact manufactured by Philips / Mullard at one of their factories in either Holland or Belgium in the 1960s. The internal factory designation for this version of the EF86 etched on the glass near the base is usually '8Y6' or possibly '8Y7'.
Click to expand...
On the back of the Tungsram is the marking, "8Y5", "L7F3". If the latter is a Mullard code then the valve was manufactured by MBLE in Brussels (Mazda), 1967.

Confirms your thoughts. :)
 
david ellwood said:
Nuts and bolts , lots of stuff got cadmium plated back in the day, as it ages it oxidises and forms a white powder, this is really dangerous stuff.

if you’re working on old gear I’d recommend you read up and make sure you know what the potential dangers are.
Click to expand...
That is good to know, thank you.
 
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