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Radford SC-2 / STA15



 
 
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  #1  
Old September 21st 04, 04:35 PM
Walther
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Default Radford SC-2 / STA15

Hello,

Im entirely new to this NG and have a single question:
does anybody have a picture of Radford SC-2/STA15 or STA25?

I happen to have found some and Im not sure what it is,
esp. the power amp has no label on it (but a serial number).

Yes, believe it or not: somebody trashed it, along with a
Thorens TD124MkII equipped with a SME 3009 - fortunately I
spotted it in the dumpster before that was emptied.

But half the tubes are smashed or missing...

Since I very much like the sound of my 1961 braun csv-13 :-)
Id like to get the radford back to life, and theres a site
with schematics on the net...

Now I have to identify the power amp first...

....any help greatly appreciated!

TIA

Walther

Please feel free to respond personally at in4tec dot de.
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  #2  
Old September 22nd 04, 05:49 AM
Walther
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Default

Walther wrote:
> Hello,
>
> Im entirely new to this NG and have a single question:
> does anybody have a picture of Radford SC-2/STA15 or STA25?


[...]

from what I learned now its more likely a STA25.
It has some BIAS adjustment gear on the front side.

Still not quite sure... ordered me some EF86, ECF82 & EL34.
Hope this will do (I have no clue of tube valve electronics).

> Please feel free to respond personally at in4tec dot de.

  #3  
Old September 22nd 04, 07:23 AM
Tonni
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Default

My G...! - How lucky can a man get?!!!

Regarding diagrams, look he
http://www.drtube.com/audioamp.htm

Does wery much hope it helps You ;-)
Good luck with You'r find... - By the way, - wheres that dumpster?!!

Best regards
Tonni

"Walther" > skrev i en meddelelse
...
> Hello,
>
> Im entirely new to this NG and have a single question:
> does anybody have a picture of Radford SC-2/STA15 or STA25?
>
> I happen to have found some and Im not sure what it is,
> esp. the power amp has no label on it (but a serial number).
>
> Yes, believe it or not: somebody trashed it, along with a
> Thorens TD124MkII equipped with a SME 3009 - fortunately I
> spotted it in the dumpster before that was emptied.
>
> But half the tubes are smashed or missing...
>
> Since I very much like the sound of my 1961 braun csv-13 :-)
> Id like to get the radford back to life, and theres a site
> with schematics on the net...
>
> Now I have to identify the power amp first...
>
> ...any help greatly appreciated!
>
> TIA
>
> Walther
>
> Please feel free to respond personally at in4tec dot de.



  #4  
Old September 22nd 04, 11:28 PM
Fabio Berutti
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Default

I took a look at the schematics. Looks like a darn good amp. Consider that
most of the value of a tube amp is in the iron (transformers). Capacitors
are not so expensive, nor are the tubes if You think a good one (*) can last
10,000 hours. I think it's really worth the pain to try and make it 100%
functional again.
Pay attention before powering on, maybe a shorted cap is waiting for You to
blow. Check with a voltmeter to find "gross" shorts, then power up GENTLY.
It was in the garbage, after all. A cheap trick is to put a lamp in series
along the line cord to drop the voltage. Start with a high resistance one
(say 25W or less) and then go up to 100W or more (this is applicable only if
You do not have a Variac). A thread on this took place some times ago on
this NG.
Pay attention, these are TUBES, it means 400+ Volts are in there. I tasted
some 430VDC once, not my cup of tea for sure!
As per the Thorens, it will be more difficult to decide if it's worth a
workover. I own a 126MkIII and I'd sell my soul before it, but if the table
support bearing is worn, well, I suppose no Swiss watchmaker will ever be
able enough to fix such a piece of old-time art.

I'll plan a trip to some German landfill one of these days... maybe I'll get
the Telefunken tubed tuner I'm looking for!

Ciao

Fabio

(*) "good" does not mean necessarily "Tiffany's". Plain, current production
Sovteks, JJ or Svetlanas are good enough for any purpose, unless You want to
keep the amp a "collector's item".


"Walther" > ha scritto nel messaggio
...
> Hello,
>
> Im entirely new to this NG and have a single question:
> does anybody have a picture of Radford SC-2/STA15 or STA25?
>
> I happen to have found some and Im not sure what it is,
> esp. the power amp has no label on it (but a serial number).
>
> Yes, believe it or not: somebody trashed it, along with a
> Thorens TD124MkII equipped with a SME 3009 - fortunately I
> spotted it in the dumpster before that was emptied.
>
> But half the tubes are smashed or missing...
>
> Since I very much like the sound of my 1961 braun csv-13 :-)
> Id like to get the radford back to life, and theres a site
> with schematics on the net...
>
> Now I have to identify the power amp first...
>
> ...any help greatly appreciated!
>
> TIA
>
> Walther
>
> Please feel free to respond personally at in4tec dot de.



  #5  
Old September 24th 04, 08:50 AM
Walther
external usenet poster
 
Posts: n/a
Default

Fabio Berutti wrote:
> I took a look at the schematics. Looks like a darn good amp.

[...]

Thank you (all) for all the advice and information you gave!

When I first spotted it in that dumpster I thought it must be.
Sure I will keep this thread alive while working on the STA25
(which it turned out to be), and put some pics on my website.

BTW, for enthusiasts from all over the world now going to flock
on german landfill sites... we got pretty much thermal handling
of waste here these days thanks to excessive politician bribing
by a now imprisoned local recycling tycoon.

So it is most likely this STA25 would have gone up in smoke
or picked out by a giant magnet and smashed (makes me shudder).

Cheers

Walther

at in4tec in Germany

I have to apologize - the address above is faked, sorry!
Id like to know a better way to get rid of spammers.
  #6  
Old September 30th 04, 08:56 PM
Walther
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Posts: n/a
Default

Hello again,

anybody interested in having a look at the "trash" I pulled from the
rubble - feel free to do! Heres a link to some pics of that find
(caveat: bandwidth required since these pictures are quite large):

http://www.in4tec.de/PICS/RADFORD/luckyfind.html

Anything I better should know about these amps (Im a rookie)?
  #7  
Old September 30th 04, 09:25 PM
Sander deWaal
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Default

Walther > said:

>Hello again,
>
>anybody interested in having a look at the "trash" I pulled from the
>rubble - feel free to do! Heres a link to some pics of that find
>(caveat: bandwidth required since these pictures are quite large):
>
>http://www.in4tec.de/PICS/RADFORD/luckyfind.html
>
>Anything I better should know about these amps (Im a rookie)?


Nice find!
This looks like a STA25. There must be a GZ34 rectifier in as well.
The SC22 preamp is powered from the main amp, looks like they even
left the octal cable in there for you :-)

Before powering up, check if the bent sheet of the SC22 doesn't cause
any short circuit somewhere. Also, check the main amp's innards for
any damage
Despite the use of an indirectly heated tube rectifier, it's still
best to power it up through a variac if possible, or use a 100W
lightbulb in series with the mains.
That way, you can monitor whether there are any bad supply capacitors.
Secondly, check the output tubes' bias, there are bias testpoints at
the rear. Keep open the possibility of leaking coupling caps to the
grids of the EL34s. In that case, they'll draw excessive current and
will soon be worn out.
Check for red glowing plates and/or screen grids of the EL34s.
If everything looks OK, you can check if the supply voltage is OK.
I think it ought to be in the 380...400V range at the first supply
cap.

Viel Spass mit deinen Verstaerker , er hat ein wirklich guten Klang
wenn alles stimmt und ist immer noch sehr beliebt bei vielen
Musikfreunde :-)

--
Sander deWaal
"SOA of a KT88? Sufficient."
  #8  
Old October 2nd 04, 06:05 PM
Andy Evans
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Default

Since these items are worth around $1,000 in good condition, it might be wise
to take it to someone familiar with them before doing anything. You may want
advice on how to restore it to start with, before retro fitting anything and
chucking anything away. Keep all the bits, whatever you do - this kind of item
needs to be in original condition as much as possible for the real money. There
are support groups for these amps - you can ask on the Leak group, which is


=== Andy Evans ===
Visit our Website:-
http://www.artsandmedia.com
Audio, music and health pages and interesting links.
  #9  
Old October 3rd 04, 02:49 PM
Walther
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Default

Andy Evans wrote:
> Since these items are worth around $1,000 in good condition, it might be wise
> to take it to someone familiar with them before doing anything. You may want
> advice on how to restore it to start with, before retro fitting anything and
> chucking anything away. Keep all the bits, whatever you do - this kind of item
> needs to be in original condition as much as possible for the real money. There
> are support groups for these amps - you can ask on the Leak group, which is
>
>
> === Andy Evans ===


Thanks a lot Andy,

Im a newbie to tube amp restauration but not to restauration at all,
normally I prefer working on motorcyles - the oldest of which, a BMW
R25/3 with sidecar has a few years more than the STA25.

I begun cleaning and examining the power amp today and now all the dirt
has vanished it looks really great! The paint is fine, the metal parts
not corroded, the chrome shiny again :-). Nothing broken, bent or gone
up in smoke, the inside looks pretty complete and functional.

The tubes still present are Mullard GB (EL34, EF86) and Mullard Canada
(ECF82), one EL34 was Valvo. I guess the Mullard was originally fitted.
Im going to replace with Philips8 EF34, EF86) and Siemens (ECF82) NOS.
Hope this doesnt make a difference or bother the purists.

One 88F Capacitor and a small Resistor near its Counterpart on the
other side seem to have been replaced in an early age of the amp - they
do not match left/right but look as ancient as the rest of the parts.

As far as I can measure with my multimeter no big capacitors are
short-circuited, both speaker outputs measure 0.8 Ohm - with no tubes
yet fitted.

I would be glad to hear that this is the correct value and no shortcut
or something...

Im going to proceed as adviced and power up with limited current first
to see if there are any leakages which are likely to lead to a damage.

And Ill gladly put some more pictures of the restauration process on my
web site - watch out at
http://www.in4tec.de/PICS/RADFORD/luckyfind.html

Thanks a lot everybody for being very helpful!

Walther



  #10  
Old October 5th 04, 11:17 PM
Walther
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Posts: n/a
Default

Walther wrote:

[...]

I have now updated some pictures of the "restoration" process
of what turned out to be a Radford STA25 power amplifier at

http://www.in4tec.de/PICS/RADFORD/luckyfind.html

feel free to take a look - but some bandwidth is required.
Any good advice of yours for the rebuild greatly appreciated!

Walther
 




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