Radford STA25 Amplifier + SC22 preamp

[Roy L]

I have been fortunate enough to aquire these items and I am looking to
restore them. A plastic pushbutton is missing from the preamp and the
aluminium control knobs have a light corrosion on them. Should I
attempt to clean these off? Also the amplifier has a valve missing.
The one in the other channel in the equivalent position is an EF86, is
it safe to assume that this is the same type?
The label on the back is slightly damaged - I can see STA25 but the
top right corner is missing. I understand that there were a few
different MK's of this amp, is there any way of identifying which one
this is?
Valve line-up is as follows:-
Rear of amp
GZ34
EL34 Transformers in EL34
EL34 Screening Box EL34
ECF84 ECF82
?MISSING? EF86
Front of Amp

Any other advice/help with this amp would be much appreciated. I
suspect that it has not been used for quite a few years!
TIA Roy

 

[Roy L]

The push button was a stock item from those push button switch
systems
that allow you to make up any combination you wish. I think they are
still
available. I've certainly still got some bits lying around. The
shaft that
the button fits on is usually the problem when one falls off. But
that
should still be available too - as they were used in many many
makes.

The knobs can be cleaned and re-anodised at home - Google should
give you
the process.


Pass on that.


You could try a post to <uk.rec.audio> - it's a low volume group but
at
least two posters there have those amps and may be able to help with
identification, etc.

IMHO, it's probably the finest valve amp of that power ever made.
The pre
is fairly early solid state technology and nothing special.

--
*'ome is where you 'ang your @ *

Dave Plowman [email protected] London SW
To e-mail, change noise into sound.

Cheers for that. I havent opened up the preamp yet but I was quite
sure that I could also see at least one valve in there, only got this
yesterday so havent done an in depth investigation yet. Research so
far appears to suggest that I have aquired a bit of a gem though.
Regards
Roy

 

[Roy L]

Has it got adjustment pots for the bias? Can you read the numbers on
the
transformers?

--
*Growing old is inevitable, growing up is optional *

Dave Plowman [email protected] London SW
To e-mail, change noise into sound.

Not had the cover off the transformer compartment yet, had the bottom
cover off though. Didnt notice any adjustment pots - just two
tagboards. Looks like an electrolytic has been replaced at some stage,
has two strapped in parallel. Just bought a Mullard EF86 which is on
its way to me so I may make a start on it this weekend. Not going to
mess with it too much - if it aint broke, dont fix it!
Roy

 

[Roy L]

I'm pretty certain that makes it an early one - later ones had
externally
accessible pre-sets for setting the bias alongside the speaker
connections. Think also my comment about the pre being solid state
also
may only have applied to later ones. But all IIRC, so don't take it
as
gospel. I believe there is a moderated email group dedicated to this
amp
which would be the place to get definitive answers. If you're
interested
in that and can't find it by Google I might be able to get the
details for
you.

--
*They call it PMS because Mad Cow Disease was already taken.

Dave Plowman [email protected] London SW
To e-mail, change noise into sound.

Thanks for all the clues, I have actually found a load of stuff on
this amp - I didnt realise quite how desirable this item was! Weird
really, In just a week I have more info on this old bit of kit than I
have on stuff just a couple of years old. I have also found that there
are a number of people who specialise in repairs to vintage valve
amplifiers - and they seem to be making a living at it. Maybe this is
an avenue the guy who was asking if there was still a need for proper
technicians ought to go down.
Certainly given me food for thought If I should ever find myself
unemployed.
Roy

 

[Tim Schwartz]

I have been fortunate enough to aquire these items and I am looking to
restore them. A plastic pushbutton is missing from the preamp and the
aluminium control knobs have a light corrosion on them. Should I
attempt to clean these off? Also the amplifier has a valve missing.
The one in the other channel in the equivalent position is an EF86, is
it safe to assume that this is the same type?
The label on the back is slightly damaged - I can see STA25 but the
top right corner is missing. I understand that there were a few
different MK's of this amp, is there any way of identifying which one
this is?
Valve line-up is as follows:-
Rear of amp
GZ34
EL34 Transformers in EL34
EL34 Screening Box EL34
ECF84 ECF82
?MISSING? EF86
Front of Amp

Any other advice/help with this amp would be much appreciated. I
suspect that it has not been used for quite a few years!
TIA Roy

Roy,

As far as I know the amp is likely to be a series I or series II, as
the series III diagram I have shows a solid state rectifier, not the
GZ-34 you mention, though the MA-25 (mono version) series II does use
the tube rectifier.

The front end tube is certainly the EF86 (a US sub is the 6267 as I
recall) It is a wonderful amp, thigh I can't honestly say its any great
improvement over a McIntosh MC225 or Marantz 8/8B, both of which are
also wonderful amps.


Regards,
Tim Schwartz
Bristol Electronics

 

[Roy L]

Roy,

As far as I know the amp is likely to be a series I or series II, as
the series III diagram I have shows a solid state rectifier, not the
GZ-34 you mention, though the MA-25 (mono version) series II does
use the tube rectifier.

The front end tube is certainly the EF86 (a US sub is the 6267 as I
recall) It is a wonderful amp, thigh I can't honestly say its any
great improvement over a McIntosh MC225 or Marantz 8/8B, both of
which are also wonderful amps.


Regards,
Tim Schwartz
Bristol Electronics

Thanks for your interest Tim, I have had to put the amp on one side
for the moment as SWMBO has decreed that I have to finish some house
redecoration before I spend time on "that thing". She doesnt
appreciate the industrial aesthetics of this loveley piece of kit! (I
am hoping she may grow to love it in time, if not then its destined
for ebay!)
Regards
Roy