Radford STA25 Amplifier + SC22 preamp

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

Reply to
Roy L
Loading thread data ...

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.

Yes.

Pass on that.

You could try a post to - 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        dave@davenoise.co.uk           London SW
 Click to see the full signature
Reply to
Dave Plowman (News)

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

Reply to
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        dave@davenoise.co.uk           London SW
 Click to see the full signature
Reply to
Dave Plowman (News)

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

Reply to
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        dave@davenoise.co.uk           London SW
 Click to see the full signature
Reply to
Dave Plowman (News)

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

Reply to
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

Reply to
Tim Schwartz

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

Reply to
Roy L

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.