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Radford STA25 Mk III -- a lot of questions.

It is here, it is working with the 149s. It sounds very good of course, and I can already hear two things - the bass is tighter than with the previous amp I had there, a Quad 306. And the sound is more punchy, the attacks are quicker, cleaner, sharper.

A quick question- this is my first experience with valves so I very much appreciate your help and experience.

The first of the smaller valves on each side isn’t glowing - are they the input valves? Is that how it should be?

Here’s a pic of each side

5-A102-A95-8412-4-A90-ABBF-30-A82-B4-AB525.jpg



D81-F376-F-B4-FE-4-B97-815-F-AF4-D60-C7-B4-D7.jpg
 
Are they EF86s? If so they have a weird mesh-plate construction so don’t glow the same way. Not all valves are the same brightness and if its working chances are its fine. The warning signs something is going very wrong is if the plates (the big grey bits) in the power tubes start glowing!
 
The valves should all glow. Maybe not equally but the cathode does have to get hot to generate electrons. Have a look in the dark.
 
The input valve is an EF86 and the weird mesh-plate is actually the screen. You don`t see much glow from an EF86 but you can usually see a little right at the bottom.
 
Thank you gentlemen. I closed the curtains and they are indeed all glowing, clearly the first not very brightly.

It’s really is true that these amps sound better after they’ve been playing for a while. I’ve had two sessions with it since it arrived and both times the same thing happened: after about twenty minutes the hairs on the back of my neck started to stand on end. Wonderful!
 
mandryka said:
It is here, it is working with the 149s. It sounds very good of course, and I can already hear two things - the bass is tighter than with the previous amp I had there, a Quad 306. And the sound is more punchy, the attacks are quicker, cleaner, sharper.

A quick question- this is my first experience with valves so I very much appreciate your help and experience.

The first of the smaller valves on each side isn’t glowing - are they the input valves? Is that how it should be?

Here’s a pic of each side

5-A102-A95-8412-4-A90-ABBF-30-A82-B4-AB525.jpg



D81-F376-F-B4-FE-4-B97-815-F-AF4-D60-C7-B4-D7.jpg
Click to expand...
Before you change the EL34,s
mandryka said:
It is here, it is working with the 149s. It sounds very good of course, and I can already hear two things - the bass is tighter than with the previous amp I had there, a Quad 306. And the sound is more punchy, the attacks are quicker, cleaner, sharper.

A quick question- this is my first experience with valves so I very much appreciate your help and experience.

The first of the smaller valves on each side isn’t glowing - are they the input valves? Is that how it should be?

Here’s a pic of each side

5-A102-A95-8412-4-A90-ABBF-30-A82-B4-AB525.jpg



D81-F376-F-B4-FE-4-B97-815-F-AF4-D60-C7-B4-D7.jpg
Click to expand...
The dimple on the EL34,s suggest they may be (East )German RFT types.RFT made EL34,s for Siemens and Telefunken so ,if they are,and they are ok ,you would have to spend a lot to better them.
 
any proper make of valve will make the amp sing. If it sounds good, it is good. If it doesnt, ask why
 
Well no. It didn't fuse anything and I think that the music kept on playing. I just ran to it and turned it off at the mains.
 
Oh no! That's heartbreaking. I hope you are able to get it fixed and the experience doesn't dent your confidence with valves. It sounds like you were really enjoying it.
 
Jeez, that's bad luck. My main system has been all valve for nearly twenty years with no incident so I think you've just been unlucky. Don't lose heart, get it fixed and get back in the groove.
 
Chops54 said:
Jeez, that's bad luck. My main system has been all valve for nearly twenty years with no incident so I think you've just been unlucky. Don't lose heart, get it fixed and get back in the groove.
Click to expand...

Indeed. I've had a number of valve power amps over the years, all of which have been couriered to me and survived, but the only kit I've ever had to put in for repair has been transistor based.
 
In fact Emporium have been very good to deal with so far, we shall see how they respond to this. What I’m hoping is that they’ll have an engineer who can repair it quickly. It sounds as though they didn’t test the equipment very thoroughly before selling it - which is surprising for such an experienced dealer. I’ll keep this thread posted about what they do.

I’m sure it was an exploding capacitor, the problem is going to be finding out why. Emporium said that the smoothing capacitors were all new, but I’m not sure who did the job.

I had 6 hours of STA25 and it was revelation - the combination with the Rogers speakers was fabulous. I want one of these amps, whether it’s this one restored or another.
 
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