Bought Altec Lancing and Sugden Monoblocks £100

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jack
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#61

Post by jack »

No-one is suggesting that you change the circuit in any way - just bring it back to original spec.

The caps always get dodgy, some silcon (or germanium) will die, some carbon will migrate about the place, but you can still do a genuine restore - the semiconductors are mostly still available and that's the main thing.

A bit of Servisol Super 10 switch cleaner for the pots & switches & stuff, some isopropyl alcohol to clean up any stray carbon or flux deposits and that's it really.

Please don't strip your old scope for tubes - ask on one of the forums if someone wants to buy & restore it first...

I have some sympathy here - I had a beautiful Tektronix 7904A with a load of plug-ins - an emotional scope for me as it was the first scope I had as a junior EE at ITT/STL - you could pretty much have bought a small house with what one of those cost back in the day.

However, the PSU developed the "tick of death" and it took up far too much space in the shack, so it went to a guy that restores Tek kit for colleges. Kind of cathartic in a way, and it freed up a lot more space on the bench.

I sold my Tek 2430A at AudioJumble this year, so am down to two scopes now - a Tek 2465A (generally accepted to be the best analogue scope ever made) and a small Tek digital scope.
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#62

Post by jack »

Paul Barker wrote:T
OK here comes a gamble. The large capacitors. Originals are 40v so I included 40v in my search. clal me a fool but an excellent result shone out from the page but over capacity. It is 15,000 rather than 10,000 40v and has lower ESR than most 14 other factors typical of a £12 product, but at nearly half the price. Has screw terminals.

EPCOS 15,000 40v Power Capacitor.
No - bad plan - you need headroom else the caps will meet a premature end - you may be lucky, most likely, not - the HT rail is +76V - the two caps in series in the PSU section would be rated at 80V, i.e. only 4V headroom and not nearly enough.

Don't go for the 40V option, there's a reason 63V caps were in there.

Also, who not just go for the SB5100s from RS - http://uk.rs-online.com/web/p/rectifier ... s/7010212/

Schottky or not, you should add 100n caps across the bridge diodes.
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#63

Post by Paul Barker »

nickds1 wrote:
Don't go for the 40V option, there's a reason 63V caps were in there.
Also, who not just go for the SB5100s from RS - http://uk.rs-online.com/web/p/rectifier ... s/7010212/
Well I take that on board but actually 40v is what was in there for the last 35 years.

Image

but the order was placed before I read your advise.

Lets make sure the household mains is reduced to 230v and see how we get on.

Diodes? Because the ones I ordered are the only soft recovery ones.
nickds1 wrote: Schottky or not, you should add 100n caps across the bridge diodes.
Yes thanks for confirmation , I copied everything you did re bypasses. Also the 470nf on the secondaries. To get rid of final RF I guess? Or does it stop back emf from diodes going back to other equipment?
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#64

Post by jack »

Paul Barker wrote:Well I take that on board but actually 40v is what was in there for the last 35 years.
I see that the originals were marked 40V - doen't make it right - those caps may have been chosen because they were very conservatively labelled.

What is certain is that no competent or self-respecting SS amp designer today would dream of using caps that are rated at just about their working voltage - they *always* provide headroom - it may just be in the mid '70s that a compromise had to be made between needed capacity (10,000uF) and space available (those caps fill the space). Modern caps are far more advanced and relatively smaller. IMHO, its a design flaw. What's even worse, is that the caps are used in series, and even with the centre tap connecting to their join, its highly likely that under operational conditions, the caps won't balance and one or the other will exceed 40V

Anyway, you've already bought the caps. Good luck! (though you can still return them to RS for a replacement!)
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#65

Post by Paul Barker »

Got you.

I'll drop mains to 220 then. That will put 35v per cap.
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#66

Post by Stuart Dean »

Hi Paul
Interesting to see you dabbling with Sugden SS kit.
I have a Sugden A48 in the loft and felt motivated to dig it out and give it a whirl. Probably last used about 15 years ago.
Surprising what you consign to the loft and then forget about. Whilst reclaiming the A48 I found a dinky little Aurex A10b amp and a Cambridge P50. Hope to re-activate these shortly.
I seem to remember the A48 sounding rather good.
Funny story concerning Sugden.
Shortly after acquiring the A48 I found a matching T48 tuner. Strange little thing which had push button preset tuning. It sounded quite impressive but had an intermittent fault in that it output would disappear occasionally and the mysteriously re-appear. I checked the power supply which seemed OK but was unable to pin down the fault. This was before you could track down circuit diagrams on the internet so I decided to contact Sugden by telephone. After a couple of attempts with the usual "the chap you need to speak too is in a meeting" or "I'll get him to phone you back" (Yeah that's going to happen isn't it) I manage to speak to someone in the service department. After explaining the problem I was told "Send it back to us and we will have a look at it". I said that I didn't want to do this the tuner cost very little and even back then it was quite old, all I wanted was the circuit details and I would attempt to correct the fault myself.
The Sugden rep then replied "If all thah wants to do is piss about then stop wasting my time" and put the phone down.

Anyway following this and after several hours of pissing about the T48 was sent to the tip as I was unable to locate the fault and the A48 took up residence in the loft where it's been ever since.

Hope you are successful in restoring your monoblocks.
Stuart
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#67

Post by Paul Barker »

Thanks Stuart.

Nice story.
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#68

Post by directwindow65 »

stuart

Nice story.
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#69 Re: Bought Altec Lancing and Sugden Monoblocks £100

Post by jack »

Whatever happened to these?
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#70 Re: Bought Altec Lancing and Sugden Monoblocks £100

Post by rufusen »

Hello, I just had the opportunity to buy a second Sugden C51 so to try the monoblock configuration but I'm not sure how to do the connections.
Do I need a special DIN cable? Different from the one that now ends with two rca? Many Thanks!
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#71 Re: Bought Altec Lancing and Sugden Monoblocks £100

Post by rufusen »

I mean P 51 ;-)
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#72 Re: Bought Altec Lancing and Sugden Monoblocks £100

Post by Paul Barker »

jack wrote: Sun Mar 19, 2017 12:39 pm Whatever happened to these?
Sorry just seen this. They are in bits with the parts I bought, like all my other projects on hold. Bigger life choices change our priorities for many seasons. Maybe one day I will pick all this up again. Or may divert my attentions further from it than it is even now and never return. But I look in here once in a while, that doesnt take up much of my precious time.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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