Quad Help!

[Dave Cawley]

I would not have recommended it if that was so!
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Electrical contact cleaner and lubricant
Ideal for cleaning crossfaders and pitch controls
Non-flammable formulation
Extension tube for hard to reach places
200ml can

Servisol electrical contact cleaner and lubricant in a can - ideal for cleaning your crossfader or pitch controls. Supplied complete with an extension nozzle in a 200ml can.

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Switch and contact cleaning lubricant. Quickly removes tarnish and other deposits. Residual lubrication film protects contact surfaces. Prevents arcing between dry contacts. Safe to use on plastics, rubber and other delicate materials

[Beechwoods]

I know you wouldn't Dave. The important bit I guess is to get one that is specifically recommended for volume controls and faders. I've heard sad tales about Deoxit and volume controls for example. Where can you get the one you mention?

[Dave Cawley]

Where can you get the one you mention?

See my post 176.

Dave

[Marco]

You can also get that stuff in Maplins

Marco.

[Tom472]

I'd say the humming or fizzing is most likely to be the PS elecrolytics in the 405. They're absolutely massive, and no matter who "services" it, they wouldn't have replaced these as they're expensive.
Once you've got it all working you're probably going to have to replace them as they'll be affecting the sound of the amp as well as the annoying hum. I think mine cost me about £30.
Like others have said, the 405 needs some tweaking to get the best from it, there's a great web article on modifying the 405 somewhere by a German guy I think - but there are companies who will do the work if you're not confident doing it yourself.

Hope you get it all sorted.
Tom

[DSJR]

The supply caps in a 405 lasted around eleven years of fairly light use before they started to leak. they're not that big in value by supply cap standards and are fairly inexpensive to replace. You have to be good at soldering though...

I'd also recommend looking at the Dada website, as they have a dual supply board that is pretty well a drop-in replacement for the caps that come out (caps have tripled in value for the same physical size, making this possible nowadays).

Other sources of buzzing could be if phono sockets have been placed instead of the DIN (there are two holes nearby that many people have used. You may have a hum loop and Quad used to supply a two core mains lead to connect the 405 series to their preamps as I recall. Purchased IEC replacements with moulded plugs will have all three mains connectors wired, thus causing an earth loop......

The 33 volume pot is possibly the weakest part of it and I think Quad had some new ones made with integral mains switch. We used both switch cleaning solvent (from RS) and, also, Servisol cleaner/lubricant, which may be better for very old carbon track pots and pre-sets (this latter was used extensively in TV workshops where TV's had the cheapest, lowest of the low standard of components fitted).

[spendorman]

There have been switch cleaners that are just that and do not provide a lubricant. These are not usually good to use on potentiometer (found out the hard way many many years ago). Switch cleaner/ lubricant is generally OK.

Again, I would say eliminate the 33 by feeding the 405 direct fron CD payer etc. to find out if its the 33 or 405 at fault. Take it from there.

Have a look at the top of those two big capacitor cans in the 405. Can you see them leaking, are the tops bulging?

If on a budget there are other suppliers than Dada and Net Audio of those big caps. Check on e bay. Dada and Net supply good stuff, but one can find cheaper and still acceptable capacitors.

[Tom472]

I'd agree with the above - the Dada board looks good, but you could buy two of those 15,000uF BHC capacitors from RS for £30 or so. Depending on what you spent on your 405 and how handy you are with a soldering iron will probably determine the best course.
But definitely try the 405 and the 33 in different set ups first to determine which is at fault.

Tom

[spendorman]

I'd agree with the above - the Dada board looks good, but you could buy two of those 15,000uF BHC capacitors from RS for £30 or so. Depending on what you spent on your 405 and how handy you are with a soldering iron will probably determine the best course.
But definitely try the 405 and the 33 in different set ups first to determine which is at fault.

Tom

There are some new Vishay BC Components Capacitors that are suitable on e bay at about £15 including postage at the moment. (I have no assosiation with that sale of course).

[Tom472]

There are some new Vishay BC Components Capacitors that are suitable on e bay at about £15 including postage at the moment. (I have no assosiation with that sale of course).

Looks like a good deal, and at least you know they're defo going to fit. Only 10mF rather than 15mF and double the ESR I believe for those caps as compared to the BHC's though.

Tom