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Old 8th January 2008, 12:01 PM   #1
thomsva is offline thomsva  Finland
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Default Soldering tubes directly to PCB?

Im scetching up a layout for a tube based preamp. I would like to use a low profile enclosure with the tubes inside. But if the tubes are standing up lots of vertical space is needed.

If the tubes are soldered directly to the pcb i could get away with 75mm internal enclosure height:

15mm space between bottom plate and pcb
2mm pcb thickness
50mm tube soldered directly to pcb
3mm space to vented enclosure cover

70mm total

Using a tube socket on the pcb would increase the total height by approximately 15mm, and I don't like that.

The obvious drawback is that changing tubes is a hassle. But is there anything else?
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Old 8th January 2008, 12:10 PM   #2
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Thomas,

Perhaps you could lay the valves on their sides rather than straight up. That would reduce required height by about 25mm.

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Old 8th January 2008, 12:13 PM   #3
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there were flying lead tubes produced that were made for just that type of use - for example
http://cgi.ebay.com/EF86-CV4086-GEC-...sid=p1638.m118


tube replacement is of course the biggest concern - AMC came out with an EL34 tube amp - model CVT 3030? - which had the EL34s soldered directly to the circuit board. Bit of a problem if you wanted to roll some tubes.
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Old 8th January 2008, 12:16 PM   #4
oshifis is offline oshifis  Hungary
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I have done it in the past but I advise against it. The glass around the pin may easily get cranked due to the soldering heat. Result is air may leak in the tube. The crank may be invisible and the leak very minor.
As you mentioned tubes need to be replaced from time to time. A tube may become noisy or just sounding dull or distorting at any time.
If you want to reduce the height, mount the tubes in horizontal position. I used silicone rubber rings to hold them. Good ventilation is also important.
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Old 8th January 2008, 12:21 PM   #5
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Use separate socket pins by Mill-Max in your PCB. Will add only 1-2 mm height over tubes alone. Digi-Key stocks these - look for .040" pin size.

These can be especially useful for tubes like 10 pin or 12 pin, where sockets are hard to find.
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Old 8th January 2008, 12:37 PM   #6
Nordic is offline Nordic  South Africa
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Cheap emergency gold sockets
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Old 8th January 2008, 01:33 PM   #7
dhaen is offline dhaen  Europe
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If mounting horizontally, best consult the manufacturers data sheet. They sometimes recommend the orientation ie which pin uppermost.
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Old 8th January 2008, 04:21 PM   #8
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Default Re: Soldering tubes directly to PCB?

Quote:
Originally posted by thomsva
Im scetching up a layout for a tube based preamp. I would like to use a low profile enclosure with the tubes inside. But if the tubes are standing up lots of vertical space is needed.

If the tubes are soldered directly to the pcb i could get away with 75mm internal enclosure height:

15mm space between bottom plate and pcb
2mm pcb thickness
50mm tube soldered directly to pcb
3mm space to vented enclosure cover

70mm total

Using a tube socket on the pcb would increase the total height by approximately 15mm, and I don't like that.

The obvious drawback is that changing tubes is a hassle. But is there anything else?

You could use Nuvistors.....

The socket and valve cant be much more than 30mm high total....

The Russian wire-ended Nuvistors could be soldered straight in or wires cut and sockets used, as I have done. They are MUCH better than the NOS American things for noise and Michrophonics. Great valves. Type 6C51N is a nice medium Mu triode, and will work well (In the right CCT) down to 12V....
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Old 8th January 2008, 08:56 PM   #9
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Chek out the Tyco/AMP 5050865-3 discrete socket
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Old 8th January 2008, 09:11 PM   #10
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Default Re: Re: Soldering tubes directly to PCB?

Quote:
Originally posted by Alastair E



The Russian wire-ended Nuvistors could be soldered straight in or wires cut and sockets used, as I have done. They are MUCH better than the NOS American things for noise and Michrophonics. Great valves. Type 6C51N is a nice medium Mu triode, and will work well (In the right CCT) down to 12V....
Also, a big heavy nut glued on a 6C51H (pronounced 6S51N) reduces microphonics dramatically.
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