Distance between tubes

[Leevi]

I got a problem with 6550 tubes that are quite large and stay now quite close
to each other (about 1-2mm). Does this matter?
/Leevi

[jim]

Guitar amps vibrate and shake--especially bass amps.  If they touch they will break.  Stout tube clips or spring retainers may not likely help much at those distances.   Also heat will be a definate problem especially with big bottles.  Use a fan or smaller tubes.  I don't think you will have good tube life in that situation.   Jim

[kagliostro]

Does this matter?

I think yes .........

if you can't arrange a different layout, think about a fan (a PC fan may be OK)

6550 are power tubes and I don't think they like only 1-2 mm between them

EDIT thinking to only that space between tubes it will be easy that when hot they also touch each other and that isn't good - consider to mount it in a different way - may be you can arrange a "special" support and mount it in a "close V" like Harley Davidson cylinders, don't remember well where, but it was already done

Some time ago a friend has serviced an old italian amp, a Davoli, in that model the tubes (don't remember the kind of tubes) were mounted near each other (not so much like in your layout) and were one up to the other .......

BIG trouble the glass arrived till to melt

--------

take one photo of your chassis with components on it (also only supported if not yet fixed on place) may be someone will be able to find a different layout for you

Kagliostro

[DummyLoad]

I got a problem with 6550 tubes that are quite large and stay now quite close
to each other (about 1-2mm). Does this matter?
/Leevi

mechanical contact probabilities aside, yes, if typical idle dissipation ratings are used, there will be a problem. for free air cooling with receiving tubes, usually the minimum spacing is 2 x diameter of the tube on socket centers. ex. diameter of 6550 is ~~50mm so then use 2 x diameter of 50mm = 100mm socket center to socket center.

i'm at a loss about the quantity of inter-electrode capacitance between the envelopes situated so close together, but i would imagine in such close proximity that there would be some - that also could be a problem.

[Leevi]

I have already started to machine the metal. Unfortunately the chassis is 1.5mm steel which
makes the work pretty hard. I cannot reach 100mm distance but try to get about 70mm (must be enough)
The old holes make the work even more challenging. Learn by doing!
/Leevi

[kagliostro]

If you have enough space

consider a 1,5mm or better 2mm aluminium  rectangular patch

on which you made the hole for the 6550 tubes at right distance

to be put above the old drilled holes

drill a little hole on each corner of the patch to fix the patch to the steel chassis

simply with a rivet

I think that will look not so bad and it will be difficult to see the mend

if you have access to a nibbler use it to make a rectangular hole were you make the first holes in the chassis, than put the patch to cover it


Kagliostro


I've both "nibbler 00" and "nibbler 000" and this last is better for this job if you have not an electric one

[Leevi]

Thanks Kagliostro but I have already fixed it.
See the results below:
/Leevi

http://i218.photobucket.com/albums/cc183/kz14100/RikstoneH140.jpg