Fan cfm

[Gil Cleeton]

The original fan on the 200 I used to own was silent. 
When I bought my present 220 the fan was noisy - it rattled when the amp
warmed up - but I cured it by drilling a very small hole in each bearing,
and injecting engine oil with a needle pump from an inkjet refill kit. I did
not have to remove the fan from the cabinet.
Buffalo Gil  W2/G3LBS

> -----Original Message-----
> From: Heathkit Owners and Collectors List
> [mailto:HEATH at LISTSERV.TEMPE.GOV] On Behalf Of Wilson Lamb
> Sent: Friday, January 12, 2007 6:57 PM
> To: HEATH at LISTSERV.TEMPE.GOV
> Subject: Re: Fan cfm
> 
> A fan that close to the tubes may cause some thermal stress problems.  I
> know this is  a factor with Eimac tubes.  The most critical area is the
> seals around the pins coming through the glass, so pushing through the
> sockets is good, but I don't know how the 200 is laid out.  I had one long
> ago, but no fan trouble.
> Wilson
> W4BOH
> ----- Original Message -----
> From: "Jan Ditzian" <ditzian at ALLTEL.NET>
> To: <HEATH at LISTSERV.TEMPE.GOV>
> Sent: Friday, January 12, 2007 12:47 PM
> Subject: Fan cfm
> 
> 
> > OK, while I am plotting modifications to the SB-201, I am also thinking
> > about the fan.  I have already disconnected the noise generator that is
> > built into the bottom of the chassis, and I am using an external muffin
> > fan (junk box, 117VAC, circa 25 years old) on top of the rig to cool the
> > tubes.  The amp is nearly dead silent.  However, in the spirit of not
> > laving things well enough alone, I am considering installing a fan into
> > the case.
> >
> > I measured, and there is barely 25 mm clearance above the Chinese 572B
> and
> > the top cover.  This means that a 25 mm depth fan might touch the glass
> > envelopes, which is probably not a good plan.  I do not know the
> required
> > cfm for these tubes, so perhaps someone can guide me here. There are
> > smaller fans (e.g., 40x40x20 mm) that run on 12VDC and would provide 8
> > cfm.  My original plan was to use a big 40x40x25 117 VAC fan and get 81
> > cfm.
> >
> > If someone has gone through this exercise and concluded that you really
> > cannot do it safely inside on top, please let me know.  I do not think
> > that the pusher approach works as well, and I would be willing to
> > compromise and put a permanent outboard 117VAC fan on top of the the top
> > cover.  I figure that it can be screwed through the holes with really
> > skinny screws.
> >
> > I expect to power the fan from 117 VAC in the chassis.  I am running on
> > 220 VAC (249 actually), so I could also use a 220 VAC fan and bypass all
> > internal power.
> >
> > The top internal plate was removed long ago and far away.
> >
> > 73,
> > Jan, KX2A
> >
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