Specs on 8928 tube?

[WB6NVH]

Anybody have a tube manual which shows the specs on an 8928?  I think this is an industrial version of something like a 6JS6 or 6LB6 sweep tube, at least that's what they look like.  Rescued an HF transceiver at a swap meet and some varmint had removed the pair of 8928 PA tubes.  Nobody seems to stock that # anymore so a sub seemed the way to go.

[WQ9E]

Which transceiver is this?  The Swan 700 used 8950 sweep tubes but I have never heard of the 8928.

Rodger WQ9E

[KD6VXI]

Which transceiver is this?  The Swan 700 used 8950 sweep tubes but I have never heard of the 8928.

Rodger WQ9E

8908 comes to mind, as well.

--Shane

[WB6NVH]

This is the Southcom SC-102 Thunderbird.  HF 4 channel base or mobile paramilitary radio circa 1968-70.  100 Watt level.  Original bottles were probably Raytheon...

[AB3FL]

Are you sure it isn't 8298?   

[Pete, WA2CWA]

I just checked the complete Southcom SC-102 manual and it is shown on the schematic and parts list as a 8928. They don't indicate the manufacturer nor a source for the tube other then through them. It's also not listed in several tube listing information for industrial/special purpose etc. type tubes. Most likely, Southcom wrote a spec for "special requirements" on tube usage, and the Company that made the tubes to the spec., probably assigned this number to it. With a little bit of engineering, you can probably get one of the more common sweep tubes to work. Might require some component changes and/or rewiring of the tube sockets.

[WB6NVH]

One of the SC-102's I have still has the tubes in it.  I'll have to dig it out of storage and see what's written on them as far as who-dunit.  It's a 6 Volt Compactron which looks just like a 6JS6, they are mounted on their sides one on top of the other. I can't recall whether 6JS6's are rated to do that.  The industrial number may just be a tube rated for mobile service with a rugged filament.  This is why I was asking if anybody had the specs for the tube, so that I could do some engineering to replace it with something more common.

I am starting to like the idea of changing the sockets to ceramic octal and using a pair of 6883's (12 volt 6146) because they are so cheap, although using 6JS6 class tubes means the sockets could stay as they are.

I seem to recall Antique Electronic Supply once upon a time listed the 8928 in their catalog, but at the time I didn't need any, and now, no more.

[KD6VXI]

One of the SC-102's I have still has the tubes in it.  I'll have to dig it out of storage and see what's written on them as far as who-dunit.  It's a 6 Volt Compactron which looks just like a 6JS6, they are mounted on their sides one on top of the other. I can't recall whether 6JS6's are rated to do that.  The industrial number may just be a tube rated for mobile service with a rugged filament.  This is why I was asking if anybody had the specs for the tube, so that I could do some engineering to replace it with something more common.

I am starting to like the idea of changing the sockets to ceramic octal and using a pair of 6883's (12 volt 6146) because they are so cheap, although using 6JS6 class tubes means the sockets could stay as they are.

If it's a 12 volt, take a peek at the 8950.  It's a 12 volt 'version' of the 6KD6 / 6LF6 / 6HF5.  Used a lot in the '10 meter' amplifiers, and some multiband amps and SillyTronix used them in their Drifttronix 1011.

The 8908, if you can find one, is a great tube, but more of a TX tube than a compactron.

The M2057 is a ruggedized 8950.  The M2057 and 8950 both run 12 volt fils.  BOTH the M2057 AND the 8950 where run in a plethora of amplifiers in the horizontal position...  I ran a PAL 350MDX, it had the original tubes marked PAL in the late 80s when I acquired it, 4 total, horizontally polarized .  The 6LF6 was also run horizontal by Palomar and I seem to recall one other mfg doing it. 

Their are a LOT of .ru tubes adaptable.  I'm sure you can find SOMETHING in the junkbox, but the 8950 is a DAMN fine tube, as is the 6KD6 series.

--Shane

[Rob K2CU]

make sure whatever type you end up using can be mounted horizontally. seom type have limits on mounting and require grid supports to be aligned vertically. 6146 has no such requirement. The issues to deal with are mechanical as in socekt hole size and height (length) of tube to fit in cage. The biggest electrical issue for these type willl be neutralization, especially on the higher bands. try  to match the rotational alignement of grid and screen connections if changing socket and or tube type. 

[WB6NVH]

The 8928 is a 6 Volt filament tube but I had some 12 Volt candidates in the junkbox.  In this radio the filaments are series wired and fed with 12V but it's of course no sweat to parallel them.  The 8950's are getting surprisingly pricey (thanks, evidently, to CB'ers) but I have some 6LF6, 6LB6 and 6JS6 in stock.

I just haven't pulled the manuals yet to see if the TV set tubes care about horizontal mounting.  The neutralization cap has a range of 5-25 pf and this radio only covers 2-10 MHz so that issue may be easy to deal with.   I guess I could always measure the grid to plate capacitance of an 8928 I do have and then do some comparisons.  My thought was that these radios would be excellent for use on the new 60 Meter band channels.

[KD6VXI]

The 8928 is a 6 Volt filament tube but I had some 12 Volt candidates in the junkbox.  In this radio the filaments are series wired and fed with 12V but it's of course no sweat to parallel them.  The 8950's are getting surprisingly pricey (thanks, evidently, to CB'ers) but I have some 6LF6, 6LB6 and 6JS6 in stock.

I just haven't pulled the manuals yet to see if the TV set tubes care about horizontal mounting.  The neutralization cap has a range of 5-25 pf and this radio only covers 2-10 MHz so that issue may be easy to deal with.   I guess I could always measure the grid to plate capacitance of an 8928 I do have and then do some comparisons.  My thought was that these radios would be excellent for use on the new 60 Meter band channels.

I can tell you from experience, the 6LF6 /6KD6 can both be mounted horizontally.  I do NOT know if their is a preferred method of placement (guide pins, etc).

I've owned a few amps over the years that took the LF6 and used it horizontal.

--Shane