: Just acquired a Gonset GSB-100 transmitter over the weekend, and : everything appears to be in order with it except for the crystal : oscillator tube (V10). The book lists a 12AT7 in this location, but the : book's schematic and the transmitter itself show a 12AV7 instead. WHich : is correct? These two tubes aren't nearly the same, but on the other : hand the transmitter works, so should I just not worry and be happy?
I don't know... There's not a whole heckuva lot of difference in the 12AU7 and the 12AT7, but I'm not sure what the differences are... So, I'm going Googleing (http://www.google.com) Back, and I came up with this... for a 12AT7 HIGH-MU TWIN TRIODE Specification and max ratings(*) Filament Voltage 6.3-12 V Filament Current 300-150 mA Plate Voltage (max) 300 V Plate Current (max) 15 mA Plate Dissipation (max) 2.5 W Screen Voltage (max) --- V Screen Current (max) --- A Screen Dissipation (max) --- W Pin Element Unit 1 Plate (Anode) Triode 2 Control Grid 2 3 Cathode 4 Filament 5 Filament 6 Plate (Anode) Triode 7 Control Grid 1 8 Cathode 9 Filament Center-Tap 12AT7 Standard version of this double triode in 9 pin miniature package. 6201/12AT7WA Milspec version of the type 12AT7. Genuine versions of these have extra thick mica wafers to help eliminate microphonics. Some have extra support rods which give even more stability. Late versions by Philips/ECG, etc don't have this feature. They really shouldn't be called 12AT7WA's (or WB or WC). 6679 Mobile communications version of the 12AT7. This tube is supposed to be able to maintain rated output/transconductance over a +/- 20% filament excursion. Otherwise, this tube is the same as type 12AT7 7728 Premium instrument grade tube made only by CBS/Hytron. This tube has heavily plated gold pins. ECC801/ECC801S Super premium grade tube made by Telefunken. The "S" version is a special selected tube. for a 12AU7 Specification and max ratings(*) Filament Voltage 6.3-12 V Filament Current 300-150 mA Plate Voltage (max) 330 V Plate Current (max) 22 mA Plate Dissipation (max) 3 W Screen Voltage (max) --- V Screen Current (max) --- A Screen Dissipation (max) --- W Pin Element Unit 1 Plate (Anode) Triode 2 Control Grid 2 3 Cathode 4 Filament 5 Filament 6 Plate (Anode) Triode 7 Control Grid 1 8 Cathode 9 Filament Center-Tap The 12AU7 is a medium mu multi-purpose double triode in a 9 pin miniature package. There are several different versions of the 12AU7. Below are most of the commonly known variations of the 12AU7. 12AU7/12AU7A The only difference between the 12AU7 and the 12AU7A is the "A" version can be used in series string filament circuits due to it's controlled warm-up cathode. Otherwise, there is no difference. 6189/5814 Both of these are "milspec" versions of the 12AU7. They may also be marked with 12AU7WA. They both have thick mica wafers which give the tube extra rigidity which minimizes any microphonic problems. Their cathodes have been specially designed so they can withstand many on/off cycles and long periods in cut-off without any degradation of performance. The 5814 has a slightly higher filament current demand than the 6189/12AU7. Some (not all) Sylvania Gold Brand versions of these tubes have gold plated pins. 5963 This tube makes a decent substitute for the 12AU7 as the characteristics are almost the same. The 5963 has a slightly lower plate voltage rating compared to regular 12AU7. The 5963 has a max plate voltage of 250V while 12AU7 has a max of 330V. This tube has a specially designed cathode which can withstand long periods of time in cut-off without hurting the tube. 7730 This is a premium version of the 12AU7 made only by CBS/Hytron. This tube has very low noise characteristics and heavily plated gold pins. These were intended for critical test instrument applications, but due to their superior low noise performance, these make excellent choices for audio applications. 6680 This is the mobile communications version of the 12AU7 which can withstand +/- 20 % variations in filament voltages without any degradation of tube performance. ECC802/ECC802S These are "premium" 12AU7's which were marketed by European manufacturers. I don't think that there was any difference in manufacturing technique, to create these, rather they are just specially tested 12AU7's that exhibit very low noise/microphonics and matched sections. 7316 This is an Amperex tube that was a premium grade 12AU7. and, while I was at it, I went ahead and got the 12AX7 info... 12AX7 Specification and max ratings(*) Filament Voltage 6.3-12 V Filament Current 300-150 mA Plate Voltage (max) 330 V Plate Current (max) 6 mA Plate Dissipation (max) 1.1 W Screen Voltage (max) --- V Screen Current (max) --- A Screen Dissipation (max) --- W Pin Element Unit 1 Plate (Anode) Triode 2 Control Grid 2 3 Cathode 4 Filament 5 Filament 6 Plate (Anode) Triode 7 Control Grid 1 8 Cathode 9 Filament Center-Tap 12AX7 This is the original version of this tube. The earliest ones were all made in the USA by the usual manufacturers like RCA, Sylvania, GE and Tung Sol. Very early ones have rater large size plates. The "plain" version without the "A" suffix can only be used in parallel filament circuits, not series. This usually isn't a problem as series circuits are only normally found in TV sets. All of the tubes will have odd voltages other than 6 and 12. If all of the tubes in your set start with 6 or 12 (except for the 5 V rectifier) , then it is a parallel circuit 12AX7A This later version can be used in series or parallel filament circuits. Many manufacturers produced plain 12AX7's well into the 60's and 70's, but I believe these are 12AX7A's marked 12AX7. 7025 This is the "hi fi" low noise version of the 12AX7. All other specifications are the same as 12AX7. Tubes marked with 12AX7 and 7025 both should be low noise, too. ECC83 This is the European equivalent to 12AX7 ECC803, ECC803S E83CC This is the "premium" version of the European 12AX7. The "S" on the ECC803S means "select" version. These are usually found on Telefunken brand tubes only. 5751 This is the "milspec" version of the 12AX7, but is also slightly different. The 5751 has the same plate resistance as the 12AX7, but the gain factor is only 70 compared to 100 for the 12AX7. The 12AT7 also has a gain factor of 70, but since the plate resistance is different, the 5751 is closer to the 12AX7. The older "real" 5751's have extra thick mica spacers and extra support rods to minimize microphonic response. 5751's also have matched triode units. Late versions produced by Philips/ECG don't have the extra support and don't perform as well as the older 5751's.
