Tube Substituti on Chart ------------------------------------------------------------ furnished by eugene welcome ===================================================================== BASE * TUBE TYPE Page 1A ## BASE * TUBE TYPE Page 1B * 0A5 * 0A5 ## 5AG * 1LH4 * ------*--------------------------##------*--------------------------* 1AG4 * 1AG4 ## 5AL * 35Y4 * ------*--------------------------##------*--------------------------* 1AG5 * 1AG5 ## 5AP * 1A3 * ------*--------------------------##------*--------------------------* 1AH4 * 1AH4 ## 5AW * 807, 5933 * ------*--------------------------##------*--------------------------* 1AJ5 * 1AJ5 ## 5AY * 6D4 * ------*--------------------------##------*--------------------------* 1AK4 * 1AK4 ## 5AZ * 1625 * ------*--------------------------##------*--------------------------* 1AK5 * 1AK5 ## 5BO *0A2,0B2,0C2,5651,6626,6627* ------*--------------------------##------*--------------------------* 1AY2 * 1AY2 ## 5BQ * 25DK4,35W4,36AM3,50DC4 * ------*--------------------------##------*--------------------------* 1V6 * 1V6 ## 5BS * 6X4, 12X4 * ------*--------------------------##------*--------------------------* 3C * 1AU3, 1G3GT/1B3GT, 1J3A, ## 5BT * 6BG6GA,6CD6G,6DN6,6EX6, * * 1K3GT/1J3, 1N2A ## *19BG6G,21EX6,25CD6GB,25DN6* ------*--------------------------## * 25EC6, 35CD6GA, 7867 * 4AA * 1LE3, 1293 ##------*--------------------------* ------*--------------------------## 5CA * 5845 * 4AB * 2X2 ##------*--------------------------* ------*--------------------------## 5CB * 5722 * 4AH * 1R4 ##------*--------------------------* ------*--------------------------## 5CE * 6AB4, 6664/6AB4 * 4AJ * 0A3,0B3,0C3,0D3,1265,1266##------*--------------------------* ------*--------------------------## 5D * 6Z4/84, 84/6Z4 * 4AM * 2C22 ##------*--------------------------* ------*--------------------------## 5DA * 5AR4/GZ34 * 4BU * 0Y4 ##------*--------------------------* ------*--------------------------## 5DE * 3DG4 * 4C * 5Z3,6DA4A/6DM4A,17AX4GTA/##------*--------------------------* * 17DM4A,80,83,1275 ## 5L * 5AT4, 5CG4, 5Z4GT, 5C4GA * ------*--------------------------##------*--------------------------* 4CB * 117Z3 ## 5M * 6F5, 12F5GT * ------*--------------------------##------*--------------------------* 4CG * 6AU4GTA,6AX4GT,6CQ4,6DE4,## 5Q * 5Y4GA/GT * * 6DQ4,6DT4,6W4GT,12AX4GT, ##------*--------------------------* * 12D4,12DM4,12DQ4,17D4, ## 5S * 6B4G * * 17DE4,17DQ4,19AU4,22DE4, ##------*--------------------------* * 25AX4GT,25W4GT ## 5T * 5AS4A, 5AU4, 5AW4, 5AX4GT* ------*--------------------------## * 5AZ4,5R4GYB,5T4,5U4GB,5V3* 4CK * 5823 ## * 5Y3GA, 5Y3GT, 5931 * ------*--------------------------##------*--------------------------* 4CN * 5644 ## 5Y * 1N5GT * ------*--------------------------##------*--------------------------* 4D * 2A3,6A3,45,1230,1276 ## 5Z * 1H5GT * ------*--------------------------##------*--------------------------* 4K * 1229 ## 6AA * 7A5,7C5,14C5,35A5,50A5 * ------*--------------------------##------*--------------------------* 4R * 0Z4A ## 6AB * 6SF5, 12SF5GT * ------*--------------------------##------*--------------------------* 4V * 0A4G,1267 ## 6AB8 * 6AB8/ECL80 * ------*--------------------------##------*--------------------------* 4Z * 35Z3 ## 6AD * 35Z5GT * ------*--------------------------##------*--------------------------* 5AB * 7Y4,7Z4 ## 6AE * 7B5 * ------*--------------------------##------*--------------------------* 5AC * 7A4/XXL,7B4 ## 6AM * 6BQ6GTB/6CU6, 6DQ6B/6GW6,* ------*--------------------------## * 12BQ6GTA, 12DQ6B/12GW6, * 5AD * 1LA4,1LB4 ## * 17BQ6GTB,17DQ6B/17GW6, * ------*--------------------------## * 25BQ6GTB/25CU6, 25DQ6A * END OF 1A and 1B ===================================================================== BASE * TUBE TYPE Page 2A ## BASE * TUBE TYPE Page 2B * ------*--------------------------##------*--------------------------* 6AR * 1AE4,1AF4,1L4,1T4,1U4, ## 7AV * 1S4 * * 5910 ##------*--------------------------* ------*--------------------------## 7AZ * 6SF7, 12SF7 * 6AU * 1AF5, 1S5 ##------*--------------------------* ------*--------------------------## 7BA * 3S4, 3Q4, 3Z4 * 6AX * 1LD5 ##------*--------------------------* ------*--------------------------## 7BB * 3A4 * 6B * 41, 42, 43 ##------*--------------------------* ------*--------------------------## 7BC * 3A5 * 6BA * 3D6, 3LF4 ##------*--------------------------* ------*--------------------------## 7BD * 3BC5/3CE5,4BC5,4CE5,6AG5,* 6BG * 6C4, 6DR4, 6100, 6135 ## * 6AJ6,6AK5,6AN5,6BC5/6CE5,* ------*--------------------------## * 408A,6AK5W/GB1220/5654, * 6BS * 2050 ## * 6028,6096,6186,6968,9001,* ------*--------------------------## * 9003 * 6BT * 3AL5,6AL5,6EB5,12AL5,5726##------*--------------------------* * 6097,6663/6AL5,6919,7055,## 7BE * 3B7 * * 7631 ##------*--------------------------* ------*--------------------------## 7BF * 5J6,6J6,19J6,1216,5844, * 6BW * 1DN5, 1U5 ## * 5964,6099,6101,7244 * ------*--------------------------##------*--------------------------* 6BX * 3V4, 6AJ4 ## 7BH * 2C21 * ------*--------------------------##------*--------------------------* 6CC * 6AR5 ## 7BJ * 6AN6 * ------*--------------------------##------*--------------------------* 6CH * 6BJ5, 6516 ## 7BK * 3AU6,3BA6,4AU6,4BA6,6AH6,* ------*--------------------------## * 6AK6/EF95,6AU6,6BA6/EF93,* 6CJ * 5641 ## * 6BD6,6FD6,6HR6,6HS6,12AC6* ------*--------------------------## * 12AF6,12AU6,12BA6,12BD6, * 6CK * 6AU5GT,6AV5GA,6BD5GT,6FW5## * 12BL6,12CX6,12CY6,12DZ6, * * 12AV5GA, 17AV5GA, 18A5, ## * 12EA6,12EK6,12EZ6,18FW6, * * 25AV5GA, 6000 ## * 18GD6,19HR6,19HS6,5749, * ------*--------------------------## * 6136,6660/6BA6,7496,7543,* 6CL * 5851, 6147 ## * 8425,8426 * ------*--------------------------##------*--------------------------* 6CN * 6BY5G ## 7BN * 2D21, GB5727 * ------*--------------------------##------*--------------------------* 6DL4 * 6DL4 ## 7BQ * 6J4, 7137, 7245 * ------*--------------------------##------*--------------------------* 6E * 25Z5 ## 7BS * 9002 * ------*--------------------------##------*--------------------------* 6F * 6C6, 6D6, 78, 1221 ## 7BT * 3AV6,4AV6,6AT6,6AQ6,6AV6,* ------*--------------------------## * 6BF6,12AE6,12AJ6,12AT6, * 6FG6 * 6FG6/EM84 ## * 12AV6,12BF6,12FK6,12FM6, * ------*--------------------------## * 12FT6,18FY6,18GE6 * 6G * 75 ##------*--------------------------* ------*--------------------------## 7BZ * 5AQ5,6AQ5A,6BF5,6DS5,6HG5* 6HQ6 * 6HQ6 ## * 6HR5,12AQ5,19AQ5,35B5, * ------*--------------------------## * 50B5,6005,6095,6669/6AQ5 * 6Q * 6C5, 6J5GT, 12J5GT, 884 ## * ------*--------------------------##------*--------------------------* 6R * 6E5, 6U5 ## * ------*--------------------------## 7CH * 3BE6,3BY6,3CS6,4BE6,4CS6,* 6S * 6AX5GT, 6X5GT, 1274 ## *6BE6,6BY6,6CS6,12AD6,12AG6* ------*--------------------------## * 12BE6,12CS6,12EG6,12FA6, * 6X * 1A5GT ## * 12GA6, 18FX6, 1217, 5750,* ------*--------------------------## * 5915, 7032, 7036, 7502 * 7AC * 6550 ##------*--------------------------* ------*--------------------------## 7CK * 2E26, 6146B/8298A, 6159B,* 7AG * 6AD6G, 6AF6G ## * 6883, 6893 * ------*--------------------------##------*--------------------------* 7AK * 1LA6, 1LC6 ## 7CM * 3BZ6,3CF6/3CB6,3DK6,4BZ6,* ------*--------------------------## * 4CB6,4DE6,4DK6,4EW6,4GM6,* 7AO * 1LC5, 1LG5, 1LN5 ##Conti-* 4JH6,4JK6,4JL6,5EW6,5GM6,* ------*--------------------------##-nued * 5JK6,5JL6,6AS6,6BH6,6BJ6,* 7AP * 3Q5GT ## See * 6BZ6,6CB6,6CF6,6DB6,6DC6,* ------*--------------------------## Pg3A * 6DE6,6DK6,6EW6,6GM6,6JH6,* 7AT * 1R5 ## * 6JK6, 6JL6, 12AW6, 12BZ6,* END OF 2A and 2B ===================================================================== BASE * TUBE TYPE Page 3A ## BASE * TUBE TYPE Page 3B * ------*--------------------------##------*--------------------------* 7CM * 12DK6, 5725, 6661/6BH6, ## 7GM * 2HA5,2HK5,2HM5,2HQ5,3HA5/* From * 6662/6BJ6,6676/6CB6,6954,## * 3HM5,3HK5,3HQ5,4HA5/PC900* Pg2B * 7056, 7732, 8084, 8136 ## * 4HK5,4HM5,4HQ5,6HA5/6HM5,* ------*--------------------------## * 6HK5, 6HQ5 * 7CV * 4GZ5,6AS5,6CA5,6CU5,6EH5,##------*--------------------------* *6GZ5,11C5,12AS5,12C5/12CU5## 7Q * 6H6, 12H6, 25Z6GT,50AX6G,* * 12CA5,12CN5,12DM5,12ED5, ## * 50Y6GT, 117Z6GT * * 12EH5, 12FX5, 12R5,17C5/ ##------*--------------------------* * 17CU5, 17CA5, 17R5, 25C5,## 7R * 6J7GT,6K7,12J7GT,12K7GT, * * 25CA5,25EH5,25F5,32ET5, ## * 1223 * * 34GD5,35C5,35EH5,40FR5, ##------*--------------------------* * 50C5,50CA5,50EH5,50FA5, ## 7S * 5V6GT,6DG6GT,6EY6,6EZ5, * * 50FK5, 60FX5 ## * 6F6GT,6K6GT,6L6,6U6GT, * ------*--------------------------## * 6V6GTA,6W6GT,6Y6GA,7EY6, * 7DB * 7498, 6AM6/EF91 ## * 9EF6, 12A6, 12EF6, 12EN6,* ------*--------------------------## * 12L6GT, 12V6GT, 12W6GT, * 7DC * 1L6, 1U6 ## * 12L6GT, 12V6GT, 12W6GT * ------*--------------------------## * 17L6GT, 17W6GT, 25L6GT, * 7DF * 3BN6,4BN6,6BN6/6KS6,12BN6## * 25W6GT, 35L6GT, 50L6GT, * ------*--------------------------## * 1614,5824,5871,5881,5932,* 7DK *1DY4A,2DX4,2DY4,2DZ4/2AF4B## * 7408, 7581A, 7751, 8417, * * 2T4, 3AF4A, 3DX4, 3DY4A, ## * KT-66, KT-88 * * 3DZ4/3AF4B, 5AF4A, 6AN4, ##------*--------------------------* * 6DX4, 6DY4, 6DZ4/6AF4A, ## 7T * 6L7, 1612 * * 6T4, 1218A, 7738, 8334 ##------*--------------------------* ------*--------------------------## 7V * 6Q7GT, 6R7, 12Q7GT, 6118 * 7DU * 6354 ##------*--------------------------* ------*--------------------------## 7Z * 1A7GT * 7DX * 7A6, 50X6 ##------*--------------------------* ------*--------------------------## 8A * 6A8GT, 12A8GT * 7EA * 6CR6, 12CR6 ##------*--------------------------* ------*--------------------------## 8AC * 7AF7,7F7,7N7,14AF7/XXD, * 7EG * 2BN4A, 3BN4A, 4BN4, 6BN4A## * 14F7 * ------*--------------------------##------*--------------------------* 7EJ * 7001 ## 8AD * 6SA7GT, 12SA7GT * ------*--------------------------##------*--------------------------* 7EN * 3DT6,4DT6,5GX6,5HZ6,6DT6,## 8AE * 7R7, 14R7 * * 6GY6/6GX6,6HZ6,12DT6,7693##------*--------------------------* * 7694 ## 8AL * 7Q7, 14Q7 * ------*--------------------------##------*--------------------------* 7ES * 1AN5 ## 8AN * 50Y7GT * ------*--------------------------##------*--------------------------* 7EW * 2CY5,2EA5,2EV5,3CY5,3EA5,## 8AO * 117L7/M7GT * * 3EV5,4CY5,6CY5,6EA5,6EV5,##------*--------------------------* * 7167, 7717, 8113 ## 8B * 6N7GT * ------*--------------------------##------*--------------------------* 7FB * 12EL6 ## 8BD * 2C50,2C52,6AS7GB,6BL7GT, * ------*--------------------------## * 6BX7GT, 6DN7, 6EA7, 6EM7,* 7FD * 12K5 ## * 6GL7,6SL7GT,6SN7GTB,8SN7-* ------*--------------------------## * GTB, 10EG7,10EM7,12SL7GT,* 7FL * 2EN5 ## * 12SN7GTA,13EM7,15EA7,5691* ------*--------------------------## * 5692,5998A,6080,6082,6188* 7FP * 2ER5,2ES5,2FH5,2FY5,2GK5/## * 6336A, 6394A, 6520, 6528,* * 2FQ5,3ER5,3ES5,3FH5,3FQ5A## * 7105, 7236 * * 3FY5,3GK5,4GK5,6ER5,6ES5,##------*--------------------------* * 6FH5, 6FY5, 6GK5/6FQ5A ## 8BF * 7K7 * ------*--------------------------##------*--------------------------* 7FQ * 2FV6, 6FV6 ## 8BJ * 7W7 * ------*--------------------------##------*--------------------------* 7FW * 6GN6, 12GN6 ## 8BK * 6SG7, 6SH7, 12SG7, 12SH7 * ------*--------------------------##------*--------------------------* 7FZ * 35GL6, 50HC6, 50HK6 ## 8BL * 7J7, 7S7 * ------*--------------------------##------*--------------------------* 7GA * 2FS5,2GU5,3FS5,3GU5,6FG5,## 8BS * 28D7, 1238 * * 6FS5, 6GU5 ##------*--------------------------* ------*--------------------------## 8BW * 7F8, 14F8 * 7GK * 2GW5, 3GW5, 4GW5, 6GW5 ##------*--------------------------* ------*--------------------------## 8BZ * 7X7 * END OF 3A and 3B ===================================================================== BASE * TUBE TYPE Page 4A ## BASE * TUBE TYPE Page 4B * ------*--------------------------##------*--------------------------* 8CH * 6AL7GT ## 8GD * 6CB5A, 6CL5 * ------*--------------------------##------*--------------------------* 8CJ * 2C51, 5670, 7861 ## 8GH * 3B2 * ------*--------------------------##------*--------------------------* 8CK * 6AQ7GT ## 8GQ * 6690 * ------*--------------------------##------*--------------------------* 8CP * 1AC5, 1AD5 ## 8GT * 6CM5 * ------*--------------------------##------*--------------------------* 8CT * 6BA7, 12BA7 ## 8HC * 2B3 * ------*--------------------------##------*--------------------------* 8DA * 1S6 ## 8HE * 6853 * ------*--------------------------##------*--------------------------* 8DC * 5636,5908,5916,6205,6206,## 8HY * 7027 * * 6943, 6944, 8414, 8444 ##------*--------------------------* ------*--------------------------## 8JB * 6CK4 * 8DD * 5643 ##------*--------------------------* ------*--------------------------## 8JC * 6DQ5 * 8DF * 6AZ5 ##------*--------------------------* ------*--------------------------## 8JP * 6DZ7 * 8DG * 6BF7W,6021,6111,6112,6832##------*--------------------------* * 6947,6948,7327,7550,7759,## 8JX * 6GC6, 12GC6 * * 7760, 7887, 7889, 8103 ##------*--------------------------* ------*--------------------------## 8K * 6K8, 12K8 * 8DJ * 5896, 5903, 6110 ##------*--------------------------* ------*--------------------------## 8KB * 6FE5, 50FE5 * 8DK * 6AD4,6AK4,5718,5719,5904,##------*--------------------------* -----*--------------------------## * * 5977, 6814, 6946, 7888 ## 8KD * 5CU4 * 8DL * 5639,5840,5899,5902,5905,## 8KG * 7591 * * 5906,5907,6788,6945,7761,##------*--------------------------* * 7762, 8064, 8211 ## 8KM * 7994, 8185, 8186 * ------*--------------------------##------*--------------------------* 8DM * 5987 ## 8KN * 7355 * ------*--------------------------##------*--------------------------* 8DQ * 5968 ## 8KS * 5DJ4 * ------*--------------------------##------*--------------------------* 8DR * 5969 ## 8KZ * 7995 * ------*--------------------------##------*--------------------------* 8DS * 5970 ## 8LC * 8068 * ------*--------------------------##------*--------------------------* 8DY * 6BA5 ## 8LD * 8070, 8319 * ------*--------------------------##------*--------------------------* 8E * 6B8, 12C8 ## 8LE * 8071 * ------*--------------------------##------*--------------------------* 8EC * 7212, 7358 ## 8LK * 3FX7, 6FX7 * ------*--------------------------##------*--------------------------* 8EL * 6AH4GT ## 8LM * 3FW7, 6FW7 * ------*--------------------------##------*--------------------------* 8ES * 40A1, 40B2 ## 8LS * 8210 * ------*--------------------------##------*--------------------------* 8ET * 6CA7/EL34 ## 8LT * 8213 * ------*--------------------------##------*--------------------------* 8EX * 6308 ## 8LW * 8254 * ------*--------------------------##------*--------------------------* 8EY * 6352 ## 8MG * 50JY6 * ------*--------------------------##------*--------------------------* 8EZ * 3A3, 3AW3, 3CV3, 3CZ3 ## 8MH * 3CA3 * ------*--------------------------##------*--------------------------* 8FP * 6BU5 ## 8MK * 3CU3 * ------*--------------------------##------*--------------------------* 8FU * 6BD4 ## 8ML * 6LC6, 6LH6 * ------*--------------------------##------*--------------------------* 8G * 6C8G ## 8MQ * 6LJ6 * ------*--------------------------##------*--------------------------* 8GB * 6BL4 ## 8MT * 3CX3 * ------*--------------------------##------*--------------------------* 8GC * 6BK4, 6BU4 ## 8MU * 2CN3A, 3CN3 * ------*--------------------------##------*--------------------------* END OF 4A and 4B ===================================================================== BASE * TUBE TYPE Page 5A ## BASE * TUBE TYPE Page 5B * ------*--------------------------##------*--------------------------* 8MW * 6EL4 ## 9AX * 6BC7, 6BJ7 * ------*--------------------------##------*--------------------------* 8MX * 3DB3 ## 9AZ * 12AD5 * ------*--------------------------##------*--------------------------* 8N * 6AB7, 6CA7, 6SJ7, 6SK7GT,## 9BA * 6DG7, 7229, 7499 * * 6SS7, 12SJ7, 12SK7, 5693 ##------*--------------------------* ------*--------------------------## 9BD * 6B3, 6V3A, 12B3 * 8Q * 6SQ7GT,6SR7,12SQ7GT,12SR7##------*--------------------------* ------*--------------------------## 9BF * 11HM7,12BY7,12DQ7,12GN7, * 8R * 6SA7, 6SB7Y ## *12HG7,12HL7,6870,7733,8448* ------*--------------------------##------*--------------------------* 8S * 6SC7, 12SC7 ## 9BJ * 2HR8, 4HR8 * ------*--------------------------##------*--------------------------* 8U * 7A8 ## 9BQ * 6BK5,12BK5,25BK5,50BK5 * ------*--------------------------##------*--------------------------* 8V * 7A7,7AG7,7AK7,7B7,7C7,7H7## 9BS * 12DF5 * * 7L7,7V7,14A7,14C7,1231, ##------*--------------------------* * 1273, 1280, 1284, 6145 ## 9BV * 6CL6, 6197, 6677/6CL6 * ------*--------------------------##------*--------------------------* 8W * 7B6, 7C6, 14B6 ## 9BX * 6AJ4, 6AM4, 6CR4 * ------*--------------------------##------*--------------------------* 8X * 7B8 ## 9CB * 6AF3,6AL3/EY88,6BR3,12AF3* ------*--------------------------## * 12BR3,12BY3,16AQ3/XY88, * 8Y * 6AG7 ## * 17BR3, 25BR3 * ------*--------------------------##------*--------------------------* 9A *6AX7,7AU7,9AU7,12AD7,12AE7## 9CE * 6216 * * 12AT7WA,12AT7/ECC81,12AU7##------*--------------------------* * /ECC82,12AV7,12AX7A/ECC83## 9CF * 9BR7, 12BR7, 8447 * * 12AY7,12AZ7A,12BH7,12BZ7,##------*--------------------------* * 12DF7,12DM7,12DT7,12DW7, ## 9CK *5CM6,6CM6,6DW5,12CM6,12DW5* * 12FV7,12U7,5751,5814,5963##------*--------------------------* * 5965A,6189,6201,6211A, ## 9CM * 50A1 * * 6679/12AT7,6680/12AU7A, ##------*--------------------------* * 6681/12AX7,6851,6955,7025## 9CQ * 6267 * * 7058,7316,7318,7489,7490,##------*--------------------------* * 7492,7494,7728,7729,7730 ## 9CV * 6BQ5/EL34,6CW5/EL86,6DY5,* ------*--------------------------## * 8BQ5, 8CW5, 10BQ5, 10CW5/* 9AC * 6S4A ## * LL86, 12FB5, 15CW5/PL86, * ------*--------------------------## * 30CW5, 45B5, 7189, 7320 * 9AD * 5879 ##------*--------------------------* ------*--------------------------## 9CY * 5AM8, 6AM8, 6HJ8 * 9AE * 5EA8,5GH8,5KD8,5MQ8,5U8, ##------*--------------------------* * 6AX8,6EA8/6GH8A,6GJ8,6HL8## 9CZ * 12G8, 6350, 6463, 6840 * * 6LM8,6MQ8,6U8A/6KD8,9EA8,##------*--------------------------* * 9GH8A,9U8A,19EA8,GB1252/ ## 9DA * 5AN8, 6AN8A, 10C8, 12CT8,* * 6U8A,6678/6U8A,7059,7643,## * 7258, 7492, 8489 * * 7687, 7731, 8445 ##------*--------------------------* ------*--------------------------## 9DC * 4BL8/CXF80,4KE8,5KE8,6BL8* 9AG * 12B4A ## * /ECF80,6JW8/ECF802,6KE8, * ------*--------------------------## * 6LN8,6LX8/LCF802,6MG8,8A8* 9AH * 6V8, 19V8, 7500 ## * 9A8/PCF80, 17A8 * ------*--------------------------##------*--------------------------* 9AJ * 4BC8,4BQ7A/4BZ7,4BS8,4BX8## 9DD * 6FC7, 7FC7 * * 4BZ8,4ES8,4KN8,5BK7A,5BQ7##------*--------------------------* * 5BZ7,5ES8,6AQ8/ECC85,6BC8## 9DE * 7308 * * 6BK7,6BQ7A/6BZ7,6BS8,6BX8##------*--------------------------* * 6BZ8,6DJ8/ECC88,6DT8,6ES8## 9DJ * 6BW4, 12BW4 * * ECC189, 6FW8, 6GM8, 6JK8,##------*--------------------------* * 6KN8,7DJ8,7ES8,8JK8,12DJ8## 9DP * 6JH8 * * 12DT8,17EW8/HCC85,17JK8, ##------*--------------------------* * 6922,7057,7803,8223,8431 ## 9DR * 6BC4 * ------*--------------------------##------*--------------------------* 9AK * 5X8, 6X8, 9X8, 19X8 ## 9DS * 5AS8, 6AS8 * ------*--------------------------##------*--------------------------* 9AQ * 3BX6,3BY7,3EH7/XF183,3EJ7## 9DT * 3A2 * * /XF184, 4EH7, 4EJ7, 6BX6/##------*--------------------------* * EF80, 6EH7/EF183, 6EJ7/ ## 9DV * 6486A * * EF184, 6EL7, 6GK7, 12BX6 ##------*--------------------------* END OF 5A and 5B ===================================================================== BASE * TUBE TYPE Page 6A ## BASE * TUBE TYPE Page 6B * 9DW * 5AT8, 6AT8 ## 9GC * 12J8 * ------*--------------------------##------*--------------------------* 9DX * 6AU8,6AW8,6BA8,6BH8,6CX8,## 9GE * 5CQ8, 6CQ8 * * 6EB8,6GN8,6HF8,6HZ8,6JE8,##------*--------------------------* * 6JL8,6JT8,6JV8,6KR8,6KS8,## 9GF * 4GS7,4LJ8,5CG8,5FG7,5GS7,* * 6KV8,6LB8,6LP8,6LQ8,6LY8,## * 5LJ8,6CG8,6FG7,6GD7,6LJ8,* * 8AU8, 8AW8A, 8BA8A, 8BH8,## * 7GS7, 9CG8 * * 8CX8,8EB8,8GN8,8JE8,8JL8,##------*--------------------------* *8JT8,8JV8,8KS8,10EB8,10GN8## 9GJ * 5CR8, 6CR8 * * 10HF8,10JT8,10JY8,10KR8, ##------*--------------------------* * 10LB8,10LW8,10LY8,10LZ8, ## 9GK * 6GK6, 6KY6,7KY6,7KZ6,8LS6* * 11JE8, 11KV8, 11LQ8,7060 ## * 9KX6,9LA6,10GK6,16GK6 * * 7716 ##------*--------------------------* ------*--------------------------## 9GM * 6CU8 * 9DZ * 5AV8 ##------*--------------------------* ------*--------------------------## 9GR * 6DB5, 12DB5 * 9E * 5T8,6AK8/EABC80,6T8A,19C8##------*--------------------------* * 19T8 ## 9GS * 12AL8 * ------*--------------------------##------*--------------------------* 9EC * 5B8 ## 9GT * 12DK5 * ------*--------------------------##------*--------------------------* 9ED * 6AZ8 ## 9H * 5687,6900,7044,7119,7370 * ------*--------------------------##------*--------------------------* 9EF * 6CS7, 8CS7, 6DA7, 10DA7 ## 9HE * 6DC8 * ------*--------------------------##------*--------------------------* 9EG * 5BE8, 5DH8, 6BE8 ## 9HF * 6DE7,6DR7,6EW7,6FD7,6FR7,* ------*--------------------------## * 10DE7,10DR7,10EW7,10FD7 * 9EJ * 6582A ## * 10FR7,13DE7,13DR7,13FD7 * ------*--------------------------## * 13FR7,15EW7,19DE7,19EW7 * 9EN * 6CN7, 8CN7 ## * 20EW7 * ------*--------------------------##------*--------------------------* 9EP * 7898 ## 9HK * 5BW8, 6BW8 * ------*--------------------------##------*--------------------------* 9EQ * 7721, 7722 ## 9HL * 6360, 6939 * ------*--------------------------##------*--------------------------* 9ER * 6BJ8, 6BN8, 8BN8 ## 9HN * 5CZ5, 6CZ5, 6EM5, 8EM5 * ------*--------------------------##------*--------------------------* 9ES * 6CM7, 8CM7 ## 9HP * 6AY3,6BA3,6BH3,6BS3,6CH3 * ------*--------------------------## * 6CJ3,6CK3,6CL3,6CM3,6DW4,* 9EU * 6GC5, 12AB5, 6973, 7061 ## * 12AY3,12BS3,12CK3,12CL3, * ------*--------------------------## * 12DW4A,17AY3,17BH3,17BS3,* 9EX * 6BM8/ECL82,6DZ8,6HC8,8B8,## * 17CK3,17CL3,17DW4A,22BH3,* * 9DZ8,11BM8,12DZ8,16A8/PCL## * 25CM3, 34CM3 * *82,17HC8,18DZ8,35DZ8,50BM8##------*--------------------------* * 50FY8 ## 9HR * 12DL8, 12DV8 * ------*--------------------------##------*--------------------------* 9FA * 5BR8,5FV8,5MB8,6BR8A,6FV8## 9HV * 12EM6 * *6JN8,6MB8,9BR8,12EC8,12JN8##------*--------------------------* * 19HV8, 19JN8, 8446 ## 9HX * 6DX8/ECL84,10DX8/LCL84, * ------*--------------------------## * 15DQ8 * 9FC * 4CX7, 6CH7, 6CX7 ##------*--------------------------* ------*--------------------------## 9HZ * 12DK7 * 9FE * 5BT8, 6BT8 ##------*--------------------------* ------*--------------------------## 9JC * 12DW8 * 9FG * 3GS8/3BU8,3KF8,4GS8/4BU8,##------*--------------------------* * 6BU8, 6GS8, 6KF8, 6KM8 ## 9JD * 12DY8 * ------*--------------------------##------*--------------------------* 9FH * 12F8 ## 9JF * 5EU8, 6EU8 * ------*--------------------------##------*--------------------------* 9FJ * 6BV8 ## 9JG * 5EH8, 6EH8 * ------*--------------------------##------*--------------------------* 9FK * 17H3 ## 9JH * 7150 * ------*--------------------------##------*--------------------------* 9FN * 6BY8 ## 9JL * 2DF4 * ------*--------------------------##------*--------------------------* 9FR * 7233 ## 9JT * 7199 * ------*--------------------------##------*--------------------------* 9FT * 6CH8 ## 9JU * 12DS7 * ------*--------------------------##------*--------------------------* 9FV * 6854 ## 9JX * 12DU7 * ------*--------------------------##------*--------------------------* 9FX * 5CL8A,6CL8A,9CL8,19CL8A ## 9JY * 12DV7 * ------*--------------------------##------*--------------------------* 9FZ * 5CM8,5KZ8,6CM8,6CS8,6KZ8,## 9K * 5763, 7495 * * 9KZ8 ##------*--------------------------* ------*--------------------------## 9KA * 6EZ8, 19EZ8 * 9G * 5686 ##------*--------------------------* ------*--------------------------## 9KG * 4CM4, 6CM4 * 9GA * 6HU6 ##------*--------------------------* ------*--------------------------## 9KH * 7239 * 9GB * 6877 ##------*--------------------------* END OF 6A and 6B ===================================================================== BASE * TUBE TYPE Page 7A ## BASE * TUBE TYPE Page 7B * ------*--------------------------##------*--------------------------* 9KN * 6GV7, 7GV7 ## 9PA * 6JC8 * ------*--------------------------##------*--------------------------* 9KP * 6FH8 ## 9PB * 7905 * ------*--------------------------##------*--------------------------* 9KR * 6FM8, 14GT8, 14JG8, 7724 ## 9PG * 4KF8, 20EZ7 * ------*--------------------------##------*--------------------------* 9KS * 7360 ## 9PJ * 8102 * ------*--------------------------##------*--------------------------* 9KT * 12FQ8 ## 9PL * 8106 * ------*--------------------------##------*--------------------------* 9KU * 12FR8 ## 9PM * 3HM6,3HT6,3JC6,3JD6,3KT6,* ------*--------------------------## * 4HM6,4HT6,4JC6,4JD6,4KT6,* 9KV * 12FX8 ## * 6HM6,6HT6,6JC6,6JD6,6KT6 * ------*--------------------------##------*--------------------------* 9LC * 6GE8, 7734 ## 9PQ * 6JU8, 8JU8A * ------*--------------------------##------*--------------------------* 9LG * 6CY7, 8CY7, 11CY7 ## 9PX * 7695, 7754 * ------*--------------------------##------*--------------------------* 9LK * 7551, 7558 ## 9PV * 6KA8, 8KA8 * ------*--------------------------##------*--------------------------* 9LP * 6CG7,6EV7,6FQ7,6GU7,8CG7,## 9PY * 8212 * * 8FQ7, 8GU7, 12FQ7 ##------*--------------------------* ------*--------------------------## 9PZ * 8233 * 9LQ * 6EQ7, 6KL8, 12EQ7, 12KL8,##------*--------------------------* * 20EQ7 ## 9QA * 4GJ7,4GX7,5GJ7,5GX7,5HB7 * ------*--------------------------## * 6GJ7/ECF80,6GX7,6HB7,6HD7* 9LS * 6EU7 ## * 8GJ7/PCF80,8GX7 * ------*--------------------------##------*--------------------------* 9LT * 6ET7, 6KU8, 8ET7, 10KU8 ## 9QB * 8278 * ------*--------------------------##------*--------------------------* 9LW * 3HS8, 4HS8, 6HS8 ## 9QD * 6GF7, 10GF7, 13GF7 * ------*--------------------------##------*--------------------------* 9LX * 1H2 ## 9QF * 6JA8, 10JA8 * -----*--------------------------##------*--------------------------* 9LY * 6GV8, 9GV8, 18GV8, 19KG8 ## 9QG * 6KM8 * ------*--------------------------##------*--------------------------* 9LZ * 6GW8/ECL86 ## 9QJ * 5BC3 * ------*--------------------------##------*--------------------------* 9M * 6CA4, 6V4/EZ80 ## 9QK * 6GJ5, 12GJ5, 17GJ5 * ------*--------------------------##------*--------------------------* 9ME * 18HB8, 35HB8 ## 9QL * 6JB6,6JE6,6JF6,6JU6,6KM6,* ------*--------------------------## * 12JB6,17JB6,22JF6,22JU6, * 9MP * 4HG8, 5HG8/LCF86, 6GY8, ## * 22KM6, 24JE6A, 24LQ6 * * 6GW8/ECL86, 6HG8/ECF86, ##------*--------------------------* * 7HG8/PCF86, 8HG8 ## 9QM * 6GQ7, 19GQ7 * ------*--------------------------##------*--------------------------* 9MQ * 6GM5 ## 9QP * 6KT8 * ------*--------------------------##------*--------------------------* 9MR * 6FA7 ## 9QR * 6ML8, 8358 * ------*--------------------------##------*--------------------------* 9MS * 7701 ## 9QT * 6KY8,6LR8,15KY8,17LD8, * ------*--------------------------## * 21LR8 * 9MX * 7719 ##------*--------------------------* ------*--------------------------## 9QU * 6JG6,6JR6,6JT6,6KV6,12JT6* 9MZ * 7737 ## * 17JG6,17JR6,17JT6,17KV6, * ------*--------------------------## * 22JG6, 22JR6 * 9NF * 7763 ##------*--------------------------* ------*--------------------------## 9QW * 6HL5,12HL5,50HN5,60HN5, * 9NH * 6DT5, 12DT5, 25DT5,6GB5/ ##------*--------------------------* * EL500,13GB5/XL500,18GB5, ## 9QY * 6LC8, 8LC8 * * 27GB5/PL500, 28GB5 ##------*--------------------------* ------*--------------------------## 9QZ * 6LE8, 8LE8, 10LE8, 15LE8 * 9NJ * 6HU8/ELL80, 12HU8/PLL80 ##------*--------------------------* ------*--------------------------## 9RA * 6JQ6, 12JQ6, 17JQ6,25JQ6 * 9NQ * 6HW8 ##------*--------------------------* ------*--------------------------## 9RF * 9KC6 * 9NW * 6HA6, 6HB6, 10HA6, 15HA6 ##------*--------------------------* * 15HB6, 28HA6 ## 9RG * 1BC2, 1BH2 * ------*--------------------------##------*--------------------------* 9NX * 6BF8 ## 9RJ * 21KQ6, 29KQ6 * ------*--------------------------##------*--------------------------* 9NZ * 6GT5, 12GT5, 17GT5, 7868 ## 9RL * 6LT8, 8LT8, 11LT8 * END OF 7A and 7B ===================================================================== BASE * TUBE TYPE Page 8A ## BASE * TUBE TYPE Page 8B * ------*--------------------------##------*--------------------------* 9RQ * 6MD8, 12MD8 ## 12DA * 6AG11, 6AY11, 30AG11 * ------*--------------------------##------*--------------------------* 9RT * 2BJ2 ## 12DE8* 12DE8 * ------*--------------------------##------*--------------------------* 9RU * 6ME8 ## 12DG * 2AH2 * ------*--------------------------##------*--------------------------* 9RX * 6CT3, 17CT3 ## 12DM * 6AR11,8AR11,8BQ11,8CB11, * ------*--------------------------## * 11AR11, 11BQ11 * 9T * 17C8 ##------*--------------------------* ------*--------------------------## 12DP * 6AS11,6AF11,6BD11,10AF11,* 9U * 1AU2, 1V2, 2AV3, 2BA2 ## * 12AF11, 15AF11, 15BD11 * ------*--------------------------##------*--------------------------* 9V * 417A, 5842 ## 12DR * 6GV5,6GY5,16GY5,17GV5, * ------*--------------------------## * 21GY5 * 9X * 5847A ##------*--------------------------* ------*--------------------------## 12DT * 8149 * 9Y * 1AX2, 1BK2, 1X2B, 2AZ2 ##------*--------------------------* ------*--------------------------## 12DU * 8150 * 10F * 6C9, 17C9 ##------*--------------------------* ------*--------------------------## 12DZ * 6JZ8, 6LU8, 6MF8, 13JZ8, * 10G * 6J9 ## * 16LU8,17JZ8,21LU8,24JZ8 * ------*--------------------------##------*--------------------------* 10H * 19Q9 ## 12EA * 2DV4, 6DV4 * ------*--------------------------##------*--------------------------* 10K * 5X9,5U9/LCF201,6U9,6X9/ ## 12EB * 6GA7 * * ECF200, 8U9, 8X9 ##------*--------------------------* ------*--------------------------## 12EJ * 6FM7, 13FM7, 15FM7 * 10L * 6Y9, 11Y9/LFL200, 16Y9 ##------*--------------------------* ------*--------------------------## 12EL * 1AJ2 * 10N * 6A9, 15AB9, 17AB9 ##------*--------------------------* ------*--------------------------## 12EN * 56R9 * 12AQ * 2CW4,2DS4,2EG4,6CW4,6DS4,##------*--------------------------* * 13CW4,7586,8056,8382,8441## 12EO * 6FY7, 11FY7, 15FY7 * * 8456 ##------*--------------------------* ------*--------------------------## 12ER * 6BA11, 8BA11 * 12AS * 7587, 8380 ##------*--------------------------* ------*--------------------------## 12ES * 6HD5, 6HJ5, 21HD5, 21HJ5,* 12BA * 7688, 7689, 7690 ## * 28HD5, 30HD5, 30HJ5 * ------*--------------------------##------*--------------------------* 12BF * 6B10, 8B10 ## 12EU * 8156 * ------*--------------------------##------*--------------------------* 12BJ * 6GE5, 6GF5, 6HB5, 12GE5, ## 12EW * 2AS2, 3BS2 * * 17GE5, 21HB5 ##------*--------------------------* ------*--------------------------## 12EY * 6HE5 * 12BL *6AX3,6BE3,6BJ3,12AX3,12BE3##------*--------------------------* * 12BJ3,12BT3,17AX3,17BE3 ## 12EZ * 6AD10,6BF11,6BY11,6T10, * ------*--------------------------## * 12AE10,12BF11,12T10,13V10* 12BM * 6FJ7 ## * 17BF11, 18AJ10, 24BF11 * ------*--------------------------##------*--------------------------* 12BQ * 6C10, 6D10 ## 12FA * 6EA4, 6EH4 * ------*--------------------------##------*--------------------------* 12BR * 5AZ3 ## 12FB * 6HF5 * ------*--------------------------##------*--------------------------* 12BT * 6J10, 6Z10, 13J10/13Z10, ## 12FC * 33GT7 * * 17AB10, 17X10 ##------*--------------------------* ------*--------------------------## 12FE * 6AC10, 6AK10, 6U10,8AC10 * 12BU * 6AL11, 6G11, 10AL11, ## * 9AK10 * * 12AL11, 12G11 ##------*--------------------------* ------*--------------------------## 12FJ * 6JM6A, 17JM6A * 12BW * 6J11 ##------*--------------------------* ------*--------------------------## 12FK * 6JN6A,12JN6A,17JN6A,33JV6* 12BY * 6AV11, 6BK11, 6K11/6Q11 ##------*--------------------------* ------*--------------------------## 12FM * 6T9 * 12CA * 6M11, 16BX11 ##------*--------------------------* ------*--------------------------## 12FN * 33GY7 * 12CN * 7984 ##------*--------------------------* ------*--------------------------## 12FP * 6BH11, 8BU11 * 12CT * 8058 ##------*--------------------------* END OF 8A and 8B ===================================================================== BASE * TUBE TYPE Page 9A ## BASE * TUBE TYPE Page 9B * ------*--------------------------##------*--------------------------* 12FQ * 4HA7/4HC7, 5HA7 ## 12HK * 3BL2, 3BM2 * ------*--------------------------##------*--------------------------* 12FR * 5HC7 ## 12HL * 6LG6, 21LG6 * ------*--------------------------##------*--------------------------* 12FS * 6HE7,12HE7,33HE7,38HE7, ## 12HN * 6CA11, 11CA11 * * 38HK7, 53HK7, 58HE7 ##------*--------------------------* ------*--------------------------## 12HR * 31AL10 * 12FT * 23Z9 ##------*--------------------------* ------*--------------------------## 12HT * 32HQ7 * 12FU * 8BM11, 9BJ11 ##------*--------------------------* ------*--------------------------## 12HU * 6MN8 * 12FV * 3AT2, 3BN2 ##------*--------------------------* ------*--------------------------## NOTE! THE TUBES FOLLOWING USE * 12FX * 6BZ3, 17BW3, 17BZ3,22BW3 ## THEIR TYPE NUMBERS AS THIER * ------*--------------------------## BASE NUMBERS AS THE FIRST 9 ON * 12FY * 6JS6A,6LR6,12JS6A,23JS6A,## PAGE 1A AND A FEW OTHERS. * * 31JS6A, 35LR6 ##------*--------------------------* ------*--------------------------## 60E3 * 60E3 * 12GC * 14BL11 ## 407A * 407A * ------*--------------------------##FM1000* FM1000 * 12GD * 6JZ6, 21JZ6 ## 1222 * 1222A * ------*--------------------------## 1236A* 1236A * 12GF * 6BN11, 8BN11 ## 1247 * 1247 * ------*--------------------------## 5642 * 5642 * 12GH * 16KA6, 21KA6 ## 5647 * 5647 * ------*--------------------------## 5702 * 5702 * 12GJ * 6LB6 ## 5703 * 5703 * ------*--------------------------## 5704 * 5704 * 12GK * 6CE3/6CD3, 34CD3, 34CE3 ## 5744 * 5744 * ------*--------------------------## 5783 * 5783, 5787 * 12GL * 14BR11 ## 5784 * 5784 * ------*--------------------------## 5785 * 5785 * 12GM * 6KE6 ## 5889 * 5889 * ------*--------------------------## 6098 * 6098 * 12GN * 6AC9, 8AC9 ## 6187 * 6187 * ------*--------------------------## 6418 * 6418 * 12GQ * 3BF2 ## 6483 * 6483 * ------*--------------------------## 6611 * 6611 * 12GS * 11BT11 ## 6612 * 6612 * ------*--------------------------## 6872 * 6872 * 12GT * 6AG10 ## 6977 * 6977 * ------*--------------------------## 7054 * 7054 * 12GU * 6KN6, 22KN6, 42KN6 ## 7077 * 7077 * ------*--------------------------## 7241 * 7241, 7242 * 12GV * 1AD2 ## 7246 * 7246 * ------*--------------------------## 7382 * 7382 * 12GW * 6KD6, 30KD6, 36KD6,40KD6 ## 7430 * 7430 * ------*--------------------------## 7561 * 7561 * 12GX * 6AF11 ## 7576 * 7576 * ------*--------------------------## 7720 * 7720 * 12GY * 6HS5, 6HV5 ## 7768 * 7768 * ------*--------------------------## 7841 * 7841 * 12GZ * 6AK9, 16AK9 ## * ------*--------------------------## * 12HA * 3AW2 ## * ------*--------------------------## * 12HB * 6BV11, 12BV11 ## * ------*--------------------------## * 12HC * 6EF4, 6EJ4 ## * ------*--------------------------## * 12HD * 6BW11 ## * ------*--------------------------## * 12HE * 6AG9, 6AL9, 8AL9 ## * ------*--------------------------## * 12HF * 6CG3, 19CG3, 25CG3 ## * ------*--------------------------## * 12HG * 6MJ8 ## * ------*--------------------------##---------------------------------* END OF 9A and 9B How to use this Chart for Tube Substitution Tube substitution is difficult without special books on it. In the early 60's Sylvania published a Tube Manual with a back section devoted to basing diagram references. This base reference gives a quick way to find which tube used the same pin connections. You have a tube type 6U8A in a receiver mixer and you do not have a replacement in your collection of goodies. Find a Tube Listings in a 50's, 60's, 70's or early 80's ARRL Handbook (The mid 60's and 70's are the most complete) and look up 6U8 * note below. It will show a base type 9AE. Look at the chart I posted and look up 9AE and the following tube types are listed. First you mentally weed-out all the tube types not beginning with a 6 except for the industrial types. Then write down 6AX8, 6EA8/6GH8, 6GJ8, 6HL8, 6LM8, 6MQ8, 6U8A/6KD8, GB1252/6U8A, 6678/6U8A, 7059, 7643, 7687, 7731 and 8445. Look for one or more of these in your goodies box. All the tubes will fit the tube socket and most likely plug in 'BUT' you have to go further. You may have found a 6EA8/6GH8 tube and you hope it is similar. Look it up in the tube manual or 6EA8 or 6GH8 as they were once separate tube types that were so close in design they now incorporate both numbers. The figure "/" between tube numbers indicates same types. The 6EA8 has the same Filament characteristics, As It Must Be * . The Plate Watts dissipation is a tad greater. Its OK to be a little higher than less than the 6U8A. You do not know if the circuit design was close to limits. 6EA8 = 3 Watts and 2.5 Watts for the 6U8A. The max Plate Voltage is slightly better, 150 versus 125v. Conditions as for Wattage applies here also. Plate resistance in Ohms is identical as there is some latitude here. Transconductance is a little more and the Amplification factor is the same. This tube will work well and probably will give better performance but since the triode section is the oscillator for the pentode section which is used as a mixer of this communications receiver, you may have to recalibrate the oscillator frequency. The 6U8C would have been the ultimate but its design is old and the 6EA8 was a newer generation design with different metals and cathode structure as well as grid structure that resulted in an improved operating tube over the 6U8. The 6U8 developed inter-electrode shorts and was noisier. The 7731 happens to be the same as a 6U8A. The 8445 would not be a good choice. Lower wattage and plate voltage ratings. More than likely it would over heat and self destruct. Possibly damaging the radio. Now if you are looking for more power such as in old tube type amplifiers say the famous Williamson Amp. There were variations with the final power tubes being 6L6GB/GC or 5881 or KT-66. You have a pair of KT-88 and you find out they all share a base type 7S. Forget it, you will gain nothing by installing the KT-88 and quite possibly get poorer results. The KT-88 has much higher plate voltage requirements as well as higher plate current all of which is not available in the smaller amp. The output transformer is matched to the smaller tubes and would not handle the increased current of the KT-88's. Also the bias voltage for class AB1 is totally different and distortion would probably result. I've tried it. It was a waste of my money. Tube substitution for RF use as in a Frequency Multiplier chain or Driver or even Output RF Amps, caution should be exercised. Substitute with tubes that closely match. Don't sub for increased power but you can substitute for improved performance. As the Tube as King in the industry came to a close the engineers were designing quieter tubes for RF receiving use. The late 50's classic 6BZ6 was used as the first rf amp. such as the Hammarlund HQ170, Collins 75S-1 and RL Drake 2B and R4 series receivers to name a few. My experience in the 60's were with the 170, 2B and R4B. I substituted a 6EW6 on the first 2 receivers and later a 6JK6 on the R4B with improved small signal reception. I was using VHF and UHF converters on these receivers. These tubes have a higher Transconductance of 18,000 micromhos for the 6JK6 as the 6BZ6 has 8,000 micromhos. Substituting the IF amp tube would be of little improvement. As the RF stage is the key for hearing the weak signals out of the noise and even more so at VHF or UHF. * Note: a 6U8/6U8A/6U8B or even C. A or B or C is nothing more than evolutionary changes the late 50's vintage 6U8 underwent over the years as a 6U8A is better than a 6U8 and so forth. It may have enough difference that the tube may not work in a critical oscillator circuit or be way off frequency. Try the substitution, as nothing ventured nothing gained. * Note: When substituting Tubes The Filament Voltage and current should closely match the original in parallel wired circuits and using a higher current fil. may over heat the filament supply. For Series String Tubes, fil. current has to match with each tube. The total series fil. Voltage should be equal to the Filament Supply Voltage. My apologies for not creating this document to fit a standard sized paper. I started out with 70 lines per page and messed up on the 5th and 6th page but some adjusting on a word processor should help in printing. I do not have the capability with my system to adjust the left and right columns and I have to rewrite a page for corrections. There are still some Electronic Buffs out there that will get some use out of this. Enjoy. 73's Gene K7EEK