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#1
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![]() "tomcatham" wrote in message ... I would very much appreciate your help. The unit has been recapped and the resistors shot gunned, most of the postage stamp caps or still in the cans and drum. At this point it looks like the wring may not be reconnected as it should be. I am checking voltage and resistants now ( not good). I have no sound from any band with ant. connected (nothing).I can put 400cps modulated at 455 signal at the imput and can trace the signal through the unit. I have every book I can find on the SP600 and the JX-17. I could very much use voltage for the following, T-8 pins left to right and 1 at the top, E13-1 through 10, E14- 1 through 8, E15- 1 through 8, E 16- 1 through 8, E 17 1 through 15. This is a learning process for me, so some of the questions will show how wet behind the 70+ ears I am. Thank you for reading Jimmy K5CSU Do you have the military manual TO 11-851? There is a high resolution version on the web. It shows the chassis layout of most of the versions of the SP-600 and gives transformer voltages. You should be able to find the numbers on the schematic and the bottom of the transformer should have the corresponding numbers on the transformer terminal board. Pages 105 and 106 show voltages and resistances at the terminal boards. Go over your recapping to see if you have mis-wired something. Note that socket voltages except for grids are given as measured with a 1000 ohm/volt meter, more modern 20,000 ohm/volt meters will read high. Grid voltages are measured using a VTVM. With the correct meter the chart voltages are close to what you should get. The BB caps should always be replaced but the postage stamp caps are silver mica types and seldom fail, although they can. They should not be shotgunned and those on the LO modules of the turret are precision values. Before anything else make sure you have not accidentally left the REC-Standby switch in Standby. Also make sure there is a shorting wire across the diode load terminals at the back. Also make sure the crystal selector is in VFO although you should hear some noise even it its in one of the crystal positions. Clean the decks of the selectivity switch, it can cause the receiver to appear dead when dirty. For trouble shooting first check the power supply voltages as given by the tube socket chart. This will start you and may find the problem. Check to make sure the tubes are in the right sockets. First, check the power supply voltages as given by the tube socket chart. Check to see if the receiver is dead on all bands or only on the double conversion bands (upper three). If its dead on all bands use a second receiver (a broadcast receiver will do) to listen for the local oscillator. Did you remove the RF deck to replace the caps there? If so did you remember to set the turret to half-way between two bands before re-installing it? If not you may have bent up the contacts on the deck. These are not supposed to be repairable but I have managed to make bent and broken ones work again with very careful straightening and soldering. If you can inject a 455 khz signal and hear it the problem would appear to be in the RF section. I would start with the LO, then first mixer, then the two RF amps. Run the set on a single conversion band to simplify things. If this is a JX-17 make sure the red knobs are not in external. Some sets have transformers with square bottom terminal boards and some have round ones. The military manual covers both. -- -- Richard Knoppow Los Angeles WB6KBL |
#3
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![]() "KG7LC" wrote in message ... Richard Knoppow;798183 Wrote: "tomcatham" wrote in message ...- The round ones too? Do you have one to look at? The square case transformers certainly do. -- -- Richard Knoppow Los Angeles WB6KBL The power Transformer hsd the ac voltages stamped on it. Have you checked all the tubes and make sure the knob is in VFO. -- KG7LC |
#4
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