Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
¿ªÔÆÌåÓýHi Emanuele, ? From your measurements: BAND 1: C7A = 450pF, L3(C&D) = 200?H Fr = 530.5kHz (1/(6.2832 x SQRT(L x C))) C7A = 50pF, L3(C&D) = 200?H Fr = 1591.5 kHz ? BAND 2: C7A = 450pF, L3(A&B) = 26?H Fr = 1.47 MHz C7A = 50pF, L3(A&B) = 26?H Fr = 4.414 MHz ? From a mathematical point of view, that should work on both bands, or be very close to ! Unless there is a hidden capacitance in the assembly somewhere, like a connecting wire that should stand in free air, but that is pushed close to the GND along it¡¯s path instead.? (I have seen that before: too long story to tell here). Hard to verify because the radio is not right in front of me ¡. I also believe that the schematic is right: on band 2, the A+B section of L3 is connected to C7A, but the antenna signal is fed to L3 C+D and coupled using mutual inductance between the coils. On band 1, L3 C+D section is connected to C7A, antenna signal fed to L3 A+B section with a 1k resistor in series and fed by mutual inductance again. I believe that the 1k resistor is there to ¡°balance¡± the Band 1 sensitivity to the one of the other bands (more or less). ? Sorry to repeat feats or opinions that were mentioned before on the thread, but I caught this boat late¡ ? 73, Jacques, VE2JFE in Montreal ? ? Jim, great job! Don, remember: 1600-500=1100 so we have 110KHz/DIV; 1600-220=1380 .. close enough. So Jim's peak stay exactly where it should: dial @1400KHz !! peak at 1380KHz. His tank works as expected! Jacques, C7 is halli original with the correct prt. no. 048-300341. It measures 50-450pF (LCR). L3 has nothing, null, nope, vacuum inside. NO CORE. L3 coils as measured by the LCR: the first coil (pins A and B) measures 26uH, while the second (pins C and D) measures 200uH. ? -- Emanuele (IU1KNR). _._,_._,_ |
Jacques_VE2JFE