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Recent content by Aztec

  1. Aztec

    Lafayette SSB-140 throws carrier on SSB PTBM058COX

    Hello everyone, I have a lafayette SSB-140 base station. The chassis is a PTBM058COX which is also similar to PTBM048. I just got through an alignment with this thing, all went well, except for the fact that when I hook this thing up directly to my antenna, it gives me a carrier on sideband...
  2. Aztec

    Cobra 29 early 23 ch info

    Issue fixed. The problem was the AGC voltage. D4 was leaking and was injecting voltage into this line which caused an uncontrollable amount of gain which overloaded the final IF stage. What I need to figure out now is how to calibrate the AGC adjustment (VR6) to its factory setting. Other...
  3. Aztec

    Cobra 29 early 23 ch info

    Still having a hard time with this. If I adjust one way, it receives with very strong sensitivity but it will only receive the carrier and no modulation. If i adjust another way it will receive but once the other person stops transmitting instead of static I have a ton of squealing in the...
  4. Aztec

    Cobra 29 early 23 ch info

    Hey guys, The problem with the receive seems to mostly be caused by the adjustment of T7 and T8. The receive chain had me a bit confused but I think I got it. Turns out this is dual conversion. Tell me if I have this right: TR 3 is the 23Mhz oscillator. I peaked T3 for maximum output of...
  5. Aztec

    Cobra 29 early 23 ch info

    Hello guys, I acquired a Cobra 29 early 23 channel version. The receiver is sounding weird, sounds raspy and this problem goes away when I try to align the IF stage. Transmit works nicely. I'm hoping to find proper alignment information for this radio. I found the schematic and you can tell...
  6. Aztec

    148 shorts out with antenna ground

    Hey guys, I got a weird problem with one of my Cobra 148s. Whenever I hook up the antenna ground the channel indicator goes off as if something is shorting. I'm gonna check it out when I get home but in the meanwhile I'd like to hear your ideas as to what may be wrong.
  7. Aztec

    PAL 200MDX P/S transistor replacements

    This is a laminated type transformer. I read those are supposed to be lower but from my testing everything seems happiest at a higher frequency. Earlier I ended up killing the mosfets by taking the frequency below 400hz, this time I put thicker wires on the battery thus more current was...
  8. Aztec

    PAL 200MDX P/S transistor replacements

    Well I fixed it kinda. And yes I figured out how to make it work with mosfets. I originally intended to rebuild the circuit as is. However even with modern day transistors it still wouldn't be efficient or stable. What I did was build a CD4047 oscillator circuit that drives two IRF3205...
  9. Aztec

    PAL 200MDX P/S transistor replacements

    Don't think that's them. These come in an old TO-36 package they look late 60s early 70s. They are germanium and PNP. That's all I know. Anyone know what the plate voltage on these tubes should be?
  10. Aztec

    PAL 200MDX P/S transistor replacements

    Hey guys, I just aquired this old mobile tube amp. It's a PAL200MDX. Unfortunately I think in my excitement I ended up killing it. I seem to have killed the two transistors that drive the transformer. They are unmarked but the schematic says they are PE250 AKA EF250. They are stud style...
  11. Aztec

    Modding PLL UPD858 in Midland 77-883

    Okay well I've been trying to figure out how I could make this thing work so that the entire dial becomes lower frequencies that are continous when this thing is placed on low. What I found suggests that this mod as is, may not actually be able to start at 26.955 on channel 40 and go from...
  12. Aztec

    Modding PLL UPD858 in Midland 77-883

    Okay I did it and it works though not how it was predicted. The mod operates on the channel selector from channel 16 to 40. On high 16-40 gets me from 27.555 to 27.805. On low it gets me from 26.755 to 26.935 on channel 33. After channel 33 it goes back down to 27.745 on channel 34. From...
  13. Aztec

    Modding PLL UPD858 in Midland 77-883

    that's perfect! I'll report back when the mod is done.
  14. Aztec

    Modding PLL UPD858 in Midland 77-883

    Ah okay understood. I'm guessing in that case I'll have to isolate pin 19 so when the switch is up, only pin 19 gets 5V. I'm thinking a couple diodes that come from pins 18 and 21 so that when pins 18 and 21 get sent high, the voltage will go to 19 from them. On the other hand when the switch...
  15. Aztec

    Modding PLL UPD858 in Midland 77-883

    Unit 399, I finally got around to performing the mod but I'm stuck at the switch wiring. I'm a bit confused by the diagram where it says to hook one throw of the switch up to 18, 19, and 21. Am I supposed to connect all of those three pins together together? If so what would be the point of...