Looking at a COLLINS 75A4 RECEIVER , need advise

Discussion in '"Boat Anchor" & Classic Equipment' started by KB4MNG, Jun 14, 2019.

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I've had an A-4 since 1973 (second owner) and it has three filters.

    Incredibly, it also has all original tubes. I only know that because the tubes are labeled "Collins" (made by RCA) and replacements wouldn't have that logo.

    It's been amazingly reliable. It was designed for lower line voltage (like 110VAC, and now we have 120VAC or a bit higher) and some Collins fans use means to reduce the voltage to what it was supposed to be, but I've never done that.

    I use it at least a few times a week. Incredibly, it's still very well calibrated (I've done zero with that) and if I dial it to 15.000 MHz when it's off and have an antenna connected and then turn it on, the first thing out of the speaker is WWV at dead zero-beat. Considering it's now 62 years old, I'd place that in the "amazing" category.

    Dial still tracks within 1 kHz across each band, and it's nearly impossible to overload.

    Probably as good as it is because nobody every screwed with it (it lacks the "golden screwdriver" problem) and it's always been in a controlled environment (never cold, never hot, never humid).

    The most interesting thing to me is it can easily "hear" anything the most modern gear can, and sometimes better. That's not "sensitivity" (which on HF doesn't matter a lot) but just good design.

    Of course, an R390A is every bit as good, but I hate the way they tune! My hand cramps up thinking about it (I had one and sold it 30 years ago...good RX but wow, not designed for "tuning around").
  2. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    Unfortunately, original 6 kHz filters are virtually impossible to find and even the R-390- series 8 kHz filters are now scarce. I do have one of the 8 kHz filters in my 75A-4 and the receiver is "OK" for AM. Many AM operators prefer the 75A-1, followed by the 75A-2, for AM operation. The 75A-2A and 75A-3 need a wider filter in the 2nd filter position and then use the crystal phasing like in the 75A-1 and 75A-2 for the proper bandwidth.

    I have all 4 of the A-Line receivers and, for AM operation, I prefer the 75A-2 followed by the 75A-1.

    For CW operation, the 800 Hz filter is OK for casual operation although I prefer a 500 Hz filter. But, such a filter is going to have to be an "after-market" device.

    As for AC mains power: The original specifications are for an input voltage between 105 VAC and 125 VAC. As such, modern line voltage is still, generally, within the original tolerance. Frankly, although there may have been such, I have not heard of any failures due to the higher line voltages of today.

    Glen, K9STH
  3. W9YAC

    W9YAC Ham Member QRZ Page

    'Advice', not 'Advise'. You are asking for advise, the person responding is giving you advise.

    I don't say these to be mean, but I see this misuse on QRZ frequently.
  4. W5INC

    W5INC XML Subscriber QRZ Page

    Mr. Glen, hits the 200w.gif square on the head with his #8 posting. Lower serial numbered units under 1500 didn't have any service bulletins/factory upgrades to them, as they were the test mules for the most part. Since you will probably need to do some maintenance on most any A-4 you purchase these days, such as replacing the deadly caps, you can purchase a lower serial number unit and spend some time/money in getting it running 100% once again. A lower serial unit here from Maple Leaf country.

  5. KP4SX

    KP4SX XML Subscriber QRZ Page

  6. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Grammar police police:
    Not really... they are also giving you advice by advising you.
    KA9JLM likes this.
  7. W9YAC

    W9YAC Ham Member QRZ Page

    You are correct; the first 'advise' was meant to be 'advice' but evidently I mis-typed and auto correct changed it to advise. It was late and I usually let things like this slide, but I posted and then regretted it. If I were to start correcting bad grammar/punctuation/sentence structure here, it would be a full time job. I suppose internet forums have a continuous 'casual Friday' approach to writing.
  8. KA9JLM

    KA9JLM Ham Member QRZ Page

    Before or after the fact ?
  9. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    I agree with you!

    My auto-spell miscorrector rats me out all the time too... but usually my grammar mistakes are my own fault. :p

    I was just picking low hanging fruit for a laugh (slow Saturday and the bands are noisy here).
  10. K6BSU

    K6BSU Ham Member QRZ Page

    I don't understand why people pay super high prices for an AM filter. Wide band filters are pretty easily constructed using L and C components, at a fraction of the price. The gentle skirt response of LC filters is more pleasing to listen to. I've made LC filters for several boat anchor radios just to listen to SW broadcast, and sometimes to the ham bands.

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