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HRO-60 Restoration: Need Advice

Discussion in '"Boat Anchor" & Classic Equipment' started by KW4H, Jul 2, 2021.

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  1. KW4H

    KW4H Platinum Subscriber Platinum Subscriber QRZ Page

    Thanks, Carl. I do have a question that you might be able to answer. The case is being stripped and powder coated; however, it will be up to me to fill in the lettering that's embossed into the metal. Can you recommend materials and a technique for this? In your many years of working on and with the HRO-60 you might have a trick up your sleeve you can share.

    73, Steve.
    Last edited: Jul 22, 2021
  2. KM1H

    KM1H Ham Member QRZ Page

    A paint stick (like a lipstick) and a rag was used at the factory. There are several choices these days according to You Tube. A way Ive done similar is a toothpick, good eyes, and a steady hand and when dry a non yellowing clear coat sprayed on the full panel that is compatible with the panel paint

    Hobby and gun shops are great idea places
    KW4H likes this.
  3. KW4H

    KW4H Platinum Subscriber Platinum Subscriber QRZ Page

    Thanks for the great tip! I searched on "paint stick" and hit pay dirt -- a product called "Lacquer-Stik" -- which included reviews from people fixing old equipment and swearing that it did the job. Dab it on and wipe it off with a rag. Picked up a white and black one -- I need to fix the lettering on some of the knobs. I love it when a plan comes together.
  4. KM1H

    KM1H Ham Member QRZ Page

    I couldnt remember that name, its the same as back in the 60's but it looks different and you peeled the paper back as needed and stuffed the stick in a pencil sharpener.

  5. KW4H

    KW4H Platinum Subscriber Platinum Subscriber QRZ Page

    A quick status on the HRO-60 and some questions. Today I wrapped up the IF alignment -- everything peaked up beautifully, both 1st and 2nd IF. Also, I followed the slide-rule tuning dial adjustment procedure and, with the tuning dial at 490, the pointer is precisely positioned at 4 Mhz on the D coil set scale. Turned all the way back down the needle aligns correctly with the bottom of the scale and zero on the dial. So, mechanically it seems fine. However, the coil sets don't align with the slide scale -- things seem off by quite a bit. I injected a 14.000 Mhz signal and the tuning point was quite a bit below 14.0 on the slide scale. Am I correct in assuming that this means I'll need to go through the coil set alignments? I believe this is probably a good stopping point until the case comes back from refinishing -- without the radio in its cabinet and the knobs installed and aligned, I'm kind of flying blind.

    Also -- what, exactly, do the numbers on the micrometer dial mean? They don't appear to be aligned in any way with frequency.

    73 - Steve
  6. N2EY

    N2EY XML Subscriber QRZ Page

    Good plan.

    They are a logging scale, nothing more.

    They don't.

    Here's why:

    The first HRO appeared in 1935. The PW dial/capacitor was designed for it.

    The idea was that the PW dial gave an extremely accurate and repeatable logging scale of 500 divisions. Each coil set had a calibration chart that was specific to the matching receiver.

    In operation, you read the micrometer dial and then found the frequency from the chart on the coil set.

    To set the receiver to a specific frequency, you looked at the chart and then set the dial to the setting.

    This gave accuracy that was excellent for the time.

    15 years later, in 1950, the direct reading slide rule dial was added in the HRO-50.

    For a history of the HRO, surf over to: HRO.htm

    73 de Jim, N2EY
    Last edited: Jul 25, 2021
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  7. KE0ZU

    KE0ZU Ham Member QRZ Page

    Here are a couple of examples. There was at least one other format as well.

    [​IMG] [​IMG]
    Last edited: Jul 25, 2021
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  8. KW4H

    KW4H Platinum Subscriber Platinum Subscriber QRZ Page

    Thanks for the additional advice and guidance. The "guesstimate" technology of the tuning system aside (and the obvious need for the realignment of the coil sets), once the IF of the HRO-60 was fully aligned today and a couple of tubes replaced, the reception was almost startling. You may not know exactly what frequency you're on, but the sensitivity of the reception and the quality of the audio was almost mind-blowing for a receiver of this age. No wonder they wanted a king's ransom for this receiver back in the day.
  9. KE0ZU

    KE0ZU Ham Member QRZ Page

    With the atmospheric noise floor on the low bands, many of the old post war receivers can hear anything any modern receiver can. Its the selectivity, noise canceling, and overload handling areas where some modern receivers have a bit of an edge. As far as knowing "what frequency you're on" that comes with increasing familiarity with your receiver. Of course a calibrator helps, but after a while you should easily be able to interpolate to within 5 KC or so. In the final analysis, if you hear em, zero beat em, and talk away. Doesn't matter where you are.
    N2EY likes this.
  10. SM0AOM

    SM0AOM Ham Member QRZ Page

    If you know what you are doing, it is possible to set the receiver to within +/- 500 Hz on the lower bands, just by using the 100 kHz calibrator and linear interpolation between the known points on the logging scale. The average number of Hz per division on the bandspread ranges at 20m and below is about 1100, so +/- 500 Hz is easily set.

    As amateur radio is not (yet) channelised, you do not have to worry about being "off frequency".

    When HRO-60s were used for point-to-point RTTY services in the 1950s,they were usually stabilised by external oscillators, which were specified to have a medium-term stability of better than +/- 100 Hz per day. This was entirely sufficient for the 850 Hz shift circuits common at the time.

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