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Thread: Swan 500c: need help with check-out

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  1. #1

    Default Swan 500c: need help with check-out

    Hi,
    I'm a new HAM and tried 2meters, but never really go into it. While I'm studying to upgrade, I bought a Swan 500c and power supply at an auction, and it is in really nice cosmetic shape - except for some dust, this was really well-taken care of. I've been working on receivers for 30 years, but have minor experience with transceivers. I'm starting to replace the electrolytics, check tubes, power supply resistors and etc., but are there any other check-out steps I should perform before applying power for testing?

    My old TV7 will not be able to test the 6LQ6's, and I saw a thread about using the cheaper 24LQ6.
    73s
    jeffrey
    KD2AZI

  2. #2
    Join Date
    Aug 2008
    Location
    SanDiego, People's Republic of California FEMA District 9
    Posts
    39,389

    Default

    Well you can't use a 24LQ6 because the heater voltage applied to the finals is only 6.3V.
    My advice other than that would be to get a dummy load, and an HF wattmeter and practice tuning up the radio.

    Keep in mind you need to follow the instructions closely in the manual due to the fact the 6LQ6s are used in such a way that continuous carrier operation will render them useless in a short time.

    The main things to remember are give the radio an hour to warm up, drift will be minimized then and remember to keep your tun-up times short.
    When it's time, and it may be sooner than you think.

  3. #3

    Default

    Sue is correct you can damage those 6LQ6's during tune up. John Bruchey who worked for Swan for many years (30 I believe) showed me how to tune up without using the Tune Mode, by just inserting carrier in the CW mode. Tune the plate and load quickly. If you dont get it the first couple of seconds un key and wait then try again. Do not do long key downs. I would check or replace the diodes and electrolytics in the power supply. Those paper caps go bad and will cause lots of AC hum or damage to the transceiver. There is also a large silver multi voltage Mallory cap in the transceiver that needs to be cheked.
    If you want to have John check the rig out before you appply power contact him.This might be safer then just powering it up for your first time. I have heard of rigs ruined or transformers ruined that way.Contact John Bruchey for info. 520-574-0247
    KE6RWB

  4. #4

    Default

    I was a Swan authorized service center for the Northeast from 1968-1974 and worked on lots of 350s, 400s, 500s, etc.

    I'd never in a million years recommend replacing anything until I knew they needed replacement. If stuff fails, it failed; but if it didn't there is no reason to replace it, because it may well last another 40 years. There's really no way to know, but most parts don't routinely fail just because they're old. The 500C didn't especially stress anything.

    The 6LQ6s can last decades if you know what you're doing, or go bad in one hour if you don't. Mine lasted at least 22 years, and when I sold the rig it still made full output power, which was about 150W (same as it was when new). There's no trick to this other than not operating out of resonance.

    Unfortunately, some hams and a lot of CB operators (who got their hands on these rigs) didn't really know what they were doing and went through lots of tubes.

    A 6LQ6 can handle about as much continuous power as the revered 6146B can.

    Problem is the manufacturers had ambitious marketing departments who decided to rate 200W rigs at 500W and stuff like that.

    I'd never assume anything needs servicing until I've proven it needs servicing. Having been a service tech for years while I was still in engineering school, our first rule was "Never fix what's not broken," as there's a 50/50 chance you'll make it worse.
    What if soy milk is just regular milk introducing itself in Spanish?

  5. #5

    Default

    Quote Originally Posted by WB2WIK View Post
    ...I'd never in a million years recommend replacing anything until I knew they needed replacement...
    Hear Hear!

    Ten or so years from now we will be seeing a premium price placed on, "all original parts" as people shy away from all the stuff that has had the blanket replacement of components done to them.

    And, it is just bad practice. IMHO YMMV yadda-yadda, let the flames begin.


    73

  6. #6
    Join Date
    Aug 2008
    Location
    SanDiego, People's Republic of California FEMA District 9
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    39,389

    Default

    Steve is very right you really shouldn't replace parts just because they are old.

    I have two radios from the same period as your Swan...
    One a Galaxy-V (5) and a Yaesu FTDX-400.
    The Galaxy's power supply is fine, the Yaesu on the other hand needs caps in the high voltage section of the power supply, the other six caps are fine, and won't be replaced.

    The tuning method described by KE6RWB will ensure long tube life.
    When it's time, and it may be sooner than you think.

  7. #7

    Default

    I like to tune rigs and amps by keying the (CW) with a keyer sending DITs. The duty cycle is 50% and the tube plate dissipation is halved.

  8. #8

    Default

    I disagree with replacing parts "just because they are old"! Paper capacitors are notoriously bad and if NOT replaced they will, in virtually all situations, cause all sorts of problems including "taking out" transformers and other very hard to obtain components and assemblies. Even if a particular paper capacitor is still good, one is on borrowed time because there is almost a 100-percent chance that the capacitor will fail in a relatively short period of time.

    Electrolytic capacitors are another problematic component. Yes, some can be "reformed". Unfortunately, in the vast majority of situations, that only prolongs the life often for only a very short period of time. It is best to just go ahead and replace those capacitors.

    Even silver mica capacitors are starting to go bad. Many are affected with what is called "silver migration" where the silver gradually moves and shorts out the capacitor. The higher the voltage applied to the capacitor the more likely it is that the capacitor will suffer silver migration.

    Bathtub capacitors, although they have been fairly long lived, are now starting to go bad. Basically, the vast majority of these are paper capacitors and most paper capacitors are problematic.

    If you want a "hanger queen", that is, a radio that sits on a shelf, never used, then it is perfectly fine not to replace any parts since the radio will never have any voltage applied. However, if you want a working radio, then you definitely do have to replace parts.

    Now, there is one area that definitely meets the requirement that little replacement is required and that is the tubes used in the unit. Most tubes last for many decades if they have not been abused. Replacing all the tubes in a unit just to replace them with newer tubes is generally not a good thing to do. That generally requires a complete realignment and probably a "touch up" in just a few months. The original tubes will last for quite a few decades in most circuits. Of course, sweep tube final amplifiers are the exception to this. Unfortunately, sweep tubes are VERY easy to damage when used as r.f. amplifiers and therefore are definitely subject to replacement.

    I have a number of tubes that were made in the 1920s that are still working fine including a few with a "sticker" on them that states that the warranty is for 5-DAYS after the date of purchase! It seems that the manufacturers were afraid that the early experimenters were going to "push the envelope" and destroy the tubes.

    Glen, K9STH

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