You never know what is inside...

Discussion in 'Amplitude Modulation' started by W7TFO, Mar 20, 2021.

ad: L-HROutlet
ad: l-rl
ad: L-MFJ
ad: L-Geochron
ad: Left-3
ad: Left-2
ad: abrind-2
  1. W7TFO

    W7TFO Premium Subscriber QRZ Page

    An oil-filled 5kW mod trans from Electro Engineering.


    When I got it the insulators were broken, so I opened it up.

    Some mineral oil, and a LOT of sand. Makes sense, as they were in Cali...maybe in the beach?

    Turns out they did it to cut back on the "talking" mod trans sometimes do.

    Didn't work, as this was a really noisy TX when I babysat it back in the early 80's


    ps...It drove a single 5CX5000 via two 4-1000's.
    K0UO and K3XR like this.
  2. K3XR

    K3XR Ham Member QRZ Page

    Guess it gives new meaning to the term "sandbagging".:D
    WQ4G and K0UO like this.
  3. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    Looks like it has been repaired, since one of the coils is covered with the original black paper insulating material, while the other, with brown paper. The Gates BC1-T at the station where I worked in mid 60s blew a plate transformer (the cheapo yellow plastic clamp that held in place the 240 line to the primary had deteriorated and crumbled, and the loose wire managed to flop over against the winding and arced through). The original xfmr was finished with the traditional black paper, but the replacement Gates supplied was finished with brown paper. Don't remember if the replacement was made by Electro-Engineering Works, or some other company. I repaired the zorched transformer and it worked OK, but the boss wanted to order a new one. I eventually took the repaired one home a few months later, along with a carload of other goodies that weren't used any more, when the boss suggested that I clean out all the "junk" that had accumulated in the transmitter building over the years.
  4. W2VW

    W2VW Ham Member QRZ Page

    Obviously that transformer just needs to be updated to the latest software.
    AG5CK likes this.
  5. W7TFO

    W7TFO Premium Subscriber QRZ Page

    The brown side is the primary with 2 windings, the black is the secondary.

    I broke the seals on this one, it is original.

  6. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    So it originally came from Electro-Engineering with the sand. On first reading I had interpreted it that a previous engineer had opened the case and poured in the sand to quieten it, and that didn't work. Maybe the factory added the sand because sand is cheaper than transformer oil.

    Do you have a photo of the case it came in?
  7. K5UJ

    K5UJ Ham Member QRZ Page

    That kind of construction with the two coils on what I call an O core (since I don't know what it is officially called) looks like iron from Quality Transformer in San Jose. They made reactors for some broadcast rigs. Looks like they have quit making chokes and reactors though. I don't think they ever made mod. transformers like Electro did. I have a 65 H reactor from QT in my 160 m. rig.
    I think the Gates plate iron was made by Basler in Highland IL:
  8. WZ5Q

    WZ5Q Ham Member QRZ Page


    Here is my oil filled 5Kw Mod Iron along with it's Mod Reactor. They are both made by Electro-Engineering. I believe they came out of a Gates BC5-P, a single 3CX-2500F3 modulated by a pair.

    My transformer also had a broken insulator but it's a fairly clean break so hopefully I will be able to repair it. You can see that in the last pic. I will also need to check the oil level as the insulator was broken before I got it so there is no telling how much oil leaked out. It's pretty full though, you can tip it and presto you've made a mess.

    1 - 5KW 1A Mod Iron.jpg

    2 - 5KW 1A Mod Iron.jpg
    3 - 5KW 30H Mod Reactor.jpg

    4 - 5KW 30H Mod Reactor.jpg

    Broken Insulator.jpg
  9. W7TFO

    W7TFO Premium Subscriber QRZ Page

    No getting into that one. Mine was a bolted on top plate with gasket.

    I'm surprised there was no water in mine from 'breathing'.

    You might run a hipot from case to the windings.

  10. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    Mike, it looks like your reactor has an auxiliary winding, probably intended for applying a small percentage of modulation to the RF driver stage. It should work for that purpose for DC driver plate voltage up to maybe 1500 volts or so.

    Gluing the insulator on the transformer back together should work, although I'd first wrap some additional layers of some kind of HV insulating material around the outcoming lead, to reduce the likelihood of it developing an arc through the crack. If oil got on either piece of the broken insulator, it might have impregnated the ceramic, making it difficult to achieve a good bond; a degreaser should help clean the broken surfaces. Proceed with the assumption that the repaired insulator will only be decorative, with the added layers of material functioning as the actual insulator.

    Looks like neither the transformer nor the reactor were designed for particularly high voltage (5 kV maximum), so it might be a good idea with each one to mount the whole thing on insulation, letting the case float with respect to ground.

Share This Page