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RCA WO-535A Help!

Discussion in 'DIY' started by blfttieq, Jul 11, 2018.

  1. blfttieq

    blfttieq New Member

    Messages:
    39
    I'm trying to get to the next level on a budget. I was gifted this scope. The scope is super clean inside and out. There are 2 variable inductors or chokes on the vertical board. One was broken in half, the other had a leg not soldered in and partly hanging loose. The devices look identical in the number of windings. This might be all that keeps the unit from working.
    I need a service manual or at least a schematic.
    Do any of you guys have a service manual or schematic? The inductors are L1 & L2 on the vertical board. 20180711_070910.jpg 20180711_070858.jpg
     

     

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  2. blfttieq

    blfttieq New Member

    Messages:
    39
    Did I put this in the right section?
     
  3. BinaryMike

    BinaryMike Pelagic EE Subscriber

    Inductors in vertical amplifiers are generally there for bandwidth extension. The circuit should work relatively well if you simply short them out, unless other defects exist.
     
  4. blfttieq

    blfttieq New Member

    Messages:
    39
    Thank you for sharing knowledge!
    I have the 1 good inductor. I'll put it in and short the other position. Then give it a spin.
    Mike what would a generic value be in this circuit? If it's not critical and since it's tunable I might put a generic variable inductor there.
     
    Last edited: Jul 11, 2018
  5. BinaryMike

    BinaryMike Pelagic EE Subscriber

    Can you measure the inductance of the good one somehow?
     
  6. blfttieq

    blfttieq New Member

    Messages:
    39
    I wish I had access to LCR, even went to local repair shop they have no way either. I did put the good 1 back in and short the other. I plugged in the scope. I used a tone generator app from a galaxy tab 3. I could only get square wave to work but it was not square looking on the scope. Also nothing below bout 1k in frequency would show up. The voltage seemed low to as I measured the output from the tab3. At least I know most everything is functional. The intensity has to be turned almost full so the old tube is well old. Lol. By extended bandwidth you mentioned, would the inductor improve lower frequency?
    Someone must have a schematic for this. I really need a sec manual.
    For the record this will be the first oscilloscope I ever used.
     

     

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  7. BinaryMike

    BinaryMike Pelagic EE Subscriber

    The next best thing to a manual for the scope is the datasheet for its CRT. With that, you can tell if the various electrodes are biased up correctly for normal brightness and focus. Check your voltmeter's limitations before proceeding!

    Inductors in vertical amplifiers generally are there to extend high-frequency response. Electrolytic capacitor failure is often responsible for poor low-frequency response. It would be rare to find a 'lytic in the signal path of a scope, but failed power supply caps can cause bizarre symptoms.
     
  8. blfttieq

    blfttieq New Member

    Messages:
    39
    Well this is very old but in great visual shape and seems to be worth recapping. Inside it looks like it was made recently, most I have found pictures of looked rough. I guess I'll start a cap list and see what I can find on the CRT. Thank you very much for your help. It would really help me move forward to have a functioning oscilloscope. I have an EICO 145 but it needs a refurb. I have a whole box of gifted ancient test gear. Including a Lafayette Condensor tester. :idea:
     

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