Ramsey CT-90 Counter Fault

Discussion in 'General Technical Questions and Answers' started by GM8UPI, Jun 8, 2009.

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  1. GM8UPI

    GM8UPI Ham Member QRZ Page

    Hi all.
    Have a Ramsey CT-90 Freq Counter. Works fine on ext ps, but when fitted with int batteries, seems to work ok (not very bright display) but batteries get v hot!!
    Looks like a short somewhere in battery feed circuit, possible a cap gone leaky. Have looked for circuit diagram on internet, but so far no luck.
    Anyone out there help?

  2. GM8UPI

    GM8UPI Ham Member QRZ Page

    OK, no takers. Found diagram on internet eventually, 2 hours searching!!

  3. KI6DCB

    KI6DCB Ham Member QRZ Page

    Have you found the trouble?
  4. N9JRN

    N9JRN Ham Member QRZ Page

    Don't feel bad my CT-50 went up in smoke yesterday.
  5. GM8UPI

    GM8UPI Ham Member QRZ Page

    "Have I found the problem".
    Not sure, is the answer.
    The manual I have now downloaded, specifically refers to using 4 x AA Nicad's, (ie 1.2v per cell) and the unit circuit shows that it will charge these, when an ext PS is connected to it.
    OK so I was trying to run the unit on 4 x AA "standard non-rechargeable" cells (ie 1.5v per cell). I did not however have the ext PS connected.:confused:
    So although the unit was working, why were these cells getting v hot? Obviously something in the circuit taking a hell of a lot of current.
    A number of diodes in circuit should have meant that the only thing taking current was on the downstream side of the bridge rectifier and 5v regulator.

    Should be a simple job to track down a possible S/C diode or similar.:)

    It will have to wait a couple of weeks!! I am in VE3 land at moment.

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