Another "What is it?"

Discussion in 'Radio Circuits, Repair & Performance' started by W1GCI, Oct 5, 2019.

ad: L-HROutlet
ad: l-rl
ad: Left-2
ad: abrind-2
ad: L-MFJ
ad: Left-3
ad: Subscribe
  1. W1GCI

    W1GCI Ham Member QRZ Page

    I found this board inside a TS-940s I picked up at a flea market. It almost looks home made. It was mounted beside the digital boards. What is it? upload_2019-10-5_13-21-38.png
  2. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    The '4027BDC" is a JK Flip Flop IC.

    What is the device connected to?
  3. K8ERV

    K8ERV Ham Member QRZ Page

    You are right, that's what it must be.

    TOM K8ERV Montrose Colo
  4. WR2E

    WR2E Ham Member QRZ Page

    [guess]sub-audible tone board?[/guess]
  5. K6BSU

    K6BSU Ham Member QRZ Page

    Now you MUST take it out and "reverse engineer" it. Post us a schematic and we (someone here) will nail it for you!
    W7UUU likes this.
  6. N1OOQ

    N1OOQ Ham Member QRZ Page

    Xtal marker generator?
    An awful lot of transistors and diodes... I think I see a Motorola logo on the other chip.
  7. K3RU

    K3RU Ham Member QRZ Page

    Might be a tuning rate reduction mod.

    The 940's stock 10khz per turn tuning rate could be slowed down to 5khz or even 2.5khz per turn with an aftermarket board.
    I have two 940's, one is stock 10khz per tuning knob turn and the other has an International Radio and Computers, Inc. "TS-940 Tuning Upgrader" installed. This "upgrader" is no longer made. I installed mine in 2007 but had it many years before that, probably bought it in the late 1980's for I think about $50 ?

    I never liked the 940's 10khz per turn and have my "Tuning Upgrader" set at 2.5khz per turn, which is actually a little TOO slow. Changing to 5khz per turn requires changing a jumper on the board.

    International Radio wasn't the only maker of tuning rate reduction boards.

    If the radio is operable, check the tuning rate - if it is LESS then 10khz per tuning knob turn then your radio has some sort of tuning rate mod installed.
  8. K7JEM

    K7JEM Ham Member QRZ Page

    What is the other IC, besides the 4027? It is hard to see a number, there may be a Motorola logo on it that is visible. Lots of parts, but only a couple of connections. What does the LED indicate?
  9. K3RU

    K3RU Ham Member QRZ Page

    P.S. I got into a "bidding war" on Ebay probably 10 years ago over one of International Radio's "TS-940 Tuning Upgrader", which ended up going for $105, roughly DOUBLE the original "retail" price. I lost the auction, as somebody wanted that "upgrader" REALLY BAD !

    Another mod board allowed one to use the "VOICE" front panel button to switch between the four memory banks. I've got one of those installed also but can't remember who made it but it probably was another of International Radio's products. Again, if the radio is operable, press the "VOICE" button and see if the memory banks cycle. Make sure the memory bank selector slide switch is set on "bank 4" for this test.

    Reverse engineering your boards purpose might not be possible without a schematic better yet a service manual for the radio.

    Good Luck.
    Last edited: Oct 6, 2019
  10. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Disconnect it and see what stops working on the radio ;)

    NN4RH and VE3LDJ like this.

Share This Page