I managed to pickup a used BK Precision 1474 oscilloscope for $10 and figured it would be a good gamble for the price, I powered it up and the CRT had no spot. I did some hunting and managed to find the original service manual as a pdf, and started working down the troubleshooting chart. I have made it as far as a section that wants me to check the voltage across a "radiator plate". So far I have found absolutely nothing that mentions what this part is, and google just wants to show me car radiators for sale. I am 16, and this is my first scope, so any help figuring out what this is would be deeply appreciated.

Schematics are here (Diagrams and schematics start on PDF page 25.)

Here is a screenshot of the chart that wants me to check the radiator plate: 1474 Scope Service Manual

Thanks in advance!

EDIT: Thanks for digging into this with me guys! :) The general consensus seams to be that it is some kind of thermal plate on a transistor or something. So I will probe around when I get home, and will update when I do!

I also added a link to schematics for those of you that know more then me to have a look at.

  • 1
    \$\begingroup\$ Completely uninformed guess: either a heatsink, or the tab of some sort of power package. \$\endgroup\$
    – Hearth
    Commented Apr 15, 2019 at 13:29
  • \$\begingroup\$ Another uninformed guess: could it be one of the components of the electron gun? Looks to be part of the high voltage section. \$\endgroup\$
    – user98663
    Commented Apr 15, 2019 at 13:56
  • \$\begingroup\$ X73-1220-03 is the vertical deflection amplifier. Looks like some (few) of the transistors on that board are the small TO-92 with radiator fin. (Schematics and stuff) \$\endgroup\$
    – JRE
    Commented Apr 15, 2019 at 14:07
  • \$\begingroup\$ The connections to the CRT are on board X68-1180. \$\endgroup\$
    – JRE
    Commented Apr 15, 2019 at 14:09
  • \$\begingroup\$ Not seeing any voltages marked on the schematic in places that would connect with a transistor. Some of the transistors on the power board (X68-1180) are marked as having heat sinks, but none on X73-1220. \$\endgroup\$
    – JRE
    Commented Apr 15, 2019 at 14:17

3 Answers 3


I think they're referring to the deflection plate connections — pins 8 and 10 on the CRT, which connect to R474/L407 and R475/L408, respectively, on the vertical output amp board X73-1220-00. This is supported by the fact that if they are "NG" (no good), then the chart concludes that the vertical amplifier is defective.

Similarly, the next step has you checking pins 10 and 11 on a different board (it says X74-1210-00, but I think they really mean X74-1080-00). These would be the horizontal deflection plates (pins 12 and 13 on the CRT), because if they are NG, they have you focusing on the horizontal amplifier.


Not an oscilloscope specialist, but I understand the radiator plate to be the heat sinking element of a thermal regulator. The temperature of a component may then be regulated by injecting heat (rather than bidirectionally) because the radiator plate is guaranteed to dissipate a certain amount of heat.


The radiator plate is the heat sink that certain transistors are mounted

  • 4
    \$\begingroup\$ This seems most unlikely given the test description in the chart. (I didn't downvote you but I think that you need to give some evidence for your answer.) \$\endgroup\$
    – Transistor
    Commented Apr 29, 2019 at 11:28

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