Re: 7723


Brian
 

Hi Stephen , I have been following most of this thread and at this point I think a warning might be appropriate . The CRT FLOOD GUN heater is likely to be across the -15v supply as its normally powered by DC . This will give a low resistance reading when measuring that supply , just be aware that its there and if possible unplug any connector associated with it - should be shown on circuit diagram unless the heater is supplied differently to scopes that I have ..
Brian (UK)

On Thursday, 6 January 2022, 22:21:13 GMT, Stephen <stephen.nabet@gmail.com> wrote:

On Thu, Jan  6, 2022 at 11:16 AM, Harvey White wrote:


You have a short to ground, especially the -15 volt line.

Standard procedure in all these cases is to disconnect the supply as a
unit.  Measuring all the resistances to ground tells you if there's a
short on the power supply itself.  Disconnecting the power supply
isolates the fault.  Disconnecting the other boards one by one (just the
leads carrying power) will allow you (hopefully) to isolate the fault to
a board not in the power supply.

If all the power leads are connected, it's difficult to determine where
the fault is.

Harvey
Agreed.  That’s what I’ve been trying to do by connecting the leads from each ribbon cable connectors one at a time.  And that’s also how I discovered that when pin 5 of P962 was connected, it was causing both ends of CR958 to be shorted to ground.

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