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Main => Monitor/Video Forum => Topic started by: fredster on November 08, 2011, 08:52:08 pm

Title: How to you know where to measure B+ by a schematic ?
Post by: fredster on November 08, 2011, 08:52:08 pm

Do you put the black lead on the chassis, then find where the number is at on the schematic to figure out where to measure B+?

Is there any hard and fast rules for figuring that out?

Set to DC, set appropriate range, probe black on the Chassis, then touch, what?

Title: Re: How to you know where to measure B+ by a schematic ?
Post by: ed12 on November 09, 2011, 12:52:00 am

can u get a tad more specific ?

ie what do u want to meter?
is it smps style?
why do u want to meter  dc side ?

monitor of what brand ?
smps of what kind ?

ed

Title: Re: How to you know where to measure B+ by a schematic ?
Post by: fredster on November 09, 2011, 01:06:07 am

I mean any brand. Can you tell by just scanning the schematic? Some of them I can pick it out, like the older ones (G07)

Title: Re: How to you know where to measure B+ by a schematic ?
Post by: ed12 on November 09, 2011, 01:12:27 pm

yes
general rule's of basic electronic's apply here.
the main input filter on NONE smp's is the best gnd point,
on smps unit's it is the b+ filter after the switching transformer
of course u are in dc mode then

ed

Title: Re: How to you know where to measure B+ by a schematic ?
Post by: kardenm on November 09, 2011, 01:22:56 pm

Good question!  For example, this board I'm working on (a Kortek KI-2-V0) has a "B+ adj" pot on the board (RV601) but schematic does not say what voltage should be or where to measure it.  

I believe this would be a NON smps.  Right?

Title: Re: How to you know where to measure B+ by a schematic ?
Post by: fredster on November 09, 2011, 11:00:33 pm

If found that Randy Fromm has some videos on youtube.  They are like an hour long, but he answered it.

He said to make sure what you ground on is really part of the ground, as some of the heat sinks are not connected to the ground.  He traced the circuit and pointed out that you can test the first diodes out of the power supply, and noted the other power supply points.

Title: Re: How to you know where to measure B+ by a schematic ?
Post by: kardenm on November 10, 2011, 10:05:11 am

Thanks fredster.
Can you post a link to the youtube videos?

Title: Re: How to you know where to measure B+ by a schematic ?
Post by: kardenm on November 11, 2011, 09:12:34 am

Found It.  These are some great videos by Randy Fromm.  He's a GOOD teacher/lecturer and really knows his subject well.

CRT monitors-Part 3 of 4 (http://www.youtube.com/watch?v=gs0wLG0f-ps#noexternalembed)

Title: Re: How to you know where to measure B+ by a schematic ?
Post by: lilshawn on November 12, 2011, 12:49:42 pm

I usually measure the b+ right as it comes out of the power supply. It will be the transformer then maybe a diode and then it will run into a choke coil. I measure the "out" side of the coil.

unless of course there is an actual b+ test point.