25" Polo Possibly in Shutdown? High B+

[whoamonga]

The B+ in my KI2 Polo is ranging from 176 to 185 vdc... I can't hear any ticking though.

I've installed a Bob Roberts cap kit, flyback, and new HOT from Mouser.

I had an issue with replacing the focus lead on the new flyback into the neckboard socket described here: http://forum.arcadecontrols.com/index.php?topic=112979.0  The focus wire still doesn't feel like it's being "grabbed" by anything.  I can always just pull the wire back out.  Is this contact maybe broke?  If the chassis isn't getting this load, would it spike the B+ like it did?

Flowchart says to replace C114, that was done with the cap kit. 

Any ideas on what to try next?  Thanks in advance!

[boardjunkie]

If its a switching PSU, the B+ wouldn't even be there under a no load condition. The PSU won't start up, it'll just sit there and try over and over.

[grantspain]

i would suggest getting a new crt socket and check D116

[whoamonga]

I'm going to have to ask for grace for being new to monitor diagnosis... how do I check D116?

[grantspain]

you need a multimeter set to diode test,lift one side of the diode from circuit and then read across the diode-it should read one way only
shame you are not in u.k as you could send it to me and i would sort it for a small fee

[whoamonga]

So I finally did a couple things to this chassis.  First up was to replace the socket, since I'd broken the focus lead on the other one...

Next up was to test D116, like you said...

Just to make sure I'm doing this right, I desoldered one leg of the diode and ran the meter at 200 ohms, and 2k ohms one way, and the meter read 1, and then the other way, and the meter read 1 again.  So I'm assuming this is a blown diode, right?

If so, I guess my question is, what diode can I replace this thing with?  And are there any other common failures if this guy blew?

[grantspain]

you are meant to use the diode test on your meter but ohms will suffice-a shorted flyback will cause that diode to blow and you should replace c121 and c168 as a matter of course
the diode is a MUR460

this is quite a rare issue,only ever seen it a few times

[whoamonga]

I definitely think the flyback was toast.  It was original... 

I'll take the chassis to work where I can get a second opinion on that diode, just to make sure.  And look to see if those two caps were replaced with the cap kit.

Thanks man!  I'm super encouraged that this thing will soon be, as Admiral Ackbar said, "fully operational!"

[whoamonga]

Got a second opinion on D116, checked out fine...  I also tested D117 as it was right next to it, fine again...

Any other suggestions for this monster?

[grantspain]

you need to prove the psu circuit is working,really need a pro on this as you have to isolate the flyback and read b+ plus all other psu voltages
b+ is a nasty voltage to take a shock from,not sure if its fatal and never tried to find out myself

[boardjunkie]

And switch mode power supplies ain't for beginners either....

[whoamonga]

Yeah, sounds like I just needta submit to ya'll's better judgement and send this thing off.  Sad, but better than frying myself, or the board.

Thanks guys!

[ed12]

hi
the :psu: will fire up no matter what,if it is in it's range
disconnect any :load side: the psu should fire up to it's reg voltage
if u as i have sccen in your pervious post's are having trouble with the foucs lead hook up ?,i would have to sit down and wonder did u remove the :neck-board from the crt well trying to :twist: this lead out ? if not u may have cracked the :crt: and this will cause :high-voltage-shut-down:,easy test is to fire it up
and if all the vacum not is gone from tube it :the neck: will have a blue glow
that is air-getting in,that is a crack which will cause shut-down,rechk cap's
if that is not your problem,but a shorted didoe ? with a multi meter in ohm's range 1-way should be different then the other
ie 1=low ohm's the other = high ohm's
in diode range
.5 to .3 depending on the diode
that is the :drop: acroos the diode,the reverse will be open
if it show's anything it is bad
happey testing

ed