ukVac.com Homepage
Forum Home Forum Home > Technical > Tech, Maintenance & Repairs
  New Posts New Posts RSS Feed - Solved - K4600 Issue B+ dropping
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Skin:


Solved - K4600 Issue B+ dropping

 Post Reply Post Reply
Author
Message
Syrup2407 View Drop Down
Groupie
Groupie


Joined: 13 Dec 2014
Location: Cambridgeshire
Status: Offline
Points: 490

Feedback: 5
Post Options Post Options   Thanks (0) Thanks(0)   Quote Syrup2407 Quote  Post ReplyReply Direct Link To This Post Topic: Solved - K4600 Issue B+ dropping
    Posted: 20 Jun 2018 at 2:11pm
Hi all,

The K4600 in my Defender packed up a while ago. After fitting a cap kit I have an issue with the B+ voltage (which should be 127V). 

When I turn on the monitor I get circa 120V which then drops (about 1V per second to below 110V), at which point I chicken out and turn off the monitor.

If I remove the X-Y board then I get 160V. With the X-Y board removed I attached a light bulb to the B+ and I get a nice stable 127V making me believe that the regulator is working correctly.

I removed the bulb and then disconnected as much circuitry as possible one by one from the monitor (neckboard,degauss wiring etc.). When I disconnect the flyback circuit the voltage goes back up to 160V making me think that this is the area of the circuit where the problem lies.

I have checked the HOT and this tests out correctly with a multi-meter.

I am led to believe that the flybacks on the 4600's are very reliable and unlikely to be the issue.

I have re-flowed the headers on all the boards (which is a typical failure point) and have gone over the boards numerous times to find suspect components and broken traces with no luck.

Do any of the monitor experts have any suggestions of what could be the problem and where I should start looking next.

Thanks in advance,

Gav


EDIT - 12/07/18 - Managed to source another chassis and swapped the flyback with the one on the faulty unit. the monitor is now up and running with a stable B+ of 127v.




Edited by Syrup2407 - 12 Jul 2018 at 8:34am
Back to Top
Syrup2407 View Drop Down
Groupie
Groupie


Joined: 13 Dec 2014
Location: Cambridgeshire
Status: Offline
Points: 490

Feedback: 5
Post Options Post Options   Thanks (0) Thanks(0)   Quote Syrup2407 Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jul 2018 at 8:38am
Hi all,

This is now fixed - needed a new LOPT, nice stable 127V B+ now and after the cap kit the screen looks nice and bright.

Cheers,

Gav


Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down



This page was generated in 0.191 seconds.