(FIXED) mtc9000 shutdown issue (poly caps?)

[Del Griffith]

Does anyone by any chance know where i can buy these 2 polycaps from ?

Among the list of faults this chassis has had causing many hours/nights of time and head scratching by myself and Mitchell Gant the current one is it keeps shutting down when trying to adjust the horizontal pot. A thread from a couple of years back by tb lilley has shown this is a possible known fault to which Ordyne suggests it's probably related to these 2 poly caps at C36 and C40 so i'm wanting to change them but am a little unsure where to get them from and if it's even possible to get like for like replacements anymore. Original thread below.

http://www.ukvac.com/forum/hantarex-9000-b_topic333632.html

I should have done a repair log on this chassis from the start as it's been a total nightmare from the off but wasn't expecting so many issues tbh, If it wasn't for Mitchell Gants help it would have gone under the hammer by now for stress relief (One poorly op wolf cab for sure)

Del Griffith2015-09-12 16:24:03

 

[Mitchell Gant]

I should have done a repair log on this chassis from the start as it's been a total nightmare from the off but wasn't expecting so many issues tbh, If it wasn't for Mitchell Gants help it would have gone under the hammer by now for stress relief (One poorly op wolf cab for sure)

First fault was bad series regulator transistor TR20 (TIPL762) causing instant shutdown.

Once fixed that led to arcing from the H.O.T. TR15 to chassis where heatsink insulator had broken down. A Carling lager can heatsink 'fixed' that enough to prove that a picture could appear on screen. But only long enough for capacitor C205 on the neck PCB to fail with smoke and a nasty smell, cooking resistor R126 in the process.

A re-cap of all electrolytics and a proper heatsink insulator fix brought it mostly to life, apart from the sensitive shutdown issue.

Latest faults were broken track under diode D18 that a previous repairer had bodged underneath PCB, and a dry joint on connector for control adjustment pot PCB (well spotted there Del!). Both these faults caused vertical scan collapse.

Not too bad for an old and previously repaired chassis. CRT itself is good so well worth repair I think. My hammer is always available if you need it though...

 

[Del Griffith]

Ha ha we'll hang fire with the hammer for now, Hopefully life in the old girl yet

 

[big10p]

My working MTC 9000 (I'm also fighting with another one, trying to get it to work) shuts down if I adjust the H freq pot too high. I thought this was supposed to happen to protect against over stressing other components, or something?

 

[obcd]

Those monitor chassis have an xray protection circuit.

If you set the screen voltage 2 high, that circuit switches off the horizontally stage. (HOT & LOPT)

 

[Del Griffith]

It could be that it is meant to shutdown for protection if to much horizontal is applied but this won't really sync the picture without it going off, Say the pot went to 10 this shuts down at about 1 so has to be some issue as it's got worse than it was a few weeks back.

I have managed to source the poly caps locally today so will post results after i've had chance to put them in and test.

 

[Del Griffith]

Last night replaced Film caps C36, C40 & C37 (planned on replacing C41 also but local shop didn't have those) Was also advised to check, D12, D13, R75 & R77 so pulled and metered those at the same time but appeared ok. Plugged it back in and fired it up (2am by now!) adjusted the Horizontal nearly up full and no shutdown, Nice Well almost! After being on about 15 mins it lost vertical hold and picture started rolling! Another issue maybe so after some more reading of fault logs i replaced Tr10 & Tr11 and tried it again.......All good, Had it on for about an hour or more this afternoon and nice solid stable picture. I'll await the next fault to occur now
Del Griffith2015-09-12 23:22:06

 

[big10p]

Nice one.

 

[Georgian2]

My working MTC 9000 (I'm also fighting with another one, trying to get it to work) shuts down if I adjust the H freq pot too high. I thought this was supposed to happen to protect against over stressing other components, or something?

Did you ever find an fix for this. I have one on the bench right now and it shuts down if the h freq is turned anti clockwise.

 

[big10p]

Did you ever find an fix for this. I have one on the bench right now and it shuts down if the h freq is turned anti clockwise.

That's a mightly long time ago for my feeble memory to recall, other than the fact I remember it was fixed. After a bit of searching, it seems the HV film caps were the culprit, according to my last post, here:

MTC 9000 switches off

Hi I've started getting an issue with an MTC 9000 that I have a MAME setup running on. Now, when I run certain games, GroovyMAME sets the required video mode, causing the x-ray protection circuit to kick in, or something. The monitor switches off, just as it does when the Hfreq pot is turned up...

www.ukvac.com

Mine only shutdown when the pot was turned fully clockwise though, I think, so not sure if your issue is the same.

 

[Georgian2]

That's a mightly long time ago for my feeble memory to recall, other than the fact I remember it was fixed. After a bit of searching, it seems the HV film caps were the culprit, according to my last post, here:

MTC 9000 switches off

Hi I've started getting an issue with an MTC 9000 that I have a MAME setup running on. Now, when I run certain games, GroovyMAME sets the required video mode, causing the x-ray protection circuit to kick in, or something. The monitor switches off, just as it does when the Hfreq pot is turned up...

www.ukvac.com

Mine only shutdown when the pot was turned fully clockwise though, I think, so not sure if your issue is the same.

Cheers. C36 was the issue.
Thank you for taking your time to respond to this old thread.

 

[big10p]

Cheers. C36 was the issue.
Thank you for taking your time to respond to this old thread.

No problem. Glad to be of some help.