Microvitec Cub Monitor fault - any thoughts on root cause

for bbc micro/electron hardware, peripherals & programming issues (NOT emulators!)
Post Reply
tonygillett
Posts: 2
Joined: Sat Jan 19, 2019 11:10 am
Contact:

Microvitec Cub Monitor fault - any thoughts on root cause

Post by tonygillett » Sun Dec 01, 2019 7:40 pm

Hi all,

I've just picked up a Microvitec Cub 1451. It was described as in good working order but unfortunately it has two problems: 1) randomly varying luminosity and 2) the focus is a bit off. Here's what it looks like:

https://www.youtube.com/watch?v=yCDUb4TfPmM

I'm pretty good at repairing Beebs and other micros (i.e. anything low voltage!) but I'm not so familiar with the insides of a CRT. Any thoughts as to possible causes? If it's a case of a recap or simple replacement of a component, I can probably handle it (hopefully without experiencing what 20kV feels like) but if a deeper diagnostic dive is required I'm probably going to seek out help.

Thanks in advance
Tony

User avatar
1024MAK
Posts: 9389
Joined: Mon Apr 18, 2011 4:46 pm
Location: Looking forward to summer in Somerset, UK...
Contact:

Re: Microvitec Cub Monitor fault - any thoughts on root cause

Post by 1024MAK » Sun Dec 01, 2019 9:12 pm

“Randomly varying luminosity” sounds like a it could be a dry / poor / intermittent solder joint or connection. Also check to see if the CRT heater at the neck of the tube is continuously lit. If the heater supply is varying, then so will the picture brightness.

Loss of good focus can be either as easy as an adjustment, or rather harder as described here. It continues here.

Mark

tonygillett
Posts: 2
Joined: Sat Jan 19, 2019 11:10 am
Contact:

Re: Microvitec Cub Monitor fault - any thoughts on root cause

Post by tonygillett » Wed Dec 04, 2019 8:41 pm

Thanks Mark, I'll study the docs. For this particular case though I've decided to send it off for repair! Not sure I trust myself with CRT repairs as yet.

Tony

Post Reply