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Help with blank screen Model III?

R

Richard G

Experienced Member
Joined
Jan 31, 2013
Messages
52
Location
UK
Hello all,

I've recently acquired a model III (diskless version :() in generally excellent cosmetic condition but it's not working.

Powering on gives me a blank screen with flyback lines when the brightness is turned up but nothing else.

I've changes the usual X2 capacitors on the PSU and checked the voltages which all seem fine. Next step might be to poke around with an oscilloscope but I'd love to know if there is a quick way of establishing if the main board is in any way functional without a screen?

Any pointers appreciated!

Richard
 
The cassette motor relay makes a reasonably loud "click" when activated. So you could try pressing ENTER twice to get past the "Cass?" and "Memory Size?" prompts. Then wait a couple seconds as it takes BASIC a little bit to get to the Ready prompt. Then type "CSAVE" and press ENTER.

You should hear a click as it starts to save then another after 3 or 4 seconds when it is done. You can type CSAVE and try again as many times as you like.

Of course, it is possible for the test to fail simply because some or all of the keys are not working.
 
Thanks gp - that's exactly the sort of thing I was searching for.

I'll report back in the morning (UK time).
 
Last edited:
Yep! Little 'plink' sound when I type CSAVE. Good news.

Just need to sort out the video now. CRTs aren't my strong subject however. This machine was dropped by the courier upon delivery and the tube had snapped off two of it's mounting posts.
I've successfully mounted it back but obviously something else awry here. Just hoping I can salvage this one.
 
Woohoo! She lives!

TRS80s_zps7ccd0f14.jpg


A bit embarrassing really: I'd noticed the contrast pot looked a little damaged when I first opened the case up. I'd checked it with a meter and convinced myself it was actually ok and completely forgot about it. It wasn't ok. What an idiot... :roll:

Anyway, I'm really pleased. Next challenge is to fix the flyback lines and make a few picture size adjustments. Anyone had this problem?
As I say, I'm no crt expert. I do have some rubber gloves at the ready though :)

Everything seems fine - just a slightly sticky '3' key but I'm sure a bit of repetitive tapping will sort that out.

Thanks for the help fellas.
 
Thanks very much Chris.

OK, this is all looking good...

Dsc00465s_zps62773099.jpg


Model III picture I posted earlier is a fine testament to my poor photography skills as the trap is about spot on.

Just need to find a suitable spot for then to reside in now.
 
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