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Author Topic: Display issue (Read 857 times)

Offline MCTNET

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Display issue
« on: 2021.July.20. 10:29:45 »
Hi all

My Enterprise has started doing this lately (video attached), this is the only TV it "works" on, the rest just say no signal.

I can't get a signal out of the RF at all, though it did used to work.

I'm using the Retrocables.es SCART cable, could it be the resistor values causing this?

I've bought an Amstrad CTM 644 from ebay as used with the CPC464, 664 etc which I'd rather use with the Enterprise than an LCD TV. Was thinking of just cutting off the SCART cable end and wiring up a female DIN connector for the Amstrad Monitor. Alternatively, I could use one of these https://www.ebay.co.uk/p/2189512396 and just plug the SCART straight into the CRT monitor. Does anyone know if I'd still need resistors if I went the DIN route, and if I bought the SCART adaptor, would the CRT be more forgiving of the Enterprise's input?

Thank you in advance :)

Offline Zozosoft

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Re: Display issue
« Reply #1 on: 2021.July.20. 13:03:07 »
The issue is: video signal generated at out-of-standard frequency.
Check the voltages: +5A, +5B and +12
If all ok, then try to fine adjust C43 or/and L2 on a motherboard.

And look the capacitors on the motherboard, if Philips used, then recommended to replace all.

Offline MCTNET

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Re: Display issue
« Reply #2 on: 2021.July.20. 21:13:43 »
Thank you Zozosoft, I will check that out.

Unfortunately today has been a bit of a disaster. Whilst taking the Enterprise apart, I didn't realise the keyboard was separate to the rest of the lid and have dropped it, breaking two keyboard keys and part of the joystick. I've left them with glue on, hopefully they will be OK.

I stopped at this point to clear up the damage, thought I would make a nice soldered printer cable (I had one but it was made from an old floppy disk cable taped to a parallel cable with the end cut off) but I couldn't get my new one to work. I checked again and maybe got the printer's strobe to the Enterprise's ready, and the printer's busy line to the Enterprise's strobe. Even with the connections corrected, I can't get it to print any more (nothing happens). I noticed that the internal speaker isn't working either, though it hasn't been for a while.

Would the parallel cable have damaged anything? It's sounding more and more like it needs a recap.

Offline Zozosoft

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Re: Display issue
« Reply #3 on: 2021.July.21. 13:08:49 »
breaking two keyboard keys and part of the joystick.
:cry:

Quote
I checked again and maybe got the printer's strobe to the Enterprise's ready,
This can't be a problem, two inputs connected.

Quote
and the printer's busy line to the Enterprise's strobe.
But this more dangerous: two outputs...
Can you test the printer on another machine?
If it is working, then need to verify Enterprise side.

The Ready signal easy can be tested from Basic (reading Port B6h):
10 print in(182)
20 goto 10
Run, and switch printer online/ofline, and see there is any change? Bit 3 are the printer Ready bit.

There is a schematic part with the Printer port.
If the Strobe dead then the primary suspect the U29 which is drive the output bit.

Quote
I noticed that the internal speaker isn't working either, though it hasn't been for a while.
The circuit there are at the bottom left corner.
Can be a caps or dead LM386.
Anyway most of Enterprise users hate the internal speaker, and cut the wire of it :lol: The stereo output much better!

Offline MCTNET

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Re: Display issue
« Reply #4 on: 2021.July.21. 19:33:25 »
Thank you for your help, I managed to get a bit of improvement on the picture by turning L2, but after turning it a little way, the plastic screw head just crumbled. Now I have no picture at all (I think L2 is just set to something the TV can't sync to)

I'm really having no luck with this Enterprise.

Is L2 replaceable, what would it be called?

It's in lovely condition, had never been opened before today (serial no sticker intact) and I've managed to repair the keyboard.

I'm not sure what to do with it, at the moment with my luck I'm thinking about putting it on ebay as repairs before I make it any worse.


Offline Zozosoft

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Re: Display issue
« Reply #5 on: 2021.July.27. 19:47:38 »
Thank you for your help, I managed to get a bit of improvement on the picture by turning L2, but after turning it a little way, the plastic screw head just crumbled.
Ohhh, nooo :cry:

Quote
Now I have no picture at all (I think L2 is just set to something the TV can't sync to)
It is totaly impossible somehow turn back?

Quote
Is L2 replaceable, what would it be called?
113CN K1881
But I can't find it anywhere...
Few years ago we bought the last 3 pcs from Netherland.

If not found any, then just possible got from another dead Enterprise :roll:

Offline John Fante

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Re: Display issue
« Reply #6 on: 2021.July.28. 09:16:50 »
Thank you for your help, I managed to get a bit of improvement on the picture by turning L2, but after turning it a little way, the plastic screw head just crumbled. Now I have no picture at all (I think L2 is just set to something the TV can't sync to)

I'm really having no luck with this Enterprise.

Is L2 replaceable, what would it be called?

It's in lovely condition, had never been opened before today (serial no sticker intact) and I've managed to repair the keyboard.

I'm not sure what to do with it, at the moment with my luck I'm thinking about putting it on ebay as repairs before I make it any worse.

Maybe try https://commodoreszerviz.hu/. Zoltan have previously fixed a machine of mine.

Offline ergoGnomik

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Re: Display issue
« Reply #7 on: 2021.July.28. 10:04:02 »
Regarding L2, once I found, and now did look it up again, a datasheet that lists two products with very similar type codes. This may help determining how those are constructed and someone could make measurements on ones that are still good. Or MCTNET could carefully dismantle his broken choke and look at what can be seen in it. Maybe there is some compatible product available nowadays.