Embarrassing newbie questions

[schombi]

Day 2 with my MTX512 and the embarrassing newbie questions start. Guess for you guys they´re super-simple, but I got stuck with them

- Since the RF-out is quite awful, I tried to use the composite signal from the monitor port with http://www.pollin.de/shop/dt/NjA5OTcyOT ... apter.html, that I had in my stock. If I press the yellow RCA cable firmly to the adapter, I get a signal on my LCD, but the RCA plug is too thick to be inserted into the adapter?!?

- Both the RF-out and the composite signal show a white cursor on a light-blueish paper. Shouldn´t I expect blue paper? On the Spectrum pale colors can be caused by aged capacitors. Same for the MTX? If so, which ones would you replace first?

- The label says MTX512 and Print peek(64122) give a "1". Does is mean I have 64KB of RAM?

- I seem to have three ROMs installed. Good, bad or normal?

More stupid questions to come, I believe...

[Dave]

Day 2 with my MTX512 and the embarrassing newbie questions start. Guess for you guys they´re super-simple, but I got stuck with them

No Problem - just wait until you see the "quality" of the answers

- Since the RF-out is quite awful, I tried to use the composite signal from the monitor port with http://www.pollin.de/shop/dt/NjA5OTcyOT ... apter.html, that I had in my stock. If I press the yellow RCA cable firmly to the adapter, I get a signal on my LCD, but the RCA plug is too thick to be inserted into the adapter?!?...

That looks just like the adapters I use, you say that the RCA plug is too think to be inserted into the adapter?
That's very odd - but it's obviously an adapter or RCA cable problem - not a problem on the Memotech side.
Obvious answer, but have you tried another cable?

- - Both the RF-out and the composite signal show a white cursor on a light-blueish paper. Shouldn´t I expect blue paper? On the Spectrum pale colors can be caused by aged capacitors. Same for the MTX? If so, which ones would you replace first?

Pass - someone else might be able to suggest things to try for this one

-- The label says MTX512 and Print peek(64122) give a "1". Does is mean I have 64KB of RAM?

Yes, the "Peek" is a much more reliable test than the label - but in your case, they both agree.
You can also tell by the RAM chips on the main board

-- - I seem to have three ROMs installed. Good, bad or normal?

Average! - Some computer boards have 2 (4000-04) and some have 3, (4000-05)

-- More stupid questions to come, I believe...

No problem !

regards
Dave

[Martin A]

Peek 64122 responding with a 1 does confirm you have 64k. The usual results are

MTX500 = 0 (32k)
MTX512 = 1 (64k)
RS128 = 3 (128k)
MTX512S2 = 4 (144k usable)
MTX500 with re-memorizor = 11 (384k useable)

The normal output is white on medium blue.

Generally the colours from the MTX are on the pale side, combine that with Memotech not choosing to use the darkest blue for the backdrop and it's likely you have the "normal" output.

There are 3 different PCB's, I think its the -04 with 2 roms and the -05 and -06 with 3. Any of those could have mask roms or eproms.

[schombi]

Thank you guys, that´s good information.

For the BNC adapter, I measured the hole is about 3mm in diameter, all my RCA plugs I tried are slightly thicker.

Yes, I can confirm my board to be a 4000-05.

[Martin A]

If you're handy with a soldering iron, you could always remove the BNC socket, and fit an RCA one instead

[1024MAK]

Three solutions to the BNC adaptor problem (assuming you don't want to modify your machine)...

First, buy another BNC to Phono adaptor from a different seller / shop.
Second, buy a BNC to phono lead (I have seen some on UK eBay, but I'm sure similar items can be found in other countries).
Third, buy a BNC to BNC lead, chop one of the BNC connectors off, and replace it with a phono connector (fitting a phono connector is easier than fitting a BNC connector)

And yes I know that that BNC to BNC leads are not common. And yes I know that phono connectors are also known as RCA connectors or cinch connectors.

I can give you a list of capacitors to change, but the most of the capacitors fitted in a MTX age better than the capacitors in a Spectrum.
I will type up the info when I have time

Mark

[schombi]

Cheers Mark! Good suggestions! Once I get the bloody BNC adapter working, I´ll focus on the pale colors and will post a picture of my screen output. Guess I should also check with a CRT and not just using my LCD, which works well with my Spectrums and SAMs.

[schombi]

Update on the situation:

No more pale colors. I ordered a BNC-to-RCA cable, which arrived in less than two days and it was only 3€ with postage included. I skipped using my LCD and dedicated a CRT to the MTX. Here the new cable gives a good picture with decent white characters on light-blue paper. Now I don´t have to mess around with the capacitors.

Two keys still give some trouble (1 and Q). Sometimes they work, but sometimes they give 2 or 3 characters, instead of one only. Guess this could be dirt? How easily can the innards of the keyboard be cleaned? To me the keyboard connector cable looks somewhat fragile and I´m afraid to break it.

BTW: I ordered a Rememorizer from Andy

[Dave]

Hi,

gald you've sorted your colour problem.

Yes, the keyboard cable is pretty fragile and prone to breaking at the point where it is crimped onto the connector.
Make sure you always lift the connector itself, rather than the pulling the cable when disconnecting the keyboard.

Sticky keys are very common.

The first thing to try is to give the keys plenty of exercise.
The keyboard may not have been used for a long time, so you should give them a good workout, that can make a big difference.

Also see this post
viewtopic.php?f=9&t=121

regards
Dave

[schombi]

New machine, new problems, more embarrassment.

By pure coincidence I got hold of a second MTX512. It arrived yesterday, but it gave me headaches from the beginning.

The label reads 512/38015, which seems to be a fairly high serial. Then I opened the computer and found a half-equipped memory board (IC sockets 15-22 empty) right to the (old?) 4000-04 main board. So IMHO all these facts don´t fit together or was Memotech the same as Commodore and they dropped in whatever was on stock?

Even worse, the unit does not appear to be working. Neither with the RF-out nor with the monitor output I can get a stable picture on my TV. This is with a known good PSU and a known good telly. There is something on the screen, somewhat colorful and shaky, but even more scaring, there seems to be lines of white blocks building up row by row. Did you ever come across such problems? The seller says it did show the command prompt before he packed the unit.

Testing the temperature of the RAM chips with the finger should be the first step? I also wonder how the memory board gets removed? My idea was: The less add-ons, the less problems, but I didn´t manage to get it off the connector. Brute force?!?

It would be a shame if I can use the unit for spares only.