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Any help with TimexSinclair 1000

J

Junior Ramos

Experienced Member
Joined
May 11, 2010
Messages
63
I have a new never opened Sinclair 1000, today was opened and tested, So I will
run 2k cassette and work fine. But to run a 16K cassette I need a 16K module.
Power off the computer and connected the 16k module, the power on and wait few minutes for the computer test the memory, but nothing happen no prompt appear
(inverse k)
Any help please
Thanks
 
What exactly happens when you turn it on? Do you get a blank screen, extra fuzzy snow or no change at all?

These are simple machines, I am thinking power supply or power regulator, maybe even caps that went bad. But what happens specifically?
 
Those 16k modules are notorious for flaky connections. Clean the contacts on the Timex card edge and on the expansion unit and see if this makes any difference.

Tez
 
The computer and the memory module are brand new and the contact of both are new xtra clean, I have a printer and it work perfect.
When connect the 16k module without a printer and power on the computer the blank screen appear in some time flicker. but the prompt not come on.
Thanks for your support.
 
Re-seat the chips, take them out and put them back. What happens is that the contacts get a very tiny amount of corrosion on them, even if you cannot see it. That can make the connections unstable, and reseating them usually breaks through that stuff.

Okay, that being said, I just re-read. The memory module may need the same treatment; though also it might be inside the thing, check there.
 
One strong recommendation I have, once you get it working, is to make a jumper cable for the 16K expansion to your computer. The 16K box likes to wiggle and mess things up while typing. A couple of connectors and some ribbon cable makes life a lot happier.

On the original problem, does anyone recall if there was a cap on the 16K expander? If so, it may need to be replaced to get the chips to come up in a "known state." I won't have a chance to get to mine for a look for a couple of days.

In the meanwhile, there's a lot you can do with 2K. I wrote any number of games with the unexpanded unit. I also found a route to machine language with just the base unit through some bug. I'm sure it's documented somewhere by now, I can't have been alone in stumbling on it.
 
Hello,
Today in the morning opened the computer and re-seat the chip mounted in socket and clean all contact in both computer and 16k module.
When power on same situation, blank screen and nothing happen, just flicker the screen for some second. the the blank screen is staedy but no prompt
appears and the computer do not respond.
Another suggest.
Thanks for your support.
 
The computer seems okay, let's focus on the memory module. Do all the pins look okay, shiny and straight inside the place that plugs in?

Also, when saunby says make a jumper cable, he means to get connectors, male and female with each one ready to mate one with the memory module and one with the board edge and wire them together; this way the computer can move a bit while you use it (hey, it's small) and the ribbon will move but the contact will never be broken and nothing wiggles.

Inside the memory module how does everything look? And make sure you are plugging everything in straight and not off-center.

As I look at mine, all it has is a notch to make sure it is in the right direction. It *can* be wiggled a bit to the left and right (like all board edge connections, even game carts).

Also better check the power supply; if not enough power is being sent over then that will also cause odd things to happen. There ae caps and things in there, too, and they go bad just from sitting, used or not. If you want to replace it a power supply from an Atari 2600 will do dandy. If you don't have one of those near it can be had at radio shack, or a thrift shop with a jumble of adapters, ready to be sifted through.
 
Hi
There are a few likely causes.
1. Something is shorted on the power leads.
Check voltage going to the memory!
2. Bit line stuck low from bad RAM in adapter.
Using thin scotch tape, mask off the data bits on the connector!
3. Control signals shorted ( like r/w or address lines )
Same as 2. mask them off on at a time to determine which one.

Look on the web for pinouts of the connector.
Dwight
 
Hi to all,
I was opened again the memory module and found a damage transistor, the transistor look like MPS 27 this is the only alphanumeric can read due is burn in.
test the transistor and are short in all way.
Any help with this part. I dont know why is burn due this is a brand new and sealed module.
Thanks for your support
 
A nice quality picture would help a lot. Since you have id'd a bad part (Factory defective, most likely) it's time to replace it. Can you solder?

A quick google search didn't give me any hits to any specific parts, so I ask for a picture.
 
Hi
A 16k module is drawn out at:
http://www.myprius.co.za/ZX81.htm

It shows a simple switcher circuit. It uses a small
pnp transistor. Several parts around it could cause it
to burn. The 22uf cap is the most obvious. If shorted it
would wipe it out. Most of the other parts might load
things down but not cause it to be toasted. A short
on the 12V rail would cause it to draw to much current
but the -5v rail would most likely have little effect if
shorted because it is a capacitive voltage doubler.
Dwight
 
I opened up my Timex/Sinclair 1016 and the transistor in mine is a National Semiconductor 2N6727. Also, I noticed that I'd been in there before. Tellingly, I had not only trimmed the collector tab on the transistor down in height by a couple of millimeters (as well as rounding the corners a bit and filing everything smooth), but I also bent back the wire ground jumper that comes over from the other board with the edge connector on it. I then put a piece of electrical tape across the top of the capacitor & transistor, all the way across the part of the board they're on.

So it looks like I once did this same repair.
 
First, Thanks to all,
Nathan, The transistor is a MPSA22 as per saleman in the Electronics shop.
Here my finding:
1. Measure all cap, and look in good condition, but my multimeter is not very good accurate.
2. Replace a Transistor as per drawing from Dwight (the NTE replacement is 159) The replacement for 2N6727 is 129P and it's a tab transistor more bigger, but not found in the electronic shop.
3. Connect and power on the computer and the computer boot and K prompt appear after ram test, But the transistor become very hot and burn in about 1 minute.
4. I replace a transistor again and measure the voltage very fast to avoid burn a transistor here is a data:
In transistor: Base = 9.02VDC Emitter = 8.99VDC
12V output = 8.89VDC
-5VDC output = 0.-350
Any suggest.
Thanks again for your great support

Updated: Aug/29/10 12:00PM
Cut the trace that supply a 12V to all RAM and the supply of 12V and -5V fix, so the problem maybe is with any RAM due the external power supply is 9V constant and all capacitor in 12V (47n) was removed.

Any comment
Thanks again
 
Last edited:
Well, my first impression would be a power supply issue, the right kind of voltage isn't making it through, and sounds like there's enough ripple to cause that, but not sure.

I have asked a friend, he might make a reply.
 
Hi
It really sounds like there is a capacitor shorted.
The way it works is that it is a simple relaxation oscillator.
When the power is first turned on, current charges the
22 uf capacitor through the coil.
This holds the transistor off until the capacitor charges.
The transitor turns on because it is forward biases.
This pulls the emitter lead down causing current to flow
in the coil.
Eventually the coil begins to have reduced voltage and the
22uf capacitor begins to charge again.
This truns off the transitor.
The voltage at the end of the coil rises because the current
can no longer flow through the transistor.
It charges the output capacitor through the diode BA221.
This cycling should continue until the 12V zener begins to
conduct. This is a negative feedback to the base of the transistor
the reduces the amount it turns on.
The voltages you are measuring would indicate that the transistor
may already be blown.
Can you make measurements with the trnasistor removed?
Measure at the emitter, base,the other side of BA221 and
the -5v line ( bottom of schematic ), all relative to ground?
Dwight
 
J Ramos, a new power supply is definitely in order, as it's over 20 years old, new or not-- the caps have most likely gone bad and it's an easy thing to replace. Be careful soldering, too, accidents can happen. Might want to add more heat sinking to the whole thing, wherever it calls for it-- transistors, regulators, etc.

So, from easiest to hardest, get a new power supply, then go from there to the capacitors then the transistors and diodes.
 
I've got one of these machines too, and unfortunately mine's keyboard is dead. I tried to repair it with a FDD cable I cut up and worked in place of the original screwed up cheap ribbon cable, but unfortunately it didn't work out.

Are these machines interesting/uncommon enough to shell out money for a proper keyboard replacement?
 
NathanAllan said:
Well, my first impression would be a power supply issue, the right kind of voltage isn't making it through, and sounds like there's enough ripple to cause that, but not sure.

I have asked a friend, he might make a reply.
Click to expand...

Hi
It is not the main power supply he is having troubles with. It
it the small supply inside the RAM package that is used to create
the voltaged for the DRAM.
Dwight
 
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