Sinclair zx spectrum

[McMurdo]

I have to say I never had any problems loading anything at all with my spectrum, I had the same Panasonic cassette player all the way through and found the whole loading process better than my Commodore 64 with its dedicated Datasette unit.
The Panasonic was quite bright/trebley on music, my old Waltham was dull-sounding and wouldnt work with the spectrum at all.

[cmjones01]

Originally Posted by repairman 1234

Hope when i get a BBC it is less touchy.

In my experience at the time and since, different models of computer had very different properties when it came to loading from tape. Looking at the circuit diagrams of the Spectrum and the BBC Micro, the Spectrum basically just connects the earphone socket straight to a pin of the ULA. The Beeb has substantial signal conditioning with several op-amps involved. The extra complexity seems to pay off: it's much more tolerant of volume and frequency response variations than the Spectrum. Not to mention the fact that if it has trouble, it'll politely ask you to rewind the tape a bit and try the last block again!

If you can make a Spectrum load from tape, a Beeb will be a breeze

Chris

[Jack Spark]

Uh oh, Chris you started it now, its only a matter of time before a C64 owner gets on here and starts saying how great it was....

I think all errors point at the moment to either the tape or the player, if that can be ruled out, then maybe look at the ULA.

[repairman 1234]

Originally Posted by ajs_derby

I'm a bit worried about that typing program not working properly. It looks like a memory or ULA fault.

Try another quick memory test: What do you get for

PRINT USR "A"

(USR is extended mode, unshifted L) ?

Many thanks for all your replies, i have been at work over the weekend so am just restarting my efforts with this now.

I have done this test and only have 32835!

I will next try downloading the test and game that Mike so kindly posted (via my IPOD)


UPDATE......

I have just downloaded the Manic Miner game and the Spectrum test files to my IPOD and tried to load them into the ZX.. It just did not seem to recognize anything was going in at all other than the odd flash of red and white lines around the screen. I have adjusted the volume several times and tried to re load without any luck.

HELP!!!

[Mikey405]

Hmm. How strange. Can you hear the tones being replayed through the Spectrum speaker Chris? They should be pretty loud. I expect the MP3 player volume would have to be pretty much on maximum, or perhaps you could plug the MP3 player into an amp and use the speaker output instead.

[repairman 1234]

Hi Mike,

Can't hear anything at all mate

Will give it a pop through an amp.

Thanks again mate,

Chris.

[julie_m]

Originally Posted by repairman 1234

I have done this {PRINT USR "A"} test and only have 32835!

Oh dear You appear to have a memory fault at location 33003.

This might explain the failure to load, if the Spectrum is just refusing to touch a file that would require more memory than it has rather than crashing.

Try running this program:

10 LET a=33003
20 LET d=128
30 FOR b=0 TO 7
40 POKE a,d
50 PRINT d,PEEK a
60 LET d=INT(d/2)
70 NEXT b
80 GO TO 20

[repairman 1234]

I have ran this program and got the following results

128 129
64 65
32 33
16 17
8 9
4 5
2 3
1 1


It repeats what looks like the same numbers with a scroll option for, well i scrolled through about ten pages of (i think) the same numbers.

Thanks for your time on this AJS.

[David G4EBT]

Originally Posted by richrussell

I would try a different tape deck -or if the one you have has tone controls, try setting them to maximum. Also you may find you need to either increase or decrease the volume to get the best results. Another thing to try is to adjust the tape head alignment to get the clearest signal - I found tapes varied quite a bit and some recordings were particularly sensitive to this.

When tapes were shiny and new, they rarely had problems, but as they get older they don't work as well - I've got quite a few Spectrum tapes that don't work at all any more. I'm tempted to try to convert them to .tap or .tzx format then recreate the audio using a PC onto a fresh cassette.

Then as Jack said - find a blank tape and try saving a short program to it. Then enter 'NEW' to wipe the memory, and try loading it back.

One of the issues with tapes that hasn't I think been mentioned is that audio (and VHS) tapes if stored for a long time, being magnetic, suffer from 'print through'. The information on the tapes degrades due to each loop of tape transferring information to the loops beneath and above it.

Any tapes for Spectrum games are likely to have remained unused for maybe 15 - 20 years, given that by the mid 90s, affordable desktop computers were well established. (Admittedly they may at that stage have only had a 40MB hard drive and 4 MB of RAM, but they were a huge advance on 48k Spectrums, which - as with crystal sets in the late 1920s very quickly fell out of favour, and been put away in the loft along with the tapes).

Really, the only way to exonerate the tapes is to see if they will load on a known good Spectrum.

To summarise, given that you can load and run a simple program by entering the data yourself (eg 'HELLO') I guess the list of possible causes of programs not loading are:

Duff tapes.
Duff recorder (head cleaning?)
Duff memory
Duff CPU
Duff connections
Operator error

Ah Spectrums - happy days!

Did I really pay £175 for a 16k Spectrum and another £50 to upgrade it to 48k?

Yes, I really did - and millions of others did too, and went on a waiting list to get one.

Equivalent to today's price taking account of inflation, to £400 + £120 - total £520!

Best of luck!

David

[julie_m]

Originally Posted by repairman 1234

I have ran this program and got the following results

128 129
64 65
32 33
16 17
8 9
4 5
2 3
1 1

That is bad. It means you have a memory fault: location 33003, bit 0 (the units) is always returning "1".

See here: http://www.worldofspectrum.org/SpectrumRepairGuide/

I think IC15 is the problem. If you are lucky, the RAM chips will be socketed and if you are extremely lucky, just pulling IC15 out and pushing it back in again will cure it. (I say it's bad if you have to replace it but if you've ever done any SMD work, even double-sided board with pins in holes are no longer scary ) If you are even luckier, you'll be able to get hold of another one.

Note that Spectrums were assembled using the cheapest RAM chips: They were made larger, but failed a test during manufacturing. Knowing where the fault is, it's fine to use them as lower-capacity devices. A few different types are specified, from different sources and having different faults, and selectable by wire links on the Spectrum motherboard. All the chips on any one board must be the same type, unless you want to get into severe track-cutting bodgery.

[David G4EBT]

Just a point to bear in mind if replacing any ICs on any PCB which are soldered directly into the PCB - not socketed. Don't attempt to desolder the IC as it will act as a heatsink and you risk overheating the board and damaging the tracks. (Even harder to do with plated through holes).

Instead, snip off all of the pins from the IC and bin it, then one at a time, clip forceps onto each pin in turn, apply a soldering iron to the pin and pull it out, which takes only a second or two. Only then used a desolder pump (if you must) to remove any surplus solder on the pads.

In the late 1980s I repaired lots of spectrums - mostly ones with blown CPUs due to kids plugging in the joystick interface with the power on. To remove the 28-pin IC on the plated-through PCB would have been next to impossible without snipping off all of the pins, but by doing that, it took only a few minutes to remove the clipped off pins, clean up the holes and fit the new CPU.

The keyboard membranes are problematical too - intemittent faults were often due to hairline cracks where the membrane plugs into the socket on the PCB. Snipping off half an inch of the membrane and reinsterting it into the socket often cured the fault. (The tracks are just electrically conducting metalic paint deposited onto plastic).


Best of luck.

David

[G8VAT Wolfman]

IF you have to replace chips they are easy..

Snip all the legs off the dud chip one by one.. unsolder and pull them out of the pcb one at a time..

suck all the holes dry..

Insert and solder the new chip.

The hard part is knowing which chip. in some cases the dud chip overheats and can be felt, but AJS seems to be on the ball and can probly point you to the culprit, unfortunately My memory isn't as good as a Spectrum these days.

[repairman 1234]

Many thanks for all your help with this one guys, i will strip it and report back on what type i have, thanks too for the advice on taking it out! I have never done any SMD work, however do have a weller de soldering station (the one with the foot pedal operated pump and the vac guage) Once i have all the pins out as described i will run the weller over the holes to clear them up.

I did have a quick look inside the other day, looked like one big socketed IC and two other soldered ones (will check and get numbers though) Maybe pics would help too

Many thanks again to all who have helped, i am going to look for another unit as well, but would still like to see this one work again if possible

As well as Dad's day i have my birthday coming very soon, so who knows what may turn up in the near future.

[G8VAT Wolfman]

Sorry repeated information above, where did that other one (4EBT) come from?

[David G4EBT]

Originally Posted by G8VAT Wolfman

Sorry repeated information above, where did that other one (4EBT) come from?

It came from me!

I can't remember what time I uploaded it or for how long it was held for checking before release, and I'm not sure if all postings are held for checking by moderators before release, but mine are. (Maybe I'm in the naughty corner?).

Sometimes messages are released almost right away, sometimes after a little while, because moderators have other things going on in their lives besides doing a voluntary job on our behalf.

However, it does mean that messages often appear out of sequence in a particular thread, and are sometimes repetitive and redundant, due to the same thing being said by several people.

I'm not losing any sleep over it - it's just a hobby after all, and it's better for people to receive the info more than once rather than not at all!

The Spectrum is an icon of mid-80s cutting edge technology, and serves as a good datum line to illustrate just how far things have come - not just technically, but price wise, when considering, for example, such things ar MPs players, 8gB memory sticks, digitial cameras and mobile phones. Laptops and netbooks are now so cheap that they're almost an impulse buy.

Who knows what the next 25 years will bring!

David,
G4EBT.
(BVWS, G-QRP).

[repairman 1234]

Ok,
I have some pics of what i have, the ULA is the only socketed IC.











Looks like i might be having fun with double sided print

[G8VAT Wolfman]

looks like later machine, there should be a revision No printed on the PCB...

I too used to repair hundreds of these from my Shop back in the eighties David, but I soon forget things when I don't do it every day.

[repairman 1234]

Thanks guy's, The revision number is 1984 issue 6A

I have bought a new Spectrum tonight with the whole kit (again)

The tape player is a newer Sony unit and i will have lots of games to try out.
I hope to load a game into the new one ok then try loading it into the old one using the newer tape player (at least i will know that the game and the player work, then i will have a better idea what is going on.

At worst i will end up with a worker and a spares unit, and at best i will have two workers!

I pick the new one up in the morning, so will post once i have a game loaded and working....fingers crossed

Thanks again for all your help chaps, and i may not be finished asking yet....

[G8VAT Wolfman]

Good luck.

[richrussell]

I seem to recall the 6A was about the last revision made, and had some quite shockingly poor quality components. Mine was a 3B, which suffered a bit from heat issues around the voltage regulator, but was fine once I got a bit more airflow round the expansion port area by putting taller feet on the bottom.