Two dead Spectrums
Hi all,
Long time since I posted on here.
I'm having a bit of a clear-out, and I've re-discovered two Spectrums I had in the loft :
One is an original Spectrum 128k : This appears totally dead. The PSU is known to work, but I can get nothing on screen (via the modulator - don't have a RGB monitor). It's definitely getting power, as the external heatsink gets warm. Can't remember if it is supposed to click when you press a key (I know it shows a menu on power-up). I've split the case, and had a look at the motherboard, to see if I could see a blown-fuse, or something. I couldn't so I'm suspecting a knackered Z80.
The second is a regular rubber-keyed Spectrum 48k; this powers up, and gives a nice blocky kaleidoscope on screen; so I'm guessing keyboard membrane ?
In both cases; I don't have the tools/knowledge/time to repair these, if indeed they are worth repairing. I would have thought the Spectrum 128k might be more worthy of salvage.
SO.....question is; can somebody suggest/recommend a repair service; ideally with some idea of cost. Maybe some on here are a dab-hand with a soldering iron, and have the service manuals. If the repair is cost-prohibitive; does anyone want to take them off my hands ? Seems a shame to throw them if they can be saved
Regards
Justin
Long time since I posted on here.
I'm having a bit of a clear-out, and I've re-discovered two Spectrums I had in the loft :
One is an original Spectrum 128k : This appears totally dead. The PSU is known to work, but I can get nothing on screen (via the modulator - don't have a RGB monitor). It's definitely getting power, as the external heatsink gets warm. Can't remember if it is supposed to click when you press a key (I know it shows a menu on power-up). I've split the case, and had a look at the motherboard, to see if I could see a blown-fuse, or something. I couldn't so I'm suspecting a knackered Z80.
The second is a regular rubber-keyed Spectrum 48k; this powers up, and gives a nice blocky kaleidoscope on screen; so I'm guessing keyboard membrane ?
In both cases; I don't have the tools/knowledge/time to repair these, if indeed they are worth repairing. I would have thought the Spectrum 128k might be more worthy of salvage.
SO.....question is; can somebody suggest/recommend a repair service; ideally with some idea of cost. Maybe some on here are a dab-hand with a soldering iron, and have the service manuals. If the repair is cost-prohibitive; does anyone want to take them off my hands ? Seems a shame to throw them if they can be saved
Regards
Justin
Post edited by The_Beard on
Comments
The 128K machine may also have a faulty internal power supply. No display at all likely means the video circuits aren't getting 12v. (A failed Z80 would give you something on the screen - at least coloured blocks, since the ULA would just display whatever's in memory at power up).
I'd offer to fix them if I was not so busy at the moment. Whatever you do, don't bin them, they can be repaired.
Are all 27 Spectrums working?
yes as i actually collect them :-D
I collect them too ;-) However, I can see about 15 motherboards from my seat now that need repairs... So whereas I might have 30 or maybe 40 Spectrums only a fraction actually works 100%.
Featuring: a very well conserved Issue 1 with the 32K expansion (below the two Saga-1 Spectrum's, leftmost column, the second one, grayish keys), and the guest start: a Sam Coup?.
All of them work, except one, a Spectrum+ (although I have several working motherboards that can be fit inside that Spectrum+).
I've always wanted to know, what were the saga keyboards like I always wanted one as a kid.
I counted 9x Spectrum, 4x ZX81, 5x Clone. The wooden thing on the left is a homemade (Spectrum driven) engraver for PCB's, feeling neglected. And yes, before you start asking, I am a married man.
Hoping that some of us are feeling less bad now....
I also had a nice place for retro-showering, but was demanded to upgrade that....:-)
The wood, the stepper motors and the electronics of this 'prototype' costed less than E. 30,- alltogether as most of it was recycled stuff, like parts taken from kitchen drawers(!). The actual fraising tool is a 20.000 rpm Dremel that fits in a standard 'mounting clamp'. Using a felt-tip pen instead of the frais tool, the shebang reproduced a complicated drawing from a vector (HPGL) file with high accuracy on paper. Due to the small diameter of the actual cutter, the cutting speed is low and the movements can easily be controlled by a BASIC program. I use a program "Raster to Vector" for turning inverted(!) print layouts into vector files.
www.brothersoft.com/downloads/raster.html
All there is to know IMHO can be found here:
http://www.majosoft.com/engraving/html/wooden_hobby_cnc_engraving_mac.HTM
http://www.luberth.com/cstep/
My own pictures at:
http://www.biehold.nl/roelof/engraving.zip
I'm married too, my wife thinks all these old computers are junk, and I'm also in NL. Nice workspace by the way...
Where are you living, maybe you could help me fix some of those pcb's?!
Tell us more about that engraver!
F.
No. I've never used one, I fix my own machines. And so it seems does everyone else who replied to this thread :-)
However, you can always talk to RWAP and see if he does repairs.
http://www.rwapsoftware.co.uk/spectrum.html
Try RWAP, A few weeks ago, they repaired a speccy 48 for me that I managed to quite seriously damage. 8-)
http://www.rwapsoftware.co.uk/spectrum.html
Is DIY Speccy fixing reasonably straight forward (with the service manual), or do you need specialist tools ?
What about the availability of parts - specifically ICs ?
The typical dead 48K Spectrum (with black paper, or pixel vomit on the screen) is often not too difficult to diagnose, because 9 times out of 10 it's the lower memory. There are some easy checks you can do, as well.
First do a search on this forum, I've posted a link to the TMS4116 datasheet a couple of times. Use this datasheet to know what pins to expect the +5v, -5v, and +12v supplies to these chips. Then test that you've got close to these voltages with a multimeter.
If you don't, the internal power supply is dead. This is almost always due to the transistor in this circuit being dead. The other clue that the internal power supply has failed is a lack of the hissing noise you normally get from a working 48K machine. If the internal power supply dies, then so does lower memory - if you read the 4116 datasheet, it warns that supplying any other of the supplies before the -5v supply means the chip will be destroyed.
If the internal power supply is working, however, the next most probable problem is one or more of the chips in lower memory (the 4116 RAM) has failed. If you have my diagnostics board, you can get the Spectrum to test itself and tell you which chip has failed :-) If not, well, what I used to do is just try and replace them anyway.
You do need some kit that will desolder ICs. It's hard to do with a soldering iron and braid or a solder sucker, it'll take you *hours*. I use hot air - nothing fancy, an electric hot air gun from B&Q that cost about ?20. So long as it gets hot enough to melt solder but not so hot you fry the board and/or chips, a hot air gun is the best thing you can have to get chips out. Gently warm the area of the board with the components you want to desolder (don't hold the board upside down, or all the small passive components will fall out when the solder melts!) until you get the area hot enough to melt the solder - then ease the chips out with long tweezers or something similar. You'll then need to clear the solder from the holes (there is a LOT of solder on Sinclair PCBs) - I use a drill press and a 0.8mm drill bit (be careful for solder swarf shorting things if you do this - I go over the board with a vacuum cleaner), but you can clear the holes with a soldering iron and desoldering braid. Don't be tempted to heat the board on one side and use a vacuum cleaner to suck on the other - I tried that, the theory being it would be a fast way to clear out all the holes - but it lead to solder being splattered all over the bottom side of the board and created far more work!
So long as the CPU is working you can build a circuit like this:
http://www.alioth.net/Projects/Spectrum-Diag/
which will test memory, and do some functional checks on the ULA, showing the results on 8 LEDs so if you can't see anything on the screen (or the screen is corrupted) you can find out what's happening.
It also helps to understand the schematic (available at WOS)
and also read the service manuals.
I only have like 10 spectrums and my wife thinks I'm crazy !