The Spectrum Resuscitation Thread

edited February 2015 in Hardware
Kicking off this thread as a place where people who are fixing/restoring Spectrums (or indeed any other piece of related hardware) can show off their work and describe any fixes implemented. Might be valuable to people like me who are just beginning to learn how to do this kind of thing well.

So earlier this week I picked up this horrifically abused Issue 3:

9267774473_81439753d5_o.jpg

What the photos don't show is that the faceplate was completely detached from the top cover, and somebody had made hamfisted attempts to restick it in the past with, among other things, blu-tack :-o

The machine was sold as non-functional, however it powered up to the copyright message with no issues, apart from a non-functional keyboard (par for the course really) and a short boot time indicating a 16K machine. Being an issue 3, that wasn't right, so opening up revealed the following:

9270547404_641874e32f_z.jpg

This machine had obviously been through the wars, as 6 of the 4116's were socketed as well as all of the 74LS chips (funnily enough, the replacement 4116's were soldered to the board, originals were socketed). ULA and CPU had also been replaced, along with TR4 and C46. Something tells me that a previous owner had forgotten that Speccy peripherals aren't hotswappable...

Anyhow doing a 'POKE 32768,85: PRINT PEEK 32768' returned 93, so consulting the service manual:

http://www.1000bit.it/support/manuali/sinclair/zxspectrum/sm/sec4_2.html#memchk

- IC18 was revealed as the culprit, and duly replaced. The machine then initialised as a 48K, and loading/running a few 48K games verified the fix.

I also took the opportunity of composite modding while I was in.

After a good wash, keyboard roller and restick, and finally a quick chop of the membrane tails to get the keyboard working, here's the finished article:

9267774935_4afcec7c18_c.jpg

It's still not much of a looker but much more presentable and functional than before.

(And yes, I know, best practice is to replace all electrolytics, but I don't have a full set spare right now, plus it's too hot to solder extensively!)

Cheers,
B
Post edited by balford on
The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
Sinclair FAQ Wiki
«1

Comments

  • edited July 2013
    as i made a thread about my + i will just post the pics up and say there will be more pics of it running very soon.

    Photo0243_zpsfd66b471.jpg
    Photo0244_zpsf509ce01.jpg
    IMG-20130712-02445_zpscec1bbea.jpg
    IMG-20130712-02446_zps072460bc.jpg
    IMG-20130712-02441_zps6a4bae81.jpg
    Photo0245_zpsa75b1a5d.jpg
  • edited July 2013
    Here's another one I picked up recently, an Issue 2 board with 5C102 ULA, complete with dead cockroach mod:

    9290201229_211ae1cede_z.jpg

    Its serial is 001-017330, which must make it one of the very first issue 2's.

    Advertised as untested, it powers up to the copyright message, but of course needs the obligatory membrane change, and a preventative recap.

    Closely examining the board, there are signs of rework around TR4 and the LM1889 has been replaced ('IC14' written on the heatsink is a giveaway here!), along with C44 and C45. All the 4116's seem to be the originals, so it looks like the TR4 failure took out the LM1889 and nothing else!

    Parts on order to refurbish this one.
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • edited July 2013
    I have about 15 Issue 2 boards and this is the first one I have seen with that specific dead cockroach mod. Just shows, you always learn something new on this forum.
  • edited July 2013
    Pierre wrote: »
    I have about 15 Issue 2 boards and this is the first one I have seen with that specific dead cockroach mod. Just shows, you always learn something new on this forum.

    It is very unusual. It has the 5C102E ULA that is normally found in issue 1 Spectrums and so requires this correction circuit.
  • edited August 2013
    So just finished the Issue 2 above this week. Changed all the electrolytics, changed the membrane and upgraded it to 48K while I was at it.

    9429258226_ddef1c9e2d_z.jpg

    Newest arrival is this +3:

    9426503763_2b9e54a1d1_z.jpg

    This is one of the cleanest machines I have ever seen. Not even dust between the keys!

    The keyboard was dead on arrival, disassembly/cleaning/reassembly of the keyboard and membrane cured the issue. Drive belt on order, then I need to source some 3" disks :)

    Finally, just thought I'd throw in a family shot :grin:

    9426496909_9e5416166b_z.jpg

    Not shown is my ZX81, which is awaiting a ZX81-CCB to make it usable.

    B
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • edited August 2013
  • edited August 2013
    Very nice.
    All my Spectrums (dead and alive) are still packed since my house move 5 months ago. Hopefully should be able to give them some TLC in the winter months when I eventually sort my man room out.
    Far too busy just now with a 6 day old baby in the house still doing bits and pieces to house and garden.
  • edited August 2013
    Here's the fruits of my last couple of days work :)

    I've seen some posts about replacing the 7805 regulator with a switch mode part which allows you to omit the heatsink. I haven't seen any pictures though, so thought I'd implement the mod on my workhorse machine (Issue 4A) and post some :smile:

    9450749341_5e6b06152b_z.jpg
    The patient in question

    9450756833_20f369f2f4_z.jpg
    A close up of the new regulator

    So with this in place, the machine runs a lot cooler, and copes nicely with extra peripherals (I loaded it with a Spectranet for testing).

    Another experiment was some replacement feet for this machine. I used a product called sugru, which basically comes in sealed packets and has a plasticine-type consistency, but cures in 24 hours to rubber.

    I had some spare, so rolled and cut some to size, and 24 hours later I had this:

    9453543696_8f35cc31e5_z.jpg

    Consistency wise it's indistinguishable from the real thing. Also sticks to the casing while tacky which is handy!

    Don't mind the colour here as this was just a test, they do the stuff in black too :-) One individual portion would do about eight separate feet I reckon.

    B
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • edited August 2013
    What are those caps you have there on the 4116's?
    Oh bugger!<br>
  • edited August 2013
    Read here, basically they have the effect of reducing screen noise that I couldn't track down elsewhere...
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • edited August 2013
    Right, so that mod obviously works - what value? I might give that a go ;)
    Oh bugger!<br>
  • edited August 2013
    I used 1uf as that was the smallest I had, your mileage may vary :)

    B
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • edited August 2013
    Cheers ;)
    Oh bugger!<br>
  • edited August 2013
    It would be interesting to see if the same results can be seen if say 470nF multilayer ceramic or 1uF multilayer ceramic types are used.

    Mark
  • edited August 2013
    As mentioned in an earlier thread, my SRBP PCB Issue 4A decided to die on me whilst playing Mantronix. No idea what caused it, the machine just died, tried to restart but gave a bright magenta screen with a continual effort to restart.

    Removed all lower RAM since it was soldered to the board and replaced with sockets. Threw in a handful of random 4116 chips and we have life! Machine starts now, although only working as a 16K machine (or maybe even less, the initialisation is REALLY short).

    Replaced a few of the elecrolytics, not all, and gave the whole board a really good soak in meths.

    Tomorrow I shall source some working 4116's and then see if I have an upper memory problem also. I shall finish the recapping either way.

    At least the ROM and Z80 seem to be OK!

    What baffles me, is the way the machine just died, very strange :( Was barely warm and had no interfaces hanging off the back. I hope it was just a capacitor decided to finally die.....

    May post a pic when the job is done :D
    Oh bugger!<br>
  • edited August 2013
    DEATH wrote: »
    May post a pic when the job is done :D

    Please do, that's what this thread is all about :smile:
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • edited August 2013
    Ok, I'll make a point of photographing it :)


    Latest: Using known good 4116 chips, replaced the randomly selected chips one by one, revealed a dodgy NEC uPD416 - replaced and the machine fired up into a 48K config :)

    Happy but still confused as to why it gave up in the first place.

    Recapping next....
    Oh bugger!<br>
  • edited August 2013
    Not sure how this works, but here goes:

    ?set=a.228280150656875.1073741826.100004246748344&type=1&l=5ed53fbeb0

    If it doesn't work, you're gonna have to add me to facebook :P

    You want to look at the second pic, the caramel coloured PCB. New sockets added and 6 new RAM chips added, plus two working randomers.
    Oh bugger!<br>
  • edited August 2013
    Sorry Death, can't see the pics :-(

    Anyhow just to bring my own bits and pieces up to date. Yesterday evening I replaced the drive belt in my +3. Fairly straightforward except for scraping the bits of old belt from off various places in the drive:

    9548407890_02bf4eb5ef_z.jpg
    Might as well have been made of cheese

    It's hard to describe just how badly this belt deteriorated! Capstan cleaned with IPA, new belt fitted and the drive worked first time.

    Next on to my ZX81. Bit off topic, but what the hell. This suffered from the classic missing back porch problem associated with the 2C184 ULA.

    To remedy this, I purchased a ZX8-CCB which adds the back porch, and outputs composite video.

    The installation instructions tell you to install the device beside the heatsink, and to solder the flying leads to the underside of the board. This would mean a dangling connector, so I gutted the modulator and added it there:

    9545633053_ebd5624fbe_z.jpg

    Once the modulator lid is back on, the modification's not noticeable (apart from the insulated wire I used):

    9545644311_6e80767ff4_z.jpg

    Job done, reassembled and tested:

    9545699985_0aa7f4a2cd_z.jpg

    The image quality is really rather exceptional!

    9545689037_44d499d019.jpg

    Only things really on my plate at this point are to recap my grey +2, and to sort out its wobbly tape drive.

    B
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • edited August 2013
    That's a very clean looking issue 1 ZX81 :p

    Mark
  • edited August 2013
    @ DEATH
    The link as posted is a web page, as in this link and not an image :-o

    Mark
  • edited August 2013
    Yeah, it's a photo album, publicly accessible I've set up on Facebook. Looks like yer gonna have to add me then - user name is Lloyd Dragonforce. I never had any of this trouble before I took my site down :P
    Oh bugger!<br>
  • edited September 2013
    Bumpity.

    So here's a Spectrum+ I picked up last week, advertised as untested, for the princely sum of 6.50. Opened it up to find an issue 4S board, my first one :)

    9664918875_b6b526014d_z.jpg

    So powered it on, and got an extremely jumpy screen alternating in green/black stripes. Right, at least something to keep me busy with this one :)

    9664935799_5d5483f37a_z.jpg

    Checked the voltages at IC6, all present and correct, so at least whatever wasn't already fried was safe.

    I proceeded to replace all the electrolytic capacitors, and removed/socketed the 4116's. Testing in my other socketed Spectrum showed two of these to be defective, duly replaced. While I was at it I composite modded the machine to bypass the dodgy modulator circuitry.

    I then plugged in my implementation of Winston's diags board, the random fill test threw up an interesting pattern:

    9664952755_7da194bdc5_z.jpg

    The diags were also failing the lower 16K tests, even though they all checked out on the other machine, so a stuck address line somewhere seemed like the most likely culprit.

    Next suspects were the LS157's at IC3 and IC4, due to the pattern (I suspected a lower RAM multiplexing issue), once these were evicted and replaced the lower 16K tests passed.

    However the upper tests revealed 4 of the upper RAM chips as dead, these were again replaced. Total body count:

    2 4116's
    4 4532's (replaced by 4164s)
    2 74LS157's.

    9665007641_b96a58532f_z.jpg

    (I know, I didn't socket the new 4164's. I ran out of sockets!)

    Powering up, the keyboard didn't work at all. Being a 4S with (supposedly) the better membrane, I took a multimeter and determined that only the last centimetre of the 8-way ribbon was non-conductive. Chopping this section out fixed the keyboard up (luckily!)

    With all this in place the hardware checked out, however we still have the problem that the case looks like crap:

    9668249322_583c0137fc_z.jpg

    A quick scrub in some soapy water, plus a liberal treatment of the case plastics with tyre dressing gel(!) left it looking like this:

    9668260090_4b9ede040c_z.jpg

    I did try and replace the faded rainbow logo with a replacement printed on photo paper, however my colour printer is playing up so the colours are all wrong. One for another day I reckon!

    B
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • edited September 2013
    balford wrote: »
    I then plugged in my implementation of Winston's diags board, the random fill test threw up an interesting pattern:

    Did you buy this from Winston or did you build it yourself? I want to get one myself.

    However the upper tests revealed 4 of the upper RAM chips as dead, these were again replaced. Total body count:

    2 4116's
    4 4532's (replaced by 4164s)
    2 74LS157's.

    This is a first for me to see that the 157's were damaged. The tolerances on these TTL chips are huge and they can just about take anything.

    Powering up, the keyboard didn't work at all. Being a 4S with (supposedly) the better membrane, I took a multimeter and determined that only the last centimetre of the 8-way ribbon was non-conductive. Chopping this section out fixed the keyboard up (luckily!)

    I have used a rubber (eraser) a few times to clean the conductive strips if they are tarnished and that also seems to work most of the times. It is however a different story with cracks on the ribbon, then you must cut back.

    I did try and replace the faded rainbow logo with a replacement printed on photo paper, however my colour printer is playing up so the colours are all wrong. One for another day I reckon!

    I like the shiny effect. I had a stick on logo printed on PVC the other day at a local printing company which came out very nice. It cost in rand R 10 for a 10cm strip. That is about 60 pence on your side.
  • edited September 2013
    balford wrote: »
    9668260090_4b9ede040c_z.jpg
    Nice and shiny :grin::-P

    And well done on the repair ;)

    Mark
  • edited September 2013
    Great work!

    Not sure I like the glossy effect though. You got it working, that's the main thing! Here's to the next 30 years of gaming on it :D :cool:

    edit; Wonder if somebody can source those little rainbow badges, they don't have to be made of metal..... Laminated photopaper perhaps?
    Oh bugger!<br>
  • edited September 2013
    Not sure I like the glossy effect though
    Don't worry, that was when the tyre gel had just been applied. It's calmed down considerably but the plastics still look like new. Must try this on a rubber key...
    well done on the repair
    Cheers Mark :)
    Did you buy this from Winston or did you build it yourself? I want to get one myself.
    I used the Gerber files here to have the board made (since I don't have the etching skill/expertise) by Elecrow. I then assembled the board myself.

    I had a few left over (minimum order is 10), if I do lay my hands on them (missing after the briefest of searches), I might offer them up for cost+P&P. I'll open a new thread if that happens :)
    This is a first for me to see that the 157's were damaged

    Yep, a big surprise for me too, would have saved me a good chunk of time testing address lines between the ULA and RAM for faults before I entertained the possibility!

    Inserting them into my other socketed machine and seeing the fault follow the chips was a eureka moment to be sure :)

    B
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • edited October 2013
    So I'm currently working on a grey +2. This one I picked up from a car boot sale about 12 years ago when my original +2 packed up.

    Recently I've changed the modulator out as the old one was rusty (machine must have spent some time stored in damp conditions), performed a recap and regulator replacement.

    I've got pretty bad noise on RF out:

    10040995656_595e422f76_z.jpg

    Composite out isn't much better:

    10040992536_f33c77a2ca_z.jpg

    I've recapped the board, replaced the 78S05, swapped out the TEA2000 and replaced TR8 and TR9 (ZTX213/ZTX650) with no change.

    Also worth pointing out that the board is a Z70700 so has TR4 in the correct orientation (Ben had a thread on this a while back).

    Any ideas on what this might be? I suspect noise on the +12v line but don't have a scope to check. Also worth pointing out that my toastrack is nice and clear using the same PSU and TV combination.

    Lastly, one of the joystick ports is broken and needs replacement. However I can't seem to find an equivalent part anywhere (I could replace both ports with right angle PCB mount metal parts, but want to keep it original). Any ideas on where I might find an identical replacement?

    Cheers,
    B
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
  • edited October 2013
    balford wrote: »
    Lastly, one of the joystick ports is broken and needs replacement. However I can't seem to find an equivalent part anywhere (I could replace both ports with right angle PCB mount metal parts, but want to keep it original). Any ideas on where I might find an identical replacement?
    From a dead machine, or from a company that sells parts from dead machines. Maybe have a look at Sell My Retro (there was one on there a few months back). Also ask Ben.

    I went looking for the very same thing a few years ago. I found a company that had a spare. Sorry, I forget the name of the company, but they also sold arcade bits as well as retro computer parts.

    Mark
  • edited October 2013
    Cool, Ben's confirmed he has some so that problem is solved :)

    To help track down the source of my noise issue, I was thinking of buying a basic hand held digital scope, something like this (I don't have the desk space for a regular scope, plus it might be overkill for my tinkering purposes).

    Any advice, snog/marry/avoid? :)

    B
    The Spectrum Resuscitation Thread - bringing dead Spectrums back to life
    zx-diagnostics - Fixing ZX Spectrums in the 21st Century (wiki)
    Sinclair FAQ Wiki
Sign In or Register to comment.