Trying to fix my ZxSpectrum+

For experts to discuss very technical stuff and newbies to ask why the Spectrum they bought off ebay doesn't work.
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Morkin
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Re: Trying to fix my ZxSpectrum+

Post by Morkin »

1024MAK wrote: Fri Jun 07, 2019 12:11 pmOther flux types should be cleaned with either flux cleaner, or IPA (the solvent, not the drink).
:lol:
My Speccy site: thirdharmoniser.com
Hyuma
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

Ok, on the next weeks i'll buy some new equipment to repair this damage. I will keep you informed on how it is proceeding. For now thanks to all! 8-)
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

Hi guys, a little update. With a software I designed the lower ram pcb scheme to be sure not to make mistakes later when I try to restore the tracks. Did I do everything right? Thanks in advance for every reply.

Image
Hyuma
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

Hey guys, it's been a bit that I didn't update my post. Here some news:


Image

Image

I put all the 7 sockets!!!!! And I'm very proud of me guys!!! Now I've a doubt, I dunno where to solder this pin:


Image it's near the blu capacitor..
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DouglasReynholm
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Re: Trying to fix my ZxSpectrum+

Post by DouglasReynholm »

Well while I'm sorry I can't help you much here, as the person that sent you here from another social media site (shhhh!), I'm impressed with the effort you are persisting with to get it fixed.
Hyuma
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

I think it should be connected to the pin 14 of IC7, but i'm waiting some confirm! :D
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Ast A. Moore
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Re: Trying to fix my ZxSpectrum+

Post by Ast A. Moore »

I only have a picture of a populated Issue 6A board, but it’s fairly high resolution. The trace form that via goes up and is likely connected to the via next to Pin 3 under the socket. It’s best to use the schematic and a tester in continuity mode and determine the exact routing by process of elimination.

Still, I hope this picture will help you:

Image
Every man should plant a tree, build a house, and write a ZX Spectrum game.

Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
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Muttley Black
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Re: Trying to fix my ZxSpectrum+

Post by Muttley Black »

Hyuma wrote: Mon Jul 01, 2019 8:12 pm I think it should be connected to the pin 14 of IC7, but i'm waiting some confirm! :D
Yes. I confirm that.

Also, clean your work with isopropyl alcohol and toothbrush before you test the unit.
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

yes, now next step will be buying rams and ZTXs
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

Time for some updates, 751 and 651 are in place!

Image

Image

Can i do some tests now? (I still don't have ram)
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

With multimeter in continuity mode i got:

ZTX 651 values:
670, 671, 1, 1

ZTX 751 values:
670, 668, 1497, 1
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

I power on without ram for some seconds and the screen is bit better then before. THERE IS STILL LIFE! :D :lol:

Now with new ZTX 651 and 7651 (without new RAMS)
After some seconds I pressed the reset button and this is result:

https://imgur.com/a/Se0bVKu


this was before:

https://imgur.com/raae8HW
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Ast A. Moore
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Re: Trying to fix my ZxSpectrum+

Post by Ast A. Moore »

Looks like the CPU can fetch and execute the first few instructions, including a jump, from the ROM, which is great news.
Every man should plant a tree, build a house, and write a ZX Spectrum game.

Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Hyuma
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

Ast A. Moore wrote: Tue Jul 09, 2019 11:38 am Looks like the CPU can fetch and execute the first few instructions, including a jump, from the ROM, which is great news.
Wow! I'm really, really, really happy today! Next step will be RAM!
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1024MAK
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Re: Trying to fix my ZxSpectrum+

Post by 1024MAK »

Hyuma wrote: Tue Jul 09, 2019 10:43 am Can i do some tests now? (I still don't have ram)
Sure! :D

Test the voltages on pins 1,8 and 9 in the position where IC6 was (or any other of the 4116 or equivalent DRAM chip positions). With the negative probe to 0V/GND (e.g. the case of the modulator or the heatsink).

Expected voltages:

PIN 1: between -4V and -5.5V
PIN 8: between 10.8V and 13.2V
PIN 9: between 4.75V and 5.25V

If all these are good, then the next stage is to sort out the ‘lower’ DRAM chips.

Mark
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“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :dance
Looking forward to summer later in the year.
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

1024MAK wrote: Tue Jul 09, 2019 3:57 pm
Hyuma wrote: Tue Jul 09, 2019 10:43 am Can i do some tests now? (I still don't have ram)
Sure! :D

Test the voltages on pins 1,8 and 9 in the position where IC6 was (or any other of the 4116 or equivalent DRAM chip positions). With the negative probe to 0V/GND (e.g. the case of the modulator or the heatsink).

Expected voltages:

PIN 1: between -4V and -5.5V
PIN 8: between 10.8V and 13.2V
PIN 9: between 4.75V and 5.25V

If all these are good, then the next stage is to sort out the ‘lower’ DRAM chips.

Mark
pin 1: -5,21v
pni 8: 12,38v
pin 9: 4,98v

yesssssssss! :lol: :lol: :lol:
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Muttley Black
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Re: Trying to fix my ZxSpectrum+

Post by Muttley Black »

Keep on walking! :)

-If it’s not problem for you, please use Postimage to upload your photos. It is easier as Postimage button is pinned on “reply” mode, but also is way better and safer for you photos to stay online for long time.-
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

I just noticed that retroleum website has lower ram module out of stock... damn!
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1024MAK
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Re: Trying to fix my ZxSpectrum+

Post by 1024MAK »

See here for another source of Lower RAM modules ;)
I have bought from here before and got good service :D

Mark
:!: Standby alert :!:
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :dance
Looking forward to summer later in the year.
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

I sent an email to the guy of retroleum and he re-stock the item! I just bought 1 lower ram! Let's wait for it!
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

Ram arrived! Check pictures. There is still issue. :?

Image

I uploaded also a video, I pressed reset button after a bit.

http://imgur.com/a/0UGyyEQ

As a test, i checked all voltage on upper Ram module on pin 8 and i have all 4.98V.
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

I double checked the wires I soldered for Lower ram traces and I discovered a wire not connected!
Image

I download OTLA software and try to load some .tap:

Image

Image

Image
Last edited by Hyuma on Wed Aug 07, 2019 7:35 pm, edited 1 time in total.
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DouglasReynholm
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Re: Trying to fix my ZxSpectrum+

Post by DouglasReynholm »

Hyuma wrote: Wed Aug 07, 2019 7:26 pm I double checked the wires I soldered for Lower ram traces and I discovered a wire not connected!
Image
Hurrah! Really happy to see this mate, I applaud your perseverance.

Also big thanks to everyone who helped Hyuma, I knew I could rely on you when they first enquired about their problems on another (inferior) website, and I suggested a better place to ask!

*sheds small tear and salutes
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

I've noticed that with OTLA loading games some are working, some others not, dunno why... and not all keys are responding when i press... maybe the keyboard need some clearing or some other to check?
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Re: Trying to fix my ZxSpectrum+

Post by Hyuma »

DouglasReynholm wrote: Wed Aug 07, 2019 7:35 pm
Hyuma wrote: Wed Aug 07, 2019 7:26 pm I double checked the wires I soldered for Lower ram traces and I discovered a wire not connected!
Image
Hurrah! Really happy to see this mate, I applaud your perseverance.

Also big thanks to everyone who helped Hyuma, I knew I could rely on you when they first enquired about their problems on another (inferior) website, and I suggested a better place to ask!

*sheds small tear and salutes
Thank you so much, friend! :oops: :oops: :oops:
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