Spectrum Computing

Hi, Recently I have purchased a ZX Spectrum top cover for my Issue 1 Spectrum. The seller claims that the rubber key mat is an Issue 1 one. How can I verify that it is really genuine and not one of the modern replacements? These are the only pictures I have. The parcel hasn't arrived yet so I am not...

Fixed!

Cpu was dead. Thanks!

Long pressing the reset button changes somehow the displayed garbage. Removing the ROM does not seem to change anything. I have inserted a test ROM interface but the program does not seem to work at all. The test ROM is for the 48k models (retroleum rom) and starts with the lower ram test. Is there ...

Hi, I am trying to repair a Zx Spectrum 128 Toastrack. It suddenly stopped working. Ran a few games for a few hours, powered off. When powered on, it displays the attached picture. Border changes some times by itself and sometimes it shows lines on the border like those displayed when loading from t...

Well it's a good idea to use older 3b boards. I did not think of the Pcf1036 chips and you are right: one more custom chip to fail. I do not have an external power supply in mind, that should provide all three voltages but the linear regulator is going to be replaced. Also the ULA is going to be rep...

Hi, As I have a lot of Spectrums in various states, I want to build a 48K rubber key version that I am going to use for playing games (usually I play games on a Toastrack machine). Which board is the most reliable in terms of the DC-DC converter? I have all types of boards from Issue1 to issue 6A bu...

The replacement ULAs are a very good initiative. But I think that a near 100% compatible replacement is not so easy to design. The original ULA is designed using bipolar transistors and the Ferranti library of components and you cannot tell if a counter or shift register or other type of gate behave...

I have the Retroleum.test rom. The ram tests are both ok. I can also run all ula tests. Keyboard is unreliable, most probably because of the missing dead cockroach. Therefore I cannot reach the code execution menu. If I press 5 to enter the More Ram test menu, it goes directly to lower ram test subm...

The test board is an issue 2 originally fitted with a 5C112 ULA. Everything working properly with this ULA. With the 5C102 ULA fitted I have tested the connection with the lower ram and it is ok. Each ula pin is connected to the corresponding pin of the memory. Since the board is actually a 16k vers...

Hi, I am trying to test a 5C102 ULA which I have recovered from an issue 2 board. The donor board was quite bad so I did not bother repairing it (maybe in the future). I am trying to test it in a working Issue 2 board. It does not appear to be ok. Spectrum powers up but the screen freezes (black pap...

I haven't tried the vLA1 but my experience with replacement ULAs is not very good. I have bought all types that exist because I use my Spectrums almost daily and I wanted to preserve the original chips. So far the SLAM128 is stable and working properly. Also vLA81 might be ok. I have tried the nebUL...

Hi, I am trying to figure out a method of cooling the ULA of one of my Spectrums (rubber key case). One method with good results is to reduce the heat inside the case by replacing the linear regulator. Personally, I do not think the heat sink on the ULA is a good method because the rubber key case h...

I am only interested in the Sinclair models, so this is my collection: 1. ZX80 in a very good condition. Just for display so far, but probably working. 2. Several ZX81 (probably 6-7) in various states, some of them have damaged keyboard membranes. One of them is modified with modern ULA and used fro...

So far the vLA128 seems to be better in terms of compatibility than the SLAM128 ULA. The computer runs ok with both but SLAM128 has some compatibility issues with my divIDE interface. When powering up the computer I often get garbage screen instead of the usual one and I have to reset several times ...

I have a cheap soldering station with temp control. I use that knob in only two situations: max power for desoldering big parts (like the RF modulator in a ZX Spectrum) and 300-350 degrees for soldering. So no need for digital control or other expensive tools. As for solder pump, I use a cheap devic...

What version of mainboard do you have?

And it's a Spectrum+ case or rubber key?

Hi, Recently I purchased some ULA replacements for the computers I use most often ( trying to preserve the original chips). In one of the ZX Spectrum Toastracks I have a SLAM128 ULA which runs without any problems. Does anyone have any experience with the vLA82 and nebULA? Are they reliable and ok i...

Well the thing is that when dealing with this kind of PCBs it is better to preserve the traces than repair them. Better destroy the chips you remove (in case you can replace them) than the pcb. You need a fine tip soldering iron, good quality solder wire, a solder pump ( electrical one is better tha...

payty the link you sent is for 200ns ram - you said 10 out of the batch work What I meant was that I have used only 10 of them. And all 10 work. I haven;t verified the others but I think all of them are ok. @1024MAK -> can the ULA be damaged in case somehow the address lines are accidentally connec...

C46 is installed ok from the factory. You need to put it back the way it was. On the issue 2 pcb, the silkscreen is wrong.

And do not attempt to power it in until you do that.

Are the wire links for selecting the upper memory type present? I remember having a similar problem with an upgraded Spectrum where the previous owner forgot to install those. What type of memory do you have? They should match the brand and type of the memory as there are four options. Edit: picture...

Hello payty that would be great if you could send me that link. would the difference of 50 ns make much of a difference on performance I have sent the link in a private message. The chips are rated 200ns which could cause problems in case they cannot handle higher speeds. But a while ago i bought 3...

Mark - The only place i can fine spectrum chips is at Retroleum.co.uk but they only use paypal i dont would these chips be correct https://www.sintech-shop.de/en/4116-memory-ic/a-3009 There is a guy on ebay that sells ITT 4116. They appear to be 200ns chips but I have changed 10-15 chips of that ty...

Another thing is that I want to repair another issue 2 board and I've got some NOS Gelec capacitors.

Should I use these? I just want to keep the board as original as possible.

Is there any danger that they are almost gone like the others that are already soldered on the board?

Hi, Recently I've bought several Zx Spectrum 48k mainboards that are in a very sorry state. I have attached a picture of one of them. I have some questions related to them: 1. Mainboard no. 1 is an issue 2 with 5C102 ULA (that is why I bought it). I want to test the ULA on a working mainboard (becau...