Spectrum Computing

... is also not always helpful. Things to look for are: can you see a heatsink above the edge-connector? Are the tracks curved (laid out by hand) ... 40 pin chips can you see? Issue one to 4S only have two (processor and ULA). Issue 5 and 6a have three (one replaces the smaller 74LS series logic ...

The biggest problem with the heatsink fitted to the ULA in the Amstrad +2 (grey), is that they often don’t fit tightly to the chip. Myself, I think a combination ...

... you to this post which has some Ferranti documentation including a ULA 2000 Series Datasheet. Please note that at no point am I telling people not to fit a heatsink to a ULA. That is up to each individual to decide for themselves. I’m just pointing ...

All Ferranti high speed ULA chips run hot. This is due to the technology used. So it’s perfectly normal for you ... ZX Spectrum 128K AND +2 (grey) ULAs. All the above ULAs are designed such that a heatsink is not needed. The operating temperature of the silicon chip die is up to 125°C. ...

... as a DC/DC converter, I’m presuming you no longer have the aluminium heatsink fitted for the 7805 voltage regulator). So the “good” news is that ... And I don’t think a different PSU will fix this. It looks like a ULA fault, but due to the nature of the fault, it’s very tricky to test for ...

... chips, ensure they are firmly pushed into their sockets. Check that the heatsink on the ULA (the largest chip) is firmly attached. Check that the 5V voltage regulator (78S05) is firmly ...

... can. And similarly make sure that the ribbons can’t touch the metal heatsink for the 7805 voltage regulator. Test also that R68 is okay, and that the appropriate connector on KB1 has continuity to R68 and IC1 (ULA) pin 20. Here’s a small BASIC program to draw vertical lines on the top ...

... then it could simply be that your TV does not like the signal from the ULA. Can you remember the part number that is printed on the ULA ( before you put a heatsink on it)? Only there are three versions. The first two ULA versions do not generate ...

... then there is no need to worry about leaving it on. As long as the heatsink for the 7805 voltage regulator is in place and the machine screw is holding the 7805 tight to the heatsink. Note that it’s normal for the ULA to run hot, and for the Z80A to run warm. The 4116 (or equivalent) DRAM ...

... IC18 pins 2 & 14 - No visual defects. Continuity to R12. IC1 (ULA) pin 25 - No visual defects. Continuity to circular pad on underside ... regulator is fine as a place to connect to the +5V supply. And yes, the heatsink is okay for the 0V/GND. I don’t see anything of concern with these ...

... curves), an IC socket (for the internal RAM expansion board) and the heatsink is not at the back, but at the front right corner. There are also ... boards apart. Issue 5A and issue six boards have the extra 40 pin "ULA" chip instead of the group of 74LSxxx chips. We do indeed think ...

Mmm... But then, why did Amstrad fit a heatsink in the Plus 2 ULA? I don’t know the answer to that. But I do know that on the two +2 (grey) machines I have, the heatsinks ...

Remember that air is a very bad heat conductor, so even if the air inside is not moving a lot, adding a heatsink will greatly help to move that heat from the chip into the air. The epoxy resin that the plastic DIL chip package is made from is also not a very good conductor ...

... point (the metal tab of the 7805 or the large 0V/GND track where the heatsink fits under the 7805 is easiest). Test between the right hand lead ... that is nearest the back of the board (D13 k) and pin 28 of IC1, the ULA. All the above tests should have good continuity, or a resistance of ...

... probe does not slip and short anything out. You can use use the heatsink tab for 0V/GND instead of the middle pin (electrically inside the ... at the +5V and +12V supplies to the video section. Test pin 14 on the ULA (IC1) for the +5V supply. Test pins 14, 15 and 16 on IC14 (LM1889) for ...

... just one of a number of topics where the discussion is about fitting a heatsink to a ULA. Okay this one is about a ZX81, but the same principles apply to rubber key ZX Spectrum ...

... probe does not slip and short anything out. You can use use the heatsink tab for 0V/GND instead of the middle pin (electrically inside the ... at the +5V and +12V supplies to the video section. Test pin 14 on the ULA (IC1) for the +5V supply. Test pins 14, 15 and 16 on IC14 (LM1889) for ...

Oh my, he’s only gone and said the special word :shock: The ULA uses bipolar transistor technology, and the matrix cells (internal logic) ... of the air in the case is not very good. The whole point of a metal heatsink is to move the heat from the device to the air. Another thing, the ...

... the 7805 voltage regulator (that’s the chip that has a large aluminium heatsink bolted on). https://components101.com/sites/default/files/component_pin/7805-Voltage-Regulator-Pinout.png ... at the +5V and +12V supplies to the video section. Test pin 14 on the ULA (IC1) for the +5V supply. Test ...

... and removing the Z80 at this point is the best next step. And as the ULA is generating a stable video picture (even if the middle part of the ... measure. The same applies to any electrolytic capacitors close to the heatsink for the 7805. The other electrolytic capacitors are not critical, ...

Yes, the ULA (marked IC1 on the print on the board) is the only large chip that normally runs warm. ... Which issue board do you have? It’s printed on the board near the front edge. The heatsink is the large piece of aluminium bolted to the board. Maybe you should take a photo ...

Hello and welcome :D Is the heatsink getting hot? Is the ULA getting warm? Are any of the other chips getting warm or hot? Power it on and give it time before deciding. ...

... multimeter, test between any +5V/Vcc point (positive/red probe) and ULA pin 20 (negative/black probe). The result should be around 6kΩ to 7kΩ ... probe) and any 0V/GND point (negative/black probe) such as the metal heatsink tab of the 7805 voltage regulator. The result should be about 7kΩ ...

... membrane stuck in the PCB connectors. In very rare cases, the custom ULA chip may develop a fault that prevents the keyboard from fully working. Also note that the two bits of brown goo on the metal heatsink (that strange shaped large piece of metal) and on the TV modulator case ...

... of the pixel. They dont move, just the colours invert. That's the ULA flash working where the random data in RAM has the flash attribute bit set. Here is a picture of the board. WHAT has been done to that heatsink :shock: It's not supposed to have a bend like that in it :( I hope ...