Spectrum Computing

Since swapping the power supplies doesn't help, the problem seems to be on the board itself. The coil seems to be a replacement - the "Samsung" coils of the 4S boards look different. Presumably, this replacement coil can be influenced by the frequency of the Murata circuit regulator and th...

Try to change your switching power supply ...

I've just read your discussion from the beginning and you wrote that there was a black screen first. :geek: I got one vLA82 from Charlie in the past wich also "produced" a completely black screen. I had a spare board where I was able to swap the ULA and could locate the faulty vLA. Charlie...

Oh yes - I found it now at retroleum. I think you got the standard ROM in slot A and DiagROM in slot B. Your scrambled screen now looks for me as the DiagROM-Test screen :shock: Maybe there is something wrong with the program of this little part... R33 (680 Ohm) and R32 (100 Ohm) are ok? I remember ...

Your 2369's are mountet in the right way - looking from top there is (flat side down, round up) Emitter left, Base middle, Collector right.

I think, you missed a connection from pin 1 to pin 28 at the ROM-socket. This connection is important because an EPROM is used instead of an ROM. I think you'll find any instructions for your "ROM-select", may be there is something to wire at the H/N connections wich is now soldered for Hi...

The scrambled screen is often a clear sign of an lower RAM fault

Minus of C65 (22µF/16V) is connected with base TR2 and plus goes to R72 and pin 13 IC14.

Maybe this could cause the issue:
https://benophetinternet.nl/hobby/vanme ... erface.pdf
because there is a NEC-ROM on your pcb ...

but it didn't work at all - sorry can't help

Ok - you're flashing your EEPROM via the tap-file with your Spectrum? I always programmed them with an TL866II. Programming with an audio-signal could be a problem - your Speccy responds with "R-tape loading error", but the EEPROM doesn't quit with a signal. It will work or not after start...

All black pcb's? Is it possible that there is an layout failure? :roll: Is pin 3 S1 connected with pin 19 IC1? Everything looks good at this board (components, soldering points), but if all 5 boards as the same make (black pcb's) it is possible that the pcb's itself have a problem ... https://i.post...

:shock: in the DivIDE 57c I had there where no component between R9 and the EEPROM. I think it is RN1 - never used it. https://i.postimg.cc/R6jG74LX/divide-57c-top.jpg https://i.postimg.cc/DWNRNVcb/divide-57c-component-side.png Imho there is something with the program in the EEPROM or the GAL(s).

Hello, i it possible to show a picture of your DivIDE pcb (both sides?). I think it could be a problem with an inkompatible EEPROM ... https://divide.cz/index.php?x=howto Was everything as described at step 14 of the manual? (Jumper 'E' not inserted) Did the BORDER flash? Have you inserted jumper 'E...

Imho it seems that the "RAS" isn't recognized. I would check R32. Is it the right value (100 Ohms)? Are the connections (IC3/4 to R32 and R32 to ULA and pin 4 of the RAM's) ok?

Have you tried to make the bridges as for an Hitachi-ROM? Possible, that you have to connect pin 1 of your ROM with pin 28 of it, like an EPROM. Maybe pin 24 must be modified - look for instructions to replace the original ROM with an EPROM ... Using a Lower RAM Module it isn't necessary to make the...

I think this mod was done in this way because something else is broken. Maybe a cut wire on the pcb by replacing a component ...

Yes, I have a copy and I've scanned into a pdf-file, but I'm not familiar to load it onto the database ...

The program is from the FORMAT Introductory Issue. The BASIC listing is printed at page 8. A short little program to list the Basic-files on a DISCiPLE disk and load them by a single key press.

The mod is described here: https://www.bytedelight.com/wp-content/uploads/2019/10/ZX-Spectrum-16K-to-48K-upgrade-kit-installation-manual.pdf The mod at IC 26 is from the Issue2-Schematics: pin10 to GND (pin8) is for "-3" RAM version and pin10 to +5V is for "-4" version RAMs - you...

Sometimes the power supply could be the reason for interferences in the picture

Yes - I build it as described in the MagPi Issue 118, page 48. It is simple to fit a Raspberry Zero with the Pirate Audio Hat. I used Photoshop Elements to reduce the size of screen-jpg's. With PiShare it is simple to transfer the files via WiFi from Win10-PC to the Pi. It is possible to use the ful...

With the OLED you can display the cassette inlays of the files

Well - return and refund is really ok. With the right psu the noise could be from a not perfectly fittet or damaged coil - so it is better to look for a better speccy. I would look for an Spectrum+ because the keyboard is much better than the rubber-key, but that is only my personal mind. On the oth...

"... working when it left home" - Have you got it with the power unit? Have you attached a power supply with the right polarisation (+ outside and - centre)? If you used a wrong power unit, you could have destroyed the former working speccy ... Your "faint electrical noise" let m...