Search found 88 matches

by Tiger
Fri Jan 20, 2023 10:04 pm
Forum: Hardware
Topic: Spectrum 128 +2 grey RAM fault
Replies: 8
Views: 2213

Re: Spectrum 128 +2 grey RAM fault

Data line 0 is IC32 on the +2 board ...
by Tiger
Fri Jul 15, 2022 10:22 pm
Forum: Hardware
Topic: spectrum 48 iss. 2 screen image not sharp/focused
Replies: 19
Views: 3403

Re: spectrum 48 iss. 2 screen image not sharp/focused

The dark screen of the ill speccy looks like a poor signal output. Have you swapped the ULA's ? Any other result with the ULA from the good speccy? I suspect one of the components in the IC 14 area if the ULA swap has no effect.
by Tiger
Fri Jul 15, 2022 9:19 pm
Forum: Hardware
Topic: spectrum 48 iss. 2 screen image not sharp/focused
Replies: 19
Views: 3403

Re: spectrum 48 iss. 2 screen image not sharp/focused

IC 3 an IC 4 are 74LS157 (and not 74HC157) types? Is it possible, that X2 is out of range (moving TC2 could sharpen the pic)? But if you touch TC2 it is better to follow the Service-Manual chapter 3.1.4. Look also for the different values for R47, R49 if you use a 5C112 or a 6C001 ULA.
by Tiger
Tue Jul 12, 2022 10:01 pm
Forum: Hardware
Topic: Issue 4B upper ram PCB tracks
Replies: 17
Views: 3879

Re: Issue 4B upper ram PCB tracks

First of all, there is no -5V on the UPPER RAMS. Pin 8 is connected to +5V (some schematics available in the WWW are really bad to read or faulty)! I think someone has cut the lines to isolate a chip one by one to find a faulty one or added an expansion board with extension RAM and "switched off" th...
by Tiger
Sun Jun 12, 2022 2:17 am
Forum: Hardware
Topic: spectrum 48 iss. 2 screen image not sharp/focused
Replies: 19
Views: 3403

Re: spectrum 48 iss. 2 screen image not sharp/focused

I think it would be good to compare the signal values of the two Iss 2 around the LM1889 to find the cause...
by Tiger
Sat Jun 11, 2022 2:10 pm
Forum: Hardware
Topic: spectrum 48 iss. 2 screen image not sharp/focused
Replies: 19
Views: 3403

Re: spectrum 48 iss. 2 screen image not sharp/focused

Only a thought 'cause I had seen some faulty recapped issue 2's: is C65 (the one directly under the modulator) placed in the right direction? Plus must be to pin13 IC14 and negative to TR2. If you look on your pcb and the modulator is on top, plus is to the right and minus to the left. On the other ...
by Tiger
Fri Mar 18, 2022 11:04 am
Forum: Hardware
Topic: Building a ZX Spectrum 3B, Looking for Parts
Replies: 6
Views: 3717

Re: Building a ZX Spectrum 3B, Looking for Parts

Here is a link for your ROM question (you could find more with "ZX ROM to EPROM' search in www)
https://spectrumforeveryone.com/technic ... -spectrum/
by Tiger
Thu Feb 24, 2022 7:38 pm
Forum: Hardware
Topic: Harlequin Rev G: just lines 🙏🏻
Replies: 2
Views: 1276

Re: Harlequin Rev G: just lines 🙏🏻

Check all your soldering points - ROM is possible, but the white border indicates that the system is "booting". Also possible is, that an IC isn't inserted correctly ...
by Tiger
Sun Jan 02, 2022 2:58 pm
Forum: Hardware
Topic: Harlequin 48K Rev. G - First Time Power Up
Replies: 19
Views: 5121

Re: Harlequin 48K Rev. G - First Time Power Up

I made such a "wired" modification (as I described above) on an 128K Harlequin and all banks where accessible with dip-switches. In the case of an 48K Harlequin it must also be possible to switch with the jumper J12. It will not work with the solution from 1024MAK (only If you make modifications on ...