ZTX651 and ZTX653 are suitable replacements for the ZTX650 normally found in TR4 position and when I last checked earlier this year, were still in production.
TR4 normally only dies if there is a short circuit or other overload on one of the outputs of the DC/DC converter.
Mark
Search found 5148 matches
- Tue May 14, 2024 11:41 am
- Forum: Hardware
- Topic: Spectrum 128 Toastrack Mishap
- Replies: 5
- Views: 207
- Tue May 14, 2024 9:49 am
- Forum: Hardware
- Topic: Spectrum 128 Toastrack Mishap
- Replies: 5
- Views: 207
Re: Spectrum 128 Toastrack Mishap
The colour encoder chip is not involved with the RGB output.
Are the +5V and +12V supplies for the video section okay?
Mark
Are the +5V and +12V supplies for the video section okay?
Mark
- Mon May 13, 2024 11:31 am
- Forum: Hardware
- Topic: Newbie question
- Replies: 6
- Views: 253
Re: Newbie question
Soldering is about a combination of good technique and practice.
So start again with a good iron and a cheap electronic kit from say eBay or another source.
There are plenty of tips on soldering both as text tips and help and as videos online.
Mark
So start again with a good iron and a cheap electronic kit from say eBay or another source.
There are plenty of tips on soldering both as text tips and help and as videos online.
Mark
- Sun May 12, 2024 3:45 pm
- Forum: Hardware
- Topic: FIXED Spectrum +2 grey RAM fault but RAM is good
- Replies: 31
- Views: 675
- Sun May 12, 2024 2:22 pm
- Forum: Hardware
- Topic: FIXED Spectrum +2 grey RAM fault but RAM is good
- Replies: 31
- Views: 675
Re: Spectrum +2 grey RAM fault but RAM is good
The joystick chip is believed to be the same as the chip in the Sinclair Interface 2. Hence it's not believed to be essential. The other thing of note, is that the data bus outputs can only drive each data line low (like open collector/open drain).
Well done on making progress
Mark
Well done on making progress
Mark
- Sat May 11, 2024 10:05 pm
- Forum: Spectrum BASIC
- Topic: New Pascalated BASIC Contest
- Replies: 4
- Views: 266
Re: New Pascalated BASIC Contest
Moved to the ZX Spectrum BASIC section, as this is a more appropriate section. I’ve left a shadow in the development section.
Mark
Mark
- Sat May 11, 2024 3:08 pm
- Forum: Hardware
- Topic: FIXED Spectrum +2 grey RAM fault but RAM is good
- Replies: 31
- Views: 675
Re: Spectrum +2 grey RAM fault but RAM is good
If the fault is or has been intermittent, poor IC socket contacts, dry jointed solder joints, and PCB track faults are still possibilities.
Mark
Mark
- Sat May 11, 2024 10:29 am
- Forum: Hardware
- Topic: ZX81 Comp. Mod, no Video
- Replies: 15
- Views: 796
Re: ZX81 Comp. Mod, no Video
The length (time) of the back porch and the trigger level have to be in the right range, otherwise it affects both line (horizontal) and field (vertical) synchronisation of the picture. If you are using a NE555, I’ve found that cheap versions from trading sites are too slow. It’s impossible to set u...
- Sat May 11, 2024 10:20 am
- Forum: Hardware
- Topic: FIXED Spectrum +2 grey RAM fault but RAM is good
- Replies: 31
- Views: 675
Re: Spectrum +2 grey RAM fault but RAM is good
Unlikely given that resistors are used to divide the data bus and the two groups of DRAM are controlled differently.
I’m wondering if the ULA is receiving all the control signals from the Z80.
Mark
I’m wondering if the ULA is receiving all the control signals from the Z80.
Mark
- Fri May 10, 2024 8:38 pm
- Forum: Hardware
- Topic: FIXED Spectrum +2 grey RAM fault but RAM is good
- Replies: 31
- Views: 675
Re: Spectrum +2 grey RAM fault but RAM is good
Yes, this is a tricky fault. You said earlier that you had changed the Z80. Did you try the removed chip in another Spectrum?
Mark
Mark