Denial

Thanks, I hadn't come across that model. It's more than twice the price of the Chinese ones, not sure I want to splash out that much.

In a long-time Linux user, c. 15 years. I've used it for my work environment for nearly all that time, the few times I have ventured into the world of Windows I wonder how anyone can use it.

Thanks for the feedback on the Willem.

I think I'm going to go for a TOP853, I've found one in stock in the UK can it claims to be able to handle 25v devices like the TMS2564.

I'm thinking of getting a programmer to use for a couple of projects. I must be able to program 27C128 (EPROM) 28C256 (EEPROM) and it would be nice to test RAM, other ICs There seem to be a few programmers about Willem TOP853 G540 Does anyone have any advice on choosing one? Thanks.

Yes, I'm intending to use a 74LS175 as a write-only register to manage bank switching so it's all controlled by software.

My first experiments didn't quite work out so I'm going to have to spend so more time debugging this. I'll post a schematic once I think I have something that works.

I would guess one of the RAM chips is faulty. The expansion pack probably consists of 4 x 2K SRAM so 3584 - Internal memory 5632 - +2K 7680 - +4K 9728 - +6K 11776 - +8K as 8786 is less then 9728 I would think the third SRAM is faulty. The KERNAL routine scans through memory until a write/read test f...

That would do. Anyone in Europe stock these?

I'd like to start tinkering again and build a few projects. Does anyone know of anywhere to get hold of boards like this old Radio Shack one these days?

Did that, too. The thing about RAM under ROM is to arrange the banking circuitry so that the RAM can be written without switching out the ROM. That way, the ROM can be copied to RAM by PEEK/POKE (or LDA/STA) the same addresses, then modified before making the switch. This would apply to BASIC and K...

Success! I've just replaced UC7 (74LS00) and the drive now powers up and I can read the directory off a disk.

There's something to be said for hardware that so straightforward to repair. They don't make them like that any more.

The drive spindle is definitely turning and the belt tension seems fine. I've found a list of chips to check on one of Ray's comp.sys.cbm postings UA1 - 74LS14 UB4 - ROM UC2 - VIA UC4 - 6502 UC6 - 74LS04 UC7 - 74LS00 UD3 - 75LS86 UD5 - 74177 I've checked/replaced the first four, I'll work my way thr...

Yes. Symptoms are

On first power up red and green LEDs come on. Drive motor also on. After a while red LED goes out but drive motor still spins.
Subsequent power cycles, LEDs and motor come on, all stay on.

Well, I've replaced both UA1 and UD2 and the symptoms are the same. In summary I've checked the output voltages of both rectifiers The 5v rail reads 4.93v I've tested the 6502 and both VIAs in my VIC I've dumped the contents of both ROMs and the md5sums match images I've downloaded I've replaced UA1...

Ah, thanks. That's the sort of test I expected. I'll update my ROM dump program to use this.

I've recently been rediscovering the various subtle ways of RS-232 connections (like using >=128 for the LFN to get CRLF at the end of a line). One thing I'm still struggling with is checking the transmit queue is empty before closing the channel. The Programmer's Reference Guide says Care should be...