exxos's Atari, Amiga & retro forum

Fixed...

Can you spot the issue:


Like these on three of the transformer posts.

BennehBoy wrote: 15 Feb 2022 10:29 Ha, I wish, remember when I was asking after yours because I wanted to buy one? :lol:

Anyhow, after a lot of frigging about I've narrowed things down, there must be a dodgy joint because during the course of metering everything out the drive sprang into life whilst I probed the output of the rectifier circuit. Initially thinking it was a duff diode/mechanical connection due to short leads on the diodes I replaced them all - which resulted in the drive still not working.

Metering there again the drive sprang into life. Putting a tiny bit of pressure on the board there the drives springs into life... so there's either a duff joint or a break somewhere, will be scoping the board later.

Ahh, right yes!! I remember now :) You should definitely get a bench PSU, they are soooo useful.

A cold joint wouldn't surprise me at all.

BennehBoy wrote: 15 Feb 2022 10:56 Fixed...

Can you spot the issue:
oops.jpg

Like these on three of the transformer posts.

I see some reflowing in your future :)

A few posts back there was a photo of the 1571 I had purchased. Perched on top of that was a new spindle motor for the final 1541 that I had not managed to get fully working.

I fitted that new motor last night and the very low spindle speed (which would not adjust) is now sorted. Unfortunately although I could load a disk directory (slowly), no larger programs would load successfully.

Given that a directory was working, clearly this was not a logic issue, but rather a signal path one.

The drive R/W head resistances were fine, so I decided that given I had some spare LM592's I would swap those out. These are differential amplifiers used to shape the signals.

Long story short, the drive is also now working, and not just fit for use as a door stop.

BennehBoy wrote: 22 Feb 2022 18:45 Long story short, the drive is also now working, and not just fit for use as a door stop.

That's a bit harsh.

I would have said fit for use as a heated vibrating footrest. :lol:

Glad you rescued it though. Well done.

BennehBoy wrote: 22 Feb 2022 18:45 A few posts back there was a photo of the 1571 I had purchased. Perched on top of that was a new spindle motor for the final 1541 that I had not managed to get fully working.

I fitted that new motor last night and the very low spindle speed (which would not adjust) is now sorted. Unfortunately although I could load a disk directory (slowly), no larger programs would load successfully.

Given that a directory was working, clearly this was not a logic issue, but rather a signal path one.

The drive R/W head resistances were fine, so I decided that given I had some spare LM592's I would swap those out. These are differential amplifiers used to shape the signals.

Long story short, the drive is also now working, and not just fit for use as a door stop.

:bravo: :goodpost:

There's still something not quite right, whilst most disks work, anything with half decent copy protection fails.

This _may_ just be an alignment issue, but I spent about 30 minutes getting it to where it is (very tiny rotations of the stepper motor adjust it, and just tightening up the screws can then throw it back out), but it may also be some of the passives and a couple of 74 series chips are marginal.

Scope out later I think to compare two drives.

This MeGaLoDOS board arrived in the post today, I found it on a German forum -> https://www.forum64.de/index.php?thread ... megalodos/

Anyhow, what's nice about it is that it can be configured to operate as just about any of the 1541 drive speeders that ever came out, there's a nice SSD1306 display with rotary encoder to change options (I'm thinking of building a similar interface to drive a 64 rom switcher).

Here're the bits:


And here it is fully built and installed:


The display also shows the current track and which rom is selected which is cool:


The display and interface are driven by an atmega, and there's a CPLD which deals with memory mapping (some of these speeders can utilise extra ram, to cache the entire disk, or just tracks).

The source code for the atmega is available and I'm considering trying to get one of my colour displays to work with it - why not, it's a bit of tinkering to do :D

Anyhow, having one unified system means I can probably offload some of my other drives.

Having a TL866 is great for burning EPROMS for retro machines, but one thing it can't cope with out of the box is reading 23xx series mask roms to verify their contents.

I figured that it should be simple enough to make an adapter because I already have some adapter boards that convert 27xx to 23xx pinout so that I can put burned roms into machines. By using some pin headers instead of a dip28 chip, and a ZIF socket instead of the 2 rows of 12 pin headers effectively this should mean I can read a 2364 mask rom by selecting any 27C64 as the device in the TL866 (disabling pin check & identification), and reading.

So here's the little carbuncle that I came up with:


And it works... here's a C64 kernal ROM read with the TL866 software:


Just thought this may be useful for those of you doing diagnosis of retro machines - rom dumps for most machines are available online so it's quite simple to verify them.

Feeling a bit confused....

I bought a DC 30V 10A bench PSU from Amazon, and it's not outputting DC, but AC???

Model in question is an Eventek KPS1505D.

2 different multimeters confirm that it's putting out AC voltage, and not DC/

I can't imagine how this is possible - should I just return it or am I doing something stupid?