The LaST Upgrade - Part 6 - PSU

[exxos]

http://www.exxoshost.co.uk/atari/last/psu/index.htm

and the homepage.

http://www.exxoshost.co.uk/atari/last/

[bullis1]

Good guide. I wasn't expecting another chapter.

[exxos]

Me neither

Though I am on the hunt for a smaller ram chip to do 4MB. Simms are old and im sure this could all fit on a smaller chip these days. Also my old boards fitted into the shifter socket to pickup the address lines. Though all the lines are in the ram area anyway, its just a matter that a simm in a socket will not fit under the PSU. As the ram area is more uniform in layout, it would be a better (and easier ) upgrade to do.

EDIT:

http://exxos.www.idnet.com/IMPULSE/atar ... d/main.htm

It was a broken link on the floppy page, links should be all fixed now.

[bid]

Wow. Thanks for this guide.

The PSU one is especially useful, and I need to complete this on all my machines.

I have 2 STes that are a bit crackly already!

... Oh, and you have a guide for the 1.44MB floppy. This has got to be one of the most useful upgrades ever. Can you tell me where I can locate the chips, and should I request a board or build my own?

Im happy with a soldering iron and ... wait. OMG. You also made an external HD floppy drive. Lol. ... WHAT A GREAT IDEA!

Jeeze. You have no idea how happy I would be with 2x 1.44MB drives on my ST. lol. ... Imagine what you could do on an ST with 3MB storage like that. Literally a full Cubase setup, alternative desktop and all the accessories etc fitting in 4MB ram. You beauty!

I have been trying to find a source for WD1772 for ages. Even my TT has only a 720kb FDD fitted. So I have no ability to use FDD with with either my PC or my Akai sampler.

I am guessing that you dont make these things any more? But if you dont, I would be happy to try and make my own. If you do make, I'd be templed to paypal you. Happy either way.

What a great guide, and answers to my problems. I am especially pleased with the parts list for the PSU caps. But also, I am going to have a go at the 1.44MB drives. Anyone know where you can get the WD1772 ??

This is a super super super guide, and really great info. Lots of fun here. Thanks!

[krupkaj]

It is interesting. What about the Falcon's power supply? Does the output look similar?

[exxos]

Wow. Thanks for this guide.

The PSU one is especially useful, and I need to complete this on all my machines.

I have 2 STes that are a bit crackly already!

... Oh, and you have a guide for the 1.44MB floppy. This has got to be one of the most useful upgrades ever. Can you tell me where I can locate the chips, and should I request a board or build my own?

Im happy with a soldering iron and ... wait. OMG. You also made an external HD floppy drive. Lol. ... WHAT A GREAT IDEA!

Jeeze. You have no idea how happy I would be with 2x 1.44MB drives on my ST. lol. ... Imagine what you could do on an ST with 3MB storage like that. Literally a full Cubase setup, alternative desktop and all the accessories etc fitting in 4MB ram. You beauty!

I have been trying to find a source for WD1772 for ages. Even my TT has only a 720kb FDD fitted. So I have no ability to use FDD with with either my PC or my Akai sampler.

I am guessing that you dont make these things any more? But if you dont, I would be happy to try and make my own. If you do make, I'd be templed to paypal you. Happy either way.

What a great guide, and answers to my problems. I am especially pleased with the parts list for the PSU caps. But also, I am going to have a go at the 1.44MB drives. Anyone know where you can get the WD1772 ??

This is a super super super guide, and really great info. Lots of fun here. Thanks!

Glad the guide is useful I developed that 1.44 mod as shown, I still have some pcbs, maybe other parts too, can always get the parts for it no problems there.

The WD1772 is normally found in ST's anyway, if you have a STE, no problem. I tested a lot of 1772s and they all seem to work , just the older VL1772 just gets a lot hotter. Version 02-02 is what people normally go for as its the latest one before the Ajax (found in STE). I'll check my parts out, have at least 10 pcbs.

I would recommend doing the PSU mods above all else. I have a LOT of other mods in mind too. So some point in the future there should be more guides up.

I will try and figure out how I wired up the external floppy, I used to sell them a long time ago, will try and do a guide for that too

[exxos]

It is interesting. What about the Falcon's power supply? Does the output look similar?

My Falcon has not had all that much use, but I will suspect age will be getting the better of it.

I will price up the caps for what I used on the STFM board, was around 20quid, hard to say exactly as I ordered some other stuff, and some stuff was in packs etc, I dont mind sending people items, I order electronics stuff every week so a few more things on there isn't a problem

[ralcool]

I would love to see how you configured the step rate logic for seemless integration for your HD mod.

Seem its based on being wired to D0 & D1.... (Pin5 and 6 of the WD) just looking.....

You can see why you removed the WD from the board. A number of signals modified. Lots of cutting.

Golden idea tho. Well done.

ST.

[DarkLord]

The WD1772 is normally found in ST's anyway, if you have a STE, no problem. I tested a lot of 1772s and they all seem to work , just the older VL1772 just gets a lot hotter. Version 02-02 is what people normally go for as its the latest one before the Ajax (found in STE). I'll check my parts out, have at least 10 pcbs.

From an article in ST Format, mostly the older WD1772's don't work, and only about 5% of the 02-02
variety doesn't. I had an 02-02 in my STacy, and I guess it was in the that 5%. Sean's HD mod wouldn't
work until I replaced it with an Ajax chip - took right off after that and worked great.

[krupkaj]

You write quality capacitors are necessary but what are the best? Which manufacturers do you recommend? Thanks for info.

Sent from my Android using Tapatalk

[exxos]

I would love to see how you configured the step rate logic for seemless integration for your HD mod.

Seem its based on being wired to D0 & D1.... (Pin5 and 6 of the WD) just looking.....

You can see why you removed the WD from the board. A number of signals modified. Lots of cutting.

Golden idea tho. Well done.

ST.

My floppy page does explain some of this somewhere. It simply looks for a command entering the WD1772, then flips 2 data bits, this changes the step rate command "on the fly". As it only does this on a command, it does not effect the data. Very simple idea, no need for any software as the WD1772 is programed by hardware

[exxos]

The WD1772 is normally found in ST's anyway, if you have a STE, no problem. I tested a lot of 1772s and they all seem to work , just the older VL1772 just gets a lot hotter. Version 02-02 is what people normally go for as its the latest one before the Ajax (found in STE). I'll check my parts out, have at least 10 pcbs.

From an article in ST Format, mostly the older WD1772's don't work, and only about 5% of the 02-02
variety doesn't. I had an 02-02 in my STacy, and I guess it was in the that 5%. Sean's HD mod wouldn't
work until I replaced it with an Ajax chip - took right off after that and worked great.

Yeah, I read the same things, I don't really understand why. Though most of these mods were done using the shifter 16mhz clock, I found this to be unstable, and when I moved to a 16mhz osc, all the problems went away. Going my how bad my PSU actually was, its amazing anything worked at all. I did list the 1772's on my floppy page that I had listed as tested and working on 16mhz. I have not done any long tests, just a few formats in 16mhz mode. I think when the VL chip started to get rather hot it used to fail on the odd track during format, but there could have been any number of issues.

When I get chance I will re-test the chips I can find.... I do feel the problem is not the WD1772 itself, but a problem elsewhere... I will have a hunt about, maybe someone has a "known not working in 16mhz mode" chip they want to send for me to test ?

[exxos]

You write quality capacitors are necessary but what are the best? Which manufacturers do you recommend? Thanks for info.

Sent from my Android using Tapatalk

I listed the part numbers on my website, these are good for rating and price, only panasonic I use now, but they also do "cheap" capacitors, but for a few pence more you can buy the caps like I have listed.

[ralcool]

maybe someone has a "known not working in 16mhz mode" chip they want to send for me to test ?

Maybe Darklord still has his defective chip? After being replaced by the Ajax.

I'd love to include the 6ms step switching into the new board I want to send him. (His fixed TOS1.4 needing a driver and all... PITA)
Patching TOS is one thing.. but hardware bypass is cool.

Can you possibly show a schematic of the V4.0 you came up with? It sounds unique.... too good to lose. The description while good, is hard to put on cad.
And I thought there was nothing left to be impressed about... you did it!

ST.

[DarkLord]

maybe someone has a "known not working in 16mhz mode" chip they want to send for me to test ?

Maybe Darklord still has his defective chip? After being replaced by the Ajax.

ST.

Afraid not, when the old chip was removed, and a new socket put in, it was
by the traditional snip the legs of the old chip and replace method. Sorry!
If I had any idea it might be needed I would have saved it.

[exxos]

maybe someone has a "known not working in 16mhz mode" chip they want to send for me to test ?

Maybe Darklord still has his defective chip? After being replaced by the Ajax.

I'd love to include the 6ms step switching into the new board I want to send him. (His fixed TOS1.4 needing a driver and all... PITA)
Patching TOS is one thing.. but hardware bypass is cool.

Can you possibly show a schematic of the V4.0 you came up with? It sounds unique.... too good to lose. The description while good, is hard to put on cad.
And I thought there was nothing left to be impressed about... you did it!

ST.

I will have to dig out my atari notes, the design is like 10 years old, could possible just work it out from the PCB as its only very simple. I did plan a second revision which would switch the ms rate better, but as I got left with a lot of pcbs last time, i never did the revision.

[exxos]

If anyone wants the replacement parts I used for the PSU, I can do tham for £16 including UK postage. Send me your email address and will send paypal invoice. I don't keep stock of them, so will have to see how many people want parts before sending the order off.

For those asking about the 1.44 mod, I have 15 PCBS left, £5 each + postage. I can supply parts also if needed, though they are pretty generic, will do a list tomorrow. I can also sell them assembled and tested (note you need your old WD1772 chip I dont supply them).

I do not plan on making anymore of those 1.44 boards, But I am planning on doing some other boards which are clock generators for my 16mhz booster. Chances are I will revamp the 1.44 board and make smaller but will also have ripple counter onboard to supply any clock speeds needed. This project will take a long time, but I will update my guides as items are prototyped

[exxos]

The HD mod parts are

1x 74HC4002N
1x 74LS151N
2x 4148 diodes.
3x 1K 0.125W resistor
1x BC548 Generic transistor.
1x 16MHZ OSC
1x 28 DIL socket (turn pin)
1x 220nF capacitor.

Other parts are IC header pins. If PSU is a little unstable, a 1MR resistor may be needed on select lines. TTL pull these high internally, but if PSU is unstable then a pullup resistor is sometimes needed. I would advise ONLY using those ICs as listed. Using any other "compatible" types may cause problems.

Instructions & various related info.

http://exxos.www.idnet.com/IMPULSE/atar ... /index.htm
http://exxos.www.idnet.com/IMPULSE/atar ... d/main.htm
http://exxos.www.idnet.com/IMPULSE/atar ... l/main.htm
http://exxos.www.idnet.com/IMPULSE/atar ... rticle.htm
http://exxos.www.idnet.com/IMPULSE/atar ... t/main.htm
http://exxos.www.idnet.com/IMPULSE/atari/faq.htm

Please note these pages are 10 years old now.

I have added a quick webstore page for this stuff...

http://exxos.www.idnet.com/IMPULSE/atari/last/


EDIT:
I just tested the module with just internal drive and it defaults to 8mhz when the floppy isn't being accessed. Then switches to 16mhz on 1.44 access Actually it seems I wired it to the floppy access LED, so it only switches to 16mhz, when needed, and only when the drive is actually running (A or B).

[rebb]

Exxos: Just out of interest, did your PSU upgrade have any affect of 50hz hum Atari seems like to output on audio.
Also drive movements etc will get thru audio out (easy to notice when loading). Thinking about replacing opamp and PSU, but instead using external one, what is the affect if i just replace the caps.

[exxos]

Exxos: Just out of interest, did your PSU upgrade have any affect of 50hz hum Atari seems like to output on audio.
Also drive movements etc will get thru audio out (easy to notice when loading). Thinking about replacing opamp and PSU, but instead using external one, what is the affect if i just replace the caps.

I've not had any hum problems on the Atari, but having working in audio, linking equipment up can cause hums, its normally a ground loop which causes it, in some cases connecting the mains earth to 0V rails can cure it, but it other cases it can casue it. Its actually a real pain in the rear.

I doubt the ST would cause a hum, its a switchmode powersupply, if anything you would get a high pitch sounds which can vary in pitch. Hums are generated between 2 sets of audio equipment, between grounds.

The problem half the time is "double insulated" equipment, where it does not have a mains earth, this is very very bad and whoever made that setup pass regulations wants shooting! With transformers the secondary can float thousands of voltages above the mains voltages! So if you have one thing which is earthed and one which isn't , you can develop a high voltage between the 2 items, I get this all the time with equipment, like when I connect my scope prob to the Atari ground I get a spark each time, same when I try and solder, have to unplug the TV from the ST as the TV ground isn't true ground, so when the grounded soldering iron tip touches anything, it blows the hell out of it. Best part is "regulations" sate any metal work must be grounded (came about sometime in the 90s I think). Half the time this causes electric shocks!

You don't sate what you got hooked to your ST, presume amplifier ? Suspect it does not have a ground connection ? If it does I bet its only on the transformer core, or maybe just the case. Actual audio ground is left "floating" upon a almost random voltage on the seconday of the transformer. This is where the "hum" actually comes from.

You may want to try just connecting a mains ground to the audio earth, I have to do that on a lot of items to cure the hum. This will clamp the floating core voltage to earth (how it should be!) Assuming thats the problem, which is most cases it is, that will cure it. Dont connect the earth with anything plugged into anything else either, you may get a electric shock or blow summert up, do at ur own risk

EDIT: PSU upgrade can't hurt with other noise like the motor etc.

[bid]

Quick question. Are there any machines that the 1.44MB mod wont work on? ... Also, are the header pins best soldered direct to the mainboard, or can you use a DIL on there?

I didnt realise at 1st, (due to not reading properly) that this re-uses the existing FDD controller. Impressive.

I'm guessing that them Ajax chips are just not available anymore, so this is really neat. I wonder why no one at Atari tried this?

I also have a very early TT that has a 720kb drive in it. It has a VL1772 02PC



There is also a wire running to the YM chip of which I have no idea what purpose it is? ... I did try it with a HD drive that I modded (below)



But I only got it working intermittently and had to remove it. I'd really like to get this sorted out, but I think I would fit a DIL as I want the option of returning it to its original spec if need be.

Once I get 1.44MB working, I'll be able to use a great program called AKAISEX that will allow me to edit sample the Akai Sampler. Plus, be able to use disks with Windows7 which M$ kindly removed support for DD disks! Which is annoying.

[exxos]

There is a drive select comming from the YM chip.

The wire on the drive looks like a HD switch line, some mods used the ribbon cable to pass the HD select signal, though dont recall much else about it.

I dont see any reasn why it wouldn't work on any atari, the STFM was pretty much the first machine, so anything after should work. Anything with TOS104 or over.

You could use header pins/sockets, I did that with my testing atari, though its pushed for room under the floppy drive so care must be taken to check it will physcially fit first. I only had a ST/F/FM/E to try the mod on, but dont see why it couldn't be used on others.

I have not had any real problems with any version of the 1772, from my own FAQ TOS100/101/102 seems to have some problems with HD floppies, but I tested with TOS104. the VL is a older 1772 and tends to get hotter, which isn't great, but it still worked. I do hope to re-test the 1772 series, though really need some guys to send me various version as I dont have any here anymore.

My mod only switches to 16mhz when needed, so this reduces thermal problems, i guess if you were constantly formatting HD floppies for hours it could overheat some chips, but in general use its never really a problem.

[bid]

Interesting. But I am still clueless what to do about this wire, if I were to fit the mod.

As I said, I did try fitting a HD drive modded for Atari use, but it did not work. So this TT seems incapable of running a HD drive un-modded... Unless of course I messed up on the FDD mod above.

Anyway, I am willing to try it out.... But maybe on my ST 1st. lol At least then I can get files onto my PC and Sampler, and maybe I just share between the ST and TT.

I have the ST and TT networked ... In the most simple and horrible way. lol. I am using a serial interface and STiNG to transfer files from one to the other. So just as long as I can get one Atari to have a 1.44 will be an enourmous breakthrough!

I really need to upgrade and get myself into the 90's! Lol

[exxos]

I would just get a MPF920 drive and do the mod as shown in my floppy guide, its the best drive around, and one of the most common too

[rebb]

EDIT: PSU upgrade can't hurt with other noise like the motor etc.

You are right about the hum part, cheap logitech speakers + bad cables and having old non schuko mains does not help with the problem Have to try isolation transformer.

Anyway ordered PSU capacitors from your page, hope it helps to get rid of rest of the audio problems (motor movement sound).