Using 117V psu 1571 drive on 230V household

[VintageVic]

So, christmas came early for me today!



A bunch of untested Commodore stuff. Already tested the C64 as working. 1541 would not
read discs, due to rw head having more poo than my 4 day old boy in his diapers! Cleaning fixed that
drive.


But to the topic; the 1571 unit is my first and I would really like to see if it is a working one.
The trouble is, that the unit has 117V psu and I live in a house with 230V power socket.



I must not be the only one with the same issue, so what was your solution ?
Converting the power supply inside the unit (somehow)? Getting external converter from 230V -> 117V ?
or.. ?

I could take recommendations here, I guess there could be a number of solutions to go with.
I have 1541-II power supplies and modern laptop psu:s that also have +5V and +12V in one, but
using those I might need to make a hole in the case and that would not look nice.

The C128's have only one power supply which seems to be busted. But that's a thing for another topic.

 

[daver2]

I have a 230V to 110/115V transformer for just such circumstances.

It might be worth looking inside at the power supply unit itself to see exactly what Commodore used.

I have been able to find the service manual and schematics for the logic board itself - but that tells me nothing about the power supply unit.

Dave

 

[Hutch]

Standard practice is to use a step-down transformer when running North American electrical devices in Europe.
For many items, like this floppy drive, the line frequency shouldn't matter.

 

[g4ugm]

Standard practice is to use a step-down transformer when running North American electrical devices in Europe.
For many items, like this floppy drive, the line frequency shouldn't matter.

Didn't some floppy disk drives have synchronous motors? I think probably only 8" ones.
It only needs 40Watts so any of the small converters that have a transformer should work, but I would look for a 100Watt type

 

[Hutch]

Didn't some floppy disk drives have synchronous motors? I think probably only 8" ones.
It only needs 40Watts so any of the small converters that have a transformer should work, but I would look for a 100Watt type

Interesting. I don't think I've seen a synchronous motor in a Commodore drive.
AFAIK, in the 1571, the motor runs off DC.

 

[Chuck(G)]

AC line-operated spindle motors, as far as I know were all on 8" drives. The Shugart SA-400 introduced the "MOTOR" line on the interface to control the DC motor.

 

[iz8dwf]

Commodore 1571 drives are divided in two categories (as Tuco would say):
the old ones with linear power supply (and heavy transformer), and the newer ones with switching power supply.
If it has a linear power supply, the only options are to either use an external (auto) transformer to step down the 230V to 115V (since the original internal transformer has only 110V and 120V taps) or substitute the internal power supply entirely with another one that can supply 5V @2A and 12V @2A (to be safe, peak currents are lower than that).
If it has a switching power supply, it might have a voltage doubler input (I'd need to open mine to check) and all it would take to transform it to 230V input is to remove or cut the jumper that transforms the full wave input rectifier into a voltage doubler.
If you're familiar with switching PSUs you know what I mean, otherwise post internal pictures of the power supply and someone will help identify what you have.

HTH
Frank IZ8DWF

 

[VintageVic]

If it has a switching power supply, it might have a voltage doubler input (I'd need to open mine to check) and all it would take to transform it to 230V input is to remove or cut the jumper that transforms the full wave input rectifier into a voltage doubler.

That would be a neat solution, if the psu could be converted.
Alright, here is what I've got:





However, I'm not that familiar with the psu's to recognize if there is a voltage doubler or not.

At least the power connector looks simple enough:


four pins for 12V, 5V and ground. If the original psu is not possible to be converted
for 230V, I'm probably going to provide correct voltages to these pins from external power supply.

 

[iz8dwf]

No luck. Single big high voltage capacitor means no input doubler. The voltage doubling circuit requires two identical high voltage capacitors, usually rated at 200V or more each.
You can either substitute it entirely or use an external step-down auto-transformer (even without the auto-).

Frank IZ8DWF

 

[VintageVic]

I went for subtitution. made a connector with +5V in the end, gnd in the middle and +12V on the other end.
plugged it on and the drive booted, great!

I then unplugged it in order to tie the cables neatly inside the unit. And then reconnedted
the power connector BACKWARDS. And merrily went on trying it again... giving 12V to 5V rail and 5V to 12V rail.

:shock::shock::shock:

it took just a couple of seconds for me to realize what I've done, but it is too late.
I've fried who knows how many chips on pcb.

The moment you realize you have done stupid and irriversible... it's not a happy one.

 

[VintageVic]

Ahha.



I let the unit be power-on state for a minute. The U20 (8521RO) and the CPU were quickly very
hot to touch. Since the U20 was on IC socket, I decided to pull it out and try again.

whoa, the drive seemed to have booted! it's a CIA chip. Ray Carlsen's chip list says U20 is either
6526A or 8521.

I wonder, if I would dare to just try to substitute any 6526 chip here (with or without the A).
I have donor C64's that might have that to give away.

 

[iz8dwf]

Ahha.

View attachment 65395

I let the unit be power-on state for a minute. The U20 (8521RO) and the CPU were quickly very
hot to touch. Since the U20 was on IC socket, I decided to pull it out and try again.

whoa, the drive seemed to have booted! it's a CIA chip. Ray Carlsen's chip list says U20 is either
6526A or 8521.

I wonder, if I would dare to just try to substitute any 6526 chip here (with or without the A).
I have donor C64's that might have that to give away.

you can use a 6526, the A version means it's rated for 2 MHz clock (which is what you find in a 1571) but a 1 MHz 6526 will probably work.
Also, the 1571 will use the 6526 only if it's connected to a C128 in C128 mode.
You can also use a partly failed 6526, as long as the serial shift register is still working.
Frank

 

[VintageVic]

Okay, I tried the 1571 with a 6526 chip from C64.
It boots fine and boots second time when the C64 boots.
But attempting to access the drive will result "Searching for..."
and the C64 gets stuck there. no any activity at the drive.

I pulled U15 (7414) and put a new one there, but no change.
I'm starting to suspect the other VIA chip, U9 - 65SC22 chip could be a possible
cause. However, I'm wondering if regular 6522 from spare 1541 pcb is
possible substitute? Perhaps not, if the 65SC22 is needed for 2mhz clock ?

 

[iz8dwf]

Okay, I tried the 1571 with a 6526 chip from C64.
It boots fine and boots second time when the C64 boots.
But attempting to access the drive will result "Searching for..."
and the C64 gets stuck there. no any activity at the drive.

I pulled U15 (7414) and put a new one there, but no change.
I'm starting to suspect the other VIA chip, U9 - 65SC22 chip could be a possible
cause. However, I'm wondering if regular 6522 from spare 1541 pcb is
possible substitute? Perhaps not, if the 65SC22 is needed for 2mhz clock ?

troubleshooting by pulling chips isn't the best way, but if you don't have at least a logic probe, I can't suggest much tests to be done
with only a multimeter. However, the 7406 (U16) would have been my first try.
However, yes, you'd need a 6522A (any incarnation, like the R-6522A, SY6522A, UM... MOS... etc...), but you might also get lucky with
the 1 MHz one (no A in the part number).
If they where socketed, you might have tried to simply swap the two 6522 and see if something changed.
Frank IZ8DWF

 

[VintageVic]

Alright,

I decided to pull U9 (65SC22). Made a clean pull without damaging the pcb:



I put an IC socket there and tried out with regular 6522 chip.
Although the drive does not work, there is a change!

Now, when read is attempted, the stepper motor moves a bit back and forth, spindle runs
and it's trying to read the disc. However, it quickly gives up to a file not found -error:



I'm thinking a few possibilities. One for sure is to buy correct 65SC22 chip. I see them online
and I will get a couple at least. This will take weeks though before I have those at my hands.

Two, the drive acts like a dirty 1541. I did gently try to clean the rw head, but it had no change.
Three, it also looks like behaviour, when there is open rw head. I'm hoping that the 1571 does
not suffer on that typically, like the mitsumi mechanics on 1541. This should be easily measured
with a multimeter however and is on my next to do list here as soon as I can find the head schematics.

Edit:
and yes, I do not have a logic probe - yet. If I learn how to use it to troubleshoot, I could get one too.

 

[iz8dwf]

Alright,

I decided to pull U9 (65SC22). Made a clean pull without damaging the pcb:

View attachment 65399

I put an IC socket there and tried out with regular 6522 chip.
Although the drive does not work, there is a change!

Now, when read is attempted, the stepper motor moves a bit back and forth, spindle runs
and it's trying to read the disc. However, it quickly gives up to a file not found -error:

View attachment 65400

I'm thinking a few possibilities. One for sure is to buy correct 65SC22 chip. I see them online
and I will get a couple at least. This will take weeks though before I have those at my hands.

Two, the drive acts like a dirty 1541. I did gently try to clean the rw head, but it had no change.
Three, it also looks like behaviour, when there is open rw head. I'm hoping that the 1571 does
not suffer on that typically, like the mitsumi mechanics on 1541. This should be easily measured
with a multimeter however and is on my next to do list here as soon as I can find the head schematics.

Edit:
and yes, I do not have a logic probe - yet. If I learn how to use it to troubleshoot, I could get one too.

Yes, I've had a failed head on one 1571, you can easily test all the coils on both heads with a multimeter.
If the heads look fine, the fault may be elsewhere. Applying 12V on all the 5V ICs might have made a bit of a mess.
Frank

 

[VintageVic]

Well, the heads just might be fine on this one, since I'm getting 10-20ohm resistance between
the pins. I have ordered one 65SC22 chip, but plan to order a couple of others from another provider.
Sometimes you wait for 6-8 weeks and nothing arrives.

There is one strange thing; during boot up, the green LED comes on and goes off very quickly. It is on for less than a second. Is this normal ? With a 1541 drive you'd expect the (red led in that case) be on for a couple of seconds before
going off.