VOGONS


Olivetti PCS33 (386 SX)/M-300 - Repairing

Topic actions

Reply 100 of 113, by pentiumspeed

User metadata
Rank l33t
Rank
l33t

Wait. Start over clean!

Ground is the reference point in point of view of voltages. Simplest circuit is one loop, Battery, resistor and load, anything in between like switch, or a transistor all in series.
When it becomes two or more circuit then this becomes 2 loops, but if you add one extra that defeats the one of loops, then you end up non-functional.

I did not say anything else extra. I was very specific about what you should create the circuit.

I repeat:

Place the resistor of 220 ohms between power good and ground. Explanation: This creates pull down circuit to keep power good low all the time and resistor value is chosen to limit current when power good is pulled high. Now to this circuit place a switch and one 10 ohms resistor between 5V (only!) in series with 5V and power good signal pin, that creates a circuit of two resistors and one switch. When this switch closes this pulls power good signal pin high to 5V level and computer comes out of permanently held in reset mode due to 220 ohm pulled the power good signal voltage low is now pulled high via 5V because 10 ohms resistor defeats the 220 ohms resistor and is now dissipating about 20mA current from 5V to ground via that switch in form of tiny heat which is safe.

Do not overthink or add extra. Just do it what I said.

Ground---220 ohm-----+----Switch----10 ohm----5V

The plus sign "+" goes to power good signal pin.

Cheers,

Cheers,

Great Northern aka Canada.

Reply 101 of 113, by dataino.it

User metadata
Rank Member
Rank
Member

Finally the circuit for the olivetti PCS-11 has arrived and I have also understood the whole pinout of the power connector.

Attachments

Reply 102 of 113, by dataino.it

User metadata
Rank Member
Rank
Member

This is the pinout of the connector, the first pin at the top is the Key-lock, if I leave it disconnected (open) the pc stops at startup and asks to close the key-lock.
For simplicity I have connected it to the Power Good

This is also the scheme to manually generate the reset and the pinout of the connector

Attachments

Reply 105 of 113, by pentiumspeed

User metadata
Rank l33t
Rank
l33t

Yes, still not correct on what is they are for, and a lecture:

Reset signal is to reset stuff, manual or automatic.
Power Good is a signal that power supply is going through intermediate voltages, there is a monitoring circuit in a power supply that controls the power good signal, as power supply starts up then once voltages stabilizes, the power good signal is sent from active high to low *LAST*. Power good is like "whoa, hold your tails while I (power supply) get ready". And this is good reason. If voltages are in intermediate state, can damage or lock up the computer, even blow the ICs somewhere else. Believe, me I have seen this happen!

Your is done same way but this is simpler circuit instead of doing complicated way doing power good signal. Remember this "power good" was IBM started this standard in 1984. But lot of computers from the beginning way back needs automatic reset to start correctly. All computers from the first computer had to be reset manually or automatic, because when everything was powered up, they were in garbage state so reset pulse is sent down to the everything and they go from confused state to beginning of "zero" and running in known in correct configuration then processor starts executing from zero address for example instead of starting in middle of video card's firmware for example. 😀

Apple II and IIe had to be manually reset by hand. Manual calculators has a lever to reset them to zero. Same concept!

The pico-power board have power good signal even in ATX pinout.

Power good is routed through a small circuit that converts this to operate the reset circuit of rest of the motherboard.

If the reset has a line over the word, this means active low. You need to convert power good signal from active low to active high in order to de-assert the reset. In other words when power good is held high the reset is held low till power supply circuit stabilizes then power good signal goes low, the reset is now de-asserted to high and computer starts.

You need a transistor and few resistors to convert high to low or low to high either way. You need a correct way of doing using power good converted to reset signal so this is done correctly and automatic.
Also add a push button connected to the reset pin for manual reset if computer crashes.

Keylock is meant for a key at the front panel to turn off the keyboard, majority of us don't use the keylock anyway. Wire that keylock pin held low permanently and forget it.

Cheers,

Great Northern aka Canada.

Reply 106 of 113, by 1ST1

User metadata
Rank Newbie
Rank
Newbie
Verax wrote on 2021-07-23, 20:12:

Good evening 😀

So, i've just got my POST card as someone mentionned i should try it out to see what happends, so here we go the result :

Olivetti BIOS does not output anything on port 80h POST diagnostics cards. Instead they output on LPT1. In eBay sometimes there are LPT plugs with the LED display which work fine. Anyhow the codes you then will see are not the same as Phoenix, AMI and AWARD BIOS.

Reply 107 of 113, by PTherapist

User metadata
Rank Oldbie
Rank
Oldbie

Thought I'd reply here to ask, since it's related to the Olivetti -

I moved my PCS-11 tonight and must have accidentally knocked the battery out. I reseated the battery + speaker and reconfigured the BIOS. But for some bizarre reason, the CPU is stuck at 8MHz instead of 16MHz. Any of you know what may be causing the CPU to be running at half speed?

I was thinking something along the lines of a Turbo mode, but there's no reference to CPU speed of any kind in the BIOS. Any clues?

Reply 108 of 113, by dataino.it

User metadata
Rank Member
Rank
Member
PTherapist wrote on 2021-10-30, 21:43:

Thought I'd reply here to ask, since it's related to the Olivetti -

I moved my PCS-11 tonight and must have accidentally knocked the battery out. I reseated the battery + speaker and reconfigured the BIOS. But for some bizarre reason, the CPU is stuck at 8MHz instead of 16MHz. Any of you know what may be causing the CPU to be running at half speed?

I was thinking something along the lines of a Turbo mode, but there's no reference to CPU speed of any kind in the BIOS. Any clues?

have u see the advanced bios setup ?

Ctrl + Alt + Shift + Canc

Reply 109 of 113, by PTherapist

User metadata
Rank Oldbie
Rank
Oldbie
dataino.it wrote on 2021-10-31, 10:48:
PTherapist wrote on 2021-10-30, 21:43:

Thought I'd reply here to ask, since it's related to the Olivetti -

I moved my PCS-11 tonight and must have accidentally knocked the battery out. I reseated the battery + speaker and reconfigured the BIOS. But for some bizarre reason, the CPU is stuck at 8MHz instead of 16MHz. Any of you know what may be causing the CPU to be running at half speed?

I was thinking something along the lines of a Turbo mode, but there's no reference to CPU speed of any kind in the BIOS. Any clues?

have u see the advanced bios setup ?

Ctrl + Alt + Shift + Canc

Thanks for this.

In all the years I've had this PC, I had no idea how to get into the extended setup, CTRL + ALT + SHIFT + DEL on a bog-standard keyboard did the trick. I set the frequency back to 16 and I was even able to increase the volume of the PC speaker something which I didn't even know was possible! Plus it let me clock the bus at 12MHz, to give a little speed boost. Very nice indeed.

Reply 110 of 113, by retardware

User metadata
Rank Oldbie
Rank
Oldbie

Sorry for OT:

pentiumspeed wrote on 2021-08-11, 22:52:

Yes, still not correct on what is they are for, and a lecture:
[...]
Apple II and IIe had to be manually reset by hand.

I hate to correct you.
But this is not fully true.
Only the Apple II revision 0 mainboard that was replaced in 1979 by Revision 1 did not have the reset circuit.
Many people upgraded their computers with a reset circuit, as well as some detail upgrades (more NTSC colors etc) that were described in the January 1978 "Red Book" and included in the Revision 1 board.

pentiumspeed wrote on 2021-08-11, 22:52:

Manual calculators has a lever to reset them to zero. Same concept!

Some early scientific calculators like my 1969 Compucorp have a reset key.
Later the "AC" (all clear) key became common, but this is no true hardware reset.

Reply 111 of 113, by zannor

User metadata
Rank Newbie
Rank
Newbie

Hi mates i am new on vogons.

I want to help you with olivetti pcs 33 if possible and i want your help too.

I have an olivetti pcs33 with an operative power supply and video output. I can send info about the power supply if necesary.

My problem is that the conner hd is not been reconiced by the computer. I can use it with no problems in other similar machine but can configure it. I changed the battery and can't hold the date on the computer...

If any of you can help me i can give more info about my problem. Thanks

Reply 113 of 113, by dataino.it

User metadata
Rank Member
Rank
Member
zannor wrote on 2021-12-02, 15:13:
Hi mates i am new on vogons. […]
Show full quote

Hi mates i am new on vogons.

I want to help you with olivetti pcs 33 if possible and i want your help too.

I have an olivetti pcs33 with an operative power supply and video output. I can send info about the power supply if necesary.

My problem is that the conner hd is not been reconiced by the computer. I can use it with no problems in other similar machine but can configure it. I changed the battery and can't hold the date on the computer...

If any of you can help me i can give more info about my problem. Thanks

did you enter the advanced bios with Ctrl + Alt + Shift + Del?