Re: PC/AT "power good" problems

[Richard Cini]

Thanks guys. Looks like some detailed work to do on the mobo. 

Anyone want to buy a lost tester cheap?

Sent from my iPhone

> On May 29, 2016, at 10:48 AM, Dale H. Cook  wrote:
> 
> At 10:30 AM 5/29/2016, Dwight wrote:
> 
>> Power to a load tester is not the same as power in a system.
> 
> That is why I never use a load tester. I built a system with a set of 
> adaptors that lets me measure voltage and current, and check for ripple and 
> noise with an oscilloscope, for each output of a power supply while it is 
> supplying the target system.
> 
> Dale H. Cook, Roanoke/Lynchburg, VA
> Osborne 1 / Kaypro 4-84 / Kaypro 1 / Amstrad PPC-640
> http://plymouthcolony.net/starcity/radios/index.html 
> 

Re: PC/AT "power good" problems

[Dale H. Cook]

At 10:30 AM 5/29/2016, Dwight wrote:

>Power to a load tester is not the same as power in a system.

That is why I never use a load tester. I built a system with a set of adaptors 
that lets me measure voltage and current, and check for ripple and noise with 
an oscilloscope, for each output of a power supply while it is supplying the 
target system.

Dale H. Cook, Roanoke/Lynchburg, VA
Osborne 1 / Kaypro 4-84 / Kaypro 1 / Amstrad PPC-640
http://plymouthcolony.net/starcity/radios/index.html 

Re: PC/AT "power good" problems

[dwight]

Power to a load tester is not the same as power in a system.
It is likely that one of the other voltages, other than 5V is
being loaded down with a shorted tantalum capacitor in
the system.
I doubt there is a problem with the supply.
Dwight



From: cctalk <cctalk-boun...@classiccmp.org> on behalf of Richard Cini 
<rich.c...@verizon.net>
Sent: Sunday, May 29, 2016 4:16:15 AM
To: CCTalk
Subject: Re: PC/AT "power good" problems

Chuck –

My wording was probably less than precise, but “never comes out of 
reset” means that it never POSTs. Nothing on the screen. No cursor. No boot 
message. No BASIC. Keyboard does reset though (I see the three LEDs blink on, 
then off). I watched for a good 5 minutes before giving up. It’s been a long 
time since I worked with this machine but I’m pretty sure there is a sign-on 
banner or something.

For comparison, I pulled my old original PC (64k/256k mobo) with 
expansion unit and 10mb HD and it took an excruciatingly long time to boot, but 
it did have a blinking underline cursor on the screen while it thought about 
booting.

Rich

--
Rich Cini
http://www.classiccmp.org/cini
http://www.classiccmp.org/altair32

On 5/28/16, 10:30 PM, "cctalk on behalf of Chuck Guzis" 
<cctalk-boun...@classiccmp.org on behalf of ccl...@sydex.com> wrote:

>On 05/28/2016 07:17 PM, Chuck Guzis wrote:
>
>> Bear in mind that the PC AT BIOS during POST goes through some
>> rather arcane protected-mode memory tests, using the CMOS "why did I
>> get here" byte when coming out of reset.
>
>...which reminds me--check the status of the "programmed reset" line
>coming from the keyboard controller.
>
>--Chuck
>

Re: PC/AT "power good" problems

[Richard Cini]

Chuck –

My wording was probably less than precise, but “never comes out of 
reset” means that it never POSTs. Nothing on the screen. No cursor. No boot 
message. No BASIC. Keyboard does reset though (I see the three LEDs blink on, 
then off). I watched for a good 5 minutes before giving up. It’s been a long 
time since I worked with this machine but I’m pretty sure there is a sign-on 
banner or something.

For comparison, I pulled my old original PC (64k/256k mobo) with 
expansion unit and 10mb HD and it took an excruciatingly long time to boot, but 
it did have a blinking underline cursor on the screen while it thought about 
booting.

Rich

--
Rich Cini
http://www.classiccmp.org/cini
http://www.classiccmp.org/altair32

On 5/28/16, 10:30 PM, "cctalk on behalf of Chuck Guzis" 
 wrote:

>On 05/28/2016 07:17 PM, Chuck Guzis wrote:
>
>> Bear in mind that the PC AT BIOS during POST goes through some
>> rather arcane protected-mode memory tests, using the CMOS "why did I
>> get here" byte when coming out of reset.
>
>...which reminds me--check the status of the "programmed reset" line
>coming from the keyboard controller.
>
>--Chuck
>

Re: PC/AT "power good" problems

[Chuck Guzis]

On 05/28/2016 07:17 PM, Chuck Guzis wrote:

> Bear in mind that the PC AT BIOS during POST goes through some
> rather arcane protected-mode memory tests, using the CMOS "why did I
> get here" byte when coming out of reset.

...which reminds me--check the status of the "programmed reset" line
coming from the keyboard controller.

--Chuck

Re: PC/AT "power good" problems

[Chuck Guzis]

On 05/28/2016 02:37 PM, Richard Cini wrote:


> Basically, the PC won’t come out of reset. I tested the power supply
> with a load tester specifically for PC power supplies and it reports
> power_good and all voltages look good on a meter. So far, so good. I
> dug out my ISA POST diagnostics card which also has a PG tester in
> it. This reports no_PG but I do see the reset pulse on the bus. Not
> sure why one would report OK and one not.

Exactly what do you mean by "won't come out of reset", Rich?  How can
you tell?  Is RESET on the ISA bus always active?

Bear in mind that the PC AT BIOS during POST goes through some rather
arcane protected-mode memory tests, using the CMOS "why did I get here"
byte when coming out of reset.

--Chuck

Re: PC/AT "power good" problems

[Alexandre Souza]

Put a 10 or 22 uf on the reset connector

Enviado do meu Tele-Movel
Em 28/05/2016 18:38, "Richard Cini"  escreveu:

> All –
>
>
>
> I pulled my old PC/AT off the shelf to see if I could get Windows 1
> running on it (since I just located the Windows 1.04 SDK which I have
> running in Bochs). It worked when shelved years ago, but it unfortunately
> suffered some case damage from a leaky battery. No damage to the mobo or
> cards thankfully. I replaced the battery with a 4-AA pack.
>
>
>
> Basically, the PC won’t come out of reset. I tested the power supply with
> a load tester specifically for PC power supplies and it reports power_good
> and all voltages look good on a meter. So far, so good. I dug out my ISA
> POST diagnostics card which also has a PG tester in it. This reports no_PG
> but I do see the reset pulse on the bus. Not sure why one would report OK
> and one not.
>
>
>
> I have a spare generic power supply (which also tests good using the same
> tester) and produces the same result. I have no cards installed but I tried
> it with floppy/hard drives both connected or not connected.
>
>
>
> I traced the PG signal from the power supply through the 82284 clock
> driver/ready interface chip and the PG is definitely there (transitioning
> L->H on power-on) and RESET is transitioning H->L.
>
>
>
> Any recommendations on where to go from here? Does anyone
> have an extra PC/AT motherboard they would be willing to part with?
>
>
>
> As an aside, would this have been a typical development machine? AT was
> introduced in August 1984 and Windows 1.04 was released in 1987 so I’m
> guessing probably.
>
>
>
> Thanks!
>
>
>
> Rich
>
>
>
> --
>
> Rich Cini
>
> http://www.classiccmp.org/cini
>
> http://www.classiccmp.org/altair32
>
>