AUVA JUKO Baby XT BXM-10

[modem7]

Do you have the ability to ground a pin in an ISA slot (connect it to ground) ?

I asked that, because if you do, you could see what the procedure at [here] reveals.

- Substitute 'V20' where you read '8088'.
-For step 1, you can use Ruud's Diagnostic ROM, because it has the byte of EAh at the required location.
-For step 2, you will need to ground pin A10 of an ISA slot.
-For steps 5, 6, and 7, you will need to cater for the fact that you are using a different type of ROM.

 

[fdiskitup]

My hypothesis about the cause of the 'continuous tone' symptom on an IBM 5150/5160 (if experienced) is at [here]. If that is correct, then on an IBM 5150/5160 exhibiting the 'continuous tone' symptom, the symptom would not disappear until the computer was repaired to the point where not only is the motherboard's power-on self test (POST) starting to get executed, but then POST execution gets at least as far as the point that the PB1 pin on the 8255 chip gets configured to output a LOW.

In regard to your clone motherboard, whatever code there is in the ROM that you fit, might be starting to execute, but just not executing far enough in the code to sufficiently configure the 8255 (which on your motherboard, will be within the flatpack chip).

Replacing the flatpack chip might be beyond my soldering skill level… but I could check chip pins with the scope, would help if i could find any information on it. I guess this part was custom, like a ULA to reduce the number of chips, but if its toast then its basically game over.

It will if the port is configured to start at 378h or 278h (the LPT ports that Ruud's diagnostic ROM outputs to). The card's documentation should reveal the answer.

I have a “winbond” multi io that has jumpers for 378h.

Until then, there are some things to try. Do you have the ability to ground a pin in an ISA slot (connect it to ground) ?

Ground from the isa slot to the ground plane on the board ?

 

[fdiskitup]

• From minuszero site : pulses on pin 13 of the 8253 chip - see here. <---- Pulses would indicate that the IBM BIOS ROM (or SuperSoft ROM) is being executed
The 8253 Chip is in the top right corner of the board, must check this tomorrow.

 

[modem7]

Ground from the isa slot to the ground plane on the board ?

Yes, or to one of the ground pins in the ISA connector.

 

[640KB]

My hypothesis about the cause of the 'continuous tone' symptom on an IBM 5150/5160 (if experienced) is at [here]. If that is correct, then on an IBM 5150/5160 exhibiting the 'continuous tone' symptom, the symptom would not disappear until the computer was repaired to the point where not only is the motherboard's power-on self test (POST) starting to get executed, but then POST execution gets at least as far as the point that the PB1 pin on the 8255 chip gets configured to output a LOW.

It's interesting that this would continue to happen with different clone ROMs since not all BIOSes first configure the PIT the way the IBM did (1/2/3 INPUT) which I believe was only for keyboard port based diagnostic codes that nobody else really bothered with (that hypothesis assuming a 5160 BIOS but you've got a Phoenix). I'm surprised that all BIOSes would exhibit that behavior since they all handle chipset setup a bit differently and in a different order. I agree that *something* is happening with the CPU because *somehow* the speaker gate and data are being turned on (and not being turned off) on the PPI. Which other ROMs did you try?

According to this (http://www.minuszerodegrees.net/5160/post/5160 - POST - Some errors.htm) the first expected beep that might occur is video card detection (though if the tone is not your standard beep it hasn't reached the point of setting PIT channel 2 to the standard beep counter). You said you've only tried a VGA adapter... have you been able to try a different video card yet (ideally MDA or CGA)? What happens if you remove the video card entirely... the same? Does doing anything change this behavior in any way - DIP switch settings, remove RAM ICs, etc? What happens if you remove the ROM chip entirely and then power up without it?

 

[fdiskitup]

CPU Swop: I tried the V20-10 CPU in my 5160 board. Seems to be dead ! The psu fan spins but no beeps or video. System still works fine with the 8088 back in place.

Im reluctant to put my 8088 CPU into the baby AT board just incase there is something wrong on the board that would fry it.

Off to ebay to find a V20 D70108C-10….

 

[modem7]

What happens if you remove the ROM chip entirely and then power up without it?

I would certainly like to know if the OP hears the continuous tone when the ROM chip is removed.

( I found an IBM 5150 example of 'continuous tone' at [here]. )

CPU Swop: I tried the V20-10 CPU in my 5160 board. Seems to be dead ! The psu fan spins but no beeps or video. System still works fine with the 8088 back in place.

That does suggest a faulty V20.

 

[fdiskitup]

Tidying up:
Turning on the power with no Bios chip installed still gives continuous tone.
Turning on the board with no cpu installed gives continuous tone.
Tuning on the board with no memory gives continuous tone
Turning on the board with no mem, bios or cpu still gives continuous tone.
putting everything back the (right way arround) still gives continuous tone.

Not even the magical power of deoxit will cure this.
Waiting for the replacement cpu….

 

[fdiskitup]

I got a XGecu T48 eprom programmer, which is actually quite a nice toy! I used it to dump the original bios from the board:
In the actual code it lists the bios version as Phoenix Ver 2.52D dated 04/20/88.
Under the bios label the chip is type "S" 27C64A-20N.
On the Phoenix Bios Label is "1288011" which I guess is just a serial number.
The fact that the rom is readable and has some readable text inside gives me some hope that the bios chip is ok.
I'm still waiting for my CPU from China...
I cant say 100% that this rom will work (yet) - if anyone tries it out let me know...

 

[modem7]

I cant say 100% that this rom will work (yet) - if anyone tries it out let me know...

I put the image into an AT28C64, which I then put onto my very-similar-to-yours motherboard.

The motherboard powered up fine. Displayed was:

Phoenix ROM BIOS Ver2.52D
Copyright (c) 1984-1988 Phoenix Technologies Ltd
All Rights Reserved

It then went on to test the RAM.

 

[modem7]

Turning on the power with no Bios chip installed still gives continuous tone.
Turning on the board with no cpu installed gives continuous tone.
Tuning on the board with no memory gives continuous tone
Turning on the board with no mem, bios or cpu still gives continuous tone.
putting everything back the (right way around) still gives continuous tone.

That is what I suspected.

I'm still waiting for my CPU from China...

There is something else you can try while you are waiting.

In an earlier post, you verified that the POWER GOOD line from the power supply was at a logic HIGH, but that is only testing some of what the POWER GOOD line is meant to be doing.
If the POWER GOOD is not initially LOW (for an adequate period of time) after power-on, the motherboard will not 'start'.
Have a read of the earlier thread at [here], then try the "ground that line for a second or two" that Chuck suggested in post #4 of that thread.

 

[twolazy]

I had a weird issue with my 5160, where it refused to even boot. Turned out the power good wire of the psu connection was dirty and needed to be bent back just a tad. I thought for sure the power supply was dead, or the board I testing was. Went thru 3 boards and none booted till I figured that out. Just food for thought.

 

[fdiskitup]

I put the image into an AT28C64, which I then put onto my very-similar-to-yours motherboard.

The motherboard powered up fine. Displayed was:

Phoenix ROM BIOS Ver2.52D
Copyright (c) 1984-1988 Phoenix Technologies Ltd
All Rights Reserved

It then went on to test the RAM.

Bonza ! a new Bios for the -0 degrees archive.

 

[twolazy]

Well now I need to get a couple AT28C64's lol!

 

[modem7]

Bonza ! a new Bios for the -0 degrees archive.

Added to the bottom of [here].

 

[fdiskitup]

Tried shorting power good (P8-1) to ground and releasing after 2 seconds, no effect.
Will loop back through the other suggestions this weekend.

 

[fdiskitup]

Update: I got 5 “new” nec v20 CPU’s from china.
I removed my 8088 from my 5160 and put the V20 in, without any swearing or bending the pins out or anything like that.
I turned on the power and got nothing. I tried all 5 v20 chips, and got nothing. Put the 8088 back in and it’s fine.
I did a search for problems with V20 and 5160 main board and discovered a post by modem7:

"I had a problem in my early 5160 where after replacing the 8088 with a V20, the machine would no longer start (just like a dead motherboard). If I removed the AST SixPakPlus card, the machine would then start. I discovered that if I updated the first revision BIOS to the third revision one, all worked - I could have both the V20 and the SixPakPlus fitted."

I put the V20 back in and removed the AST 6pak and now it boots with the v20.
my 5160 bios is 11/08/82. I suppose I could update it, but that's a project for another day.

Back to the subject of the thread :
The Juko Baby AT - has known good CPU, has a known good bios.
Memory 44256 and 4164 chips might be suspect,

 

[modem7]

I did a search for problems with V20 and 5160 main board and discovered a post by modem7:
...
I put the V20 back in and removed the AST 6pak and now it boots with the v20.
my 5160 bios is 11/08/82. I suppose I could update it, but that's a project for another day.

Noted is that you are writing about your good IBM 5160, not the subject Juko motherboard.
This explains the behaviour that you wrote of in post #26.
At [here] on my web site, I write of that sometimes seen V20+SixPak behaviour.

Back to the subject of the thread :
The Juko Baby AT - has known good CPU, has a known good bios.
Memory 44256 and 4164 chips might be suspect,

You did swap banks 0 and 1, but yes, there could be multiple faulty RAM chips.
Later, I will see how the Phoenix 2.52D BIOS behaves when there is a bank 0 problem, and report back - I cannot do that test right now.

Is it possible for you to do the test that I pointed to in post #21 ?
For step 1, you can use the Phoenix 2.52D BIOS, because it has the byte of EAh at the required location.

You now have an EPROM programmer. Have you received the parallel (LPT) port POST code reader yet? If so, give Ruud's diagnostic ROM a try, looking at the progress of codes that it sends to the LPT port (at 378h and 278h). Also, we can provide some crude custom code to put into an EPROM, code that sends codes to the LPT port you have at 378h.

 

[modem7]

Back to the subject of the thread :
The Juko Baby AT - has known good CPU, has a known good bios.
Memory 44256 and 4164 chips might be suspect,

You did swap banks 0 and 1, but yes, there could be multiple faulty RAM chips.
Later, I will see how the Phoenix 2.52D BIOS behaves when there is a bank 0 problem, and report back - I cannot do that test right now.

I brought out another XT clone motherboard, verified that it worked, then put the 2.52d BIOS into it.
The 2.52d BIOS displayed what I expected.
I then removed a chip from RAM bank 0, then powered the motherboard back on.
The motherboard appeared 'dead' - no video and nothing from the speaker.

I then swapped out the 2.52d BIOS for 'Ruuds Diagnostic ROM'. A beep from the speaker. The ROM reported on-screen that there was a problem in the first 2 KB of RAM, and as I expected, I observed the ROM send the byte of 8E to the parallel port POST code reader.

Your symptom is different, in that you hear a continuous tone/beep. Based on what you have done and reported so far, I believe that there is a problem on either the address or data buses.

 

[fdiskitup]

I have the parallel post code reader.
With standard phoenix bios it gives “00 FF”. It really doesn’t seem to get anywhere after I flick on the power.
with Rudds Diagnostic rom, i get a short beep, then several things flash on the post code reader before it hangs :
the sequence reads :
01 04
02 00
03 FF
04 00
05 01
06 02
07 03
08 04
09 7E