english greek

The Newbrain Forum

Anything about the Newbrain Home Computer

You are not logged in.

Add to: Mr. Wong Add to: Webnews Add to: Icio Add to: Oneview Add to: Folkd Add to: Yigg Add to: Linkarena Add to: Digg Add to: Del.icio.us Add to: Reddit Add to: Simpy Add to: StumbleUpon Add to: Slashdot Add to: Netscape Add to: Furl Add to: Yahoo Add to: Spurl Add to: Google Add to: Blinklist Add to: Blogmarks Add to: Diigo Add to: Technorati Add to: Newsvine Add to: Blinkbits Add to: Ma.Gnolia Add to: Smarking Add to: Netvouz Information

#1 08-07-2015 08:47:42

filbip
New member

(Hover for details)
Registered: 08-07-2015
Posts: 8
Reputation :   

A french AD not booting

Bonjour,

my NewBrain AD (french version) was my first computer. I bought it in 1982/83.
It has not booted for 25 years.
I plugged it yesterday. It started but the display dimmed gradually in 3 or 4 seconds.
It did this 3 times and it did not light up anymore.

I changed the 2 (10uF) timing capacitors with no success.
I still have to check the starting sequence on IC451. I will change other electrolitic capacitors too.
Your suggestions are welcome.

Thanks

 

#2 10-07-2015 06:51:08

Colin
Veteran

(Hover for details)
Location:  : Teesside, England.
Registered: 26-07-2008
Posts: 34
Reputation :   

Re: A french AD not booting

Greetings
Was it the Monitor output that dimmed or the VFD built in display that dimmed. If it was the monitor output then try to replace IC412 (74LS257).If it was the VFD built in display the problem could be the small converter board NewBrain VFD(NEC FIP16ASR) which is a TDK CD-1683N!. Check out my "Service Manual Rev 4" available for download from this website. If you find the problem please let me know so that others can benefit from your experience.
Regards Colin

 

#3 10-07-2015 08:17:52

filbip
New member

(Hover for details)
Registered: 08-07-2015
Posts: 8
Reputation :   

Re: A french AD not booting

Hello Colin,
on first switch on, it booted. I saw "READY" on the VFD before it vanished.
There was no monitor nor TV connected.
Later, I tried to switch on with a TV tuned to c36 but there was no visible signal and no more light on VFD.
I changed the 2 timer capacitors. No luck but the starting sequence on pins of IC451 is OK.
I tested the capacitor #33 (47uF). It was zero uF !
I replaced it with a spare 33uF. No success.
As soon as I receive the replacement capacitors, I open it again, change the electrotitics and check the VFD circuit...
Thanks for the service manual ;-)

I expected to read my old programs on cassettes. Without operational Newbain, I tested the Digitizer v2 and V3 with no success. No more square waveform after 25 years. Even after some Audacity treatments. I can detect some One and Zero but no readable Pilot sequence.
I hope to write a new cassette in a few days to compare ;-)

Regards

 

#4 13-07-2015 22:42:36

filbip
New member

(Hover for details)
Registered: 08-07-2015
Posts: 8
Reputation :   

Re: A french AD not booting

Hi,
no luck. My Newbrain does not boot with some new electrolitics.
I lack some skills to succeed :-(
Regards

 

#5 14-07-2015 06:08:15

kluder
Seasoned

(Hover for details)
Registered: 24-04-2009
Posts: 24
Reputation :   

Re: A french AD not booting

Hi

Have you, voltage from the PSU and can supply the correct power, also referred in Service Manual.
Remember to clean the area around the electrolytes well within the new mounted and change them all even those in the PSU.
Two pages describing repair.
http://www.8bit-homecomputermuseum.at/r … epair.html
http://www.8bit-homecomputermuseum.at/r … brain.html

Greetings
Klaus


use google to translate
 

#6 14-07-2015 16:50:39

filbip
New member

(Hover for details)
Registered: 08-07-2015
Posts: 8
Reputation :   

Re: A french AD not booting

Hi Kluder,
thank you, I did read these pages. They where very useful for my tests.
After a first intervention (timing caps), tensions and start sequence were good on IC451 (O-5V between pins 7-6 and 7-4).
I have already damaged some printed circuit area. I do not have an effective flux for corroded zones under elctrolitics. Now, there is no more 5V between pins 4 and 7 :-(
I prefer to stop here for now.

It was my first laptop in its homemade case :

http://www.newbrainemu.eu/components/com_agora/img/members/123/NewBrainCase1.jpg

This image has been resized, click here to view the full-sized image.

Last edited by filbip (14-07-2015 16:54:58)

 

#7 19-01-2020 13:29:44

filbip
New member

(Hover for details)
Registered: 08-07-2015
Posts: 8
Reputation :   

Re: A french AD not booting

Hello everybody,
five years after, I succeed to boot using the composite video output connected to the SCART connector of a TV.
VFD does not work. There is no voltage on the output of the VFD DC-DC converter.
I can see "Newbrain basic / Ready" on the monitor but the keyboard is unusable.
The bottom line seems to work (repeat, home, space, arrows) but none of the other keys are usable. They give an other character from another key beside.
I can't hit newline so I can't hit "print free" or any command sad

Edit:
Finally I found that DCDC output (-24V) is necessary for reading keyboard. On AD models, no keyboard without DCDC sad
As a workaround without DCDC board, I picked -14V from top leg of the resistor 2 on mainboard near the power socket. I soldered a wire to the pin 3 of the missing DCDC board to feed VBB on pin 13 of IC 406. I can now use the keyboard and verify that all banks of memory are up and running... smile

Edit Jan 31, 2020:
I found a seller in Germany who could provide me a spare TDK CD-1683N.
It revived the VFD but the keyboard went crazy. Characters were displayed without hitting the keyboard. I suspected the instability of the voltages (-24V and -31V) at the output of the DCDC. To filter the ripple I ended up adding two 68nF ceramic capacitors in parallel with the two 10uF filtering electrolytics already changed next to the converter.
The keyboard problem is gone.
This AD is now fully functional cool

Last edited by filbip (31-01-2020 10:02:50)

 


Add to: Mr. Wong Add to: Webnews Add to: Icio Add to: Oneview Add to: Folkd Add to: Yigg Add to: Linkarena Add to: Digg Add to: Del.icio.us Add to: Reddit Add to: Simpy Add to: StumbleUpon Add to: Slashdot Add to: Netscape Add to: Furl Add to: Yahoo Add to: Spurl Add to: Google Add to: Blinklist Add to: Blogmarks Add to: Diigo Add to: Technorati Add to: Newsvine Add to: Blinkbits Add to: Ma.Gnolia Add to: Smarking Add to: Netvouz Information

Forum Tools

Board information

Board statistics
Total number of registered users: 138
Total number of topics: 103
Total number of polls: 0
Total number of posts: 372
User information
Newest registered user: flypie
Registered users online: 14
Guests online: 3726

Powered by Agora 1.0.4 Acropolis

© Copyright 2007 - 2008 Joomla Me!. All rights reserved.

Powered by Elxis - Open Source CMS.
Copyright (C) 2006-2020 Elxis.org. All rights reserved.