Date : Sun, 21 Sep 2003 21:47:17 +0100
From : Andrew Hancock <Andrew.Hancock@...>
Subject: Re: Two BBC Micros need some help!
Okay no further on the power supply problem, so any help tracking power
supply faults would be appreciated.
All I can tell you is the supply 5v/12v/-5v supply looks rather low,
unloaded disconnected from Beeb motherboard.
Testing voltages when connected to the Beeb motherboard loaded, there seems
very little voltage 1v possibly.
It's better with the Beeb No.1 Issue 4 (remember Beeb No.2 Issue 7 just a
broken supply, although now it's alive and well, because I taken good power
supply with good beeb!).
I've found after ready Mike Tomlinson BBC Repair Guide from the archives, I
can get a working Beeb if I remove the 1770 Upgrade Board from IC78 (disc
controller socket). I've replaced all the logic required by this disc
controller interface, and checked all the usually links and "special links
for 1770 disc interface" are correct, but when the 1770 Upgrade Board is
fitted to the IC78 socket, I get a continuous town at power-on.
I've found if I remove the WDC1770 chip from the upgrade daughter board,
that the Beeb power's up fine.
I've not got enough logic at present to install the original 8271 kit that
was removed, I must have used the 4013/4020 elsewhere!
Do you think the 1770 controller chip is duff?
Is it a good test to try and install the original 8271 interface?
Regards
Andrew
-----Original Message-----
From: Andrew Hancock [mailto:Andrew.Hancock@...]
Sent: 20 September 2003 18:47
To: 'bbc-micro@...'
Subject: [BBC-Micro] Two BBC Micros need some help!
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Hi Beeb Fans
I've eventually got around to unpacking some BBC Micro stuff from store. In
went into store in 1986! Unfortunately, the first items unpacked haven't
survived the misuse to much!
1. BBC Micro B No. 1 at power up, Usually Startup Beep stays on.....Cassette
motor relay clicks, and cassette motor LED stays lit.
Issue 4 Board, Model A, expanded by me to Full Model B later as years went
by. Fitted with Acorn 1770 DFS.
2. BBC Micro No.2 Model B at power up does nothing. No lights, no beep, no
cassette motor click.
Issue 7 Board. Fitted with Acorn 0.9 DFS 8271. No other roms, expansion
boards.
Both models were purchased from new and used every day until they went into
storage.
Q1. Any quick tips, guidelines before I download the BBC Service Manauls?
Q2. Which should I concentrate on? No.1 on No.2?
I've done the usually things, ensure all socketed chips are inserted fully,
and I've tested the voltages.....
Beeb No.1 Voltage 5.53v
Beeb No.2 Voltage 4.74v
Beeb No.2 voltage looks a little low, is this within tolerance?
I could swap motherboards over very quickly and check the second
motherboard?
Regards
Andrew
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