My dead A410/1 PSU :-(

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2 total messages Started by Glenn Garrett Sun, 04 Oct 1992 16:12

#471

Author: Glenn Garrett
Date: Sun, 04 Oct 1992 16:12

37 lines
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Hello everyone
A question on the Arc PSU (410/1). Recently, I managed to make that
lovely age old mistake of shorting all the power outputs to ground, which
promptly killed my PSU.
 
After having got over the initial shock of realising that the PSU was   
not going to come out of its coma easily (like an old BBC supply would),
I had to connect up an old disk drive power supply I had spare -  
fortunately it was powerful enough to power the computer and hard drive.
 
Anyway it would seem that the main power transistor is gone (short
circuit), along with R4 and the two fuses. There may be other
components too. I would like advice - should I try and get hold of
another power transistor, (but there may be other components too),
or am I going to have to shell out 50 quid for a new supply?? I am not
over well-endowed with money!
 
1. Has anyone made the same mistake as I and what repair procedures were needed?
2. Can anyone tell me the value of R4 as it is burnt to illegibility?           
3. Has anyone got a spare supply going cheap, either new, second-hand or
not working?                                                                    
                                                                                
Any help much appreciated - please mail me direct and I will post a             
summary to the group. Interestingly, my current supply does not have
-5V and the only side effect of this seems to be that the sound from
the computer doesn't work! :-( I think a 7660 IC should cure this 
though if I get time to wire one up.
 
Many thanks - Glenn Garrett, (a normally silent CSA fan).

PS Any comments on the rumour that ARM3's are soon to drop in price? 
_______________________________________________________________________________
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Re: My dead A410/1 PSU :-(

#475

Author: Clive Jones
Date: Sun, 04 Oct 1992 23:27

18 lines
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In article <1992Oct4.161201.224@mnemosyne.cs.du.edu> ggasrren@nyx.cs.du.edu (Glenn Garrett) writes:
>                      Interestingly, my current supply does not have
>-5V and the only side effect of this seems to be that the sound from
>the computer doesn't work! :-( I think a 7660 IC should cure this 
>though if I get time to wire one up.

I expect you'd find the serial port didn't work either. These are the
only two parts of the machine that use -5v.

Personally, I learned my lesson when some inductive effects blew my
BBC Master's PSU, and I subsequently tripped the RCCBs in the lab by
trying to 'scope components under test from mains voltage - fiddling
with power supplies is not that fun. I'd either get a 20-25v
unregulated power supply and put some voltage regulators for the
appropriate levels on the far side, or, better, just buy a proper
replacement PSU - it's what I did.

--Clive.

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