Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!zaphod.mps.ohio-state.edu!sdd.hp.com!decwrl!shelby!bloom-beacon!world!kenny
From: kenny@world.std.com (Kenneth R Crudup)
Newsgroups: sci.electronics
Subject: Re: IBM monitor repair notes
Message-ID: <1990Sep2.080208.17209@world.std.com>
Date: 2 Sep 90 08:02:08 GMT
References: <55022@iuvax.cs.indiana.edu>
Organization: Software Tool&Die, (Boston), MA
Lines: 39

In article <55022@iuvax.cs.indiana.edu>
  commgrp@silver.ucs.indiana.edu (BACS Data Communications Group) says:

>          IBM MONITOR REPAIR NOTES: MODELS 8512, 8513, 3192
>          -------------------------------------------------

I'll be damned....someone else has to farg with these (I do this kind of
stuff at my when-I'm-not-in-a-contract job. We component level guys get
treated like kings, esp. if you're the only one! :-)

>Symptom:  Horizontal line across screen, remainder black.

>Failed component:  Vertical amplifier (large IC attached to heat sink; 
>TDA-1670A manufactured by SGS, whose quality control is infamous). 
>People at IBM have told us that this chip is a weak point.
>The replacement IC may last indefinitely, or may fail in a few days.
>We have not tried Sylvania's replacement, ECG 1862.

I have. (Can't get anything else quickly). The ECG seems to be OK. One
thing to note- ECG says clearly that Vcc max on these is 35v, which leads to:

>When the IC fails, a 2.2 ohm 1/4-watt resistor in series with the 
>power supply lead (diode and capacitor leading to a flyback pin) burns 
>beyond recognition.  This resistor is used as a fuse.  The value is 
>not critical (may be up to 20 ohms)

I have found that if I use anything less than 20 ohms, I kill the ECG.
I usually stick 33 in there. No problems so far. I think that the problem
the OEM part has is due to an overvoltage situation. Also, another thing
that kills vert deflection is the the large electrolytic on the "cold"
end of the vert deflection coil (sorry I don't have part numbers). Even
though the (highly unreliable) dual-polarity ohmmeter test shows cap action,
the part shorts under load.

-- 
Kenny Crudup, Unix Systems Consultant	nubian!kenny@ima.ima.isc.com
14 John Eliot Sq. #2B, Roxbury, MA 02119-1569	(617) 442 6585

"If you want romance, get champagne. But if you wanna score...get 'Bolt 45'!"