[sebhc] H89 strange problems....

[Dwight Elvey]

Hi
 If the rectifiers don't fix it, try a different
version of HDOS or at least a different boot disk.
The fact that the drive is also acting up is real
suspicious. Also, that both units are having the same
problems. I'm thinking that there may be an issue
with the drive head load. If it is being turned on
and off rapedly it might cause funny things to happen
the fact that the video is doing funny things sounds
like some form of ground coupling. You might check
with your scope, the logic ground at several places
relative to the filter cap on the power supply( including
the video circuits ). Don't forget to look at the 12v
lines as well.
Just some more thoughts
Dwight


>From: davidwallace2000 at comcast.net
>
>A couple of other possibilities (remote ones, but...)
>
>1.  Magnetic fields from some piece of equipment nearby
>
>2. 
>
>-------------- Original message -------------- 
>From: "Robin England" <robin.england at dial.pipex.com> 
>
>> Thanks guys! I was beginning to think I was going crazy! I'll replace the 
>> bridge rectifier and solder the connections directly, will let you know the 
>> results! 
>> 
>> 
>> ----- Original Message ----- 
>> From: "Joe Smith" 
>> To: 
>> Sent: Wednesday, January 18, 2006 5:37 PM 
>> Subject: Re: [sebhc] H89 strange problems.... 
>> 
>> 
>> > I used the big rectifier that Radio Shack used to carry..Part NUmber 
>> > is: 276-1185 
>> > 
>> > At 11:56 AM 1/18/2006 -0500, you wrote: 
>> > > Robin; 
>> > > 
>> > > Those are hum bars in your video, and your troubleshooting is in 
>> > > the right area -- the power supply. One weak point in these units 
>> > > is the bridge rectifier. It's the large one in a metal case with 
>> > > four push-on terminals. Replace it with one rated for higher current. 
>> > > 
>> > > While you're at it, replace the connectors with soldered 
>> > > connections to both ends of the wiring to the bridge. The molex 
>> > > connector would frequently fail from overheating due to the current 
>> > > it carried. Soldering the wires to the bridge and the circuit 
>> > > board will remove this as a future problem. 
>> > > 
>> > > After fixing many of these back in the day, I sent it in to 
>> > > Heath/Zenith and they published it as a service note. 
>> > > 
>> > > Paul Pennington 
>> > > Augusta, Georgia 
>> > >-- 
>> > >Delivered by the SEBHC Mailing List 
>> > 
>> > Joe Smith 
>> > joebandit 
>> > jtsdadinaz 
>> > Conbuilder debugger /Programmer 
>> > 
>> > -- 
>> > Delivered by the SEBHC Mailing List 
>> 
>> -- 
>> Delivered by the SEBHC Mailing List 
>--
>Delivered by the SEBHC Mailing List


--
Delivered by the SEBHC Mailing List