[vcf-midatlantic] Repairs to a Heath WH19 Terminal

Matt Patoray mspproductions at gmail.com
Thu Mar 16 00:07:59 EDT 2017


Jason,

That is great news! That is also too much AC on a DC rail, I would suspect those caps and get replacements, 1500 uF would be hard to find but a 2200 would be ok in this case, remember those older electrolytics may have a tolerance of -20% +85% and modern caps are all +- 20% or better. 

Sent from my iPhone

> On Mar 15, 2017, at 10:17 PM, Jason Perkins via vcf-midatlantic <vcf-midatlantic at lists.vintagecomputerfederation.org> wrote:
> 
> Replacing the shorted cap and blown current limiting resistors results in
> signs of life!
> 
> https://goo.gl/photos/nk5kvxuCT2VGztgf6
> 
> Good: The terminal works! https://goo.gl/photos/TPoPQ1c8QajthkZM7 (yes, I
> tested with a loopback adapter, then with a usb to RS232 adapter before
> hooking it up to the Lisa :) ) The terminal draws 51 watts running. Nothing
> inside seems to be getting unusually hot.
> 
> Problems: The display has a major wave.
> https://goo.gl/photos/wXKydMr5syKU1SWd7 Guessing there are more bad caps in
> the video section. The 65V input, and 53V rail in the monitor have .5v of
> ac ripple. Perhaps the big 1500uf electrolytic is going bad...
> 
> The keyboard didn't work very well at first, but after typing on it for a
> bit it now works perfectly.
> 
> -J
> 
> On Mon, Mar 13, 2017 at 12:10 PM, Jason Perkins <perkins.jason at gmail.com>
> wrote:
> 
>> Man what a small world... My other big not-work time investment is
>> TDIClub, looks like the OP of that article is into TDIs a bit as well!
>> 
>>> On Mon, Mar 13, 2017 at 11:56 AM, Neil Cherry <ncherry at linuxha.com> wrote:
>>> 
>>>> On 03/12/2017 11:25 PM, Jason Perkins via vcf-midatlantic wrote:
>>>> 
>>>> You were right, the big .22 600v cap C232 was shorted. I've placed an
>>>> order
>>>> from DigiKey, hopefully the impending snow doesn't delay things too
>>>> badly.
>>>> 
>>>> -J
>>>> 
>>>> On Sun, Mar 12, 2017 at 6:55 PM, David Gesswein via vcf-midatlantic <
>>>> vcf-midatlantic at lists.vintagecomputerfederation.org> wrote:
>>>> 
>>>> On Sun, Mar 12, 2017 at 05:43:22PM -0400, Jason Perkins via
>>>>> vcf-midatlantic wrote:
>>>>> 
>>>>>> 
>>>>>> There aren't many things on that ground return from the flyback, I'll
>>>>>> 
>>>>> take
>>>>> 
>>>>>> them out one at a time till I find the shorted part.
>>>>>> 
>>>>>> The caps to ground look like the most obvious path to create a short.
>>>>> 
>>>> 
>>> Queue eerie Twilight Zone Music:
>>> 
>>> http://hackaday.com/2017/03/13/raspberry-pi-hitches-ride-ins
>>> ide-vintage-terminal/
>>> 
>>> ... but he quickly determined that a bad cap was shorting out the -12VDC
>>> rail ...
>>> 
>>> hehe
>>> 
>>> --
>>> Linux Home Automation         Neil Cherry       ncherry at linuxha.com
>>> http://www.linuxha.com/                         Main site
>>> http://linuxha.blogspot.com/                    My HA Blog
>>> Author of:      Linux Smart Homes For Dummies
>>> 
>> 
>> 
>> 
>> --
>> Jason Perkins
>> 313 355 0085 <(313)%20355-0085>
>> 
> 
> 
> 
> -- 
> Jason Perkins
> 313 355 0085



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