Comet displays help

Rhm

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When I turned on I noticed no displays. Checked all fuses and didn't see nothing obvious. Where do I start? Thanks.
 
You need to check the high voltages on the power supply. They provide power to the displays. Some info can be found here:
http://www.pinwiki.com/wiki/index.php?title=Williams_System_9_-_11#Display_problems
The fact that a fuse isn't blown points to a power supply problem. Most likely you'll find one or more of the voltages are low. It is usually a fairly simple fix involving a few inexpensive parts on the power supply.
 
I checked power supply and have the -100 volts on pin 3 but no + 100 volts on 3j5 pin 4. Now what?
 
Then the components in the table in the document at Pinwiki are suspect. It could be one of them, or one of the resistors (R1 I believe.)

Can you do board repair? If so, order the components in the table from greatplainselectronics.com and you'll be back in business. If it were me, I'd replace all the Zeners (ZR1-4), and the power resistors at R1 and R4. Be ready to replace some of the other components (Q1-4). We're talking a few dollars worth of parts, not much, so buy everything and replace the common components that fail while you are at it.

If your displays are nice and bright, you can lower the voltage to -91 and 91v by replacing ZR2 and ZR4 with 1N4763A diodes instead of 1N4764A diodes. This will increase the life of your displays. If your displays were dim due to age, put back in 1N4763A diodes to keep the voltage at -100 and 100v.

Also be aware that the SDS201/SDS202 in your power supply at Q1 and Q3 are not available any more and the replacements are MJE15030 and MJE15031. When using the replacements, you need to cross the legs. PM me and I'll give you details.
 
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I've never done anything like this before. Is there someone I can send to and would do all that? If so who and how much?
 
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