Control/Dimming NSI 9800 Issues

[Chris Brooks]

I'm working this summer at a small theater (so little budget for parts) and they have some NSI 9800 dimmer packs. One of them has six of the eight dimmers acting a bit strange. 1-5 will only come up to 50% (5 being a more recent issue), and 7 being burned on. I've found that the issue with 7 is the TRIAC, but I'm not finding any information about the other five. Has anyone had a similar issue with these dimmers, and if so, is there a way to fix the ones only being at 50% or at least would the TRIACs on the ones at 50% be salvageable?

 

[microstar]

According to the NSI spec sheet on the 9800, they use dual SCR's and not a Triac. Haven't taken one apart for a while, so I don't know if that means two discrete devices or an SSR. If two discrete SCR's, going to 50% might mean that one of the two is open. I would try to ID the parts and replace if you are comfortable doing that.

 

[Chris Brooks]

They're surface mount chips. Never have felt comfortable messing with those.

 

[JD]

They're surface mount chips. Never have felt comfortable messing with those.

The parts that failed are not surface mount. Three common configurations: Triac, Back-to-Back SCR, and SSR. All have heavy wire running to them. If any of these devices fail shorted, it's full on. An SSR usually is a single package that actually contains two SCRs inside. SSR/SCRs can fail where one of the SCRs opens, leaving only one working, thus the 0-50% (or somewhere around that point depending on the curve.)

 

[Chris Brooks]

MOC 3022 chips are surface mounted SSRs and the part in question.

 

[Mac Hosehead]

These are very similar to the SCRs used in the NSI 9800.
http://www.nteinc.com/specs/5500to5599/pdf/nte5552-I_58-I.pdf
The SCRs are mounted to an assembly that is screwed to the heatsink. Each assembly contains two circuits and power is connected with spade lugs. A 9800 would have 4 of these.

These SCRs typically fail with a short so the problem circuits could have something other than a failed SCR. A burnt trace on the PCB is a possibility.

The SCR driver chip that you mention, MOC 3022, provides isolation from line voltage but does not carry the current that dims the circuit. It can be another point of failure. I believe it has pins so it is not surface-mount.

 

[JD]

MOC 3022 chips are surface mounted SSRs and the part in question.

MOC3022 is your opto-isolator (Photo triac) and NOT the part you are looking to replace unless it was burned out when your SCR failed.
It is a 6 pin DIP package with leads as compared to an SMD device.
The post above contains a link to a generic SCR that will most likely work in your application.

 

[microstar]

Found these pictures and parts listing for the 9800 on the Full Compass website. Pretty cheap just to replace the entire module:
http://www.fullcompass.com/prod/205298-Leviton-PC044-N00-000

 

[JD]

Found these pictures and parts listing for the 9800 on the Full Compass website. Pretty cheap just to replace the entire module:
http://www.fullcompass.com/prod/205298-Leviton-PC044-N00-000

View attachment 14916 View attachment 14917

Wow! For $29, why even bother with the soldering iron! Good find!!!

 

[garyvp]

I'm working this summer at a small theater (so little budget for parts) and they have some NSI 9800 dimmer packs. One of them has six of the eight dimmers acting a bit strange. 1-5 will only come up to 50% (5 being a more recent issue), and 7 being burned on. I've found that the issue with 7 is the TRIAC, but I'm not finding any information about the other five. Has anyone had a similar issue with these dimmers, and if so, is there a way to fix the ones only being at 50% or at least would the TRIACs on the ones at 50% be salvageable?

We still use three 9800 (25 years old) and have one back up. For the burned ones that are always on, it is the double pair SCR firing cards - there are four in the 9800 - see picture. You have two choices - 1) you can replace the dual SCR cards that are burned out - an easy fix. You can get the parts here:http://www.fullcompass.com/prod/205298-Leviton-PC044-N00-000. All you need is a screw driver and needle nose - Remove the front panel, uplug the card (photo before!), unscrew cars - 20 minutes on the bench. In the attached picture you can see a card where the terminal was fried off from an over load - yours is from a short - where more typically the SCR chip is burned.

Or, 2) If you are handy with circuit boards, you can get the SCR chips from NSA or digikey (cheap) and solder them in yourself .

One thing, this condition is due to instruments that have a direct short coupled with the aging magnetic circuit breakers in the 9800. THEREFORE, you must test each fixture on the bench before plugging it into the dimmer, or you will repeat the problem. After the last time we had this happened (the light tech tried the same shorted instrument in three channels in a row - three new cards). We spent the off season rewiring 30 instruments.

For the other issue you may need a replacement main board(I find them on EBAY some times.) Let me know if you want to pursue this - I may have one.

You could also buy a similar NSI 8800 vs 9800 on EBAY - less wattage, but 8 channels and similar service connections, : http://www.ebay.com/itm/nsi-8800-dimmer-/292129016218?hash=item44043f099a:g:-4gAAOSwurZZJlRb


Good luck on this.

 

[Chris Brooks]

Thanks for the information, especially about what the MOC 3022 does (which is still slightly confusing since there is another opto-isolator chip with each side). However, now the fan isn't working (though I'm not sure if that is from accidentally jostling things while removing/replacing the cards or from the temperature management having previously had issues). Luckily for our first show I can just change the hard patch at intermission.

 

[FMEng]

Fans are a frequent failure item when the bearing lubrication dries out. There are common sizes, voltages, and air flow ratings, which makes replacement pretty easy.

 

[JD]

which is still slightly confusing since there is another opto-isolator chip with each side)

Could be the original design was calling for a photo-scr isolater, which would have required two, and then the bean counters spoke up and said it would be much cheaper to use the photo-triac. Because of popularity, photo-triacs are MUCH cheaper and just as good. Since it would have been a direct drop-in, there was no point to redesigning the board.

 

[Apmccandless]

Call leviton. They still do free phone tech support for these. I had this happen to me a few years ago after a power surge took out another device on the line. Replaced the rs485 chip no help. There are 2 pins inside toward the top of the main board that had to be shorted on boot there was an entire instruction page how to do it that they sent to me but I cannot find it in my email. I will say leviton has given great tech support for these considering how old they are.