RussWig

Thanks. As far as calibration goes, I was more concerned with the fact that this system was installed in 1989 and aside from adding a DMX to AMX signal converter, nothing has been done to it. The campus recently replaced several 3 Phase transformers and I was worried that our source voltage may have changed as a result. Just wanted a way to verify that everything is working as it is supposed to. I will try the load test suggested. FYI, all of these boards show between 25 and 26 VDC at J1 & J2. And they read between -9 & -10 VDC at J3, however the board that was causing problems read -11 VDC at J3. RW...

Update: I replaced C1 as well as the crusty R1 on the board that was giving us the problems and it has fixed the issue. It has been in for a week now and "on" 24/7 as a stress test. All is rock solid. I'm going to replace the C1s & R1s on all of the remaining boards. If I can find the time I plan to compare the J3 set point on the boards as they are, prior and post repair. I may even scope J3. My initial check of J1 & J2 shows about 26VDC, at least on the 3 boards in the rack with the faulty one. Still looking through files to find a calibration process but no luck yet. Thanks for all the help! RW...

Yes thanks, we spoke with them but all they want to do is upgrade us to the digital version. Nobody seems interested in fixing the old boards or supplying information as such... The Caps are on order as are the r1 resistors so I think all will be well shortly. RW...

Dave, Yes, you are correct. I found the JTA1205-3 to be defined as both a SSR and a Triac in the spec sheets I found, but I was forgetting that F2 is also tied to the incoming AC (along with F1) to supply the fan. My problems are, without removing the SSR and gaining better access to Q1, I can't really see how they are connected. Traces are not clearly visible. IDing Q1 as an N4922 says it is an NPN with the Collector going to R5, the Base going to connector PA3, and the Emitter going to the Negative Rail (unconfirmed because the pull handle obscures the trace, however I can see no other connection path) and that doesn't seem correct. I still don't have direct access to the PCB so I can't trace continuity. I am ordering new caps as well as new R1s. Based on the data I can find on the SSR it says it is 8VDC but is only rated for a 25VAC output, no current rating. (https://www.onlinecomponents.com/en/ixys-integrated-circuitsclare/jta12053-12693622.html?ref=searchads360feed&utm_term=JTA1205-3&&utm_source=bing&utm_medium=cpc&utm_campaign=1287&utm_term=jta1205-3&utm_content=12693622&gclid=df7ca860f5bc1a8f7a6fca7230b8a3e4&gclsrc=3p.ds) Clarity is not forthcoming...

Dave, After getting a bit more info, here is my schematic. Tell me what you think. https://drive.google.com/file/d/1lh92OXHXZqSZZ5au44nB61w0wbmDJ2Yl/view?usp=sharing RW...

New Info: SSR is a JTA1205-3 and I had a chance to get a couple of more pictures (linked below) Picshttps://drive.google.com/file/d/19O2kIMWgD6WoOye6sRk6k9n7rQya1auT/view?usp=sharing, https://drive.google.com/file/d/1M2_p_THXH99yCN5OjD-geA8whybOqAkl/view?usp=sharing, https://drive.google.com/file/d/1dtN5C6ff5a5ngKND30FcIFOP1E0lDWxZ/view?usp=sharing, https://drive.google.com/file/d/1xPH1-BGwqM7zJD7Y7ABSh49Xruu0iixp/view?usp=sharing Ordering new C1 Caps and R1 Resistors. RW...

Yes, it is an SSR! from the Electronics Section of the 1991 version of the User's manual: " 4.1 Fan Housing A removable Fan Housing at the bottom of the CD80 Rack contains 6-12 Ramp/De-multiplexing cards (usually called "Ramp Cards") and 3 Power Supply Cards. This circuitry converts the incoming control signal to appropriate signals for Dimmer Module power control. A "full rack" Fan Housing contains 12 Ramp Cards. A “top half rack" Fan Housing contains 6 Ramp Cards (#1 -#6). A "bottom half rack" Fan Housing contains 8 Ramp Cards (#1 & #2 for signal sensing and fan turn-on, and #7 -#12 for dimmer control). Fan housings with “split" control (different portions of the rack are controlled by different control consoles) are also available. These are custom units and are not discussed in this manual. A. Ramp Card Ramp Cards provide control signal demultiplexing and analog to pulse width conversion. Up to 192 dimmer levels are time multiplexed on the ANA (analog) line of the control cable (control terminal 4). Levels vary from 0-5VDC, representing dimmer output levels of 0-100%. A differential clock on the CLK- (minus clock) and CLK+ (plus clock) lines (control terminals 1 and 3) synchronizes the dimmer rack with the control console. The multiplexing scheme conforms to the USITT AMX192 Dimmer Signal Specification. 6KW and 12KW dimmers require 2 clock cycles or dimmer positions. Each Ramp Card contains the following circuitry: 1) clock receiver and reset detector 2) counter/decoder circuit 3) analog buffer 4) analog de-multiplexer 5) A.C. zero crossover detector 6) square law curve generator 7) output solid state relay driver 😎 power supply B. Power Supply Card Power Supply Cards condition AC power from the three power phases, and supply AC line reference sources for the Ramp Cards. Each Power Supply Card also has an SSA for fan power (used only in the phase A and phase B cards), which is energized from the Ramp Card when system clock signals are present. A fuse on the Power Supply Card provides overload and short circuit protection for this SSR. " Full manual available here: https://www.theatrecrafts.com/archive/documents/cd80rack_operatorsreference.pdf Also, I have a partial ID of Q1 as N4922 (from a subsequent pix I got): https://drive.google.com/file/d/1A-TklNh-Sz8AhiG5oIyI5qHVX1bkRBnW/view?usp=sharing Thanks All! RW...

Thanks Dave, My analysis is very similar to yours with the exception of they're being any real "power supply" function to these boards. I think they would be better named "power monitor" as they feed a reference signal from each phase to the ramp board in order to inform it. But you may be correct, there may be a local low voltage need that is generated internally on each board. This is why I'm seeking a schematic. Also having limited physical access to the equipment that I'm troubleshooting is not helping. That will change as the current production winds down in about three weeks. Obviously R1 is the prime suspect given its physical condition. I am told that all the boards across the racks exhibit the same overcooked resistor. My plan is to start with this component, changing it to a higher wattage version in order to increase its lifespan. My other thought concerning what the symptoms are telling me, is that possibly a diode has gone out and the reference signal is partially half-waving, but only partially because of the capacitor that is involved. If the reference signal is a sawtooth I could see the ramp board trying to compensate resulting in the varying of the intensity of the associated circuits and dimmers. Again, I'm not on site to be able to actually verify any of this. Thanks again to you and the others for your input on this I will report back as soon as there's something to report! RW...

OK. Here's a link to a Google Drive folder with photos of the PCB: https://drive.google.com/drive/folders/1Eurqza_twW6FjbvtxseQVGnVzBPogeeF?usp=sharing fingers crossed. RW...

Don't know what to say, I pasted them into the body of the message. I'll try putting them on Google Drive and post a link. RW...

Thanks, I put in a request with Service providers on both sides of the pond. Will put up better pix when I get access to the rack again. RW...

Thanks, I just left a request with them. RW...

Best I can do right now. Have no access to the theater at the moment. I put in a request with Service providers on both sides of the pond. Thanks

Hello, I have an old CD80 Dimmer system in my University Theater. (240 dimmers in 3 racks). I am getting an oscilating or pulsing group of instruments who all share the same phase in one of the racks. Moving one of the 03-722777-010 "Power Supply" cards between racks causes the problem to move as well so I'm confident I have found the culpret. I've been looking for replacements or a schematic of the card so I can try rebuliding with new components. There isn't much on the card and aside from the baked R1 I can't find anything obvious. If anyone has a source for parts, or access to a schematic or calibration procedure, it would be most helpful. Strand has nothing in their archive and just want to sell me a digital upgrade...