80's Strand CD80 Problem

[RussWig]

21 hours ago, DrV said:

Here's a partial schematic of what you have. The pins are numbered from the top and A is the component side, B is the solder side. As you can see R1 has no bearing on how the circuit works. If my guess is correct about the two invisible diodes in the bottom right (D5 and D6 in my schematic) then what you get is a train of pulses at twice line frequency on pin P2B. These are -ve going w.r.t. the +V rail and their amplitude is adjustable by the trimpot. As most things Strand of this age use -ve signalling this makes sense as the zero cross point is nice and clearly defined at the time when the waveform is at its most positive i.e. equal to the +V rail.

I still think you'll find that C1 is the problem as any ripple on this line is going to affect the level of this waveform.

I haven't completed the bit around Q1 as I can't see where it goes and K1 is still mystifying me! If you do get a chance to give us more info on K1 please do as it troubles me...😒

Dave

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...

[RussWig]

On 2/14/2022 at 10:52 AM, RussWig said:

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...

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...

 

[RussWig]

On 2/13/2022 at 1:15 PM, DrV said:

Here's a partial schematic of what you have. The pins are numbered from the top and A is the component side, B is the solder side. As you can see R1 has no bearing on how the circuit works. If my guess is correct about the two invisible diodes in the bottom right (D5 and D6 in my schematic) then what you get is a train of pulses at twice line frequency on pin P2B. These are -ve going w.r.t. the +V rail and their amplitude is adjustable by the trimpot. As most things Strand of this age use -ve signalling this makes sense as the zero cross point is nice and clearly defined at the time when the waveform is at its most positive i.e. equal to the +V rail.

I still think you'll find that C1 is the problem as any ripple on this line is going to affect the level of this waveform.

I haven't completed the bit around Q1 as I can't see where it goes and K1 is still mystifying me! If you do get a chance to give us more info on K1 please do as it troubles me...😒

Dave

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...

[DrV]

Hi Russ, you've drawn K1 as a triac and the way you've drawn it the fan would be running from the low voltage D.C. rail on C1. I suggest you redraw it as a conventional relay and it will make more sense. I haven't got my notes in front of me but I think the second mains fuse was for the fans. So the 'coil' connections would be on the 1k resistor and the V+ rail and the 'N/O contact' connections would be between the second fuse and the edge connector contact.

None of this part of the circuit has any bearing on the fault you are seeing of course - all it does is utilise the V+ rail to energise the fan relay.

I'll be very surprised if replacing the cap doesn't fix the issue.

Edited February 21, 2022 by DrV
Typo

[RussWig]

29 minutes ago, DrV said:

Hi Russ, you've drawn K1 as a triac and the way you've drawn it the fan would be running from the low voltage D.C. rail on C1. I suggest you redraw it as a conventional relay and it will make more sense. I haven't got my notes in front of me but I think the second mains fuse was for the fans. So the 'coil' connections would be on the 1k resistor and the V+ rail and the 'N/O contact' connections would be between the second fuse and the edge connector contact.

None of this part of the circuit has any bearing on the fault you are seeing of course - all it does is utilise the V+ rail to energise the fan relay.

I'll be very surprised if replacing the cap doesn't fix the issue.

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...

 

[DrV]

It's not very clear but this datasheet  shows it to be a much more realistic 5A 120V r.m.s. device. Don't sweat it - assuming the fan(s) are ok, once you've replaced the cap all will be well!

[indyld]

I mostly work on multi layered boards without schematics. Continuity mode is the way. 

[Bryson]

If you decide not to do component-level repair, or if you need hard-to find parts, Johnson Systems (of Calgary, Alberta, yes my bias is showing) are generally the people to talk to about replacing the control side of CD-80s and keeping them going.

[RussWig]

8 minutes ago, Bryson said:

If you decide not to do component-level repair, or if you need hard-to find parts, Johnson Systems (of Calgary, Alberta, yes my bias is showing) are generally the people to talk to about replacing the control side of CD-80s and keeping them going.

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...

[Bryson]

Indeed, they want to replace the control electronics rather than repair the originals.

[RussWig]

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...

[DrV]

Great. As far as calibration is concerned, I wouldn't worry too much. The setting won't have changed significantly from the last time it was calibrated so if the dimmers are behaving as expected then it will be fine. If you'd replaced something like the transformer then you would need to calibrate it but replacing the cap won't have changed anything much. If you want to check it, connect a decent load to one channel that is on that phase and check the a.c. output at full and 10% then connect the exact same load to a channel on another phase and compare. Perhaps also monitor the input voltages too to check it is the same.

Glad you've got it going anyway.

Dave

[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...