CP65 installation issues (adding Cat 441 card)

[PeterClay]

Hi All,

I am having an issue at my cinema trying to install the Cat 441 card Surround and Subwoofer, which seemed to cause the centre channel/eq card to fail. our initial setup was as follows.
4.0 sound L,C,R,LS
NEC projector with IMS1000 - sound going to a DMA8plus
'from digital' terminals on the CP65 from the DMA8 are L,C,R,LS,S/W. the RS from DM8 was connected to the LS terminal.
'to amps' terminals we had L,C,R,LS going to a 4 channel amp a QD 4960, which then went out to the speakers.

Today we tried installing the Cat 441 card to enable subwoofer and stereo surround, setup was as follows.
We left the 'to amps' terminals as they were L,C,R,LS going to the QD4960, we then added a QSC1850 amp using the RS,and S/W terminals.
We then seperated the RS and LS wire from the DMA8 and had the LS, to LS and RS to RS at the 'from digital' terminals on the CP65.

Once everything was in place we installed the Cat 441 card ensuring the jumpers were set to stereo etc... and powered up. We ran some pink noise thnrough the system direct from the projector as we don't have the Cat85c card, and turned each amp channel up 1 at a time. All channels were working playing pink noise except the centre channel.

We did lots of troubleshooting changing cables round etc... from one channel to the other and between amps, and always we would get nothing from the centre.

In the end we reverted everything back to original wiring removing the Cat 441 card, and still the centre channel was no longer working. It was at this point we tried changing the Cat 64 EQ card, (we luckilly had a spare) and thankfully the centre channel is working again.

We are reluctant to try again as I can only assume something we did somehow fried the centre EQ card, but im not sure how this could have happened.

Does anyone have any wiring diagrams showing how the wires should be connected as the only thing I can think of is we maybe put the RS and S/W negative wire to the wrong ground terminal on the 'to amps' part of the CP65.

Sorry for the long post and hope everything makes sense above, if anyone has any ideas or suggestions would be greatly appreciated.

Peter

[Dave Macaulay]

I don't have the CAT441 retrofit instructions and can't recall if it required backplane traces cut - I'm pretty sure it did on a CP55.
The signal path diagram shows no connection between the card and the screen EQ boards. So the CAT64 failing may just be coincidental?
You should be able to use any ground terminal for audio ground or shield, they are unbalanced outputs. Many installers would leave the shields not connected at the processor, only connected at the amp end. I've seen them connected and not, did not hear any hum difference either way.

[PeterClay]

Hi Dave,

thanks for the info. When we powered everything up the pink noise we played was outputting through all the individual channels including the sub and RS channel that I believe the Cat 441 card handles so it seemed everything was wired correctly, the only issue was the centre channel not working which we obviously put down to the installation of the card, and possible ground issue.

im hoping it was just a coincidence as the CP65 was installed around 25 years ago second hand, so the eq cards have done pretty good for that time frame I think, however could it possibly have anything to do with voltages on the qsc1850 amp that we were using and the qd4960? I can’t see why that would matter as the centre channel has always been on the qd4960 and we didn’t change that wiring, but just trying to think of all possibilities before we try doing the upgrade again.

peter

[PeterClay]

another thing I've been thinking is that the fader has always been set to 3 when doing a show, when the installation manual says to setup with pink noise at fader level 7, which is way to loud for our cinema. since putting the spare centre eq card in and re doing the pink noise/eq procedure I noticed that setting the fader to 3 and then adjusting the gain, the gain was already maxed out so I had no adjustment. I've since re done the gain on all the channels lowering the gain on the Cat242 card and setting the fader to 5. Once this was done I played some test footage, and the sound level was still acceptable with the fader to around 3, 3 and a half.

could it be possible that with the cat 242 card having all the gains maxed out, and installing the subwoofer 441 card caused the centre channel card to 'blow' due to too much power/gain or am I over thinking things.

Peter

[Alan Lyman]

I think youre just unlucky.The cat 441 has no influence on the cat64.maybe you took out cards with power on,which is a GREAT no go.That definately can burn a card.
I would try again.


Alan

[Sascha Roll]

Peter, clearly you have no idea how to properly set up a CP. Get a professional technician.

[Dave Macaulay]

Yeah, you're really best to do levels and EQ at fader 7. Then you can set the fader wherever you want for the sound level you really want.
It's also an industry standard.
Yes, sound mixers must be deaf to seriously expect the loudness of most releases if played at 7 - never mind the blown speakers. Maybe they know that almost every cinema plays at 5 or maybe 5.5 and have increased the level of soundtracks to trick us?
At 7 the various channel trims on the CP65 cards should not be at max or min. There are board jumpers to select high or low output signal levels. Opinions differ on the best amplifier gain knob setting, and there is a way to find the optimum setting for minimum thermal noise. But noise is not much of an issue in cinemas, and turning them up all the way eliminates the problem of marking and repeating a setting - plus any changes made are very visible. If the processor levels work out reasonable, I usually set amps to full gain. Personally I dislike fader caps, the most common problem with older amps is dirty faders and the caps make a simple "crank it up and down a few times" fix slightly to very much harder.

Amplifiers, excepting very rare failure modes, have no effect on the device driving them. They just take the analog audio signals from the CP65, they do not feed any voltage or whatever back that could do any damage. I would check the CP65 PS voltages to make sure it hasn't started going bad.

[Mark Gulbrandsen]

Yes, but this must be a really old CP-65... because they normally came with a 441! Installing a 441 in place of a 241 in most cases does require back plane modifications and diode additions. Sorry, it's not normally a plug and play deal because its a later modification. The last one I did was about two years ago in a home screening room. Get someone that is Dolby certified to do the job correctly for you. In the mean time I will watch for a bright flash and resultant mushroom cloud coming from your part of the country. Or in the meant time get a job in the armed forces as a nuclear reactor engineer on board a submarine where if you do any more damage at least the whole mess is contained.

Mark

[PeterClay]

attached is some photos of the back panel showing how it has always been setup, basically as mono surround with no Sub.
I read the installation manual front to back every night for the last 3 or 4 weeks before starting this project and from what i've read the equalisation procedure is pretty simple, i'm simply asking on here if I maybe missed something as to why the centre channel stopped working after installing the Cat 441 card, and when we replaced the eq card it started working again.

What we did exactly from the photos attached was to loosen the terminal screws and removed the entire red blocks away from the processor, which then enabled us to seperate the two red wires seen soldered to the LS terminal on the 'from digital' photo. These wires came from the DMA8 and were labeled left surround and right surround individually so we then re soldered the left to LS and right to RS. We then re-attached the red terminal tabs back to the CP65 and tightened all the screws again checking that the wires did line up with the correct terminals.

Then on the 'from amps' photo we again loosened the terminal screws and removed the red tabs section again allowing us to solder a couple of wires from the S/W terminal and the RS terminal which in turn went down to another amp we had aquired. again once this was done we re-attached it back to the CP65.

The whole time the unit was switched off with the power leads removed so as to avoid any issues.

Once all the physical connections were made and speakers wired into the amps, we then opened the front of the CP65 and installed the 441 card, (we did not remove the eq cards as I ran some pink noise before doing any re-wiring and used an RTA and could see there was no need to change eq settings on the L,C,R channels).

Once everything was installed and double checked all connections we powered up and started testing each channel individually with pink noise, turning up each volume control on each amp channel one at a time. All channels produced pink noise including the now separated LS and RS channels, and the newly added S/W channel, the only channel that was not producing any sound was the centre channel. At this point we powered down, double checked all wiring connections and systematically went through changing cables etc.... to rule out all possibilities. When this did not solve the issue, we decided to revert all wiring back to how it was at the beginning and removed the 441 card. The centre channel was still not producing any sound. It was at this point we found a spare eq card and tried switching it and sure enough the centre channel was working again.

I'm hoping that it was just a coincidence as posted by some above, but posted here for any advice before attempting again. Also the reason for trying this upgrade myself is due to geographically it is not possible to call a technician round (look up www.visitalderney.com and you will see why).

I really appreciate all the advice so far and hopefully we can soon have proper surround sound in our humble little cinema.

To clarify NO SOLDERING WAS DONE TO ANY TERMINALS WHILST ATTACHED TO THE CP65, we always removed them from the CP65 first.

If it does look to be just a coincidence then we will try again, if not, we will look to get our integrator to have a go at their next service visit of the projector, but that will not be for sometime yet.

Peter

[Geoff Newitt]

Hey Peter! Excuse the sales pitch - but we here at Omnex would be more than happy to send an engineer to Alderney! We have quite a good stock of parts for legacy sound processors, and could do a good deal on new equipment, if your budget would stretch that far. I'm sure you can find us via your favourite search engine - we have engineers all over the UK, and a Manchester phone number...

Meanwhile - it sounds to me like an unfortunate coincidence. Cat 64 failures are rare but not unknown. It seems that you have been properly cautious; separating the Ls and Rs feeds from the DMA8+ and changing the outputs to the amps shouldn't stress the Cat 64 in anyway. I'd have to do a bit of digging to remember if backplane mods are necessary when upgrading an early CP65 from Cat 241 to Cat 441 - it was quite a job in the CP55 - but I do have an early CP65 (with a Cat 241, I think) in the pile of junk in my garage, which I'll have a look at when I get the chance.

I'm a big fan of the old analogue processors - they will remain repairable long into the future, while some of the more modern stuff - technically better, for sure - will be undone by the obsolescence of various chips.

[Gordon McLeod]

One other possibility is the bypass relays did they get disturbed ?. Also I would always recomend that one uses the pinknoise card as it does allow a insertion point mid way in the system

[PeterClay]

Hey Peter! Excuse the sales pitch - but we here at Omnex would be more than happy to send an engineer to Alderney! We have quite a good stock of parts for legacy sound processors, and could do a good deal on new equipment, if your budget would stretch that far. I'm sure you can find us via your favourite search engine - we have engineers all over the UK, and a Manchester phone number...

Meanwhile - it sounds to me like an unfortunate coincidence. Cat 64 failures are rare but not unknown. It seems that you have been properly cautious; separating the Ls and Rs feeds from the DMA8+ and changing the outputs to the amps shouldn't stress the Cat 64 in anyway. I'd have to do a bit of digging to remember if backplane mods are necessary when upgrading an early CP65 from Cat 241 to Cat 441 - it was quite a job in the CP55 - but I do have an early CP65 (with a Cat 241, I think) in the pile of junk in my garage, which I'll have a look at when I get the chance.

I'm a big fan of the old analogue processors - they will remain repairable long into the future, while some of the more modern stuff - technically better, for sure - will be undone by the obsolescence of various chips.

Hi Geoff,

thanks for the kind offer. We do actually have a contract with another integrator, and normally in emergency situations we would get them to come over to do any repairs.

this sound project is just something I’m trying to do without the need to get them, however if it did turn out to be something we can’t do (backplane mods) then we would organise with them at their next scheduled service to include sorting out the processor, but I don’t think we are due another service now till around November.

although everything I’ve read regarding backblane mods are for the cat300/350 cards I think, the Spectral recording cards.

next thing we are going to look at before trying again is the power supply and bypass module. We do have 2 spare processors out back with cards so can take the power supply from one of them if it is something wrong with it.

[PeterClay]

Thanks everyone for all the advice. I've attempted installing the card and it all now seems to be working fine. I have done the EQ process and it sounds great now with stereo surround, I have a slight issue with no sound from the SUB but I know that to be either a cable issue or the speaker issue, as I can see there is definitely a signal going from the processor to the amp, when I turn the amp up the signal light illuminates, and if I turn the gain up on the 441 card it starts to clip, and turning the gain back down the signal light goes away. So I just need to do some testing with the cable from the amp to the sub and also some testing with the actual sub, as it is a second hand speaker donated. Other than that slight issue, everything else is great.