I work at a small college that has a Contel Executone 3672 phone system installed. It's been there since the early 90's. This morning, all the phones in the building started ringing at the same time. When you pick up the handset all you hear is a lot of "high-voltage" static. I have reset the system several times, cleaned the various components, etc. but nothing has worked. Everytime I turn the system back on, all the phones start ringing continuously. My question is this: What's the best way to troubleshoot my problem? Should I be looking at replacing the ring generator unit or the DC/DC Converter or something else? Any help on this would be greatly appreciated.

My guess would be the DC/DC Converter. It's been so long...someone else will jump in and I will grab my book when I get home tonight and check back.

The DC/DC converter has test points on the front face. Check them with a good digital voltmeter. The +5 volts DC is perhaps the most likely culprit since it affects the processor and IC's directly. I seem to recall that there is a screw-type adjustment that can be made but please be very careful in turning it, as in fractions of a tick while you watch the meter. If anything, try adjusting it downward first to get a feel for the sensitivity of the adjustment process.

If that doesn't have any positive effect, chances are that you will need a new DC/DC card. That's about the only thing that fails in those systems and it's usually due to excessive heat. You may also want to try leaving the cover off and even pointing a fan toward it to see if there's any change in behavior. Fortunately, I don't think you will have too much trouble locating a replacement since that was quite a popular system.

I metered the front test points and I'm getting 3.8 v on both the +5 and +14 ports. When I try to change the +5 adjustment screw, there is no change whatsoever in the voltage reading at either test point. I'm assuming from this that the DC/DC board is shot. I guess I'll check ebay.

Please don't check e-bay for something like this. PM sent.

I have a new DC/DC converter installed and still have a problem. When I turn the system on and meter the test points, I'm getting 14v on the +14v test point, but only 2.2-3.6v on the +5v test point. Is this correct? Turning the adjustment screw causes all the relays in the system to click like crazy and then the +5v led gets real dim. Maybe something else could be the problem? Any help would be greatly appreciated.

I would say that is out of tolerance, in skimming through the manual I didn't find the tolerances. It looks like you got the plus 14, I think I'd put a meter on it and start pulling packs to see what's dragging it down. Do all your testing from the blocks so as to eliminate any possible cable problems. Your voltage should be close to 5.

Found the tolerances in section 801, your only allowed 1%, which would be about .5volts. I'd check them all while your at it to see if everything in within specs.

I just detached the ring generator unit and now the system meters perfectly. I'm thinking a power surge may have damaged the RGU. Sound possible?

Anything is possible, that's why I suggested what I did. See if other features are working without the ring generator.

Okay, I have replaced the Ring Generator Unit (Part #2993607) and the voltages are perfect. I'm getting +5v and +14.08v. My problem now is that when I first pick up a phone and listen for a dial tone, the dial tone is not steady--it makes the same sound that you would hear if you placed a "do not disturb" feature on your phone. After about 3 seconds, the sound changes to a normal dial tone sound. If you try to dial any extension or "9" to access an outside line, all you hear is the sound you get when a phone line is unavailable. Does anybody know whether this might be the EPB card? I've tried pressing the round black reset button on this card, but no difference.

Have you gone through the programming? Have you taken a couple of phones to the block and connected them there to eliminate any possible cable problems? Unplug all the station cables or pull the packs, except the one your testing and test from the blocks, if it's not a programming issue. Personally I wouldn't replace any more packs until you've tested further. Did this take a power or lightning hit?

Edit: I see you suspect a power surge, if this is the case you could have many bad packs. start with just the processor and one pack and see what works and what doesn't, again do this from the blocks.

I have not gone through the programming. To be honest, I'm not sure how to do that. Is there a service manual available that would explain the process? If so, how could I get a copy?

Yes there are. Just click on the manuals link at the top of the page. You could pull all packs except one station card and processor and see what you get also.

After acquiring a manual, I was able to initialize the system and get the system into a partially functional state. Individual phone extensions can now dial one another, but the phones do not ring, only the ringer led lights up on the phones. Also, phones cannot access outside lines when they press '9'. We can receive calls from the outside world, but no ringer--only leds lighting up. I've read through most every page of this manual and I'm having difficulty determining if I'm still dealing with programming issues or bad hardware. Any thoughts?

When you say the phones don't ring, are you referring to the multi-line sets, the analog sets or both? Since you have initialized the database, remember that only extension 100 will ring on incoming calls, so some programming of the CO lines will certainly be required.

You may also need to identify the station type. It's been years since I worked on this system, but I know that other systems that were similar in architecture had this requirement. Check the manual under station programming, specifically on programming page B to see if there's anything there about station ID.

The ring generator only applies for analog (single line) telephone sets, so this would not affect ringing on multi-line sets. Have you tried taking a known working single-line set and connected it directly to the blocks?

As for the outgoing "dial 9" issue, you probably have more CO line ports than you have actual lines. Place the unused CO line ports into trunk group 0 and that should solve your outward dialing problem.

Okay, station IDs are all set to '0' for 'keyset' by default, so I'm not sure if anything there needs to be changed. We've got five incoming lines, so I do have more ports than actual lines. How do I place the unused port into a trunk group? The manual doesn't use the exact same language and I'm a little fuzzy on proper procedure. Also, multi line phones are ringing, but SLT phones do not. Thanks so much for everyone's help. I feel like I'm learning a heck of a lot in a short time from some very experienced people.

You answered your own question as to why the SLT's don't ring. You have to remove all non-used CO lines. I think it maybe time to seek some help locally.

It sounds as if your replacement ring generator may not be good or at least not properly connected. It's only used to ring single-line sets.

By default, all CO line ports are in group 1, which is accessed by dialing 9. When you dial 9, the last equipped CO line port will be seized. Since you only have five lines, you'll need to place lines 6 through 36 into another group, preferably group 0. I am shooting entirely from the hip here, but I believe that you'll find it under CO line programming in the manual.

Section 701 system programming. Then use programming reference guide also, it's in the back of my manual. Read though it first, CO Line Groups are under flash 30 (Ed was correct 0 is non used).

Ed he stated all sets were defaulted to key sets.


Edit: Station types are under flash 40 (to change to SLT)

Thanks for all your help. After moving lines 6 through 36 to Line Group '0' I was able to access outside lines. Also, I was wrong about all sets defaulting to key sets. Everything is functional as of this moment...thank goodness. I truly appreciate everyone's input. You have helped me save our college hundreds of dollars in repair bills for which I'm very grateful.

Thanks for letting us know, glad you're up and working. :thumb: