Phone Systems

Previous Thread
Next Thread
Print Thread
Rate Thread
Joined: Mar 2005
Posts: 25
OP Offline
Joined: Mar 2005
Posts: 25
I've had a 1A2 system with a 620A modular panel and a 641A modular panel with a 79B2 power unit using 4 CO lines on the 620A and one MOH on the 641A), which has been working perfectly for several years. Without warning the lamps on all four lines quit working. Additionally ringing on inbound calls rings continuously. I have dial tone on all lines and all telsets dial out correctly (without illuminated lamps) and all sets receive calls (with continuous ringing and no illuminated lamps). Hold does not work (disconnects inbound call after depressing hold button). There is a Melco ICM on the 5th line which continues to work correcting including buzzing appropriately and the lamp lights.

I have checked all fuses multiple times including with a continuity tester even though the pop-out is not out on any of the fuses. All the power unit fuses are tested with continuity tester and don't appear blown). I have rotated all the line cards with no difference in performance. I have replaced the interrupter with others of same model from two other power units. I have moved the interconnect cable from the 620 panel to each of the four jacks on the power unit to insure that the jack is okay. The interrupter motor does not make a sound, although I'm not sure it actually does on this unit. My experience with interrupters is only on a 551B shoebox.

I've exhausted all the tests I know how to perform.

Bottom line: None of the lamps illuminate and the ringer on inbound calls is continuous rather than interrupted.

Any suggestions on how to proceed? 10vac supply fried? Interrupter fried?

Bill Bentsen

EMP & Lightning Home Surge Protection
EMP - Click Here!
Joined: Feb 2005
Posts: 12,291
Likes: 2
Online Content
Joined: Feb 2005
Posts: 12,291
Likes: 2
Any suggestions on how to proceed? 10vac supply fried? Interrupter fried? I've exhausted all the tests I know how to perform.

Without even thinking further, did you check the voltages to see if they are all there?


Last edited by hbiss; 01/22/21 03:43 AM.

CALIFORNIA PROPOSITION 65 WARNING: Some comments made by me are known to the State of California to cause irreversible brain damage and serious mental disorders leading to confinement.
Joined: Jan 2005
Posts: 15,287
Likes: 3
Moderator-Vertical, Vodavi, 1A2, Outside Wire
Online Content
Moderator-Vertical, Vodavi, 1A2, Outside Wire
Joined: Jan 2005
Posts: 15,287
Likes: 3
Your 10 volts AC output from the 79B2 has failed. This voltage is used for all lamps and the interrupter motor. If you can locate the ST terminal in the upper left quadrant of the 620 panel, touch a known good ground to it. If the motor starts running, then it is you lamp ground that is missing. Again, this is an issue within the power unit itself. You might want to try to common all of the ground terminals on the power supply together just in case.


Moderated by  ChrisRR, EV607797, Silversam 

Link Copied to Clipboard
Advertising Sponsor
Most Recent 5 Post
Coaxial Cable
by dexman - 03/04/21 03:53 AM
Netlink or CCIS
by Yoda - 03/02/21 02:32 PM
SX200 ICP & ASU Bad ports
by Barrontel - 03/02/21 03:15 AM
NEC SV8100 Inmail Utility
by Sam Juniper - 03/01/21 11:02 PM
IP office and routing calling groups
by High Mesa Communications - 03/01/21 10:56 PM
Popular Topics (Views)
Forum Statistics
Most Online5,661
May 23rd, 2018
Today's Birthdays
Newest Members
Sam Juniper, B Ledford, Jonie4, James Wright, TechnoloJay
49,425 Registered Users
Get Tech Support Now! Click the banner below
Get Tech Support Now!
Top Posters (30 Days)
dexman 23
Ruben 22
pvj 11
Linked Banner to your Product or Website
EMP Shield for Commercial - Home & Vehicle
Use Coupon code SAVE - Click Here!
Who's Online Now
28 members (Touch Tone Tommy, phonemeister, sundance, byacey, dexman, RATHER BE FISHING, justbill, hitechcomm, Mercenary Roadie, newtecky, BobRobert, hbiss, jeffmoss26, oldpoleclimber, JBean3329, kjwiewall, High Mesa Communications, Coral Tech, dans, telecom guy10, Daniel, Canteleco, Ruben, Yoda, nfcphoneman, Joel J., Bob3470, Avidcomm), 563 guests, and 48 robots.
Key: Admin, Global Mod, Mod
Custom Island 58
Contact Us | Telephone System Tech Support | Terms of Service

Sundance Communications is not affiliated with any of the above manufacturers.
©Copyright Sundance Communications 1998-2021
Trusted Partners