ins_asag@jhunix.hcf.jhu.edu (Steven Gabriel) (06/22/91)
I hope it is not too gauche to write to this newsgroup about a dumb terminal, the Z19. I am very fond of it, but the power circuit board gets extremely hot. We have to resolder certain connections periodically to keep it going. I wonder if there are any replacements or tips on how the scorched diodes can be modified/enhanced to prevent this heat buildup. Grateful for any suggestions; the local Heath store does not want to talk about this part.
querubin@uhunix1.uhcc.Hawaii.Edu (Antonio Querubin) (06/27/91)
In article <8783@jhunix.HCF.JHU.EDU> ins_asag@jhunix.hcf.jhu.edu (Steven Gabriel) writes: >I hope it is not too gauche to write to this newsgroup about >a dumb terminal, the Z19. I am very fond of it, but the power >circuit board gets extremely hot. We have to resolder certain >connections periodically to keep it going. I wonder if there >are any replacements or tips on how the scorched diodes can >be modified/enhanced to prevent this heat buildup. Grateful >for any suggestions; the local Heath store does not want to talk >about this part. Zenith came out with a standard mod for the power supply board in both the H/Z-19 and H/Z-89. The mod basically moved one set of secondary transformer leads from a molex connector directly to the large bridge rectifier. This did two things. It prevented the circuit traces on the power supply board from acting like fuses in case the bridge rectifier shorted out. It also prevented the molex connectors from overheating and causing the solder connections on the circuit board to become brittle. After the mod is installed, if your bridge ever shorts, the fuse will work as designed and the circuit will not be damaged. To install the mod, remove the molex connector that attaches to the power transformer secondary. There will be two large yellow wires. Push down on the molex pins and pull the yellow wires out. Cut off the molex pins. Remove the molex connector that attaches to the big bridge rectifier. Identify the leads that carry AC to the bridge. Unsolder these two leads from the bridge and remove them from the molex connector also. Strip the ends of the yellow wires and solder them to the bridge rectifier where the previous two wires had been removed. It's also a good idea to remove the power supply board and resolder any solder connections that look cracked or brittle. When I was a Heath tech, I made it a practice to always do this mod on every H/Z-19/89 that walked into the store.