| bh | Microtel VTX-202 Telidon Terminal Unit Log |
| Manufacturer: | Microtel |
| Model: | VTX-202 |
| Serial Number: | 569 |
| 1981 (date stamps on various ICs) | |
| Date of Receipt: | 2015 Sep |
| Source: | SPARC |
| State upon Receipt: |
Missing keyboard.
Written on top: "Telidon Display Terminal/ Works very well, internal dialer, etc. / $15.00". |
| Date: | 2015 Sep |
| Procedure: | On first power-ups, display is filled with red DEL characters. On later power-ups, Telidon boot display is drawn. Convergence appears to be off somewhat, blue drive is intermittent or slow to warm up, intermittent alterations in colour of one of the boot-drawing rectangles. Horizontal hold also needed tweaking. |
| Date: | 2015 Sep |
| Procedure: | Cleaned with some wiping and dusting. |
| Date: | 2015 Sep |
| Procedure: |
Communications and configuration elements of decoder electronics reverse-engineered.
ASCII characters successfully displayed via transmission through RS-232 DB25 port. NAPLPS escape codes based on Dillon article ineffective however. Telidon protocol codes may differ from NAPLPS. Could use Telidon protocol doc. Jumpers of IC31 replaced with 8-unit DIP switch block. Jumpers of DIP-6 replaced with new header. |
| Date: | 2015 Sep |
| Procedure: | Leaking internal batteries removed. 2 button cells were present, not clear whether the 3rd position was for a cell or used as a switch. Cells were labeled 50mAh. Some corrosion on PCB scraped off. |
| Date: | 2015 Sep |
| Procedure: |
Top corner mounts of monitor adjusted with neoprene washers, mounting frame was bent slightly to accept monitor.
The installed monitor, while dated 1981, appears not to have been the type the terminal interior was actually designed for.
Blue drive and bias adjustments on monitor tweaked to brighten blue display level. Much improved and more consistent with the red & green. Colours at this time seem stable, although convergence is still off slightly in some screen areas. White now looks like white. Horizontal hold trimmer was erratic, cleaned with alcohol, much better. |
| Date: | 2015 Sep |
| Procedure: |
NAPLPS test code successfully displayed.
Code based on 1983 BYTE articles, sending SO to get to PDI set.
Dillon specification does not apply, ESC 25 41 not needed to get into NAPLPS mode.
After running for a couple of hours vertical sync was lost (not necessarily a monitor fault). Powering cycling brings up screen of DELs. OK after turned off for awhile. Reset switch added to rear panel so decoder can be reset without power cycling. IC socket soldered at location DIP-2 to accommodate plug to reset switch. |
| Date: | 2015 Oct |
| Procedure: |
Data from the 4 firmware ROMS and 2 address-mapping PROMS captured.
2 colour-encoding PROMs remain to be done.
In process of removing 68A09, pin 20 bent at right angle. Bent back and works but metal will be fatigued. |
| Date: | 2016 Apr |
| Procedure: |
Unit returned from Victoria for monitor repair.
Vertical height of raster collapsed by about half.
Tweaking vertical size adjustment will bring back height, but with foldover at top of raster.
Upon removal of monitor circuit board, long crack in board found, which had been previously repaired. Reworked to improve workmanship but does not solve height problem. Monitor reverse-engineered to produce schematic. Voltage noticed to be dropping excessively at collector of TR202. C407 bad, dried out and may have been overheated. Replaced with 15uF/200V from a CFL. |
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Unit Log
Microtel VTX-202 Telidon Terminal |
bhilpert 2015 Sep |