{"id":534,"date":"2016-01-31T23:20:38","date_gmt":"2016-01-31T23:20:38","guid":{"rendered":"http:\/\/int03.co.uk\/blog\/?p=534"},"modified":"2021-03-08T18:08:45","modified_gmt":"2021-03-08T18:08:45","slug":"vectrex-repair-black-screen-no-vector","status":"publish","type":"post","link":"https:\/\/int03.co.uk\/blog\/2016\/01\/31\/vectrex-repair-black-screen-no-vector\/","title":{"rendered":"Vectrex Repair (Black Screen \/ No Vector)"},"content":{"rendered":"

I’ve wanted a Vectrex Console for quite a while, and finally acquired a broken Vectrex for a reasonable price on eBay (where else) with the idea of repairing it…<\/p>\n

It didn’t begin well when the courier who delivered the package left it hidden behind a car… overnight… in the rain:<\/p>\n

\"hermes1\"<\/p>\n

It was sitting in a puddle, and got a fairly good soaking. Here’s the Vectrex emerging from the box:<\/p>\n

\"hermes3\"<\/a><\/p>\n

Fortunately, after drying it out carefully, it didn’t look like it had sustained any serious damage, so I set about trying to repair the fault.<\/p>\n

Exactly as described by the seller, when it was powered on, the game sounds were playing, but the screen was completely black, not even a white dot visible on maximum brightness.<\/p>\n

Looking at the troubleshooting guide<\/a>, the first suggestion for “No Vector” is to “check for +\/-5 VDC and -13 VDC at connector J204. Left to Right -5, GND, +5, -13”. When I checked J204 on the Logic Board, the -13V DC rail was missing (just measured about 0.67V which looks like a diode voltage drop). I checked the other end of the -13V wire on P204 on the Power Board, with the same result. This confirmed the wires and connectors were OK, and it was a problem on the Power Board.<\/p>\n

From the service manual<\/a>, here’s a diagram of the -13V power supply circuit on the Power Board:<\/p>\n

\"vectrex-13v-repair1\"<\/a><\/p>\n

The two lines at bottom right are the incoming power supply which is about 9~10V AC. The Diodes D106 & D107 and the Capacitors form a voltage doubler, boosting this to 18~20V, which is then regulated by a 13V Zener DZ102.<\/p>\n

I switched off power and tested D106 and D107 in circuit with a DMM, and it looked as though D107 was short-circuit. The resistor R106 looked fine. Since there were only a few components, and the 34 year old (!) Electrolytic capacitors were probably not in the best shape, I decided to replace the whole -13V regulator circuit.<\/p>\n

The -13V rail is only used by IC301 (the MC-1408P8 DAC) and the circuit diagram even states “TO IC301 PIN3 ONLY” next to the -13V line so, after a quick visual check of the Logic Board and connectors, I couldn’t see any obvious signs of a short on the -13V rail which might cause it to fail again. It’s always worth checking before replacing parts though!<\/p>\n

To do this repair, the whole Power Board needs to be removed, which involves removing 5 connectors, removing the HV lead (CAUTION: ensure it is discharged first<\/strong>) and desoldering 2 ground leads, 3 power leads and 4 leads connecting the CRT deflection yoke. The board is secured with two small cross-head self tapping screws.<\/p>\n

Here’s a close up of the components to be replaced (C120, C121, C122, D106, D107 and DZ102):<\/p>\n

\"vectrex-13v-repair2\"<\/a><\/p>\n

This picture highlights them more clearly:<\/p>\n

\"vectrex-13v-repair3\"<\/a><\/p>\n

After removing the components, the most difficult part of the repair was clearing solder from some of the holes connected to the ground plane…<\/p>\n

Once the original components were removed, I was able to test them out of circuit and found the following:<\/p>\n