Electrohome G08 Manual

G08 Vector Monitor FAQ & Guide Page 11 of 39   The pinouts for the HV 10-pin header are as follows: 
 
Pin # Description 1 Y 2 X 3 -9.1 VDC 4 +9.1 VDC 5 GND 6 GND (heater) 7 +6.3 VAC (heater) 8 +126 VDC 9 NC 10 VG2 (variable gain; 
part of brightness circuitry)  
 
The HV PCB has three controls on it: R917 (frequency control), R918, and R933 (sensing voltage). 
Frequency control regulates the voltage the transformer puts out. Sensing voltage controls the level 
at which the HV supply will shut itself off...

G08 Vector Monitor FAQ & Guide Page 12 of 39   CRT Neck Board  
The CRT neck board is a 4” x 4” PCB with a large tube socket mounted directly in the middle of it. 
It connects to the end of the monitor tube. The board controls the color guns of the tube. 
 
The neck board has a few controls on it. One side contains a single “blue gain” control, while the 
opposite side has “red cutoff”, “red gain”, “green gain”, “green cutoff”. 
 
The color drive circuits accept a 4-volt maximum signal on the RGB inputs....

G08 Vector Monitor FAQ & Guide Page 13 of 39    
Part Number Summary  
 
This following list summarizes all the Electrohome part numbers for the G08 monitors. These 
numbers do not reflect the issue numbers between the deflection board revisions. 
 
  
Monitor Electrohome 
Part Number G08-001 Manual   EHT Supply Assembly G08-001 02-170003-01 Deflection Amp PCB Assembly G08-001 02-170005-01 CRT Socket PCB Assembly G08-001 02-170006-01 Heat Sink Assembly G08-001 02-170004-01 G08-003 Preliminary Manual  EHT...

G08 Vector Monitor FAQ & Guide Page 14 of 39    
HOW IT ALL WORKS  
 
Inputs come in from the game boards (most commonly the Sega G-80 system XY timing and 
control boards) and are fed into the input protection board. The input signals then go to the 
deflection board, and the deflection board does its stuff. The deflection board sends an “OK, these 
signals are cool” signal to the HV unit, which turns on and provides the HV to the picture tube and 
the AC to the heater. The deflection board then feeds...

G08 Vector Monitor FAQ & Guide Page 15 of 39    
REPAIR PREPARATION  
 
So you have a G08, and you have no idea of its condition. Well, let’s do a few basic things before 
we fire it up (“fire it up” might be a poor choice of words here ;-)). 
 
1) Start by dismantling the monitor.  
 
First, discharge the monitor tube. There is high voltage under the monitor’s anode cup if the 
monitor has been powered up recently. It may not be necessary to discharge a monitor tube that 
has been sitting for a while,...

G08 Vector Monitor FAQ & Guide Page 16 of 39  Test the deflection transistors through the connectors. Please read the procedure in “Appendix 
B” before continuing.  
 
Unlike the Wells Gardner 6100 color XY monitor, which uses 2N3716 and 2N3972 transistors 
in a push-pull configuration, all the transistors in the G08 should be identical (unless you have 
an original G08-001 which used the MJ15003 for one set, and MJ15004 for the other set). 
 
Deflection Transistor Harness Connector 
 
Pin Description 1...

G08 Vector Monitor FAQ & Guide Page 17 of 39   
Most shorts will occur between the collector and either the base or emitter. If your test through 
the connector reveals a short, pull the transistor and test it separately. If it is good out of circuit, 
you may have accidentally shorted either the base or emitter against the heat sink, or the 
transistor socket may have been bent. If the transistor tests bad detached from the heat sink, it is 
ready for the garbage. 
 
If you have to replace transistors,...

G08 Vector Monitor FAQ & Guide Page 18 of 39   
Test the diodes on the HV and deflection boards. Put the negative test lead on one end of the 
diode, and the positive test lead on the other end of the diode. Then reverse. You should get a 
“definite” reading only in one direction (due to testing in circuit, you may see a negligible 
reading in the other direction). 
 
Test the transistors on the HV and deflection boards. This is a little hard to do in-circuit, but 
you should get a definite reading in at...

G08 Vector Monitor FAQ & Guide Page 19 of 39    
DEBUGGING THE MONITOR  
 
Ok, to debug the monitor, you will need a known working game boardset and power supply. Hook 
up the power and video inputs to the monitor.  
 
 
WARNING: Working with monitors of unknown operating condition can be EXTREMELY dangerous. The Electrohome G08 is no exception. If fact, there are probably more horror stories about this monitor than any other. Proceed with extreme caution.  
 Symptom:  No picture; No fuses blow; All is...

G08 Vector Monitor FAQ & Guide Page 20 of 39    
Wiggle, press or flex the 10-pin connector on the HV unit. Intermittent connections can cause the 
HV to drop out. If this restores HV, reflow and resolder the HV header pins until the intermittent 
connection is repaired.  You may want to try replacing the connector pins as well. 
 
If the voltages on the 10-pin connector look good, and there is still no HV, there is something 
wrong with your HV unit. At this point, it probably wouldn’t hurt to try...