Electrohome G08 Manual

Page 1 of 39  The Evil, Infamous, Unreliable, Flaming... 
Electrohome 
 
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                /       \   /        \   /        \ 
               |   ___   | |   ____   | |   ____   | 
               |   |  |__| |  |    |  | |  |____|  | 
               |   |  ___  |  |    |  |  \        / 
               |   | |_    |  |    |  |  /  ____  \ 
               |   |___| | |  |____|  | |  |____|  | 
               |         | |          | |          |...

G08 Vector Monitor FAQ & Guide Page 2 of 39    
INTRODUCTION   
Ok, enough making fun of the G08 :-). It is actually a pretty strong monitor considering the work 
that it does, and when it is working it is a fairly impressive color vector monitor. There are horror 
stories about this monitor, and most of them are true (and the list is long), but on the other hand, 
there are others have had theirs for 15 years without it breaking down once. Before working on 
your G08 monitor, read through this entire...

G08 Vector Monitor FAQ & Guide Page 3 of 39   The second model was the G08-003 (there does not seem to be a G08-002). The most notable 
change in the G08-003 was the addition of two “current limiting” boards that are plugged in 
between the deflection board and the heatsink mounted deflection transistors. These boards provide 
current limiting and short circuit protection for the deflection transistors. All four deflection 
transistors were upgraded to 2N6259 transistors, and a HV regulator board was...

G08 Vector Monitor FAQ & Guide Page 4 of 39    
“At the time I came to work at Sega, the G-80 setup was already there. I think Astro Blaster was 
one of the first to use the configuration. For the time it was pretty impressive. The modular design 
got some things done that would have been very difficult to do on a single board. The main CPU 
was not being taxed with sound/speech operations, so the speech was excellent for that time, and 
the sounds were nice, too.  
 
They had already begun working on a...

G08 Vector Monitor FAQ & Guide Page 5 of 39   PART DESCRIPTIONS  
 
The following sections describe the different major assemblies of the Electrohome G08-003 vector 
monitor. Before we delve into the different parts of the G08 monitor, it is important to discuss the 
different schematics that exist. The best schematics to reference are included in the Tac/Scan, 
Zektor or Star Trek manuals (these three manuals, aside form a couple of minor formatting 
changes, are cut-and-paste the same). These manuals...

G08 Vector Monitor FAQ & Guide Page 6 of 39   The Input Clamp board has a pinout as follows: 
 
Pin # Description Specification 1 Horizontal Input +/- 4V maximum 2 Vertical Input +/- 3V maximum 3 Common Ground 4 Red Input +4V @ full brightness 5 Green Input +4V @ full brightness 6 Blue Input +4V @ full brightness  
 
Deflection Board  
The deflection board is the large PCB mounted to the bottom of the chassis (7” x 10”). The G08-
003 version will also have two vertically mounted PCBs (2” x 2”) connected...

G08 Vector Monitor FAQ & Guide Page 7 of 39   Issue 5 deflection boards have places for resistors R636, R637, R736, R737 screened on top of the 
board. Issue 5 deflection boards may be found with or without diodes D601, D602, D701, and 
D702 populated. If your deflection board has these diodes, just leave them installed. They do not 
appear to make a functional difference. 
 
There are even different issue numbers for the foil patterns screened on the bottom of the deflection 
boards. These issue numbers...

G08 Vector Monitor FAQ & Guide Page 8 of 39   The circuit of D409, R410, and R411, in combination with IC900 on the HV board, is a spot-killer 
that prevents the electron-beams from burning a hole in the phosphor surface of the CRT when the 
monitor is turned off. 
 
The outputs of the “X” and “Y” deflection amps can swing between +60V and -60V. This voltage 
is high enough to provide up to 8 amps, peak-to-peak, of current through the deflection coils. The 
power input of the deflection board is an...

G08 Vector Monitor FAQ & Guide Page 9 of 39  manual’s parts list and schematics.  However, they came back in the parts list for Tac/Scan, 
Zektor and Star Trek. 
 
· R635 and R735: Some G08 deflection boards have a ‘teepee’ of resistors in these locations. 
As noted in the schematics, there should be a single 3-Ohm 20W resistor in each location. 
Some have been replaced with two 1.5-Ohm resistors teepeed together. It is unclear why 
this modification was done to some G08-003 deflection boards. 
 
· Two...

G08 Vector Monitor FAQ & Guide Page 10 of 39   out there that has better secondary breakdown characteristics than a 2N6259, but you will never tell 
that by looking at just numbers, you need to see a breakdown chart. This will show you where 
secondary breakdown is. 
 
For example, looking at the 2N3716 data sheet you will see that at full voltage (80 volts) the part 
will withstand 0.2 amps. That is only 16 watts allowed for what is supposed to be a 150-watt part! 
Compare that with a 2N6259 that can...