Electrohome G08 Manual

							G08 Vector Monitor FAQ & Guide Page 21 of 39    
Assuming you are using your G08 monitor with the Sega G-80 vector game boards, you will need 
to add the following two capacitors to the X-Y Timing board on the G-80 game boardset. Install 
two 100pF, 50V ceramic capacitors in locations C32 and C33. Install C32 between pin 2 and pin 6 
of U2. Install C33 between pin 2 and pin 6 of U3. 
 Symptom: Blowing Main Fuses 
 
If a monitor is blowing main fuses, check the deflection amp power transistors Q605, Q606, Q705 
and Q706, WITH THE POWER OFF. Shorted transistors or diodes in the deflection amplifiers will 
also blow main line AC fuses. 
 Symptom: One Or More Colors Is Missing 
 
Check the transistors and diodes on the Input Clamp board for shorts or opens when one or more 
colors is missing from the display, and the G-80 game boards are known to be good. Check the 
connections from the Input Clamp board to the deflection board. 
 Symptom: Picture Flickers In and Out 
 
This is a difficult problem to solve, as this symptom can be caused my many things: 
· Fluctuating voltages from power supply 
· Bad connections of XY pair with card cage in G-80 game boardset 
· Bad connections of ribbon cables between XY pair in G-80 game boardset 
· Bad connections to HV unit 
· Bad connections at the Input Clamp board (cracked solder joints) 
· Bad connections at the deflection board (cracked solder joints) 
 
I would start by reseating the connections to the game boardset, the XY pair, and the ribbon cable 
between them; resolder the pins on the Input Clamp board and deflection PCB.  If that does not fix 
it, you will need a scope to see where the signal is getting dropped. 
  
						

							G08 Vector Monitor FAQ & Guide Page 22 of 39   Voltages 
 
The following G08-003 voltages are measured during running of the monitor (taken from the 
Zektor manual): 
 
 All Readings are DC Level Voltages 
 
                
 
 B=BASE E=EMITTER C=COLLECTOR AN=ANODE CA=CATHODE 
 
                
 
                                    D401 CA 63.0  D403 CA 63.0  D400 AN -63.0  D402 AN -63.0                        ZD400   59.0  ZD401   9.0  ZD402   -9.1                            Q400 B 59.0      Q401 B 9.7           E 58.8        E 9.1     
      C 63.5        C 17.0     
                       Q600 C 34.5 Q700 C 35.9 Q601 C 0.8 Q701 C 0.5                       Q602 C -0.5 Q603 C 63.5 Q604 C -63.9                           Q605 C 63.9     Q606 C -63.9          B 0.1       B -0.1    
      E 0.1       E -0.1    
                       Q702 C -0.8 Q703 C 63.5 Q704 C -63.5                           Q705 C 63.9     Q706 C -63.9          B 0.1       B -0.1    
      E 0.1       E -0.1    
                       Q901 E 8.0 Q902 E 0.0 Q903 E 0.0          B 7.5   B 0.3   B 0.5    
      C 0.3   C 0.5   C 3.0    
                       IC 600               IC 900                 Pin 1  0.0   Pin 10   0.0   Pin 1  0.4   Pin 10   1.7     Pin 2 4.2  Pin 11  0.0   Pin 2 0.0  Pin 11  8.7 
    Pin 3 0.0  Pin 12  -9.1   Pin 3 0.1  Pin 12  8.7 
    Pin 4 0.0  Pin 13  0.0   Pin 4 -9.1  Pin 13  2.3 
    Pin 5 0.0  Pin 14  0.0   Pin 5 9.0  Pin 14  9.0 
    Pin 6 9.1  Pin 15  0.0   Pin 6 0.7  Pin 15  0.5 
    Pin 7 7.5  Pin 16  0.0   Pin 7 1.7  Pin 16  0.1 
    Pin 8 0.0  Pin 17  0.0   Pin 8 7.5  Pin 17  8.7 
    Pin 9  0.0   Pin 18   4.2   Pin 9  0.1   Pin 18   0.0 
                                      
						

							G08 Vector Monitor FAQ & Guide Page 23 of 39   INSTALLING A CAP KIT  
 
Zanen Electronics 
5023 52nd Street 
Lubbock TX 79414 
806-793-6337 
Fax: 806-793-9136 
Zanen Kit #110 Bob Roberts also sells cap kits. Bob provides a 
kit for the G08 Vector Monitor. 
 
[email protected] 
http://www.therealbobroberts.com 
 
Key: 
· Q = Transistor  
· R = Resistor  
· C = Capacitor (all polarized electrolytic)  
· F = Fuse  
· D = Diode  
· ZD = Zener Diode  
 
Note that the capacitors come in two types:  
                                            _____ 
                 _____                      |   | 
               --|   |--        radial-lead |   | 
                 ~~~~~                      +---+ 
               axial-lead                    | | 
 
Note: if you cannot find an exact replacement for one of the capacitors, you may keep this in mind. 
A capacitor with a difference that is less than 5% of the original value should work just fine. Back 
in the days of the G08, electrolytic capacitors had tolerances that were typically over 20%. So a 
modern capacitor will probably be a lot closer to the ideal value than the original cap that was in 
the chassis when it was new. 
  
						

							G08 Vector Monitor FAQ & Guide Page 24 of 39   
CAP KIT SUMMARY: 
 
There are some known problems with Zanen and Bob Roberts G08 cap kits. Below is a 
recommended list of parts. Almost all of the suggested replacement capacitors are upgraded in 
terms of voltage rating and should make your G08 monitor last longer and run cooler. 
 
G08-003 Cap Kit Parts List PCB Location Part Description Upgrade Notes      Deflection C401 1000uf 160V Radial Capacitor Yes Original was 80V Deflection C405 10uf 50V Radial Capacitor Yes Original was 25V Deflection C406 10uf 50V Radial Capacitor Yes Original was 25V Deflection C411 22uf 350V Radial Capacitor Yes Original was 250V Deflection C601 47uf 35V Radial Capacitor Yes Original was 16V Deflection C701 47uf 35V Radial Capacitor Yes Original was 16V Input C800 10uf 50V Radial Capacitor Yes Original was 16V Input C801 10uf 50V Radial Capacitor Yes Original was 16V Input C802 10uf 50V Radial Capacitor Yes Original was 16V Input C803 10uf 50V Radial Capacitor Yes Original was 16V HV C900 4.7uf 35V Radial Capacitor Yes Original was 16V HV C901 4.7uf 35V Radial Capacitor Yes Original was 16V HV C904 22uf 35V Radial Capacitor Yes Original was 16V HV C905 22uf 35V Radial Capacitor Yes Original was 16V HV C911 100uf 35V Radial Capacitor   HV C916 47uf 200V Radial Capacitor Yes Original was 160V  
 
Note: some of the capacitor locations will differ slightly from the descriptions above, depending on 
the deflection board revision you have. Generally speaking, you will be replacing all electrolytic 
capacitors on the deflection and HV boards. If the list above states C405, it could be C407 on your 
board. Make notes on what capacitors you remove, and replace those locations. 
 
Capacitors C601 and C701 on the deflection board appear only on the schematics and are not listed 
on the parts list of any manual. C601 and C701 are connected to pins 12 and 6 of IC600 
respectively. 
  
						

							G08 Vector Monitor FAQ & Guide Page 25 of 39   
CHASSIS TRANSISTORS 
 
All the monitor chassis transistors are mounted in a socket with two machine screws. No soldering 
is necessary; just unscrew the old one and replace. You cannot put these chassis transistors in 
backwards; the leads are offset so they will only fit into the chassis and screw down in one 
direction. If you put the transistors in backwards, the screw holes will not line up.  
 
Make sure you install a new clear plastic Mica insulator between the transistor and the metal 
monitor chassis. New ones are not included in the Zanen kit! If you have some white heat sink 
grease, put a light coating on both sides of the Mica insulator.  
 
NOTE: The transistors shipped with the Zanen and Bob Roberts kits are 2N3716s. These 
transistors are not sufficient to work with the G08 monitor. Replace them with 2N6259s (if you can 
find them) or MJ15003s. Keep the 2N3716s for your other vector monitors! 
 
Deflection Transistors Location Part Number Notes Q605 2N6259 Substitute is MJ15003 Q606 2N6259 Substitute is MJ15003 Q705 2N6259 Substitute is MJ15003 Q706 2N6259 Substitute is MJ15003  
 
Important: after replacing the above transistors, before plugging them back into the deflection 
board, use your DMM set to Ohms and check the continuity between the metal monitor chassis and 
the metal case of the above transistors. There should be NO continuity!  Unscrew the transistor and 
check the mica insulator or pins to make sure they are not touching the heatsink. If there is 
continuity, you will usually burn out R636, R637; R736, R737, and others in the pre-amplification 
stage. You will probably also take out the deflection transistor involved as well.  
 
You will most likely find bad solder joints at many of the connector pins, which should always be 
reflowed. 
 
If you have a G08-001, the MJ15003 transistors should be hooked up to pins 1-4 on the P600 
connector (Y amp) and pins 5-7 on the P700 connector (X amp). MJ15004 transistors should be 
hooked up to pins 5-7 on the P600 connector (Y amp) and pins 1-4 on the P700 connector (X amp). 
Check your G08-001 schematics for reference. 
 
  
						

							G08 Vector Monitor FAQ & Guide Page 26 of 39   
G08-003 DEFLECTION BOARD 
 
Not all of these parts are necessary for a monitor rebuild, but are good to have on hand. For 
capacitors, see “Cap Kit Summary” section above. 
 
NON-Zanen Deflection PCB Parts Location Part Description Upgrade Notes     F400 5 amp Slo-Blo Fuse  Replacing these is a good idea F401 5 amp Slo-Blo Fuse  Replacing these is a good idea F600 4 amp Slo-Blo Fuse  Replacing these is a good idea F700 4 amp 125V Slo-Blo Fuse  Replacing these is a good idea ZD400 1N5263B 9.1V, 1/2W 5% Zener Diode   ZD401 1N5239B 9.1V, 1/2W 5% Zener Diode   ZD402 1N4739  9.1V, 1W 5% Zener Diode Yes Replace with a Motorola part Q201; Q251 2N3904  Current Limiting Board Q202; Q252 2N3906  Current Limiting Board Q602; Q603 MPSU10  Cross is 2N6558 or NTE171 Q702; Q703 MPSU10  Cross is 2N6558 or NTE171 Q601; Q604 MPSU60  Cross is NTE240 Q701; Q704 MPSU60  Cross is NTE240 D400; D401 MR502  200V, 1A or 1N5402  G08-801 is a MR752 (200V, 6amp) D402; D403 MR502  200V, 1A or 1N5402  G08-801 is a MR752 (200V, 6amp) D404; D405 1N4003 ER, 1A 200V or 1N5059  G08-801 is a 1N4001 (200V, 1amp) R400 60-Ohm 120V Non-inductive Resistor  Original is a Thermistor R636; R637 1K ¼W Resistor   Schematics note 100-Ohm resistors R736; R737 1K ¼W Resistor  Schematics note 100-Ohm resistors  
 
  
						

							G08 Vector Monitor FAQ & Guide Page 27 of 39   
G08-003 HIGH VOLTAGE UNIT 
 
Not all of these parts are necessary for a monitor rebuild, but are good to have on hand. For 
capacitors, see “Cap Kit Summary” section above. 
 
NON-Zanen HV PCB Parts Location Part Description Upgrade Notes     ZD903 1N751 Zener Diode   ZD904 1N751 Zener Diode   Q900 Power transistor, 5A 1400V  Hitachi 14-601-36 Q901 2N3906   Q902 MPSU07   Q903 2N3904  Found on back of PCB L900 12 uH Horiz. Delay Choke  8 uH on G08-001 D901 Rectifier, 1A 1400V  GI1-1400 (NTE506 cross)  
 
  
G08-003 NECK BOARD 
 
I have never had to replace a part on a neck board yet (seems it was the only board Electrohome got 
right the first time). So, I have no recommendations for replacement parts. 
  
						

							G08 Vector Monitor FAQ & Guide Page 28 of 39   MAKING THE MONITOR MORE RELIABLE  
 
Ok, so now you have a working G08 monitor (hopefully). Here are just a few things you can do to 
the monitor to prolong its life just a bit longer. 
 
 Input Clamp Board Modification 
 
Replace the tape on the back of the input protection board with a strip of electrical tape or other 
non-conductive material to prevent it from shorting to the metal bar it is typically mounted on. 
 Deflection Board Modification 
 
For capacitors, see “Installing A Cap Kit” section of this document. 
 Deflection Transistor Modification 
 
From Zonn Moore: 
The biggest problem with the Sega G08 is the underrated Deflection Transistors (The second 
biggest is all the proprietary ICs). To fix the transistor problem you can do just what Rick suggests. 
Parallel two power transistors for each one currently being fan cooled. 
 
The thing to do is to get two of each transistor, connect the bases and collectors together. Then 
connect a resistor from each emitter to the place the old emitter used to go... 
 
   +---------------------+--------------> to old collector connection 
   |     to old base     | 
   |      connection     | 
   |          ^          | 
   |  C       |       C  | 
   +->|       |       ||               | to old emitter connection 
                (Pretty bad drawing huh?) 
  
						

							G08 Vector Monitor FAQ & Guide Page 29 of 39   The 0.39-ohm resistor allows the transistors to be hooked in parallel without one transistor going 
into thermal runaway and trying to drive the whole load itself. (A good place to find out more 
about hooking transistors in parallel is a Voltage Regulator handbook of some kind) 
 Heat Sink Modification 
 
From anonymous:  
 
“The deflection transistors mounted on the heat sink can be more efficiently cooled (and therefore 
will last longer) if you place them on the inside of the heatsink instead of on the outside. To do this: 
 
1) Remove the heat sink assembly from the monitor chassis by removing the screws on the 
side of the chassis and disconnecting the fan and deflection transistor harnesses from the 
deflection board. 
2) Remove two upper or lower screws from the fan so that the heat sink assembly can be 
split in two. 
3) Unscrew the deflection transistors from the heat sinks. 
4) Place the transistor sockets on the outside of the heatsink, and then mount the transistors 
on the inside of the heat sink. Make sure to reinstall the mica insulators with a thin layer 
of silicon grease on both sides of the mica insulator. 
5) Reassemble and remount the heatsink. Before hooking up the harness to the transistors 
again, do a transistor test through the connectors (as mentioned previously in this 
document) to make sure that they are mounted correctly, and that there are no shorts. 
6) Reconnect the fan and deflection transistor harnesses to the deflection board and retest 
the monitor. 
 
The deflection transistors should now run much cooler.” 
 
One of the main problems with the fan-cooling setup is that the airflow through the closed cabinet 
is pretty miserable. You may want to consider running your Sega XY cabinet with the back access 
door removed. 
 HV Unit Modification 
 
For capacitors, see “Installing a Cap Kit” section of this document. 
 Neck Board Modification 
 
None available as of this version of the document. 
  
						

							G08 Vector Monitor FAQ & Guide Page 30 of 39    
TUBE REPLACEMENT  
If you are unfortunate enough to come across a G08 with a bad tube, there is still something you 
can do about it. 
 
You can replace the tube. As mentioned before, the tube is the same as the one used in the Wells-
Gardner 6100 series color XY monitors. You can also buy a brand new color vector tube 
(19VLUP22) from Richardson Electronics (1-800-222-2787) for around $165. It will not come 
with the tinted gel, nor a deflection yoke or convergence rings, so you will have to transfer those 
from the broken tube and reconverge the monitor colors. 
 
From Mark Jenison: 
 
“I tried doing a tube swap with a 19VJTP22 tube from a Wells-Gardner monitor (4900 or 4600, 
can’t remember). I did not have any luck. While the picture was fine, I could not adjust out the 
green band down the middle of the picture. Apparently this is due to the fact that the deflection coil 
could not be positioned far enough down the neck tube (because the degree of the neck tubes are 
different), but more importantly, the deflection coils are not angled to work well with a 90-degree 
tube. I hear you can do this with a WG6100, which uses the same tube, but that’s because it’s 
deflection coil is shaped slightly differently.”