Electrohome G05-805 repair and tube swap

G05-805 Tube swap.

From a friends cocktail cab.

The monitor came to me slightly faulty, the Contrast adjuster on the deflection PCB was totally out of spec. and was replaced. Also the Focus adjuster on the HV PCB was bad causing brightness issues on the monitor, this was simply 'worked' back and forth a few times and the issue cleared. The HV and deflection PCB's had previously been repaired and now was all good.

I also the chance to swap the tube over for a NOS one that was sold on the UKVac forums a few years back.

Needless to say the new tube gives a great image and only takes around five seconds from cold to show an image. Here's a few photos of the process. Yoke swap was interesting to see how moving it around altered the screen image.

Bonanza Enterprises Super Breakout Cocktail cabs

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Smartmeet 7 (12-08-18)

Sega Hang-On Arcade PCB fix

My Hang-On game failed recently while on, I returned to the game and the monitor was showing a black display and the attract sound appeared to be playing as normal. I re-powered the game and got the same black display with no sounds, test mode didn't work.

I check the PSU voltage and the 5V was steady across the four board stack.

I used my logic probe to quickly scan through some pins on the CPU, Clock and all data or address line were either high or low and not toggling as expected.

I opened the schematics and headed for the clock circuit on the CPU board.

Image below:

I had a good pulsing clock signal passing through the 74112 Flip-Flop, moving along the signal chain pin 4 of the 7404 Inverter was showing no signs of life, from this point on in the circuit the clock signal is divided up and sent to different areas of PCB, with the CPU being an essential component ro receive the clock signal to do anything like run the game.

I 'piggybacked' a new 7404 on top of the suspect one and the game started playing. I removed the IC and checked it in my tester. All 6 Inverter gates were faulty.

With a new IC soldered in place, the game is working fine again. The faulty IC was manufactured by Fujitsu with a date code of 8547, this era of IC's made by Fujitsu have a reputation for failing, Sega arcade PCB's do seem to have a fair amount of them installed...

Revival: Generation X 2018

Had a great weekend as mentioned by all, nice to catch up with old buddies and meet some new forum folk! Here's a few of my photos taken across the weekend.

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Off we go... Myself, Alex and Dave Flynn sharing the ride up to Walsall.

Dino fever. No they're not for sale and we can't 'just put them in the back of your car'... ;)

The Nintendo Arcade area.

Nice view from the event hall.

A well deserved beer on Friday Evening with the gang.

Place your bets, how long until the Asteroids stops working.

A few Cabarets.

the British IBM on stage Saturday afternoon.

Pinball Alley

Where the hell did Marty go to, he's an impostor...

Me topping the high score on SHO beginner courses....

Er... Mame on a Vectrex!!!

The Pacman master takes a break to play some T&F.

Atari Video Pinball PCB repair missing playfield bits

I decided I needed to play Video Pinball today, its not been turned on since my time off work over Christmas. Well the game had decided to go a little bit faulty, I didn't immediately notice, but there was a section at the top of all the game text that had been chopped off, the four game flippers also had a black line running though them.

The game played fine apart from these graphical errors, test mode reported no errors. See the photo below showing the faults I mentioned. You can see the lines in the flippers and just about see where the top line of the text missing.

The Circuit for the Playfield is a fairly small section of circuitry. The CPU writes data into RAM that defines the Playfield picture, the Sync timings then select this data which in turn addresses the Playfield ROMS (C5, D5) with the data from these passing through a shift register (C6) where the output is mixed as part of the final analog output video.

Using my trusty logic probe I checked all the clock signal and confirmed all address and data lines were active and not stuck high or low. Well I couldn't see anything the would normally highlight a fault. Thinking more about the fault, I deduced it was unlikely to be the RAM or ROM at issue; when the flipper button was pressed the graphic moved perfectly and wasn't corrupt as such, if the ROM(s) had gone faulty the missing line would move when the graphic was rotating.

Looking like a fault I had seen in another repair, I decided to remove the 74LS166 shift Register so it could tested in my MiniPro programmer, my hunch was correct and it was declared as faulty.

So despite having over 80 pots with different IC's, I didn't have any 166's, I 'borrowed' one from a Super Breakout PCB which has become a bit of a donor for random parts I've needed to use...

With the 166 replaced the game is back to looking and playing perfectly again.

Until the next game breaks, thanks for reading, Mart.