Tempest - bring it back to life

[level42]

By the way.....ALL transistors always have THREE connections: Base, Collector and Emitter.

However sometimes (like with TO-3 case transistors) the "body" is one of those connections.

[ckong]

Thanks,  just wanted to post that link. This one is also useful :

https://www.dragonslairfans.com/smfor/index.php?topic=3685.0

[level42]

You made a typo ....you mentioned 2N2792 while you meant 2N3792

From the equivalent thread:


2N3792 (PNP) => 2N6609,MJ21195,MJ21193,MJ15016,MJ15004,2N5684,2N5884,MJ15023,MJ15025, MJ4502,MJ2955,2N5876

The bold ones I have actually seen working myself so might be worth to try and find these.

Try www.reichelt.nl too.

About measuring resistors in circuit: there is no general rule. It totally depends on the circuit it is in. If you meausre a value that is pretty close to spec, it's _probably_ OK.

F.i. If you put two 1000 ohms resistors in parallel and you measure across one of them, you will get a reading of 500 ohms. There will pretty often be resistors, but also other parts in parallel across resistors so in that case your measurements will be off and unreliable. The only way is to de solder one leg in that case.

So what you can do is: measure resistor in circuit, if value OK, pretty sure it is OK (but not 100%). if value is way off, desolder one pin and check again.

[level42]

http://www.reichelt.nl/MJ-2955-ISC/3/index.html?&ACTION=3&LA=446&ARTICLE=12189&artnr=MJ+2955+ISC&SEARCH=Mj+2955

Pretty good price !

Note that I had to insert a space between MJ and 2955 to find it....so sometimes only search with the 4 numbers or try some other part of the name...

[level42]

Should you order from Reichelt, I need some heatsinks....I'll look up exactly which one's tomorrow

[ckong]

Thanks for all the info,  André 

[synonym9]

I took the monitor out of the Tempest (I want to pull the HV board and test it in the Black Widow cab to see if that solves the BW problem) and I noticed just a tiny, tiny bit of fosfor burn.    Well, was to be expexted of course, I wonder if one will see a lot of it during gameplay.



Does someone by any chance has a spare tube? (yeah, keep on dreaming).

The Asteroids-tube I found (my two Asteroids was converted when I found them) also got one dark spot in the middle.

[level42]

Almost every Tempest monitor I've seen has burn-in.

Crappy 6100's....

[synonym9]

Almost every arcade-monitor I have seen is slightly burned in....but what are dots in the centre???
My Asti-tube only got one...but also as strong as in the the Tempest-tube.

We will see how my Tempest-Tube looks like when it is arrived.

[level42]

Simple: those vector games got defective in some way causing the electron beam to stop moving. When there are no signals to deflect (bend) the beam all over the screen like it normally does in game/attract mode, ALL the energy of the beam hits one tiny spot in the center of the tube. This causes a very bright spot in the center and if it stays there for some time (BITD the machines of course usually were turned on from morning till late at night, some even 24h.and often barely attended) it will burn the phosphor at that spot, causing the dark dot.

Of course there were circuits designed to prevent this from happening (the spot killer) but this clearly didn't always work. In theory, when the vector monitor doesn't get any deflection signals from the game PCB, the beam will be dimmed to a safe level. But these circuits often failed. In fact, I repaired one 6100 which had completely the wrong type of transistors in the spot killer circuit from the factory (!) which surely made the spot killer none functional....they mixed up with transistors that were used on other sections of the deflection PCB, in other words, they grabbed transistors from the wrong source for these locations. Clearly not only production quality was lousy but also quality checking because you'd expect every monitor to be checked completely, including the spot killer function....

I am old enough to remember that when I was a kid spot burning also sometimes happened with then already old B/W TVs. What happened with those was that when the TV was turned off, naturally the deflection stopped but sometimes the beam still continued (I guess because of caps getting bad...not sure really) while this should be dimmed too at that moment.

[level42]

Nice quote from Jed Margolin's website www.jmargolin.com :

The Amplifone Deflection Amplifiers also contain a circuit that looks at activity on the X and Y inputs. If  it doesn't find what it feels is an appropriate amount of activity it turns off the Beam to prevent it from burning up the screen phosphor. This is the infamous Spot Killer.

Even with the Spot Killer, screen phosphor burn was a common occurrence during software development. One time I saw a runaway Vector Generator burn off the phosphor in the middle of the screen, then burn completely through the shadow mask, and start to burn through the glass

[synonym9]

Ahhh...I see, so not necesserely the deflection unit needed to fail, also when a game-PCB did not work correctly the beam stood in the center?
From my experience the the color rasters did not do that. I have one machine which got a neckglow but is dead otherwise. The guys here in DLF told me that this is logic if the PCB does not work, you only got snowing on the screen when the monitor got a tuner, still it does not make that spot in the middle...so is it a vector-monitor-phenomenom?

[Etienne MacGyver]

yes indeed that is.

[level42]

Yes except for what I described about ancient B/W TV's......

The reason why is that a TV has internal circuitry that will move the beam "automatically" all the time, line by line from top to bottom and then back to the first position again, wether there is a signal or not. When there is no signal (snow) this still happens so no burn in.

http://youtu.be/aBjBG9Sen0w (Posted this one before)

This is also why, in essence, the electronics from a vector monitor are much more basic. There is no need to create the signals that make the beam move, the game PCB does that.

Of course the above video and explanation is only true for old fashioned analogue TV which has been gone from the air for years in our country already, Digital works completely differently....


Oh one thing more: deflection failures do still happen on CRT TVs and raster monitors but it's very very very very unlikely that both X AND Y deflection fails at the same time, so what you get then is a horizontal or vertical bright line...

[Etienne MacGyver]

and that is the famous vertical collapse (or horizontal, wich is much more rare to happen)



this is the vertical collapse i experienced with my minipong...