BW Vector monitor repair log (G05-802/V2000 hybrid)

[level42]

Remember the BW vector monitor I bought from Rémi ?

Took a bit of time to work on it today. This monitor is a "hybrid". That means it has a G05-802 HV cage and a WG V2000 deflection board.
This combo should work normally, the Elektrohome G05-802 and WG V2000 are very similar (although not 100% the same).

Started the investigations with the usual cap check. Everything looked fine on the HV cage. On the deflection board most caps (there only 5) were OK, but I did measure some weird values (R only) on C603. Since this is one of the parts in the X (or Y I don't know, nor does it really matter) deflection circuit so I compared it to the values of C703 and those were different although still not what I expected.

Anyway, I decided to desolder both to be 100% sure. Measured them and they were fine. SO.....there had to be something else wrong.

The next thing you check in electronics are the semi-conductors. Those are most likely to fail. So I checked the "large" 4 transistors on the board (using my DVM in diode test) while still on the PCB and sure enough I had a full short on all three legs of transistor Q606. Desoldered it and yes it was bad, all legs shorting.
It was a SK3200 transistor which I found (by some googling) that this is equivalent to NTE50 and MPSU57.....MPSU57 mmmmm I remembered these are also used on Amplifone deflection boards so I checked and indeed this was true.

Because of this I had some replacements for these transistors on stock, being CEN-U57 which are compatible.

Soldered it in but that was not the end.

Transistors often "blow" because another failing part. For that reason I already decided to check the big "bottle" caps on the chassis as well, but before that I wanted to be sure everything was OK on the deflection PCB. So after soldering in the new transistor I again checked the values with my DVM in diode test and compared it between the X and Y deflection circuits and I had different values again (or still)....
So...there had to be something wrong still !

Took a look at the schematics (great to have paper one's now, it is still easier to work with IMHO) and I saw diode D608 was not too far from it in the circuit...checked it (again DVM in diode test) I had a full short on that too in both directions.

That diode is a 1N4001 and that is about the most common diode in the world so replace that too..

More later...

[level42]

Yep....dug a bit in my work tool case and found a 1N4003 which will work fine. Only difference with the 1N4001 is that it will withstand a higher reverse voltage, that never harms.

Soldered it in and once again, measuring time, repeating the same measurements again and......STILL there was a problem. I measured about 800 Ohms across the Base and Emittor of the fresh Q606, while at the same position on Q706 I measure somewhere in the Megaohms....this can't be right !

OK, so what's up on the other side of Q606 ? Schematics say: Q605. Measured it, had almost a short on both outer legs in both ways....that can't be right. Desoldered it, measured again, yep another blown transistor !

As you can see, since an electronics circuit is a chain of components, one can blow up the other easily...

Now....Q605 is a 2N3906......mmmm sounds familiar too....didn't I just saw a lot of those on a string in my parts boxes ?

Searching I find this:




A shitload of 2N3904's !!! This reminds me of a song by Alenis Morisette: "it's like ten-thousand spoons when all you need is a knife".....
In this case I can't use the part even though the number is very similar. The 2N3904 is a NPN transistor, while the 2N3906 is it's complementing equivalent PNP. To translate this a bit it means they are perfectly the same, but exact opposites.....

Can't find any 2N3906 so I just ordered 10 at RSonline for the whopping sum of €0,50 (ex.19% VAT).....that of course does mean I have to wait with work on this.

Now.....the most likely why this "chain" of semiconductors blew is because one of the big "bottle can" transistors gave up life....

So I brought down the bare frame and CRT to check them. While I was in the attic I also brought down a WG6100 that belongs to Franck. Figured since I'm "on the go" with vectors I'd check parts on that one as well (plus a deflection board from Béla)....

[level42]

OK, checked out the bottle caps (and cleaned the CRT and frame...nice now !) and all seem OK !

So maybe this time it wasn't one of the bottle caps being the cause....

Can't wait for those transistors, do final measuring and then assembling it and giving it a test spin using my Asterock....

[Etienne MacGyver]

Nice to folow your progress Andre, i like the "tracking down" the problem step by step guid youre making here !

[level42]

Transistors came in yesterday. Soldered it in tonight. Remeasured everything and YES we have equal values all around !

The FAQ mentioned to check all resistors and diodes if something has "blown" in the deflection amp circuits so I did, all show their specced values.

So here it is, nice and clean. I replaced all fuse holders with Euro sized one's, luckily Wells-Gardner was so nice to make plenty of holes for the fuse holders so I didn't have to drill any.

I had also "ordered" a set of slow-blow (T) fuses from......and got them two days ago

I checked all the solderings of the wires coming in to the board and they are still very sturdy.

I don't like the big resistors being used at R100 and R101. They are 10 Ohms in parallel and definitely not the original one's. The resistors should be 3.9 Ohms, but these of course are about 5 in parallel, on a low value resistor that is a pretty big difference. However I'll try and see if it works and how hot they get.
The B/W vector FAQ says that later revisions had the resistors replaced by heavy gauged wires instead but most of the boards I've seen still have them....AFAIK they are only there to "soften" the in-rush current at start up.
It would be weird to have two "heaters" like that running all the time for just that if it isn't really necessary...

Anyway here it is cleaned, checked and (hopefully) fixed. The yellow arrows point to the replaced parts.


Next up was the HV cage/PCB. Cleaned the cage (incl. HV cup and wire and diode connector):


and the PCB:



Regretfully I forgot to take a "before" pic, but believe me it is a difference between night and day !

Checked all the caps, they're all fine. Checked the diodes and transistors: all fine.
Seems like we are good to go:



There is no way to check the huge HV diode so hopefully it's OK. I redid the thermal grease on both transistors on the cage.

So, time to reassemble it:


Doesn't that look sweet. Cleaned EVERYTHING

Two more things to do:

- replace the termal grease of the big "bottle" caps on the frame
- check the CRT with my rejuvenator. I notice that this CRT has pretty dark corners....well there is a "new" tube coming anyway.....

Serial sticker:


Next 29th it will become 32 years old, let's hope we can celebrate it while it's running !!!

[Superully]

wonderfully documented, andré, an interesting read. let's see / hope that all your hard work paid off! i'm really curious ... 

[Belike]

Very nice André, the technical overview is very detailed and clear, very ueseful for noobs like me.

[level42]

Thanks guys ! Will test it tonight on to Asterock. If things are OK THE WG6100s are up next

[level42]

Ah, found some "before" pics on the for sale thread by Rémi:








Yeah....think it improved a little bit

[Belike]

If things are OK THE WG6100s are up next

[level42]

Aaargghhh....well testing the repaired G05-802 doesnt turn out as easy I thought it would be...

First of all the key for the backdoor got bent during Eurocade transport, so much that I couldnt turn the lock anymore and it eventually broke off.  O well, good time to install one of my new locks (with all the same keys). Drilling out locks is one of the less fun jobs in this hobby IMHO but as always I won.

So opened the cab and actually this was the first time I plugged it in since Eurocade   so I HAD to play a game or three to see if everything was still working of course

Then it was time to unplug the monitor in the Asterock and......then I noticed I had forgotten something.....Sidam used a different connector for it......  

So now I have two choices: either replace the deflection board and HV cage or somehow interconnect the two connectors. The first method has the Big disadvantage that I won't test the tube as well which I really want, so I will try to hook up th connectors in some creative way....

[level42]

Something else I noticed: the deflection board on the Asterock monitor doesn't have the big resistors so they must be bridged wit wire but I can't see it on the component side.Will have to take a look at that later...

[level42]

OK....I tried to make the simplest "bridge" I could think of....using some solid core wire pieces I had cut up and folded them "in" the connectors. This worked OK on the Sidam (harness) side, but since the monitor has male pins it was impossible to keep them steady and making contact.

So I dug in my parts for pins. I found them, but they were all male too 

BUT, I also had female pins for the "Hantarex" type of connectors. Although these are rectangular shaped, they fitted well enough for a short test.

So I crimped the wires and connected everything after having made a table using the info from the Asterock manual and the Electrohome manual.

Thank you Sidam, for using plastic wire clips that will let you remove the harness and put it back again later, it was a piece of cake to get the connectors low enough......I love Sidam more and more !


Sorry, out of focus, but you get the idea... left the Sidam harness connector, right the Electrohome....


Wired it up, checked everything three times and then it was "show time" !

http://youtu.be/_KxvbENhTvE

[Superully]

[Etienne MacGyver]