Please help me get my 25" California Speed monitor working again!

[dudenohair]

Hi!  I smoked my Neotec NT-2501 Chassis for my California Speed.   Anyway, I've also ended up with a 27" monitor out of a Sega Virtual ON Cybertroopers game that is known to work.    What I would like to know is if I could put the 27" chassis on the 25" tube so it would fit in my California Speed game.  I believe the 27" monitor is Nanao, but I do not know the model since it isn't shown on the monitor.   The 25" tube is RCA A63AHC26X.  The 27" tube is Hitachi A68KSA30X.  The neck board connectors both look the same and look like 8 pin connectors.   Can anybody tell me if it is safe to hook up the 27" chassis to the 25" tube?  Anybody's help is greatly appreciated.

[lilshawn]

Biggest issue is going to be the deflection system. The yoke.

the tube pins will be the same because it was standardized back in the 70's only small maufacturer differences exist (red green blue colors swapped around. etc.)

the yoke (resposible for deflecting the beam across the screen) is a very tuned piece. if the rating is changed even slightly it can cause all sorts of issues, from simple size issues all the way to complete destruction of the yoke and board.

how toast is the 2501? the chassis is a pretty simple design... Take a couple of photos and post them up with a description of the problem that happened...what it did, then what it's doing now (or not doing) perhaps someone here can let you know if it's fixable.

[dudenohair]

Lilshawn,

Thanks much for your informative reply!

Smoked is an exaggeration!  More of a pop.  I suspect one of the transistors, but I don't know which.  The monitor suffered from vertical collapse before it failed.  I traced the collapse problem to something in one of the ribbon cables to the neck board.  I rigged a "Fix" by using a wire tie to tension the cable so the collapse wouldn't occur.  Worked great.  When I went to put the monitor back in, I forgot to hook up the remote adjustment board before turning it back on.  There was some sort of faint whine and the picture never came on.  The whine was in the vicinity of one of the transistors so I got out the volt meter and accidentally created a short... hence the pop.  A couple of fuses were blown, but I think a transistor was also taken.  I've already unsoldered a K1358 FET, but then I am not sure which one is really bad.   I read some place that the whining indicates a certain transistor is shorted, and that is the one I checked when I caused the other short, and that was the K1358.

Seeing how I am obviously not good at monitor troubleshooting (see above sad story), I was thinking the easy route would be to swap the chassis.

[dudenohair]

As I remember more clearly, the noise the monitor made after forgetting the remote adjustment board was an increasing whine/whistle followed by a tick and the whine would begin again.

[lilshawn]

yeah, the remote board being disconnected causes the deflection section to run wide open and is very stressfull to the HOT (Horizontal Output Trasistor). poking it and shorting the legs was icing on the cake 

most often they fail shorted. it will cause the power supply to continuously start-up then shutdown start-up shutdown over and over due to the short.

you could possibly just replace the HOT and be up and running again.

best way to test it is to use your volt meter set to ohms range test between the middle and each of the 2 outside legs... they should both read very high resistance (several thousand ohms) or open (infinite). if you find it reads low resistance (like 0 ohms) it's definitely bad...but reading very low or open may still be bad too. I've had lots of transistors that test fine, even with a B&K transistor tester... only they fail at high voltage and loads used during operation.

I'm not sure exactly which one it is, as i don't have a schematic or the monitor in front of me to see, but the HOT is the biggest transistor often mounted in the vicinity of the flyback (LOPT) transformer the 2SK1358 sounds about right. If you are able to source a replacement give it a try. (2SK1358 is equivalent to an NTE2377)

[dudenohair]

Thanks again!  I'm starting to get my confidence back!

I happen to have some schematics for the NT-2501.  I unsoldered Q101, which was attached to the largest heat sink, but I don't think it is the HOT.  It seems to be in the power supply circuit.  I thought this was the one ticking, but I could have been mistaken by the time I got the chassis out of the monitor for unsoldering.

http://screencast.com/t/TnZDACo0rlm

I think Q402 is the HOT, but I don't know what I am looking at here:

http://screencast.com/t/8W0dalIc5ET

[lilshawn]

yep q402 is your HOT. 2SD1379? D1879? can't really tell from the schematic...it's got a trace running through it. i would go with whatever is in the chassis itself if possible since we can't be 100% sure about the part referenced in the schematic.

q101 is in the power supply section. this is the one that is turning off and on. it has an overload protection built into it where if the load is too high (shorted component) it will shut off and attempt to start up again. this is the ticking you hear as it tries over and over to start up. tick tick tick tick tick....

q101 feeds very high speed pulses to a transformer (t101) to produce all the volts needed for the rest of the monitor. (125 volts 12.5 volts 25.5 volts) the 125 volts (now DC volts) gets fed to a transformer where it gets stepped up (probably 1000 or so volts) and fed to the q402 HOT and is switched off and on to drive the high voltage transformer and the horizontal deflection coil.

the HOT's job is very stressful and high voltage work (switching off and on 15, 25 some even over 30 thousand times a second. and in some monitors 1000's of volts at a time) it is very susceptible to voltage getting shorted where it's not supposed to.

[dudenohair]

Ok, so I took out my HOT Q402 with the adjustment board fiasco, and then I misdiagnosed the issue by following my ear to the wrong component, Q101.  I killed Q101 with my fumble fingers and voltmeter.  Do I need to change anything else besides these two components, or did something else likely short out too?  I think I shorted the Q101 to heat sink ground when I messed up with my volt meter. 

Now I know why the techs at work use very sharp probes with tape wrapped around them.  (I'm not a tech).

Any good sources for these types of components?  I used to think you could get anything at Digikey or Jameco, but it looks like this stuff is impossible to find in quantities less than 1000.

[lilshawn]

okay, if that's the case in addition to q101 and q402 you might need to replace IC101 (TDA4605). it's the controller for q101. if you shorted the legs you've likely toasted the chip by sending high voltage back into the chip through the control pin on IC101...  rip open an old computer power supply...you might get lucky and find those parts (IC101 and Q101) in there. they are pretty standard SMPS power supply parts. if not...

 check your yellowpages (or google) electronic repair or television repair or electronic parts for your area. call a few and let them know the part #'s your looking for, if the don't have them...ask them where you think you could call or who might have the part. ive called 3 different places looking for parts...asked one where i might be able to get them in town...guy offered up the others i called but also the name of a different company...they had the part. didn't even know they existed...and I've been buying parts for years.

you can buy onesies off ebay if you don't have an electronic supply place.

[dudenohair]

If I recall, I may have shorted one of the legs to ground (heatsink) rather than to the other leg.  The fuse blew instantly.  I may be ok on the IC?

[dudenohair]

Q402 has C1543 marked on it.  Ring any bells?

[lilshawn]

Q402 has C1543 marked on it.  Ring any bells?

it doesn't. part 2SC1543 (toshiba) datasheet says it's like a 32 volt transistor @ 0.02 amps the HOT tranistor is 1500v @ 6+amps it should look about like this:

NOT THIS:

If I recall, I may have shorted one of the legs to ground (heatsink) rather than to the other leg.  The fuse blew instantly.  I may be ok on the IC?

you can try without replacing the chip...it very sensitive to spikes but depending on the circumstances of the failure it might be okay.

[dudenohair]

DOH!

C5143 ... not C1543.   That is what I get for trying to remember a 5 digit number while coming up to the 2nd floor from the basement with 3 kids in the house.

The complete number on the installed Q402 is in two lines:

C5143
     7E

I could find 2SC5143 for sale on ebay and it is a HOT.

The drawing has Q402 D1879 on the schematic next to the transistor, and then appears to have an alternate number C4542 in the margins.

I could find data on 2SD1879 (1500V transistor) and 2SC4542 (1500V transistor).   

Why is 2S always added to what is printed on the transistor?

I hate to keep bugging you, but you seem to have some magic transistor resource that is nowhere on the internet as far as I can tell!

[lilshawn]

DOH!

C5143 ... not C1543.   That is what I get for trying to remember a 5 digit number while coming up to the 2nd floor from the basement with 3 kids in the house.

The complete number on the installed Q402 is in two lines:

C5143
     7E

I could find 2SC5143 for sale on ebay and it is a HOT.

The drawing has Q402 D1879 on the schematic next to the transistor, and then appears to have an alternate number C4542 in the margins.

I could find data on 2SD1879 (1500V transistor) and 2SC4542 (1500V transistor).   

Why is 2S always added to what is printed on the transistor?

I hate to keep bugging you, but you seem to have some magic transistor resource that is nowhere on the internet as far as I can tell!

7E would just be a date of manufacture or batch code. no biggie.

the 2S ive added with it is the generic id number classing it as a particular type of transistor. it's shortened on the transistor to just C in your case.

2SA   high frequency PNP BJTs
2SB   audio frequency PNP BJTs
2SC   high frequency NPN BJTs
2SD   audio frequency NPN BJTs
2SJ   P-channel FETs (JFETs and MOSFETs)
2SK   N-channel FETs (JFETs and MOSFETs)

often manufacturers will change the "S" to another letter (Hitachi sometimes uses "H" (2HC1234)) so you would search for a replacement part by number and buy that one from them.

but you are more likely to find a proper 2SC1234 number than a shortened C1234 number so I always use/ask for/give the full number.

let's not get into the ambiguity surrounding tiny surface mounted component markings. 

I fix and repair arcade machines for a living as part of an amusement company. You get to learn the in's and Out's of identifying parts to replace them when all you have left is a blob of burnt transistor. I have stacks of cross-reference books to replace obsolete and discontinued parts. so knowing what specification the original part is, really helps in obtaining a replacement.

a good website for finding information and datasheets on parts is alldatasheet.com another site i've used to try and cross-reference obsolete parts is datasheetarchive.com often the results of a search will come up with a page from a cross-reference book that can be used to look up the original part number then lists off all the other manufacturers part numbers of a similar or better replacement. another is NTE (http://www.nteinc.com/) they make replacement parts, often old/obsolete/discontinued parts... the cross-reference isn't 100% all the time but the parts are available. they are a little expensive, but for something they don't make anymore, it's worth it.

it looks like you have a couple of part numbers there (2SD1879  and 2SC4542). likely they used either one during the original manufacturing of the chassis (as they became available or discontinued or replaced with better versions).... search them both out, whichever you can obtain or get a better price on, go with that one. 

[dudenohair]

OK, after waiting almost a month, my parts came in.  I replaced the two transistors we have been talking about and I fire it all up and the thing has no picture, but is still doing the beeping thing.     What is next?

[lilshawn]

you might have a bad vertical deflection chip.

you will need to start isolating the different sections and disconnecting them one by one until it comes back up again. try removing L103 and then power up the monitor...only for a few seconds, just enough to see in the power supply is coming back up again. (not flub flub flub or tweet tweet tweet or whatever noise it's making...don't leave it on in this configuration, we only need to see if something in the 25 or 12 volt section is causing the overload.

if it still doesn't come up it's something in the high voltage section we need to find. if it powers up, it's something in the 26 volt or 12 volt sections.