25K7193 -where is C69?

da66en

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Where is C69 on a 25K7193. Either I am blind or I cannot find it. Is there dedicated pads that are silkscreened on the PCB, or is this capacitor piggybacking other pads? I may have read somewhere that it is piggybacking C36, but I may have misunderstood what I read.

Thanks.
 
on some models it is soldered on underneath.
on the later models is is silked on the parts side.

not all models need/requier it.

Peace
Buffett
 
on some models it is soldered on underneath.
on the later models is is silked on the parts side.

not all models need/requier it.t

How do you know if your model needs it? Mine is a 25K7193 P538.

Soldered underneath? C69 is a 1600V cap, so it would be pretty big and easy to notice right?

Thanks.
 
There are pads and it is silkscreened on my PCB, but it is empty (C69). Instead it was jumpered over. My C36 is 6800pF.

I guess my original question still stands - how do you know if you need C36 or not? Is it required with certain flybacks?

Should I change my C36 to be the more traditional 6100 or 6200pF?

Thanks.
 
It depends on whether your C38 is 4-legged or 2-legged. 2-legged usually have C69 with it somewhere, but you'll sometimes have to remove it after a rebuild that includes a new flyback in order to get it to work...
 
It depends on whether your C38 is 4-legged or 2-legged. 2-legged usually have C69 with it somewhere, but you'll sometimes have to remove it after a rebuild that includes a new flyback in order to get it to work...

My C36 is 2-legged, 6800pF.

I found the pads and silkscreen for C69 but it is empty.

I didn't do it, bought it from someone who capped it and replaced the fly. But it still blooming (and high voltage is not stable), and it's bothering me enough to give me another look.
 
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Ok, I need help. My 7193 has a C69 silkscreened on the board, but the previous owner didn't populate it and instead put 6800pf on C36. C36 on this board is silkscreened as the 2 leg type.

In this situation, how should C69 be jumpered to remove it? Or no jumpers, just leave the silkscreened location empty?

Thanks.
 
OK i need pics to see what the underside of your chassis looks like.

in my experience if the chassis had a C36 and a C69 then you need both independently on the board not tied together.
if they are tied together it will not work. this was a later design from what i have seen.

and if you do need a C69 the value is .0036uf/1600v

and C36 is the standard value of .0061uf/1600v

and check R103 if it is out of tolerance by more than .5-.7% the chassis will stay in HV shutdown.

hope this helps.

Peace
Buffett
 
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OK i need pics to see what the underside of your chassis looks like.

Thanks for your response Buffett. Here is a photo of underside:

IMG_3308.JPG


Ok - here's the weird thing. The guy who did this previously added a jumper from the ground of C36 and connecting it to C37 and D15 (where C69 was supposed to connect). The result is that many areas around this spot is now grounded. See the attached picture, I circled the jumper

short.JPG


in my experience if the chassis had a C68 and a C69 then you need both independently on the board not tied together.
if they are tied together it will not work. this was a later design from what i have seen.

and if you do need a C69 the value is .0036uf/1600v

and C68 is the standard value of .0061uf/1600v

When you typed C68 above, did you mean C36?

Why would you need C69? If I look at older 7000 schematics they don't have a C69, so if I don't have C69 what harm is it? I tried to ask this earlier but no one really answered that.

I've seen in a few places that 6800pf (or .0068uf) is good enough. Do you not think so?

and check R103 if it is out of tolerance by more than .5-.7% the chassis will stay in HV shutdown.

Thanks, I'll take a look at it. I am not getting HV shutdown but my KV output at the cup is varying a few KV and is getting over 27KV (which I believe is near shutdown level). The reason I am looking at this is because I am getting blooming (hopefully related to my KV not being stable) and my raster not centered. The raster position jumper is next to C69, so hopefully removing that odd ground connection fixes this problem.
 
yea i trying to type from memory i will edit my post when i get a chance.
when i do please edit your quotes to reflect the correct info.

that chassis looks to have used the old 4 legged C36. a 2 legged cap will work with the jumper. but you will need to undo the other mods that were done.

my suspicion is that he added in the bigger cap because:

A: that is all he could find.
B: adding the extra value to C36 would compensate for the lack of not having C37.

so if i am correct you will need C37 and the diode that goes there to undo the previous mod.

have you checked your B+,VR, and the big resister hanging on the outside of the chassis to see if all were within tolerance.

Peace
Buffett
 
yea i trying to type from memory i will edit my post when i get a chance.
when i do please edit your quotes to reflect the correct info.

that chassis looks to have used the old 4 legged C36. a 2 legged cap will work with the jumper. but you will need to undo the other mods that were done.

my suspicion is that he added in the bigger cap because:

A: that is all he could find.

From the back it looks like a 4 legged C36. But on the front it has 2 leg C36 and 2 leg C69 on the silkscreen drawings.

If you think it's reason A (owner didn't have parts to full repair it), then should I just change C36 to 3600pf and add C69 at 6100pf? Is there any reason to not do this?

B: adding the extra value to C36 would compensate for the lack of not having C37.

so if i am correct you will need C37 and the diode that goes there to undo the previous mod.

I have a C37 and D15. If it doesn't look like I have them in the previous pictures is because I pulled the legs on one side to test them.

It was after I pulled C37 and D15 that I noticed the jumper I pictured in my previous post is grounding C37 and D15.

have you checked your B+,VR, and the big resister hanging on the outside of the chassis to see if all were within tolerance.

B+,VR,big resistor - that's the same thing, right? Yes, they check out OK.
 
only use 1 cap at C36 .0061uf/1600v and jumper the pads.

your B+ should be 130vdc

IC4 is your Voltage regulater check it for shorted pins.

OHM the big resister on the side of the chassis to see if it is in tollerance.

i have seen chassis marked with both caps locations and had the 4 legged cap on the chassis. there are 47 diffrent varriations of the K7000 and they changed during production runs and no documentation was provided.

so you can try it like i have sugested or you can wait for someone else to chime in.

if it does not work like i sugest then we can go from there.

Peace
Buffett
 
only use 1 cap at C36 .0061uf/1600v and jumper the pads.

This is my feeling right now, but I don't know how to jumper the pads. In my picture of the circle I showed how it was jumpered before but that jumper doesn't make sense - it seems like it shorts half of the components there to ground.

your B+ should be 130vdc

IC4 is your Voltage regulater check it for shorted pins.

OHM the big resister on the side of the chassis to see if it is in tollerance.

Thanks. I looked at these already but I can double check.
 

Back from work, so I can look at this in more detail. What's listed above won't work on boards with C69. In fact I am pretty sure that the last guy who worked on this chassis did the above jumpers on my board without thinking (see PCB picture in above post with red circle highlighting the jumper mod).

Here's a very blurry picture of the top side showing C36 and C69. C36 is populated (the big red one), C69 is not populated (you can see the empty position behind C36):

c69.JPG


The reason is why Bob's jumpers won't work, is because this is what it does on my board (orange and red wires are his jumpers):

badbob.jpg


As you can see, I don't need to do one of the jumpers (red) because this board already has a PCB trace to connect the collector of HOT to both C36 and C69. I can't do the other trace (orange) because it connects several points to ground.

What do you guys do when you cap these boards? Do you replace both C36 (3600pf) and C69 (6100pf), do you remove C69 and use 6100pf for C36, or do you leave them alone?

Thanks.
 
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if in fact that you need both.
then that model will not work with the mod.

i would populate it with both caps and undo the jumper that is in there now and see what you get.

i have never had to replace either cap on the models that required both caps.
but i am sure i will in the future so i guess i better stock a few of the other C69 caps.

Peace
Buffett
 
Doing the modification Bob Roberts shows on a board that does have a C69 screened but only using a C38 will work. I know I've done it before...
 
I'm not the only one who's noticed this:
http://forums.arcade-museum.com/showpost.php?p=1915024&postcount=116

gamefixer also implied that you can do the Bob Roberts jumper on C36/C69 boards with 19" chassis but not 25".

Going to order a C69 to repopulate the missing part.

Yeah, I had a hell of a time with two chassis that some one else worked on. By the time I got them they were dead. I un did the mod, put the right caps on the board (bought the caps from Wells) and they both came to life. While they were jumpered "wrong" they didnt blow anything up or pop any fuses which added to me being perplexed at the time.
 
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