B+ = 154V but should be 110V. Can't adjust???

rmcelwee

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I have a Sharp XM-2001N in a Blasteroids cab I just bought. The video was barely visible and I just put a complete cap kit in it (monitor, audio, filter). I did not check the B+ before installing the kit but afterwards when I got no video I checked it. It shows +154V and when I tried to adjust it really wouldn't do anything (maybe changed to 152V but I was worried over the high voltage so I turned it off. Any ideas?
 
I have a Sharp XM-2001N in a Blasteroids cab I just bought. The video was barely visible and I just put a complete cap kit in it (monitor, audio, filter). I did not check the B+ before installing the kit but afterwards when I got no video I checked it. It shows +154V and when I tried to adjust it really wouldn't do anything (maybe changed to 152V but I was worried over the high voltage so I turned it off. Any ideas?

compare the voltage to the manual

the reg ic i701 and each test point on the scr701

are they wrong too?

you can ohm the scr for a short

http://www.arcade-museum.com/manuals-monitors/Sharp_XM2001N_Schematic.pdf
 
OK, I did some checking. My SCR meters to a range of 0 - 1.4k (manual says it is a 1K so I'm guessing that is close to spec).

The voltages on the reg ic are all wrong. The schematics lists them as:
1 - 6.4V
2 - N/A
3 - 9.6V
4 - GND
5 - 5.2V
6 - 18.2V
7 - 9.3V

The real readings are:
1 - 0.9V
2 - N/A
3 - 23.7V
4 - GND
5 - 5.6V
6 - 25.4V
7 - 18.2V

The manual lists the input voltage out of the iso transformer as 100VAC and mine meters out to +110VAC. Not sure if that is a huge problem or not.
 
The manual lists the input voltage out of the iso transformer as 100VAC and mine meters out to +110VAC. Not sure if that is a huge problem or not.[/QUOTE]



most transformers are + or - 10% so its within spec's at 110vac
 
Shutdown!

Your in shutdown for sure.

I would ohm any supply lines.

Most caps replaced are on supply voltages.

simply put your ohm meter on any and all Plus side of the E-caps

you replaced, to confirm no obvious short to ground.

if none then you might if R703 is good

then lift one end of D604 to enable the ic to run if its good.

Odds are you made the problem, look over your work!!!

Since it was working.
 
if none then you might if R703 is good

Odds are you made the problem, look over your work!!!

I didn't check the caps but I did check R703 in circuit. It is reading 153ohms and spec is 150. I see the neckboard cracked in the past and has been repaired. I'm wondering if I busted one of the repaired joints when I pulled it off. Not sure if this can cause my problem or not but I bet it will be good to go over it anyway. I'll take a closer look tonight.
 
Your in shutdown for sure.

simply put your ohm meter on any and all Plus side of the E-caps

you replaced, to confirm no obvious short to ground.

if none then you might if R703 is good

then lift one end of D604 to enable the ic to run if its good.


OK, I checked all caps that I replaced for continuity to ground. There was none. I also looked over the neckboard and checked for continuity where it was cracked. Everything checked out fine.

Next, I pulled D604 and the monitor fired right up. It looked like hell but I didn't know if I could run it like that long enough to do some adjustments so I shut it down. I'm going to pull the chassis and freshen up some solder joints since I have some spare time. Ideas on what to check next?
 
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