Amplifone blowing F1

scottmaggie

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Donor 4 years: 2011-2013, 2024
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Hi guys. Still working on my SW. Got the HV working fine but still issues with the deflection board.

It keeps blowing fuse F1 (3A SB).

I have pulled and checked every single transistor and the 4 big diodes. The 4 deflection transistors are new but I swapped them again anyway. I also replaced all the caps and triple checked the polarity.

I also checked all the harness wires and pins.

Guess I am down to the resistors and small diodes... any direction on those is appreciated.



PS: The boards, wiring, HV, cabinet all work 100% with known good parts.
 
update - progress yes & no

1N914 diode at CR2 that is right in line with the F1 fuse was bad. Replaced it but still blowing F1. Pulled and tested the other diodes - all tested good.

Guess I have to pull the deflection transistors and start again since replacing the CR@ diode...
 
progress but still down...

Replaced the 2 deflection transistors by F1 a 3rd time - no change. Went ahead and swapped the U07 and U57 even though they tested good earlier.

Results: PROGRESS. The fuses are now all stable. BUT:

The LED blinks several times on power up before finally settling off. The screen now gets a glow but no picture.

Anyone have some thoughts on what to look at next?
 
Replaced the 2 deflection transistors by F1 a 3rd time - no change. Went ahead and swapped the U07 and U57 even though they tested good earlier.

Results: PROGRESS. The fuses are now all stable. BUT:

The LED blinks several times on power up before finally settling off. The screen now gets a glow but no picture.

Anyone have some thoughts on what to look at next?

The Spot Killer is meant to do that (Blink) to kill the beam until the game starts it moving

Looking at Problem at present
 
spot killer

All the ones I have seen the LED goes on at power up, stays on a sec or two then goes out. This one blinks repeatedly for around 15-20 seconds then goes out.

The screen starts to glow but no picture at all.

...Tube & HV board are fine with another known good deflection board.
 
All the ones I have seen the LED goes on at power up, stays on a sec or two then goes out. This one blinks repeatedly for around 15-20 seconds then goes out.

The screen starts to glow but no picture at all.

...Tube & HV board are fine with another known good deflection board.

Got it . . :)
 
thanks...

Going to check those again now. Also note it's a Green deflection board. It does not have the diode mods to R6 & R29 yet though parts on the way from Bob Roberts.

All the "W" zero ohm resistors have been replaced with clipped leads from the caps when I did the cap kit.
 
focus block wires?

What do you mean by the focus block soldered wires? The harness wires have all been removed, cut, re-installed and checked.

All the fuses are good - F1,2,3,4.
 
summary so far...

1. This is the green board
2. all new caps
3. all new fuses
4. harness wires cut and reinstalled
5. new Q4 U57 & Q5 U07 (changing these stoppped F1 from blowing)
6. all new deflection transistors, Q6,7,16, 17
7. All "w" zero ohm resistors replaced with wire
8. All diodes & transistors were pulled and tested (though anything could have blown since...)
9. No mods have been done as of yet.

Cabinet is known good - boards, wiring, HV. I have a beige deflection board that works perfect so 100% the issue is on this green deflection board.
 
small update

No progress but in a "touch test" R29 one of the 2 big resistors, is getting boiling hot within seconds of power up. Compared to the working deflection board which is just warm.
 
Do you have a scope? Your likely going to have to trace the circuit from the molex to the base of the U57/U07s. Start by testing the the T092 transistors in the preamp circuit to make sure one of those isnt shorted. Good luck!


Andrew
 
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