Ok Dave The signal on the 475A looks good nice square wave

However on the HP1740 Bad same as image I post at beginning

 

Ok Dave The signal on the 475A looks good nice square wave

However on the HP1740 Bad same as image I post at beginning

so the signal is working at TP9?

 

Hey Dodgy, what parts of L'pool are you?
I know Woolton quite well. Ran around Calderstones Park many times.

 

The signal on the tek 475 works at tp9 ? yes

 

The signal on the tek 475 works at tp9 ? yes

SO the fault is further in then, need to look at the next point which is page 117,
look at the manual and see where pin 3 of the IC A5A1 is.

 

Hey Dodgy, what parts of L'pool are you?
I know Woolton quite well. Ran around Calderstones Park many times.

near Lydiate, i cant run too Fat!!

 

Something doesn't jive.
I suspected that the problem is further along if it appears on both Channel A and B.
But from here on the signal should be DC coupled.

 

I see it on the schematic but not the board?

 

I see it on the schematic but not the board?

When you find it look at pin3 ( input), and pin 18 (output),

its a square ic 18 pins
LOOK at page 114 , its shown there!!!

 

Im looking for A5a1

 

Im looking for A5a1

yes ,if you look on page 114 it shows where the ic is, looks like its on a separate pcb.

 

I will look on the other pcbs

 

I will look on the other pcbs

Looks like its located on pcb A5 see page 53, the pcb is vertical mounted at the side of the crt.


PS what time zone are you in??

 

us mountain time it 1pm

 

Ok Im looking at the A5 PCB it has 4 adjustable pots . the only IC is a large white ic
located center of board. its an HP 624 chip it has 9 pins on each side . Im looking at the side towards the 4 pots

 

dodgydave you said

"When you find it look at pin3 ( input), and pin 18 (output),"

now should I connect the scope to pin 18?

 

Dave I didnt know until now it was that late in Liverpool. 10pm
Thank you for your help

 

Ok Im looking at the A5 PCB it has 4 adjustable pots . the only IC is a large white ic
located center of board. its an HP 624 chip it has 9 pins on each side . Im looking at the side towards the 4 pots

Yes that's the one, test the input on pin 3 and output on pin 18.

 

I got a corrupt sine wave on both 3 and 18 about 6v magitude
pin 10 is the same.

The generator is set at 1v ac square wave 1kz .
I did this without the hp1740A turned on . power plug unpluged. Thus, only the generator is providing the signal

 

When I turned the hp1740a on guess what?

now the output is the same both the
tek475 and the hp1740a

So now we have similar screen images to the one in my original post. this must mean something.