Re: Tek 577 D1 Repair (B07xxxx)


Jack2015
 

6. B072023
2020-Nov-15~30: Broken Trace
The last trace's broken into two traces:1st half of last trace and 2nd half of base trace.

<https://groups.io/g/TekScopes/photo/255563/24?p=Created,,,100,1,0,0>

The solution:Mod c265 1uf --->0.27uf on A1 Board,to improve discharging timing.

https://groups.io/g/TekScopes/photo/255563/25?p=Created,,,100,1,0,0
https://groups.io/g/TekScopes/photo/255563/26?p=Created,,,100,1,0,0

7. B072023 & B108637 (Mod:11 Steps)
2020-Dec-1~15: Retrace / Double Trace issue(even steps)
<https://groups.io/g/TekScopes/photo/255563/21?p=Created,,,100,1,0,0>

I prefer to eliminate the double trace and keep the 10th step,my solution is 11 steps(12 traces)
why 11 steps(12 tarces)?
a.it will eliminate double trace.
b.refresh rate/per trace:
11 traces(10 steps): 240/22 traces(11x2,double trace)=10.9 times/s
12 traces(11 steps): 240/12 traces(no double trace)=20 times/s
c.12 traces is 3 times of 4 (zero crosses):this will improve flickering.

The solution is simple and easy(eliminates double trace issue only at Fast step rate):
Put a 68K ohm resistor(>=1/4 W,5%) in parallel with R319(9.76K,A1 board)

new R319=68kx9.76k/(68k+9.76k)=8.535K ohm
New voltage of Pin 3 of U305B(adjustable by "Number of Steps"):
Min:30mV(1 step) to Max 4.75Vdc(10 steps)------->Min:26mV(1 step) to Max:5.28Vdv(11 steps)

Before and After:
<https://www.youtube.com/watch?v=67dBVDpUBUk&;;feature=youtu.be&ab_channel=JackSu>

<https://groups.io/g/TekScopes/photo/255563/26?p=Created,,,100,1,0,0>
<https://groups.io/g/TekScopes/photo/255563/27?p=Created,,,100,1,0,0>
<https://groups.io/g/TekScopes/photo/255563/28?p=Created,,,100,1,0,0>

By changing R319 we can get more max steps(max 12v/0.5v=24 steps).

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