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The UF4004 vs BAV21. BAV is same speed with 50ns recovery but 250V, UF4004 is 400V and higher current at the same speed. I have BAV21 in stock, I'd have to order in the UF4004s

+75 to +110

The HV area is now lot better I have cleaned thoroughly the entire area with IPA and now I have steady -2950. This also resolved the problems at the Obama where now I have basically zeroes at pins 2

While surfing the web, I came across this link entitled "Tektronix CRT History" by Peter Keller. It may be of interest to the group.

What voltage range do you see at TP1665 when you change grid bias. No need to re-measure, just ballpark numbers you remember. Especially the sign, positive or negative voltage. Ozan

It is a bit low in capacitance but it is not the reason for the failure. However, I would replace it anyway since you removed it and it was stressed by high voltage. Ozan

I thoroughly cleaned the entire HV area with IPA and now the 2950V is steady while before it would drift slowly down to 2800 and even further The grid bias changes the voltage at TP1665 but does not

Behavior of your 485 is changing over time so some of these comments may not apply to current state of the scope but here is my feedback: This means the regulation loop (U1624) thinks HV voltage is

Well, I'm glad it wasn't my design that was in error. :D I'm interested in why the opamps popped too, I wonder if there is a bodge that can be added to existing units to protect the opamps from this

most likely the peaks on V+ ( or inputs)? exceeded max for the 741...had it happen a lot on equipment in implanters....we also had walking wounded which would sometimes work and well sometimes do

Ozan, Thanks, that makes a lot more sense now. I will run through and check all the connections from the LV regulator to the other boards (a nice, easy check that can be done with the power OFF). I

I would second this part of the post. I had a similar failure on a 475 and traced it to a bad restorer diode. The only way that I was able to locate the problem was using a 5 On Tue, 16 Mar 2021,

Third update: I made some experiments and found out that, once I let some current flow (200mA), the blinking stops and the display is steady. Then I tested the module in may "Rack"-TM5006 frame, and

I can only speculate why the 741s didn't like the unfiltered rectifier output as +Vs, but suspect the capacitor at the (+) input may have caused excessive input current as the device was violently

On Tue, 16 Mar 2021, 22:42 Ozan, <ozan_g@...> wrote: > > > > I checked the DC recovery diodes in the HV supply as listed in other > thread > > (all under the plastic cover and they are ok. > >

wrote:

I'm not sure what's going on today I turned it on and I measure 2963V on the HV spot. 50V point measures 49.73V

Hi, After having repaired several scopes (not only Tek's, but other brands also) with this symptom they invariably had leaky DC restorer diodes. Testing these diodes for leakage must be done at high

Thank yuou Clark, I will do. Next week-end i'll try the complete program. Max

Hi folks, I'm getting ready to move and need to find a good home for a 547 with 1A1 and B plug ins. Dusty, but stored in a low humidity storage area. It worked the last time I powered it on a few