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HP 1741A oscilloscope - restoration project

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lowimpedance:
Thats quite some bbq-ing there  :P, I assume its now clean though !. The manual on this site is ok and has the Horizontal op circuit.

https://elektrotanya.com       ,scroll down for the search window. Read the supply circuit descriptions etc.

Given the damage you really need to isolate the LV power supply from the rest of the unit to fully debug it first as the 120 and 48V rails are
referenced to other supplies and if those are not fully functional things will go bad quickly. So best to trouble shoot in isolation then when working
look for other damage (beyond the horizontal OP PCB as well).  So just to confirm you only get 26V across C5 and 188V across C3 ?. Does that change when
the supply PCB is isolated from the res of the instrument ?. BTW be mindful of the voltages your playing with in the 1741 and follow best safe practices.

jeno:
Thank you very very mutch, this manual is very useful, i was searching it for days but couldnt find it, whithout the manual it was very hard to understand the working principle, now I vill start measuring all the resistors and all components one by one, I really want to get this boy up and running. Thank you very mutch.

jeno:
Can someone recomend me some good modern day replacement tranzistors for the A11 board? Only one of the tranzistors survived there, and I cant find any information for those Iwas thinking about BD439,Bc547 and their PNP brothers but Im not sure that those will be fine.

jeno:
Now my three main supplyes are good, I had to make some little adapters for the LM723 from DIL14 to TO100package, I couldn't get TO100ones, But my +120v and +48v rails are busted, I'm measuring +186volts at the +120v and 26volts at TP5 across C5 I have 78volts, but betwwen the negative side of C5 and GND I'm measuring -52 volts. Across C3 I have 186volt, and betwwen the negative side of c3 and GND I'm measuring -7.5volts. These measurments does not change id I disconnect the power tranies, the power supply is disconected from the rest of the circuits. All the transistors seem fine, what can cause this problem?

jeno:
I finaly managed to fix the power supply. All the voltages are oke, when the LVPS is isolted from the rest of the scope, but when I connet it I see no trace, the LEDs are working, and the 48v rail drops to zero. Can I get in contact whits someone for help, or some tips, what can cause that? Thank you.

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