Tektronix 434 s/n below 500000 faulty ps.

[Craig]

Tek part number 152-0497-00 is a KBP06-4 , 600V 1.5A, max surge 60A

Farnell part number 238429 is a Vishay 2KBP06M-E4/51 , 600V 2A max surge 60A, and is a drop in modern replacement. Less than a quid. Make sure it is dead first with your meter - desoldering a bridge is not easy and risks damaging the board, so best check first.

Craig

[johnmcgivern]

Thanks Craig found cold solder joint on diode bridge redone all of them have 325vdc at Q1080 and collectors of Q1030, Q1032 but no lights on front panel or low voltages present.
I am not sure how to check low voltage supplies to gnd ie resistance. Can you explain how to check the different resistances to gnd so I can find out where the short is hopefully. Do you have to remove the plug ins ie P114 etc.

[Craig]

We're now away for a week - so signing off for now.

Craig

[johnmcgivern]

Well deserved Craig after putting up with me ha ha have a good time mate.
Go safe, John.

[johnmcgivern]

Hi Craig, hope you had a nice few days. The latest on scope smoked the other day found HV cap smelly will send to mouser for replacements 5kv. I will replace 5 high voltage as they are in awkward positions so while I am in there I may as well do them.
Going for a few days golf with the club so scope on hold for a week or so thanks again for your help.

John.

[johnmcgivern]

Just a quick update awaiting HV caps from Mouser delivery 28th of March
Many thanks. John.

[johnmcgivern]

Hi back again gents, received all components from mouser.
Decided to turn scope on again before replacing anything.
R926 smoked.
Removed P126 plug.
The left side has an arrow then pins 2/3 then a 2 pin plug to the right 5pins shown on schematic but it is 2 separate plugs.
The red/black wire and pin 2 on the same plug have continuity I can't find where the wires go to on the schematic.
What does the arrow on the plug denote it's a red/black wire?
What would cause R926 to smoke?
Panel lights on and fat trace on display with P126 left plug removed.

[Craig]

Let me understand the time sequence here:

1. You had it working, basically
2. You ordered high voltage caps from Mouser
3. You have not yet installed them (I forget why you thought you needed to do this....)
4. You applied power to the scope before doing anything at all after item 1 above
5. R926 burnt
6. You removed P126, which was a 2-pin and a 3-pin connector side by side - without noting what went back where? I always, without fail do this, usually using my phone to close up photograph.

Does that about sum up where you are?

[johnmcgivern]

Hi Craig, hope you had a nice holiday.
1) Bought new components but did not fit.
2) Turned on scope R926 smoked, turned off scope.
3) Removed 3pin plug P126.
4) Turned scope on have primary voltages, front panel lights on, had thick trace but today heard arcing noise but not sure where from possibly one of the timing neons after this arcing noise lost thick trace.
5) replaced R926 but have not plugged P126 back in yet but I know where it goes.
What would cause R926 to smoke.

[Craig]

Hi Craig, hope you had a nice holiday.
1) Bought new components but did not fit.
2) Turned on scope R926 smoked, turned off scope.
3) Removed 3pin plug P126.
4) Turned scope on have primary voltages, front panel lights on, had thick trace but today heard arcing noise but not sure where from possibly one of the timing neons after this arcing noise lost thick trace.
5) replaced R926 but have not plugged P126 back in yet but I know where it goes.
What would cause R926 to smoke.

If no other resistors are getting hot, or show signs of having recently overheated, I'd check for a shorted C296 (10nF 500V ceramic)