# Scope leader LBO 508 A High voltage capacitors

#### gilbert gh

Jun 14, 2018
3
Hi,
I have oscilloscope Leader LBO 508 A .It worked fine Years ago.Now I wanted to use it again , and when I switched it on, it worked fine , but after some minutes the lines on the screen fade away and it went dark. Next time same but in shorter time , now when I switch it on ,only control lamp went on , nothing on the screen.
I opened it and voltages on testpoints 1 2 3 4 are ok , but on tp 5 (should be -2000v) nothing.
930v ac is present , desoldered and tested diodes D112-113-114-115 : ok .
desoldered and tested hv capacitors c 117-118-119-120-121 : 117 and 119 defective (12pF & 2pF) rest around 500nF=0,5µF.
I want to replace all five but these are oil capacitors MARCON K160DCLU504K not to find in Europe.
What can I use instead ?
Thanks,
Gilbert

#### kellys_eye

Jun 25, 2010
5,469
Most major component suppliers will have 0.47μF/1600V capacitors in stock and they would suit the application in place of the oil-filled versions - modern component manufacturing technology not requiring the oil for insulation these days.

Googling around I can see 'OEM' oil filled replacements are around $40 EACH!!!!! but bog standard devices that will do the same can be had for$5-\$10.

If you were keen to retain original appearance you could find a capacitor that fits INSIDE the existing packaging and do what a lot of antique radio restorers do and 'stuff' it (i.e. put the modern part inside the old housing).

Here's a selection from Farnell:

http://uk.farnell.com/w/c/passive-c...rs/prl/results?voltage-rating=1.6kv&st=0.47uF

#### gilbert gh

Jun 14, 2018
3
Thanks , I want to order
Wima MKP1T041007H00KSSD MKP 1 µF 1600 V/DC
Is that a good replacement ?( two in series gives 0,5µF)

#### kellys_eye

Jun 25, 2010
5,469
That would work and half the voltage across each capacitor (although I'd put 'balancing' resistors across them) although you don't need to hit 0.5μF that accurately - 0.47μF in a single package would work just as well.

#### gilbert gh

Jun 14, 2018
3
Thanks for the info

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