Safgan (DT-520) Oscilloscope

[pwdrive]

"I'll be fully Rubberised and goggled-up"

Utube please....

Lawrence.

[pwdrive]

From the description so far I presume you are saying that there is a capacitor connected in series with a mystery component, that series circuit being connected in parallel with the intensity pot track?
I may be wrong but if the above is the case then I can't see what a diode would do, a resistor yes but not a diode.
On another slant could the mystery component have been a ferrite bead?

Lawrence.

[Refugee]

It might be part of the EHT regulator as it is on the pot track and not the switch. I would not expect there to be enough currant to blow a capacitor though unless it is mains EHT.

[AlanBeckett]

bobsy.

Have you blown yourself up yet?

Alan

[Bobsy]

bobsy.

Have you blown yourself up yet?

Alan

Just a little singed! lol - Motivated me into buying a fluke ! I think I solved my problem that's why I'm returning to share
No schematics for my DT-520 however I spotted this schematic for the DT-410 (see attachment) which has given me all the clues I need.
It seems the Diode is a 'Zener 75v' straddling the intensity Pot (limiting the max voltage across the pot), which means the Cap (rated 250v on my DT-520) is pretty safe & connects to 'Centre' post on Pot! The cap looks like it is limiting noise on the output.
I'm just awaiting delivery of the Zener & am very hopeful at this point.
I'm glad I never gave up on this - When you grab a Tiger by the Tail its sometimes best not to let go!

[AlanBeckett]

Bobsy,

Have you found a Circuit then?
That looks like a Zener across the Intensity Pot to limit the Voltage across it. If it's dead 1N5374A would probably suffice.

Alan

[Bobsy]

Bobsy,

Have you found a Circuit then?
That looks like a Zener across the Intensity Pot to limit the Voltage across it. If it's dead 1N5374A would probably suffice.

Alan

Just a little singed! lol - Motivated me into buying a fluke ! I think I solved my problem that's why I'm returning to share
No schematics for my DT-520 however I spotted this schematic for the DT-410 (see attachment) which has given me all the clues I need.
It seems the Diode is a 'Zener 75v' straddling the intensity Pot (limiting the max voltage across the pot), which means the Cap (rated 250v on my DT-520) is pretty safe & connects to 'Centre' post on Pot! The cap looks like it is limiting noise on the output.
I'm just awaiting delivery of the Zener & am very hopeful at this point.
I'm glad I never gave up on this - When you grab a Tiger by the Tail its sometimes best not to let go!

[AlanBeckett]

Well done.

Alan

[Bobsy]

There doesn't seem to be much difference between the DT-520 & DT-410 looking at the pics (just the focal Pot being re-positioned - top left on DT-410 & below Intensity Pot on DT-520). Thanks all for your help and if anyone needs the DT-410 Schematic (full) just email me.
   
   

[Skywave]

Quote, Bobsy: "I'm glad I never gave up on this".
Quite: as I've frequently maintained: "Never forget the 3 Ps: Persistence, Perseverance and Patience". And you've finally fixed it: well done.

Al. / Nov. 5, 2013 //