#107 Email Q&A FT 747 problem - Which scope to get

[The Radio Shop]

It is question and answer time.
Why causes the FT-747 to jump frequency?
What scope do I need for CB radio repair?


Video from Alan w2aew RF sampler
https://www.youtube.com/watch?v=y4Zt_LJX1Tc

[km4gig]

Speaking of scopes ... I picked up a leader LBO502 a few months ago, and it has a problem. It seems to work OK for 30-45 minutes then the trace goes dim or completely disappears. Then I can turn up the intensity a little and the trace comes back for a while then goes away again. This cycle repeats until the intensity is turned all the way up and the trace goes away for good until I turn it off and let it have a nap.
The filament seems to be OK, and the sweep circuit seems to be ok since I always have a good waveform. So I'm suspecting something in the HV power circuit or the CRT is going. I don't have a HV probe, so how would you suggest attacking this?

73,
Jon

[The Radio Shop]

I would be more concerned with any capacitors you can find in the power supply area and focus area. This is definably a capacitor issue.

[km4gig]

I sort of suspected this due ti the age, but wanted a second opinion from someone with experience. Looks like I have some caps to buy. Thanks for the reply.

[km4gig]

Not sure if I told you, but this problem is solved. In the end, it was the four 0.5uf 1.5KV caps in the HV rectifier that fixed it. Thanks for the help.

[km4gig]

Now for my next question .... What's your opinion on these USB digital scopes like the OWON or Hantek? At the moment I only have the single channel Leader, but I'm getting to where I need 2 channels. Plus it would be nice to have some of the digital scope features. But as usual, I don't have a lot of cash to lay out for a scope.

[sonoma]

radio Tech is good at repairing these scopes and other test equipment. a couple years ago my BK 2040 was acting up and just looked at one he had repaired and I was able to find a bad cap that was causing a problem and a few dirty contacts.

[The Radio Shop]

Hi Jon,
Glad you got that fixed. Those caps are always a problem.
Been really busy here myself.

As far as a DSO, I would get the Rigol 1054Z. A little more money but a great scope and hackable to 100MHz.
But I would also have an analog scope. Some digital scopes do not like RF.

[The Radio Shop]

Hi Jon,
Glad you got that fixed. Those caps are always a problem.
Been really busy here myself.

As far as a DSO, I would get the Rigol 1054Z. A little more money but a great scope and hackable to 100MHz.
But I would also have an analog scope. Some digital scopes do not like RF.

Thanks for the kind words sonoma. Also good to see you. Where you hanging out these days?