Electronics Forum => Electronic Video Blog => Topic started by: The Radio Shop on March 12, 2017, 04:04:25 PM
Title: #107 Email Q&A FT 747 problem - Which scope to get
Post by: The Radio Shop on March 12, 2017, 04:04:25 PM
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
Title: Re: #107 Email Q&A FT 747 problem - Which scope to get
Post by: km4gig on March 13, 2017, 12:18:48 AM
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
Title: Re: #107 Email Q&A FT 747 problem - Which scope to get
Post by: The Radio Shop on March 13, 2017, 05:16:37 AM
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.
Title: Re: #107 Email Q&A FT 747 problem - Which scope to get
Post by: km4gig on March 13, 2017, 04:24:41 PM
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.
Title: Re: #107 Email Q&A FT 747 problem - Which scope to get
Post by: km4gig on April 06, 2017, 03:05:43 PM
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.
Title: Re: #107 Email Q&A FT 747 problem - Which scope to get
Post by: km4gig on April 06, 2017, 03:10:18 PM
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.
Title: Re: #107 Email Q&A FT 747 problem - Which scope to get
Post by: sonoma on April 27, 2017, 09:01:29 AM
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.
Title: Re: #107 Email Q&A FT 747 problem - Which scope to get
Post by: The Radio Shop on April 29, 2017, 08:09:37 AM
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.
Title: Re: #107 Email Q&A FT 747 problem - Which scope to get
Post by: The Radio Shop on April 29, 2017, 08:10:54 AM
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?