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Yaesu YO-100 As A Service Scope




 
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Author Topic: Yaesu YO-100 As A Service Scope  (Read 4897 times)
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Ed WA4NJY
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« on: March 15, 2016, 10:36:35 PM »


 Is there any way to use a YO-100 as a scope for circuit testing, even in a limited way?

The manual kinda alludes to that but no details.

Any input will be appreciated.

Ed WA4NJY
Bradenton, Fl
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W3GMS
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« Reply #1 on: March 15, 2016, 11:11:18 PM »

Not saying you could not use it in a very limited manner, but its not designed as a bench scope for working on gear.  It has no vertical amplitude calibration nor any horizontal sweep calibration.  Vertical sensitivity would likely be an issue as well. 

Used solid state bench scopes are very reasonable these days, so I would suggest you pick up a good used bench scope.  I like Tektronix, but other prefer other brands.  The Tek 465 / 475 are some of my older favorite vintage scopes. 

Here is a link you may find helpful. 

http://www.usedoscilloscope.org/used-tektronix-oscilloscope/475-475a/

Joe-GMS 
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Ed WA4NJY
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« Reply #2 on: March 16, 2016, 12:45:12 PM »


 Thanks Joe.  What I am trying to do is isolate a random loud pop (speaker) out of a Drake receiver.  Hoping to connect a scope after each of the stages and wait for the spike.

All electrolytics have been replaced, etc.

I was thinking if the spike is RF, it may show up on this monitor scope.

Thanks,
Ed
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« Reply #3 on: March 16, 2016, 01:53:02 PM »

Hi Ed,

If you think the pop is coming from the audio stage, you may want to try a signal tracer.  They are a great tool for finding audio anomalies since you can hear the result through the signal tracers speaker.  If you don't have a signal tracer and small audio amp and a speaker would also do a good job. 

Saying that, if you like to do trouble shooting, I find having a good scope a must. 

Joe-GMS
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WD8BIL
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« Reply #4 on: March 16, 2016, 02:04:44 PM »

My R4A was doing the same thing. Turned out to be a sticky T/R relay in the T4X.

Just another data point.
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Ed WA4NJY
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« Reply #5 on: March 16, 2016, 04:50:48 PM »


 Thanks guys,

 The receiver is a stand alone radio so not connected to a TX.  I guess I can connect my audio tracer to the detector output and confirm the pop is coming from upstream or down.

 My first thought is the problem may be a bad cap somewhere.  Most are discs with a few foils.

 Darn nice radio and I have the K4OAH service CDs.  They have been very helpful.

 tnx, Ed
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KO6YB
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« Reply #6 on: March 16, 2016, 07:32:25 PM »

Hey Joe, Nice website, that one about used o-scopes. I think he goofed by leaving out the Tektronix 7000 series, especially like the 7603 and the 7904. I even got a 7104 dirt cheap in excellent shape.

Stan
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N8ETQ
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Mort


« Reply #7 on: March 16, 2016, 08:44:10 PM »


Hey Ed,


       I hope the "Pop" is rapid in nature, starring at a scope
for minutes on end sux. Maybe you could "Pull" audio from
an earlier stage and pipe it through another audio amp and
then just listen for a while..

Just a thought.

GL

/Dan




 Thanks Joe.  What I am trying to do is isolate a random loud pop (speaker) out of a Drake receiver.  Hoping to connect a scope after each of the stages and wait for the spike.

All electrolytics have been replaced, etc.

I was thinking if the spike is RF, it may show up on this monitor scope.

Thanks,
Ed
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W3GMS
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« Reply #8 on: March 16, 2016, 10:37:08 PM »

Hey Joe, Nice website, that one about used o-scopes. I think he goofed by leaving out the Tektronix 7000 series, especially like the 7603 and the 7904. I even got a 7104 dirt cheap in excellent shape.

Stan

Thanks Stan.  I have a bunch of the 7000 series stuff as well.   Spent many hours in my career using a 7104 with various plug in's.    All good stuff but they are kind of big!  They are very reliable and just keep working.  For sig generators I always like the HP stuff.  For scopes its always been Tek. 

Joe-GMS   
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« Reply #9 on: March 17, 2016, 07:35:05 PM »


 Is there any way to use a YO-100 as a scope for circuit testing, even in a limited way?

The manual kinda alludes to that but no details.

Any input will be appreciated.

Ed WA4NJY
Bradenton, Fl

The YO-100 has a convenient audio input RCA jack on the back and a 200mV p-p per cm sensitivity 10Hz-40KHz. Why can't this be used for audio?

If more gain is needed, make a super simple outboard amp in a little box, with a gain of 10 or so using half a 12AX7, then duplicate with the other half, so you now have x10 and x100, and capacitor couple the in and out to BNC jacks on the front of your box. Now have added 20mV and 2mV per cm with an outboard preamp. Why not? Very simple stuff.

Here, I drew up the schematic for a preamp like this with response of about 10Hz to >100KHz, and it includes reference to the circuit in the RC-25 book. The resistance coupled amplifier circuits are from the RCA engineers and will work fine. I think it is a worthwhile thing to try out for the audio tracing. Plus, it can protect the front end of the scope, although it has a tube there too so no worries.

If you think a 47K input Z is too low for your troubleshooting, you can put a 470K or 1M resistor in for R8 and change C4 to 0.1uF. If you rate C8 at 1KV, then you can measure signals in plate circuits having up to 500-600V on them.

No matter what, the output of the preamp can't spike over 90V because that's its B+, and the YO-100's C1 audio input capacitor to its 12BY7 grid should be able to handle that (check and see).

Th RC-25 tube manual is online many places including here:
http://www.bunkerofdoom.com/tube/man/index.html

So I hope you can have some fun, use that scope, and not have to spend a bunch of $ on an expensive scope unless you want to. Buy the cat or dog some treats with the money you save.  

One note the caps should be non-electrolytic, that is important. Inexpensive kinds are perfectly OK, the typical junkbox orange drop or little rectangular plastic ones etc. are OK for this. Not critical. An exception might be the C1, C5 50uF cathode decoupling caps, and even C6 the 10uF unit, but the idea is to improve stability by avoiding leakage.


* rc amp-sch.png (12.01 KB, 752x627 - viewed 426 times.)
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