Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Mar Sat 23, 2019 1:51 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 18 posts ] 
Author Message
 Post subject: Prec E200 sig gen. HK SM2420 Freq. cntr, Textronix 465 scope
PostPosted: Feb Sat 09, 2019 2:06 am 
Member

Joined: Mar Thu 03, 2011 8:53 pm
Posts: 1014
Location: Davis, CA
I recently acquired the E200 signal generator to use as a backup. I have the one with the 80 rectifier. Circuit diagram is at http://bama.edebris.com/manuals/paco/e200/. The diagram for my generator is the one starting with serial number above 1301.

I have gone through the generator and changed the electrolytics, paper caps and out of spec resistors.

The generator seems to be working ok as I can hear the tone in a working radio at the correct point on the radio dial using a loop placed near the radio.

I am not getting the correct readings on the frequency counter when I connect the generator to the counter. This counter gives the correct readings when connected to my other generator. Here is a summary of what I have observed.

1. In the Unmod. setting the counter reads twice the generator setting.

2. On the Mod. setting there is no change in the counter reading up to a setting of 5 on the Mod. dial. Above this setting the counter reading drops to a lower value but not the correct value.

3. For the above, both RF dials were on the max settings. When the RF-1 dial setting is lowered the counter reading drops.

Any ideas on why the counter does not read correctly.

Thanks, Bob


Last edited by rck46 on Feb Sat 16, 2019 2:11 am, edited 2 times in total.

Top
 Profile  
 
 Post subject: Re: Precision E200 signal gen. and Heathkit SM2420 Freq. cou
PostPosted: Feb Sat 09, 2019 1:57 pm 
Member

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 3471
Location: Sunbury, Ohio 43074
That generator uses harmonics as most of that era do. If you put a scope on the output you will probably see a pretty messy sine wave that is probably confusing your counter

_________________
Preserving the history of electronics, one boat anchor at a time! :)
www.bbtvtestequipment.com


Top
 Profile  
 
 Post subject: Re: Precision E200 signal gen. and Heathkit SM2420 Freq. cou
PostPosted: Feb Wed 13, 2019 12:03 am 
Member

Joined: Mar Thu 03, 2011 8:53 pm
Posts: 1014
Location: Davis, CA
I do not have an oscilloscope to check. I am wondering about the RF signal strength. Seems to be low even with both RF dials at the max setting. I not too sure how to measure the output so I measured the voltage across the generator RF output and got .011v at 40% modulation. Compared it to the output from my Precision E200D signal generator which produces about .045v at 40% modulation. Is this an indication of low output and if so what should I look at to correct?

Thanks, Bob


Top
 Profile  
 
 Post subject: Re: Precision E200 signal gen. and Heathkit SM2420 Freq. cou
PostPosted: Feb Wed 13, 2019 2:05 am 
Member
User avatar

Joined: Dec Sun 21, 2014 6:37 am
Posts: 1810
Location: Portland, TN, USA
Bob, I’ll take a shot at helping, as I have an E-200C and have refurbed a couple of the older E-200 series generators as well as several of the E-200D models. I like them all. Like several of us, I seem to have attracted way more generators than anyone needs. :roll:

Your output seems low. According to some documentation I have it should be more like at least 0.3 to 0.5 volts or more. I can verify this tomorrow on my C if needed. I’ll have to drag it off the storage shelf and onto the bench.

One area to look at is the attenuator box, the pot's within it and R1 which I’m remembering is buried in the panel connector. Follow the signal from the plate of the 6SJ7 outward to the front panel, after checking out the intervening components before powering up.

Meanwhile, you might try carefully reducing signal into the counter, starting from when you’re reliably seeing twice the expected frequency, and looking for a possible “sweet spot” where the frequency drops to the correct reading. You’ll need to move quite slowly to give the counter time to settle to the correct reading. I’ve seen this work before, but not always, depending on what counter you’re using.

The problem of course is that the level that gives you a correct reading may not be suitable for your purposes otherwise, but you’ll have an idea of the dial accuracy at that point in any case.

I seem to remember that Mr. Carlson did a video on adding a mod to this specific generator to provide a high-level output for a counter to solve this issue. However, since you have the E-200D, that may be more than you want to do.

Since I work mainly on communications receivers, I moved on to an HP 606B (my favorite) and an HP 8656B for most of my needs. I really need to find a home for some of these others one of these days.

_________________
73, de Chuck K4CCW

"The question is not what you look at, but what you see." Thoreau


Top
 Profile  
 
 Post subject: Re: Precision E200 signal gen. and Heathkit SM2420 Freq. cou
PostPosted: Feb Wed 13, 2019 5:50 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5165
Location: Rochester NY USA
The distorted waveform this makes will change with a cable attached unless it's terminated (50 Ohms with a 50 Oh cable). But that will drop the level even more. I've had some success using a series resistor (the resistor plus the input capacitance of the counter attenuates harmonics). I would add a "high level" output jack on the generator with a series resistor inside (reduces loading too, so counter doesn't affect output level). But there's a chance this will radiate.


Top
 Profile  
 
 Post subject: Re: Precision E200 signal gen. and Heathkit SM2420 Freq. cou
PostPosted: Feb Thu 14, 2019 12:18 am 
Member

Joined: Mar Thu 03, 2011 8:53 pm
Posts: 1014
Location: Davis, CA
Hello again Chuck. You helped me out about a year ago with my Precision E200D generator.

I am familiar with Mr Carlson's video on the E200C and probably watched it 2 or 3 times while I was working on my E200. His video is here:https://www.youtube.com/watch?v=eE7J4Kpbe6w. I followed his suggestions to change the RF connectors to the BNC type and installed R1 in a grounded shield.

As matter of information I noticed that several of the original installed resistors were different from the values shown on the circuit diagram as follows. I have listed the original design value, the actual installed value based on color code, the measured value of the original installed resistor, and the value of the replacement resistor.

R2: design: 4k, installed: 3.6k, measured: 4.3k, replaced: 3.9k.
R3: design: 300ohms, installed: 390, measured: 432, replaced: 390.
R9: design: 250k, installed: 270k, measured:325k, replaced: 270k.

I went through and checked out everything in the attenuator box (R1, C5, V3, and V4) and also checked R2, R3, R6 and the AVC control (V1 on the circuit diagram). Everything looked ok except V1. It was not working properly. I gave it a shot of deoxite that cured the problem and I am now getting a much stronger RF signal. I can now hear a loud tone in a radio when a loop is placed next to it.

I followed your suggestion to find the point on the C band where the reading on the frequency counter drops to the correct reading. The counter reads correctly between 580kc and 680 kc. At 600 kc the dial reads correctly. At other points on the C band the frequency counter reads double the dial reading. On all the other bands the dial reads approximately correct - I would say within 1% or so of the frequncy counter reading.

I think I have a useful genrator now.

Mr Carlson made a change to the R9 and C10 values to correct the modulation frequency. You can see this at minute 45 on his video. He changed R9 to 158k ohms from the original 250k and changed C10 to.047mfd from the original .1mfd. Is there any way of knowing if these changes would be appropriate for my generator?

Thanks, Bob


Top
 Profile  
 
 Post subject: Re: Precision E200 signal gen. and Heathkit SM2420 Freq. cou
PostPosted: Feb Thu 14, 2019 1:32 am 
Member
User avatar

Joined: Dec Sun 21, 2014 6:37 am
Posts: 1810
Location: Portland, TN, USA
Great! Always glad to help.

No need to mess with the audio freq unless you just don’t like the tone. Some, like the D use 1000kHz, others use the older 400 hz, some both in various generators.

_________________
73, de Chuck K4CCW

"The question is not what you look at, but what you see." Thoreau


Top
 Profile  
 
 Post subject: Re: Prec E200 sig gen. HK SM2420 Freq. cntr, Textronix 465 s
PostPosted: Feb Sat 16, 2019 2:26 am 
Member

Joined: Mar Thu 03, 2011 8:53 pm
Posts: 1014
Location: Davis, CA
My neighbor just gave me a Textronic 465 scope. I know nothing about scopes or how to use them but thought I would hook it up to the E200 signal generator and see what I would get. I attached a cable from the E200 RF output to Channel 1 on the 465. I played with the dials and adjustments but could not get anything meaningful. I have attached a picture of what I am seeing. Can someone give me some advice on how to make the adjustments?

Thanks, Bob


Attachments:
textronix 465.JPG
textronix 465.JPG [ 104.15 KiB | Viewed 321 times ]
Top
 Profile  
 
 Post subject: Re: Prec E200 sig gen. HK SM2420 Freq. cntr, Textronix 465 s
PostPosted: Feb Sat 16, 2019 2:39 am 
Member
User avatar

Joined: May Wed 18, 2011 2:40 am
Posts: 3734
Location: Littleton, MA
Adjust the "A Trigger Slope Level" outer knob (dark gray) to about the mid-point. The "trig" light should illuminate when you have it near the right spot. Turn off any modulation on the signal generator. What frequency is the signal generator set to? From the photo, I'd guess that you need to turn the sweep time down to a smaller period (higher frequency).

_________________
Steve Byan http://www.byan-roper.org/steve/steve-at-play/


Top
 Profile  
 
 Post subject: Re: Prec E200 sig gen. HK SM2420 Freq. cntr, Textronix 465 s
PostPosted: Feb Sat 16, 2019 8:56 pm 
Member

Joined: Mar Thu 03, 2011 8:53 pm
Posts: 1014
Location: Davis, CA
Steve: I'm actually hooked up to the E200D signal generator. I was able to adjust the A Trigger Slope Level so the trig light is illuminated. Modulation is off and signal generator set at 1500kc. I now have a single vertical line going slowly across the screen. The line extends from the top of the screen to the bottom of the screen. Is the sweep time knob the one labeled "A & B Time/Div and Delay Time"?

Bob


Top
 Profile  
 
 Post subject: Re: Prec E200 sig gen. HK SM2420 Freq. cntr, Textronix 465 s
PostPosted: Feb Sat 16, 2019 10:32 pm 
Member
User avatar

Joined: May Wed 18, 2011 2:40 am
Posts: 3734
Location: Littleton, MA
rck46 wrote:
Is the sweep time knob the one labeled "A & B Time/Div and Delay Time"?

Yes.

It sounds like your sweep is set to something on the order of 1 second per division. Set it to about 0.5 or 0.2 µs/division for a 1500 kHz input signal.

_________________
Steve Byan http://www.byan-roper.org/steve/steve-at-play/


Top
 Profile  
 
 Post subject: Re: Prec E200 sig gen. HK SM2420 Freq. cntr, Textronix 465 s
PostPosted: Feb Sun 17, 2019 9:21 pm 
Member

Joined: Mar Thu 03, 2011 8:53 pm
Posts: 1014
Location: Davis, CA
Steve:

When I first turned on this instruments this morning and set the sweep time knob to .2us I got the top half of a sine wave on the scope screen. After a few seconds the trig light went off and the image went away. I tried fiddling with the A trigger knob but could not get the trig light to come on although it would occasionally blink on and off. I was hooked up to Ch 1 at this point and I noticed that the volts/div light was not working.

I switched over to Ch 2. With the sweep time knob set at .2us, and the volts/div set at 50m the trig light came on and I got this image. At times the image blinks on and off. If I change to a higher volt/div setting the trace goes away. What should the AC-ground-DC switch be set on. I get the same image on AC and DC and a straight horizontal line on the ground setting. I just went and looked at the scope again after typing this and the image was gone and the trig light was off. After a minute or two the image blinked on for a few seconds and then went away.

Could any of these problems be caused by dirty controls?

Thanks, bob


Attachments:
Textronix 465-2.JPG
Textronix 465-2.JPG [ 107.33 KiB | Viewed 251 times ]
Top
 Profile  
 
 Post subject: Re: Prec E200 sig gen. HK SM2420 Freq. cntr, Textronix 465 s
PostPosted: Feb Mon 18, 2019 5:28 pm 
Member
User avatar

Joined: Apr Sun 22, 2018 5:53 pm
Posts: 39
Last pic looks as if you now have sine wave, but have the Volts/div set too low, try turning that to higher volts/div to reduce the amplitude so that the entire sine wave is visible on the CRT. Doc


Top
 Profile  
 
 Post subject: Re: Prec E200 sig gen. HK SM2420 Freq. cntr, Textronix 465 s
PostPosted: Feb Mon 18, 2019 10:23 pm 
New Member

Joined: Feb Fri 09, 2018 9:26 pm
Posts: 15
It looks to me like channel 2 input has the BNC connection used, and channel 2 is selected for display, but the channel 2 input is set to ground in the Textronix 465-2.JPG image (the tab is between the AC and DC positions under the Volts/div control). Since there appears to be a sine wave on the display, the scope may not be working correctly.


Top
 Profile  
 
 Post subject: Re: Prec E200 sig gen. HK SM2420 Freq. cntr, Textronix 465 s
PostPosted: Feb Mon 18, 2019 11:09 pm 
Member

Joined: Mar Thu 03, 2011 8:53 pm
Posts: 1014
Location: Davis, CA
Doc: I agree. I think I am seeing part of the sine wave but when I switch to a higher volts/div setting the trace disappears.

PPFH2QVO: The photo is hard to see details. The AC- ground-DC switch is actually on DC. When I change it to the ground setting I get a horizontal line across the screen.

Bob
.


Top
 Profile  
 
 Post subject: Re: Prec E200 sig gen. HK SM2420 Freq. cntr, Textronix 465 s
PostPosted: Feb Tue 19, 2019 12:01 am 
Member

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 3471
Location: Sunbury, Ohio 43074
rck, this model scope is notorious for dirty switches, and especially in the input attenuators. Rotate the volts/cm switch many times from end to end and see if it clears up. Do the same, really, with every switch and rotary and knob on the thing. Might be all it needs.

_________________
Preserving the history of electronics, one boat anchor at a time! :)
www.bbtvtestequipment.com


Top
 Profile  
 
 Post subject: Re: Prec E200 sig gen. HK SM2420 Freq. cntr, Textronix 465 s
PostPosted: Feb Wed 27, 2019 10:15 pm 
Member

Joined: Mar Thu 03, 2011 8:53 pm
Posts: 1014
Location: Davis, CA
Barry: I took the cover off of the unit to see if I could clean the switches. Access is limited and I was reluctant to try and do any cleaning. I rotated the volts/div switches many times and now am getting a fairly steady sine wave on CH2. I do not get any response on CH1. Can you spray these switches with deoxit to clean them or is there an accepted method of cleaning them? Any ideas why no response on CH1?

Thanks, bob


Top
 Profile  
 
 Post subject: Re: Prec E200 sig gen. HK SM2420 Freq. cntr, Textronix 465 s
PostPosted: Feb Wed 27, 2019 10:45 pm 
Member

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 3471
Location: Sunbury, Ohio 43074
rck, rather than my typing a book, if you dig around on the internet there are some explanations, and a few youtube videos, on these scopes. I don't recall if any of them went specifically into the switches, but NO, I do NOT recommend spraying into them, even if yhou can get at them sufficiently to do so.

Channel 2 being dead is likely to be either a component failure in that input section, or some issue with the pushbutton switches that select the channels. Or possibly the AC-GND-DC switch.

At the risk of repeating myself, I repeat..... you usually need a scope to fix a scope. Failing that, you can do some checking of voltage levels in the input circuitry, but it could also be in the circuitry that does the channel selection itself (add/chop/invert etc).

only can guess. But if channel B is stone cold dead, it is not likely to be the attenuator itself. Possible, but highly unlikely

_________________
Preserving the history of electronics, one boat anchor at a time! :)
www.bbtvtestequipment.com


Top
 Profile  
 
Post New Topic Post Reply  [ 18 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: Bluetrain1950, Dave Tilotta, pmeltech and 10 guests



Search for:
Jump to:  


























Privacy Policy :: Powered by phpBB