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EICO 320 Signal Generator - Printable Version

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+--- Thread: EICO 320 Signal Generator (/showthread.php?tid=13002)


EICO 320 Signal Generator - Crist Rigotti - 08-25-2015

Guys,
I got this generator at the Dallas spring auction for like $10. I ordered all new caps and resistors. Also changed the outputs to BNC. It was a bit of a rust bucket. After I painted the chassis, I rewired the whole thing and installed new caps and resistors.

I calibrated it like the instructions say to at 10KC. Seeing that this is an inexpensive signal generator, the signal doesn't track very well with the dial scale - no surprise there. I always use a freq. meter anyway.

Works well enough to align my restored AM radios.

It was fun and easy to do.

I have before and after pictures.

[Image: http://i1060.photobucket.com/albums/t458/crigotti/EICO%20320/100_0596a_zpsvgozwp7b.jpg]

[Image: http://i1060.photobucket.com/albums/t458/crigotti/EICO%20320/100_1873a_zpsv4fswff0.jpg]

[Image: http://i1060.photobucket.com/albums/t458/crigotti/EICO%20320/100_0597a_zpsyl9nefrt.jpg]

[Image: http://i1060.photobucket.com/albums/t458/crigotti/EICO%20320/100_1876a_zpsxryrxnjw.jpg]

[Image: http://i1060.photobucket.com/albums/t458/crigotti/EICO%20320/100_0590a_zpsqfykk4ik.jpg]

[Image: http://i1060.photobucket.com/albums/t458/crigotti/EICO%20320/100_1871a_zpsymllxojv.jpg]

[Image: http://i1060.photobucket.com/albums/t458/crigotti/EICO%20320/100_1872a_zpsmsyafafr.jpg]

RE: EICO 320 Signal Generator - codefox1 - 08-26-2015

You did a great job! These "oldies" stabilize once on for about 20 minutes, and yes, check with digital meter, but for AM radios, dial setting is usually "close enough."

RE: EICO 320 Signal Generator - Radioroslyn - 08-28-2015

What some folks do is get the calibration good at the low end (for the IF frequencies) and use the BC stations to align ant/osc stages.

Terry

RE: EICO 320 Signal Generator - Crist Rigotti - 08-28-2015

Thanks guys!

RE: EICO 320 Signal Generator - Mitch - 07-27-2016

Top notch restoration.  The coil section looks a lot like the Heathkit SG-6/7 series.  Probably the same tubes as well.  

Oh, and the early Eico blue enameled panels look so nice when you clean them up. 
A good application of car wax makes them 'pop'.  Really love that blue!!!!!

Mitch

RE: EICO 320 Signal Generator - PhilcoMike - 07-27-2016

Cool! Now you want to make me get mine out of hibernation and refurb.

Thanks,

Mike

RE: EICO 320 Signal Generator - Joe Rossi - 07-27-2016

Great resto. Icon_thumbup   I am jealous at how neat you have dressed the wiring and components!  Joe

RE: EICO 320 Signal Generator - TV MAN - 07-28-2016

Very nice resto! I like seeing our test equipment restored as well as radios. After all, this is what helps bring our old radios back to life. I am curious about the gold thing (diode I assume) connected to your line cord. Is this replacing the old? What did you use?

RE: EICO 320 Signal Generator - Crist Rigotti - 07-28-2016

(07-28-2016, 08:19 AM)TV MAN Wrote:  Very nice resto! I like seeing our test equipment restored as well as radios. After all, this is what helps bring our old radios back to life. I am curious about the gold thing (diode I assume) connected to your line cord. Is this replacing the old? What did you use?

Thanks to everybody for the nice comments.

The gold thing is a dropping resistor to bring the line voltage down to 115Vac from 120vac.  I'm not sure it is really needed, but I'd rather err on the safe side.  There was no resistor before.

BTW, since there pictures were taken, I've added the extra trimmer caps (which takes it from a 320 to a 322) for each coil which made the dial more accurate, but I use a frequency counter with all my signal generators.

RE: EICO 320 Signal Generator - gregb - 07-28-2016

Another first class job Crist, keep up the great work!

Gregb

RE: EICO 320 Signal Generator - PhilcoMike - 07-29-2016

Crist,

Can you post a photo/values where you added the trimmer caps?
I may want to make that mod too.

Thanks,

Mike

RE: EICO 320 Signal Generator - Mitch - 07-30-2016

I've restored about a dozen or so Heathkit/Eico/Knight signal generators.  Got at least eight more awaiting their turn.  Each one is a lot of fun to do and the transformation always satisfying.  

Now I do the dropping resistor just a little differently.  I add it in the secondary, just between the transformer and the 1N4007 diode which replaced the selenium rectifier.  It limits the inrush current to the first filter capacitor, (usually a 20/22 ufd).  A half watt resistor is all thats needed.  I determine the value of the added resistor by clipping a 10K pot where the new resistor will be.  Then adjust the pot to dial in the proper voltage for the B+.  It runs between 200 ohms and 1K.  All depends on how much voltage drop was across the old selenium diode and what the present voltage you've got coming out of the wall.  

I'm wondering if your approach is better or worse than mine?  Does the resistor run warm?  Mine doesn't.  I'll have to post a photo of a similar signal generator that's in the restoration queue, so you can see how my approach looks.  I'd bet you could make valid arguments for doing it either way.  Something to ponder.  

Mitch

RE: EICO 320 Signal Generator - Crist Rigotti - 07-31-2016

(07-29-2016, 04:08 PM)PhilcoMike Wrote:  Crist,

Can you post a photo/values where you added the trimmer caps?
I may want to make that mod too.

Thanks,

Mike

Here are 2 pictures.  I forgot I etched a board to hold the trimmers.  Made for a neat and tidy installation.  The trimmers are 10pf to 60pf.  I think I got them from the Ukraine.

[Image: http://i1060.photobucket.com/albums/t458/crigotti/EICO%20320/100_4106a_zpsnjawjkcp.jpg]

[Image: http://i1060.photobucket.com/albums/t458/crigotti/EICO%20320/100_4108a_zpsfcj0kzoe.jpg]

RE: EICO 320 Signal Generator - PhilcoMike - 08-01-2016

Thanks Crist!

Mike

RE: EICO 320 Signal Generator - Crist Rigotti - 08-02-2016

This thread got me thinking about what a pain it is to hook up my frequency counter to this generator. I really can't use the RF output because I can turn it down pretty low so low that the frequency counter becomes inop.

So I added another BNC jack just for the frequency counter. The "pick-off" is just before the attenuator pot. I used a .01 uf cap just like on the RF output jack.

Works real well. I can turn down the RF jack all the way down without affecting the frequency counter.

The pictures describes what I did. Pretty simple.

[Image: http://i1060.photobucket.com/albums/t458/crigotti/EICO%20320/100_4115a_zps2af6w8ym.jpg]

[Image: http://i1060.photobucket.com/albums/t458/crigotti/EICO%20320/100_4116a_zps8gbryfya.jpg]