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 Post subject: EICO-322 Signal Generator-How to fix this issue ?
PostPosted: Apr Tue 07, 2020 7:53 am 
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Joined: Mar Mon 02, 2020 4:59 am
Posts: 43
Hi All,

EICO-322 Signal Generator has an issue below although I have recapped all capacitors.

Band B: frequency discrepancy of the signal is 5 -10 kHz less. For example if I set signal generator at 550 kHz, I would catch this signal at 540 to 545 kHz (I used a working digital Grundig radio S350 radio to check)

Band C: frequency discrepancy of the signal is much more than band B, about + 100 to + 200 kHz. For example if I set signal generator at 1300 kHz, I would catch it at 1400 kHz.

I checked voltage of the two tubes and they seemed normal. Schematic is attached.

How can I troubleshoot/fix this issue ?


Thanks

O.C


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IMG_9221.JPG
IMG_9221.JPG [ 955.18 KiB | Viewed 292 times ]
Capture.PNG
Capture.PNG [ 268.49 KiB | Viewed 292 times ]
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 Post subject: Re: EICO-322 Signal Generator-How to fix this issue ?
PostPosted: Apr Tue 07, 2020 12:24 pm 
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Joined: Jun Sat 09, 2007 8:14 am
Posts: 4137
Location: Florida
Does it have adjustable coils?

RRM


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 Post subject: Re: EICO-322 Signal Generator-How to fix this issue ?
PostPosted: Apr Tue 07, 2020 12:50 pm 
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Joined: Jul Wed 22, 2009 3:07 pm
Posts: 836
Hi O.C,

I think this generator is as good as it gets!
There is not much to adjust in this generator, all the coils inside are air-core coils, no adjustment there.
There is a trimmer cap parallel with the variable tuning cap, C11, an 50pF air trimmer cap.
You calibrate the generator with that cap at 1MHz, there is a cal sign on the dial.

If you want to calibrate it, do it as follows:
Make sure the pointer is centered (mechanically) on the variable cap.
Let the generator warm up, set the band and dial to 1MHz, and then adjust the trimmer cap that the output is 1MHz, with no AM on.
If you want to be really thorough, drill a little access hole on the side of the case so that you could adjust that trimmer with the case on.

Regards, Peter


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 Post subject: Re: EICO-322 Signal Generator-How to fix this issue ?
PostPosted: Apr Tue 07, 2020 1:03 pm 
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Joined: Jun Sat 09, 2007 8:14 am
Posts: 4137
Location: Florida
I've seen data saying the 320 used air core coils but the 322 was updated to adjustable ones. That's why I asked the OP about that. EICO sometimes changed things on the fly.

RRM


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 Post subject: Re: EICO-322 Signal Generator-How to fix this issue ?
PostPosted: Apr Tue 07, 2020 1:04 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 108
Location: Great Salt Lake Valley
The Eico 322 Signal Generator was sold as an Increased Accuracy 320 generator. If it was built as a 322 it should have 4 additional trimmer caps mounted on the rear of the chassis (see photo). They adjust Bands E, D, C, & A left to right looking from the rear. Band B is adjusted with the trimmer mounted near the main tuning capacitor same as the 320. This is documented in an addenda sheet to the construction manual for the 320 - 322 Signal Generator.


Attachments:
Eico 322-2_4195.jpg
Eico 322-2_4195.jpg [ 569.13 KiB | Viewed 262 times ]
Eico 322 Addenda Sheet.jpg
Eico 322 Addenda Sheet.jpg [ 713.67 KiB | Viewed 262 times ]

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 Post subject: Re: EICO-322 Signal Generator-How to fix this issue ?
PostPosted: Apr Tue 07, 2020 1:14 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 108
Location: Great Salt Lake Valley
Looks like you can get a copy of the construction manual on ebay. Make sure it has the addenda sheets included.

https://www.ebay.com/itm/EICO-Model-320 ... xyQ45Q9-Vk

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 Post subject: Re: EICO-322 Signal Generator-How to fix this issue ?
PostPosted: Apr Tue 07, 2020 3:18 pm 
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Joined: Mar Mon 02, 2020 4:59 am
Posts: 43
My signal generator has 4 additional trimmer caps mounted on the rear of the chassis as in the photo above.

Quote:
If you want to calibrate it, do it as follows:
Make sure the pointer is centered (mechanically) on the variable cap.
Let the generator warm up, set the band and dial to 1MHz, and then adjust the trimmer cap that the output is 1MHz, with no AM on.


I will try this way to calibration the signal generator. What about the 4 additional trimmer caps? Should I adjust one of them if there is still a frequency discrepancy in each relevant band (E, D, C, & A)?

Thanks.


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 Post subject: Re: EICO-322 Signal Generator-How to fix this issue ?
PostPosted: Apr Tue 07, 2020 4:05 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 108
Location: Great Salt Lake Valley
Yes, if Band C is off after setting Band B, readjust generator to 1.6Mhz and repeat adjusting Band C trimmer for output on your radio set for 1.6Mhz.

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