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Old 18th Feb 2021, 2:57 pm   #1
Scotorvm
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Default Columbia 357 - restored but unable to tune in properly

Guy's, last year during lock-down I restored to the best of my ability a Columbia 357, all is good, stations are now coming in loud, however I cannot tune in any station without other stations playing in the background.

I don't think an aerial issue as I have sets of similar age tuning ok to 1 station.

Any tips welcome, I don't have a signal generator etc. I have replaced all valves now for NOS.

Is this a component issue or do I need to tweak anything?

All condenser block caps and out of value resistors have been replaced.

Thanks
Lee
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Old 18th Feb 2021, 4:03 pm   #2
cathoderay57
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Default Re: Columbia 357 - restored but unable to tune in properly

Hi Lee, some questions:
How loud is the background station interference?
Is it just one background station all the time or does the background station change when you tune to another frequency?
Does this happen just at night or during the daytime as well?
It isn't unusual to get interference from another station on Medium Wave at night time. It would be unusual to get such interference on Long Wave but I don't know how strong the R4 LW signal is where you are. My best guess is that the radio is showing poor selectivity and the best way to improve that would be to realign it. Without a signal generator that is going to be a challenge and you would possibly do more harm than good tweaking the trimmers, unless you get a sig gen and follow the instructions in the Trader Sheet. Cheers, Jerry
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Old 19th Feb 2021, 7:09 am   #3
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Default Re: Columbia 357 - restored but unable to tune in properly

I haven’t a circuit for the 357 but other Columbia radios with similar model numbers appear to be TRF sets not Superhets, if yours is a TRF then selectivity can be more problematic.

Has Gerry states alignment could well be out but without the proper equipment you could make it worse.
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Old 19th Feb 2021, 8:15 am   #4
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Default Re: Columbia 357 - restored but unable to tune in properly

Quote:
Originally Posted by cathoderay57 View Post
Hi Lee, some questions:
How loud is the background station interference?
Is it just one background station all the time or does the background station change when you tune to another frequency?
Does this happen just at night or during the daytime as well?
It isn't unusual to get interference from another station on Medium Wave at night time. It would be unusual to get such interference on Long Wave but I don't know how strong the R4 LW signal is where you are. My best guess is that the radio is showing poor selectivity and the best way to improve that would be to realign it. Without a signal generator that is going to be a challenge and you would possibly do more harm than good tweaking the trimmers, unless you get a sig gen and follow the instructions in the Trader Sheet. Cheers, Jerry
Thanks Jerry, I will try the set again today and will get back re the questions you asked. The set came from an antique shop, so no idea of the history.
Cheers
Lee
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Old 19th Feb 2021, 8:26 am   #5
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Default Re: Columbia 357 - restored but unable to tune in properly

Quote:
Originally Posted by Nuvistor View Post
I haven’t a circuit for the 357 but other Columbia radios with similar model numbers appear to be TRF sets not Superhets, if yours is a TRF then selectivity can be more problematic.

Has Gerry states alignment could well be out but without the proper equipment you could make it worse.
Hi Frank, I have trader sheet for 587 for Marconiphone and HMV models, this set is a clone I think.
I have attached the circuit alignment procedure, was wondering if anyone can suggest a 2nd hand cheapish generator that would help with this.

Thanks
Lee
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Old 19th Feb 2021, 9:37 am   #6
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Default Re: Columbia 357 - restored but unable to tune in properly

Those instructions are for a superhet so ignore my post about TRF. i will try to find the manual but others will probably know the details before I find anything.
My Trader sheet 587 is for an Ultra 55
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Last edited by Nuvistor; 19th Feb 2021 at 9:46 am.
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Old 19th Feb 2021, 10:12 am   #7
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Default Re: Columbia 357 - restored but unable to tune in properly

I've been looking into this myself recently as a signal generator is on my wish list. David from this forum sent me a wealth of information.

In a nutshell, the most popular hobbyist vintage gear seems to be the Heathkit rf1u and the Tech or Altai TE20D.
The ones I've seen on popular auction sites are often however untested and uncalibrated. Maybe someone here can sell a good working example to you.

Alternatively, there are some modern chinese ones such as the item featured in this video (https://youtu.be/S9usQLFKZLk) that is highly rated, although you may need the one that goes up to 100mhz for FM work. Priced at around £100 but you will need to add customs duty, vat and courier handling fees.

The cheaper chinese signal generators you can get for £20 or so distort at the higher khz range and are a waste of money from what I've read.

In any case, I'm sure the people in the know will be able to elaborate or correct me as necessary

Gabriel
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Old 19th Feb 2021, 10:32 am   #8
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Default Re: Columbia 357 - restored but unable to tune in properly

Trader sheet 577 by the look of it, IF frequency is 125Khz so image signals could cause problems.
Sorry can’t suggest a sig gen.
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Old 19th Feb 2021, 6:36 pm   #9
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Default Re: Columbia 357 - restored but unable to tune in properly

Thanks guy's, a wee video of the issue.

******************************yYr4qMRJkAtaxMh69

On MW, LW no stations, transmitter in Shieldhill, Scotland.
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Old 19th Feb 2021, 6:41 pm   #10
Scotorvm
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Default Re: Columbia 357 - restored but unable to tune in properly

Quote:
Originally Posted by Gabe001 View Post
I've been looking into this myself recently as a signal generator is on my wish list. David from this forum sent me a wealth of information.

In a nutshell, the most popular hobbyist vintage gear seems to be the Heathkit rf1u and the Tech or Altai TE20D.
The ones I've seen on popular auction sites are often however untested and uncalibrated. Maybe someone here can sell a good working example to you.

Alternatively, there are some modern chinese ones such as the item featured in this video (https://youtu.be/S9usQLFKZLk) that is highly rated, although you may need the one that goes up to 100mhz for FM work. Priced at around £100 but you will need to add customs duty, vat and courier handling fees.

The cheaper chinese signal generators you can get for £20 or so distort at the higher khz range and are a waste of money from what I've read.

In any case, I'm sure the people in the know will be able to elaborate or correct me as necessary

Gabriel
Thanks for the info Gabriel, going to look into a signal generator
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Old 19th Feb 2021, 6:44 pm   #11
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Default Re: Columbia 357 - restored but unable to tune in properly

Quote:
Originally Posted by cathoderay57 View Post
Hi Lee, some questions:
How loud is the background station interference?
Is it just one background station all the time or does the background station change when you tune to another frequency?
Does this happen just at night or during the daytime as well?
It isn't unusual to get interference from another station on Medium Wave at night time. It would be unusual to get such interference on Long Wave but I don't know how strong the R4 LW signal is where you are. My best guess is that the radio is showing poor selectivity and the best way to improve that would be to realign it. Without a signal generator that is going to be a challenge and you would possibly do more harm than good tweaking the trimmers, unless you get a sig gen and follow the instructions in the Trader Sheet. Cheers, Jerry
Hi Jerry, I have attached a wee video to hopefully answer any questions.

Thanks.
Lee
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Old 19th Feb 2021, 9:00 pm   #12
cathoderay57
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Default Re: Columbia 357 - restored but unable to tune in properly

Hi Lee, from the sound of it the IF passband is too wide because you can hear a station over what appears to me to be an unusually wide tuning range; there should be sharper tuning points than there appear to be. Circuit alignment is the way to go. Without a sig gen then previous comments apply; however, you won't do too much harm if you tune into the "double station" frequency and then follow the Trader Sheet guidance to adjust the image suppressor. I suspect the IF bandwidth is also too wide as well but tweaking the image suppressor meantime is worth a try until you get a sig gen. Cheers, Jerry
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Old 26th Feb 2021, 3:46 am   #13
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Default Re: Columbia 357 - restored but unable to tune in properly

Sounds like an awful interference issue. Perhaps a fluorescent light?
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