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Old 28th Oct 2004, 10:22 pm   #1
jsel84
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Default Stromberg- Carlson 515M

I went up state this week and found this big old Stromberg- Carlson 515M. at an estate sale.
Its one of those floor models.
I got the radio working I changed all the paper caps but noticed the supply cans were in great shape , they tested very good. When I fired it up I brought up the voltage slowly and it seems to be fine in the supply section. Should I change the caps ??
My question is the Fm section only has 41 meg to 52 meg.
Is this usless to us??
regards
Jim
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Old 28th Oct 2004, 10:30 pm   #2
jim_beacon
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Default Re: Stromberg- Carlson 515M

Jim,

if the caps show no sign of leakage, you could leave them, but if the chassis is difficult to remove, it may be better to do them know, to save re-visiting the set in a couple of years.

It may be possible to build a converter to bring the current FM allocation down to the old one - they may even have been marketed around the time of the change over, much as band III to band I tv converters were in the UK (in fact it would be easy to modify one of the old TV converters to do what you want...).

Jim.
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Old 28th Oct 2004, 10:38 pm   #3
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Default Re: Stromberg- Carlson 515M

Aren't those frequencies an old police band? If so, it probably AM as opposed to FM, so I doubt that conversion is practicable. Apart from anything else the FC stages used are pretty conventional for these frequencies, but would not be efficient at 88 MHZ and above, apart from the FM conversion.

Actually, at one time on this side of the pond that band could have been used for receiving BBC TV sound, but not for many years...
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Old 29th Oct 2004, 5:28 am   #4
jsel84
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Default Re: Stromberg- Carlson 515M

Thanks for the reply guys. I think the conversion is above my head at this time. This radio has two chassies one for the AM with its own tuning condenser. The other chassie has the FM section with its own tuner.
When I tuned it in I really didn't hear any thing (FM section). I also didn't change the caps??.
It would be cool if I could get this to receive FM of today.
The radio has two 6V6s for the out put with a great deep sound. The cab has its own tone chamber for the bass, with a 10 speaker.
Thanks for any advise.
Jim
link to the Radio
http://www.nostalgiaair.org/Resources/570/M0021570.htm

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Old 29th Oct 2004, 6:52 pm   #5
quantum
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Default Re: Stromberg- Carlson 515M

An unusual circuit - the second chassis is certainly for FM reception, although the IF frequency, at 4.3MHZ is much lower than the 'standard' 10.7MHZ. I think that while changing the RF, aerial and oscillator coils and associated trimmers could theoretically bring your coverage up to 88-108MHZ I doubt whether the 6AC7 RF amp and the 6SA7 frequency changer would be very efficient at these frequencies, if they function at all.

Having said that, I have seen a WWII circuit which did employ a 6K8 as a frequency changer on frequencies up to 112MHZ...
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Old 2nd Nov 2004, 4:39 am   #6
jsel84
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Default Re: Stromberg- Carlson 515M

Thanks for the replys.
I guess I'll leave the FM section as is for now.
I do have a question on the short wave section and with a cap on the fixed push buttons on the AM section. This section has its own coils that can tune in small portions of the AM band.
The cap is C25 on the print out when I tested the cap it test good but I think way out of spec. On the cap it states 85MMF
then a+ over a - 4,25 then p3056 erie ceramicon, N680L.
when I tested it on my cap tester I get .0001??
The weird part is I can't find this cap on the parts list for the AM section. I see it for the Model 505 but not for the 515-M, very odd
Any advise on this.
I think it should be .00085 uf, is this correct?
When I replaced it with a disk type I had to retune the coils for each band??.

The short wave section at one end has more stactic than I think should be. I do get stations in and only the stronger ones block out the stactic.
I noticed on my other short wave radio it is cleaner at the same section at least I think so.
I 've only retuned the RF and IF cans to 455.
Thanks for any advice on these two points.
regards
jim
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Old 2nd Nov 2004, 11:14 am   #7
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Default Re: Stromberg- Carlson 515M

Be careful with the value of the caps - 0.0001uf is 100pf, and given the margin of error and tolerances you get with caps and cap testers, I would say that your 85pf cap is not too much out. A 0.00085uf cap is 850pf, much to great...

Difficult to say anything about the static - perhaps this set is more sensitive than your other SW receiver, perhaps that set has a better AVC system cutting out background noise even when a station is not tuned in - best to align the set first thoroughly before worrying about it.
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Old 3rd Nov 2004, 10:26 pm   #8
Norm_Leal
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Default Re: Stromberg- Carlson 515M

Hi Jim

A schematic can be found here:

http://www.nostalgiaair.org/PagesByM...0/M0021570.pdf

Stromberg Carlson 515M was made just before WW2. The FM band was changed after WW2. Your radio will receive lower US TV frequencies but not FM radio.

Norm

Last edited by Paul Stenning; 26th Dec 2004 at 4:35 pm.
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Old 5th Nov 2004, 12:43 am   #9
jsel84
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Default Re: Stromberg- Carlson 515M

Thanks for the reply.
I have the readio just about all tuned up.
I did get a simple tube tester. It checkes all the emisions, leakage, and shorts.
I tested all the the tubes except the 80 there is no socket or listing for that tube on this tester.
I did notice that one one of the 6V6s there shows leakage on that tube??
I also have a question on a vintage 1960 guitar amp that I am working on for a friend. The supply caps test good but I see the little dimple popping out with a whole, yet it tests good and there is no hum what so ever. Do I change them??
As it goes guitar colectors like when amps are orginal
thanks for the advise
Jim
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