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Old 5th Oct 2018, 10:04 am   #1
Mrgroovy
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Default Aga Baltic AH37. Need help identifying old capacitor from 1930s radio

Hi. This is my first post here, so let me briefly introduce myself. I just recently found an interest in vintage tube radios and have already started collecting a quite few old pieces. I have two years formal education from vocational school in electronics almost twenty years ago, so my skills are a bit rusty to say the least. I live in Norway.

So then,

I recently bought an old radio from Swedish company Aga Baltic. It is a cathedral type radio with 4 tubes in it. The model is AH37 and according to my research it was manufactured in 1932. I have not found any schematics. I've cleaned it up inside, changed the bad wires and connected a new three prong cord. All 4 tube lights up and there is even sound (albeit weak) coming from it. I also swapped out a 10uF electrolytic cap which was the only electrolytic cap I could positively identify. When powered up there is quite a loud hum coming from the power transformer. I thought that changing the electrolytic cap might eliminate this, but it wasn't all that easy. The 10uF electrolytic is hooked up to what seems like a centre tap (ground right?) from the power supply. Some of the other connections (pardon me for not being absolutely accurate here) from the power transformer goes to what seems to be a multi-sectioned capacitor of unknown brand. There is a logo on it which could be the letters HS or SH? I don't know. There is a total of three of these caps underneath the chassis, all from the same manufacturer, with the largest one directly connected to the power transformer. I suspect it to be bad since both sides of the metal can around it is bulging out. The can is labelled 1+2+4+2 1500V - and 0,1UF 500V - . I guess the straight line (-) after the 1500/500V means DC as opposed to ~/AC?

Can anyone tell me something about this? What type of capacitor is it really? It is easy to find a replacement? I don't mind using single replacement caps; it is probably the only option, but I really don't know what kind of capacitors I should use.

Thanks!
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Old 5th Oct 2018, 10:54 am   #2
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Default Re: Need help identifying old capacitor from 1930s radio

That's a multi-section capacitor, not wholly dissimilar to the one in this post:-

https://www.vintage-radio.net/forum/...99&postcount=8

Your best bet is to "restuff" it by fitting new capacitors inside the can. You may be able to lift the Paxolin lid slightly, snip all the wires off its underside and then dig out the contents of the can. This will save a lot of unsoldering and resoldering of wires.

The figures on the Paxolin show quite clearly which caps go where. Any capacitor of more than 1uF is likely to be of the electrolytic type and therefore polarized. Their negative ends will likely be connected externally to the chassis, possibly by the long bare wire linking several terminals.

Lower value caps are not polarized and can be connected either way round.
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Old 5th Oct 2018, 11:01 am   #3
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Default Re: Need help identifying old capacitor from 1930s radio

I am rebuilding a similar capacitor box from a Columbia that has 10 capacitors inside it. The block in yours contains multiple capacitors that are wired to the tags at the top. You cannot leave the old capacitors in circuit as they leak (behave like resistors) and can overheat or at the very least stop it working properly. It looks like someone has made some recent changes as there is a modern electrolytic in there so it is possible someone has already taken the box apart.

If it were mine, and the fact it is still bulging, I would rebuild the block but be warned that it is messy work as the block looks to be filled with bitumen. Take plenty of pictures before you dismantle it and of course you need to know the value of each capacitor and the tags they are connected to before you start.

Then its a case of extracting the old capacitors and working out a way of fitting replacements back inside. Because you do not want to take it apart again I would use 630V film capacitors and not electrolytics.

PS: Post crossed with Graham, our recommendations are the same but I don't believe you would find any electrolytics in a 1932 capacitor block.
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Old 5th Oct 2018, 11:23 am   #4
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Default Re: Need help identifying old capacitor from 1930s radio

Hi Graham,

Thanks for the reply, and for the suggestion on how to restuff the cans. I think, if I am not mistaken, that only the top right connector on the 0,1UF section is connected to ground. At least there is continuity between the top right connector and the chassis/ground, and not continuity between any of the other connectors and ground. Could always be a short somewhere perhaps? Electrolytic capacitors of 1500V is not really easy to find, and probably not cheap? My best bet would be to couple four 450V in series and match the capacitance and voltage required for each, right? And as for the the 0,1uF, is that most likely an electrolytic as well? These mystery multi-section cans are only the start of this enigmatic radio. There are six other normal looking capacitors inside, all with capacitance values in CM. I read that 1000cm is approximately the same as 1100pF?

I'll attach a few more pictures. The brown electrolytic 10uF is now changed with a modern one.
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Old 5th Oct 2018, 11:32 am   #5
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Default Re: Need help identifying old capacitor from 1930s radio

Hi PJL,

Thanks. The modern electrolytic is actually the one I changed. It was definetly bad cause when I took it out it was all loose inside, sounding like a percussion shaker. As you can see the voltate rating is very high, but it should not be a problem if these are not electrolytic as you now suggests?
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Old 5th Oct 2018, 12:18 pm   #6
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Default Re: Need help identifying old capacitor from 1930s radio

"Take plenty of pictures before you dismantle it and of course you need to know the value of each capacitor and the tags they are connected to before you start."
The values are printed into the paxolin plate.
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Old 5th Oct 2018, 12:28 pm   #7
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Default Re: Need help identifying old capacitor from 1930s radio

The SH logo is for Siemens & Halske
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Old 5th Oct 2018, 12:39 pm   #8
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Default Re: Need help identifying old capacitor from 1930s radio

I've never seen an electrolytic capacitor with a value of less than 1uF. The 0.1uF capacitor won't be an electrolytic and can be replaced with a polypropylene or similar type.

If you decide to use electrolytic capacitors they'll need to be connected the correct way round, Given that some of the electrolytics will be smoothers it's strange that one side is not grounded. I suggest a bit of reverse engineering,

Quote:
Originally Posted by Mrgroovy View Post
Hi Graham,

Thanks for the reply, and for the suggestion on how to restuff the cans. I think, if I am not mistaken, that only the top right connector on the 0,1UF section is connected to ground. At least there is continuity between the top right connector and the chassis/ground, and not continuity between any of the other connectors and ground. Could always be a short somewhere perhaps? Electrolytic capacitors of 1500V is not really easy to find, and probably not cheap? My best bet would be to couple four 450V in series and match the capacitance and voltage required for each, right? And as for the the 0,1uF, is that most likely an electrolytic as well? These mystery multi-section cans are only the start of this enigmatic radio. There are six other normal looking capacitors inside, all with capacitance values in CM. I read that 1000cm is approximately the same as 1100pF?

I'll attach a few more pictures. The brown electrolytic 10uF is now changed with a modern one.
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Old 5th Oct 2018, 12:39 pm   #9
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Default Re: Need help identifying old capacitor from 1930s radio

Quote:
Originally Posted by McMurdo View Post
The SH logo is for Siemens & Halske
Thanks, you saved me hours searching in blind for this!

Pretty satisfied with this purchase. I only paid 100NOK for the radio, thats less that 10 quid! (9.3 to be excact) It has a field coil speaker as well that looks to be in near mint condition! It is a very well preserved piece of gear considering its age.
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Old 5th Oct 2018, 7:05 pm   #10
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Default Re: Need help identifying old capacitor from 1930s radio

A couple of semiconductor diodes made in 1932?
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Old 5th Oct 2018, 7:48 pm   #11
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Default Re: Need help identifying old capacitor from 1930s radio

Has the sound output valve been changed from the original to a side contact type? The valve holder looks different to the others, looks like nut and bolt fixing as opposed to rivets and there's a bright patch on the chassis in the shape of the old square valve holder.

Lawrence.

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Old 5th Oct 2018, 8:16 pm   #12
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Default Re: Need help identifying old capacitor from 1930s radio

Wow, you must be right. Well spotted! I really didn't notice the bright spot and that the tubesocket must have been replaced. I guess this has been a mod done way back since the radio didn't show any sign of being worked on in the last 70 years as far as I'm concerned. The tube in question is actually a Telefunken AL1. According to radiomuseum.org the original tube is a E 453. The E 453 and AL1 seem to have similar properties, to my limited knowledge at least? The other three tubes are identical to the ones spesified on this page here: https://www.radiomuseum.org/r/agabaltic_ah37_ah_3.html
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Old 5th Oct 2018, 9:47 pm   #13
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Default Re: Need help identifying old capacitor from 1930s radio

Quote:
Originally Posted by TrevorG3VLF View Post
A couple of semiconductor diodes made in 1932?
Which are you refering to?
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Old 5th Oct 2018, 10:12 pm   #14
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Default Re: Need help identifying old capacitor from 1930s radio

Quote:
Originally Posted by Mrgroovy View Post
The tube in question is actually a Telefunken AL1. According to radomuseum.org the original tube is a E 453. The E 453 and AL1 seem to have similar properties, to my limted knowledge at least? The other three tubes are identical to the ones spesified on this page here: https://www.radiomuseum.org/r/agabaltic_ah37_ah_3.html
The E453 is an indirectly heated cathode valve, the AL1 is a directly heated cathode valve, hence the centre tapped resistance across that valves heater and the bias resistor and bypass capacitor from the centre tap to chassis.....So far as I can make out.

Lawrence.
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Old 6th Oct 2018, 9:03 am   #15
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Default Re: Need help identifying old capacitor from 1930s radio

Interesting. Does that mean that the one 10uF electrolytic capacitor (the brown-reddish one I have swapped out with a modern type by now) was probably not there in the first place? And if so, were there really no electrolytic capacitors originally installed in this radio?

I'm also having a hard time finding replacement capacitors for this radio. Non-electrolytic 4uF 1500V+ capacitors aren't really common values these days. The ones I have found that come closest in value are way to expensive to justify spending on a radio, in my opinion at least.

I found some high voltage film caps (1600v) on justradios.com which can probably work on most but the largest caps. The largest caps being the 1uF, 2uF, and 4UF/1500V) and smallest caps being the 0.22nF to 0.55nF/1500V. I figured that 200CM which is the smallest value capacitor I found in this radio equals 220pf=0.22nF. Please correct me if I'm wrong. You can see one of these small black capacitors in one of the pictures above. Is that what is called a molded paper capacitor? As I said, they are high voltage 1500V~ with capacitance values in CM and manufactured by ERO. Was unable to find any info on them on the web.
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Old 6th Oct 2018, 9:30 am   #16
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Default Re: Need help identifying old capacitor from 1930s radio

I would question the need for 1600V capacitors. They were probably used because they were available. 450V electrolytics should be fine.

I think you need to draw out the circuit for the PSU and output stage to see what mods have been done.
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Old 6th Oct 2018, 10:15 am   #17
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Default Re: Need help identifying old capacitor from 1930s radio

Quote:
Originally Posted by Mrgroovy View Post
Quote:
Originally Posted by TrevorG3VLF View Post
A couple of semiconductor diodes made in 1932?
Which are you refering to?
Sorry my mistake, I will get my eyes refurbished.
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Old 6th Oct 2018, 10:39 am   #18
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I would question the need for 1600V capacitors. They were probably used because they were available. 450V electrolytics should be fine.

I think you need to draw out the circuit for the PSU and output stage to see what mods have been done.
Thanks. I'll try that and see if I can post it here. As for the 450V caps, do you think that the other small (molded paper?) caps, there are 6 of those in total, would suffice with a 450V rating as well even though they too are rated 1500V?
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Old 6th Oct 2018, 10:51 am   #19
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Default Re: Need help identifying old capacitor from 1930s radio

Quote:
Originally Posted by Mrgroovy View Post
Interesting. Does that mean that the one 10uF electrolytic capacitor (the brown-reddish one I have swapped out with a modern type by now) was probably not there in the first place? And if so, were there really no electrolytic capacitors originally installed in this radio?
There's a good chance that the old 10uf was an original fitment, possibly performing the same circuit function as its replacement is doing now, there were two common methods of implementing an arrangement for obtaining the bias voltage for the valve in mains operated receivers, one way was the use of a resistor (usually bypassed with an electrolytic capacitor) connected in series between the cathode and chassis, the other way was by connecting the cathode directly to chassis and connecting the chassis to the centre tap of the mains transformers HT winding via a low (ish) value resistor, the -ve voltage (with respect to chassis) developed across that resistor would then be used as source for the grid bias voltage.

Lawrence.
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Old 6th Oct 2018, 10:51 am   #20
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Default Re: Need help identifying old capacitor from 1930s radio

630V easier to find in non electrolytic than 450V. Depending on the set's HT voltage, 400V might well do, except for any across the output transformer primary (or op valve anode to ground) where 1600V would be more suited.
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