I saved many. None were useful. And the values tend to be huge.
I probably decontructed over 50 consoles. The best cabinets got a repurpose by a buddy, and i used a few as shelving units.
@Pano makes/has made modern interpretaions from scratch… if i needed something like a console that is the route i would take.
Other than the glow… how much use is the radio section?
dave
Well, do pots ever drift like carbon composition resistors? The 50KΩ is at 1KΩ.
The 500KΩ is 506KΩ (per DDM), but super stiff, seriously considering removing and soaking in SiliKroil.
Now if you had one or both for less cost then a budget new pot, I go that route, just trying to achieve working close to factory, not a contemporary amplifier; as I understand, conductive plastic is superior to carbon and be the contemporary choice. Correct?
Can you please share the reason why large values (which be helpful to define) are a negative?
Very useful! When you are working on a project, are you in the ideal listening position? Even if are, paying enough attention to really notice the pitch of every note? I grew up on stereo sound, but, if listening off axis, or worse, another room (which the doorway converts stereo to mono), there is no benefit to stereo. Now if must have stereo FM, free multiplexer plans are out there and one does not look to difficult to build (considering it for the Telefunken). Even better, the KW band has band spread, which is not available on lower end receivers and bet couldn't get one with band spread for the price paid for a console. Now if don't listen to KW band, then yes, a SS receiver is superior (mine pulls in the few week signals we get here better than the Körting).
Even with all original components, the Telefunken was pulling stations half way across the world, not knowing it had or how to use, band spread, just had to listen intimately. I used to listen to a station in South Carolina, was like listening to a local AM station back home (here all stations are weak). I really hope since Telefunkens are far more common, can perform an alignment/tuning and surpass reception of simply restoring.
Seems the question was missed: what is the minimum to maximum percentage matching on resistors?
I am thinking 5 percent to 0,2 percent. Körting get the low end, it isn't super HiFi after all.
I am thinking 5 percent to 0,2 percent. Körting get the low end, it isn't super HiFi after all.
A dream you will not achieve. There will be many (most?) passive parts to swap out, and they re very unlikely to be as “colourful” as the old ones, particularily the capcitors which are much better today.
Are there any station syou can get? Most i went thru did not have FM.
But each to their own. Have fun, good luck.
dave
Sorry was not clear, I am meaning electrically and functionally, not the sound.
There are just a few components out of value, mostly capacitors, the benefit of Germanic engineering.
Additionally, I am not looking for coloration if significantly degrades the sound. In fact, if the tone is not to my liking, now having a close schematic and having fun tracing, know which are in the audio path. The Telefunken I am on the fence about replacing all the carbon compositions, not checking their values, with Vishay thin film resistors. It has been in an unconditioned room for many years in humid Oregon due to my friend's medical emergency, so if do check, might find most out of specification anyway.
I thought the vintage Jensen speakers were meh, until hooked up a quality amplifier, then switched to budget copper speaker wire (didn't know the sin of aluminium), and finally new capacitors, ginormous difference! Do they sound factory new? No, they sound better and I am happy with that.
Amazing, well then, I see your point, thank you for indulging. And yes, both get good FM with original components, the Körting get buzzy when turned on a florescent lamp in the garage, suspect the filter capacitors.
Yep, I love to be able to afford to scratch build an amplifier, but right now, not an option (biggest cost is the resistors, lot of and add up quickly). I do think some value, have seen some unexpected circuitry and getting better at tracing PCBs (though I much rather do point to point).
Thank you for the well wish.🙂
.
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I also have many potentiometers recovered from disassembled tube consoles and TV sets, and I confirm that most of them are only useful as replacement to restore vintage radios, because the shaft diameter may be not compatible with modern knobs, and the value is usually at least 500k up to several megaohms. This was fine back then, but today you don't want a volume potentiometer with this value because it is very likely to work as antenna for any stray radio frequency from LED power supplies, smartphone chargers etc. Another drawback of high value potentiometers is that they make a low pass filter with the input capacitance of the following stage; the cutoff frequency changes while rotating the shaft and may even dip below 20KHz, so you may have different audio quality depending of the volume knob position. This was desirable on tube radios and sometimes described as advantage: turning the volume knob to increase the volume of distant stations also decreased the audio bandwidth and background hiss.
My suggestion is to avoid a bulk replace of components. Check and replace them in small batches instead, starting from the paper capacitors (they are all leaky, for sure), then repair the power supply and audio amplifier, and go upstream from there up to the RF stages. This way if someting does not work anymore after a replacement, you are more likely to find the issue quickly. To further reduce the residual background hum and hiss you may also need to reroute a few wires. I use 5% 1W resistors; 1% on the phase splitter of push-pull amplifiers. Your output transformers looks to be of the standard consumer quality of the time. Limited low frequency bandwidth and about 3W clean power. Penetrating oil is usually enough to cure stiff potentiometers, it may require a few applications. No need to remove and soak. Oxidation of the switches of this style of chassis may be a issue, some are service friendly and some not at all. This is the second thing I check after the transformers, before investing time and money on a restoration. Those old brown circuit boards are meant for low temperature solder. Be sure to use only old fashioned 60/40 solder wire and set your soldering iron to low temperature, if you use modern "green" solder wire and the matching high temperature settings, you will detach the traces from the board.
My suggestion is to avoid a bulk replace of components. Check and replace them in small batches instead, starting from the paper capacitors (they are all leaky, for sure), then repair the power supply and audio amplifier, and go upstream from there up to the RF stages. This way if someting does not work anymore after a replacement, you are more likely to find the issue quickly. To further reduce the residual background hum and hiss you may also need to reroute a few wires. I use 5% 1W resistors; 1% on the phase splitter of push-pull amplifiers. Your output transformers looks to be of the standard consumer quality of the time. Limited low frequency bandwidth and about 3W clean power. Penetrating oil is usually enough to cure stiff potentiometers, it may require a few applications. No need to remove and soak. Oxidation of the switches of this style of chassis may be a issue, some are service friendly and some not at all. This is the second thing I check after the transformers, before investing time and money on a restoration. Those old brown circuit boards are meant for low temperature solder. Be sure to use only old fashioned 60/40 solder wire and set your soldering iron to low temperature, if you use modern "green" solder wire and the matching high temperature settings, you will detach the traces from the board.
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Thank you pcan for the big help. 😀
So are you saying pots can drift in value and should replace with a new contemporary unit?
So then what is the ideal maximum value?
I have some vintage solder a friend loaded me, then quit speaking to me. I bet even leaded pipe solder work. The modern stuff frustrates me, have to set the iron to 850*C to get the supposedly.
What is the maximum temperature for these older boards?
So are you saying pots can drift in value and should replace with a new contemporary unit?
Thankfully the tone controls have a threaded shaft (for mounting the indicators), worse case, get a replacement chuck for my drill press, drill a hole into the shaft, and tap to the needed thread.
This is interesting. How the higher resistance make them more sensitive to RF?
Now point it out, that makes sense the pot would act as a low pass filter.
So then what is the ideal maximum value?
Are you saying one type of component in one section at a time, or one section at a time?
That was why planned to do it that way. Plus, a motivator as can hear how great it sounds and want to finish.
How would I know what wires these are?
I appreciate knowing this. Do you match the resistors or accept either 10 percent or 2 percent difference?
Well then, be interesting to see where the low end cut off is.
The tone controls are open switches, as you can see from the picture, so easy to clean, also easy to get dust in.
Well too late, already have my mind made up, plus, worse case, don't see why couldn't bypass the tone controls, not something I use anyway. Why change the sound from intended?
Really appreciate this help, probably explains why the trace on the Heathkit lifted (used a piece of wire to repair).
I have some vintage solder a friend loaded me, then quit speaking to me. I bet even leaded pipe solder work. The modern stuff frustrates me, have to set the iron to 850*C to get the supposedly.
What is the maximum temperature for these older boards?
So then leave components that are way out of specification, like a film capacitor at 10MegΩ?
Hi Adriel, sorry to hear you have been out of action for a while, but interesting to follow your new project!
I have ventured a couple of times down a similar path to you and discovered it is not always plain sailing. The complications are the construction of these old mass produced devices, with an incomprehensible rats nest under the chassis, tired or dirty mechanical parts (switches and pots), and the urge to create something different than the original spec of the system.
If you want to understand old radios then it can be a lot of fun looking at a 1930's example which will most likely be an All American 5, with a straightforward superhet design, with lots of space to trace the circuit and replace defective parts, and simpler switching.
Since yours is using PCBs then that solves the rats nest issue, but it will not be so easy to trace the circuit and maybe the best you can hope for with that part of the circuit (the radio tuners) is to replace the parts that have a history of issues (certain brands and types of capacitor) and otherwise keep it as original as possible.
I like to hook a bluetooth receiver up to the old radios I have looked at, since all the ones I have seen had a gramophone input. If you can arrange for that type of input with your console then you can appreciate the sound of the simple tube amplifier and large speakers, usually an improvement over a bluetooth speaker package. On the old 1930's radios there is often a field coil loudspeaker, and I could not believe how good they sounded!
On the amplifier side I don't think there is any need to deviate too far from the original design and specifications of parts. The whole console is the sum of its parts, so improving one part will not make a noticeable difference IMO.
Once you have fixed the parts that could cause reliability issues and managed to hook it up to a modern music source you will probably be pleasantly surprised how satisfying it sounds.
The output transformers are quite small, but matched to the specs of the speakers and so on. It is not so easy to go any further, and if you do, what are you going to end up with? Are you thinking of transplanting the output section into another system?
Cheers Richard
I have ventured a couple of times down a similar path to you and discovered it is not always plain sailing. The complications are the construction of these old mass produced devices, with an incomprehensible rats nest under the chassis, tired or dirty mechanical parts (switches and pots), and the urge to create something different than the original spec of the system.
If you want to understand old radios then it can be a lot of fun looking at a 1930's example which will most likely be an All American 5, with a straightforward superhet design, with lots of space to trace the circuit and replace defective parts, and simpler switching.
Since yours is using PCBs then that solves the rats nest issue, but it will not be so easy to trace the circuit and maybe the best you can hope for with that part of the circuit (the radio tuners) is to replace the parts that have a history of issues (certain brands and types of capacitor) and otherwise keep it as original as possible.
I like to hook a bluetooth receiver up to the old radios I have looked at, since all the ones I have seen had a gramophone input. If you can arrange for that type of input with your console then you can appreciate the sound of the simple tube amplifier and large speakers, usually an improvement over a bluetooth speaker package. On the old 1930's radios there is often a field coil loudspeaker, and I could not believe how good they sounded!
On the amplifier side I don't think there is any need to deviate too far from the original design and specifications of parts. The whole console is the sum of its parts, so improving one part will not make a noticeable difference IMO.
Once you have fixed the parts that could cause reliability issues and managed to hook it up to a modern music source you will probably be pleasantly surprised how satisfying it sounds.
The output transformers are quite small, but matched to the specs of the speakers and so on. It is not so easy to go any further, and if you do, what are you going to end up with? Are you thinking of transplanting the output section into another system?
Cheers Richard
I would check and maybe clean or replace the potentiometers as last step, only if they are noisy or totally out of specification. Other parts needs more urgent attention. As first step it should be enough to use penetrating oil to ease the rotation if they are stiff, and a small amount of deoxit to clean the moving contacts. Paper capacitors and any visually broken one are the first parts to be replaced, because a faulty capacitor may easily damage other components. The same is true for main filter electrolytic capacitors. After this first step, you can turn on the device safely and start the section by section repair. The troublesome switches are the ones driven by the piano keys on the front (see the arrow on the picture). Inside that component there are metal contacts thay may be still good, but more often are now completely black or green from oxidation. You should check all contacts with the ohmeter. A spay cleaner while operating the key may be enough to lower the resistence and bring it back at normal values. If this does not work, you need to dismantle the switches and clean them manually. They are custom parts and if you break one of them and are unable to find a donor chassis, you cannot go any further on the restoration path.
About your further questions: good modern resistors have a very narrow tolerance even when they are labeled 5%. No matching should be necessary. I mentioned the wires because on consumer radios the wiring was often built to minimize cost, and should not be assumed as the best possible one. As example, a radio I restored a while ago had screened cables to and from volume control routed directly under the power transformer. Rerouting them in a more sensible way drastically reduced the background hum. It is funny to think that the original owner of the device suffered for years for a issue that can be fixed so easily at almost no cost. The radio was repaired at least once back then, and the serviceman did not bother to fix the hum issue.
High impedance circuits are more vulnerable to radio frequency interference because fields induce currents in conductors according to the law I*R=V. A small induced current of 1nA across a 1k impedance would give you only 1uV of noise. That same induced 1nA current across a 10 megaohm impedance would give you 10mV of noise.
You can buy lead solder wire today, it is still manufactured and sold. It is not legal anymore to use it to produce new commercially sold equipment, but it is still ok to use it for maintenance and repairs. I use Felder branded solder wire.
About your further questions: good modern resistors have a very narrow tolerance even when they are labeled 5%. No matching should be necessary. I mentioned the wires because on consumer radios the wiring was often built to minimize cost, and should not be assumed as the best possible one. As example, a radio I restored a while ago had screened cables to and from volume control routed directly under the power transformer. Rerouting them in a more sensible way drastically reduced the background hum. It is funny to think that the original owner of the device suffered for years for a issue that can be fixed so easily at almost no cost. The radio was repaired at least once back then, and the serviceman did not bother to fix the hum issue.
High impedance circuits are more vulnerable to radio frequency interference because fields induce currents in conductors according to the law I*R=V. A small induced current of 1nA across a 1k impedance would give you only 1uV of noise. That same induced 1nA current across a 10 megaohm impedance would give you 10mV of noise.
You can buy lead solder wire today, it is still manufactured and sold. It is not legal anymore to use it to produce new commercially sold equipment, but it is still ok to use it for maintenance and repairs. I use Felder branded solder wire.
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Hi Richard. Thank you for the care, it is appreciated. 🙂
Is anything plain sailing?
I thought mechanically restoring Dad's 1964 Käfer he bought in 1968 wouldn't take long, yet, over four years and counting. No benefit working on my own, for samples, the windshield was interesting doing it solo (still have sides and the curved back window to do when have a headliner to put in) and a bit of a challenge lifting the 100KG engine multiple times.
I am aware and enjoy challenges. As for creating something better, I have no urge, if wanted something better, I would start from scratch, as point to point, when done well, is superior.
Firstly, where would I get the money? I would expect them to be well over $100, a fifth of my monthly income from government disability (because my disability prevents me from working). Secondly, I know enough to be satisfied, I rather just get the two I have repaired. Since no one knows about inductance in receivers, thankfully found a source for carbon composition resistors.
I have had no difficulty tracing the audio section, please see attached. I could also do for the radio, however, a bit more difficult and not all that motivated... It worked before plus more interested in the amplifier section...
Does the gramophone input not go through filtering, such as RIAA? I can't tell on the schematic, maybe you can?
Worse case, the board uses tags, could add a second set of shielded wires to a jack in the back, already a smaller factory hole (wouldn't work if wanted stereo RCA). This is where I think the Telefunken has a one up, seem to recall has an auxiliary input from the factory.
I don't have a MP3 player, wish had a CD player (or better, replace the few CDs I have with vinyl), but do have a laptop and use YouTube for background music. Which can be dangerous as sometimes find artists I want to have on LP, a year ago bought from Sweden two of a female Swedish folk singer, as she has such an amazing voice.
I have used her in the past and loved the sound, so can't wait as only going to be better.
As for modern music, not too modern, I was not listening to anything post about 1980, though about two years ago got into 1980s electronic and pop music (coming from a love of glam rock). Nothing will get me to listen to the 1990s that I grew up hearing, it is garbage.
Correct. The external speakers connect to the transformers.
What does size have to do with it? The SE Hammonds I was looking at for the applier build (now set aside, probably forever) are also small.
Is ten percent of original value qualify as out of specification?
What about capacitors with a resistance higher then 100KΩ?
Especially for valve rectified, hopefully by using this years ago without knowing better didn't damage it.
I am aware, though never have had them be an issue, all work and no noise. Still will get contact cleaner treatment.
As for five versus one percent resistors, was finding the one percents the same or less cost, weird.
Now I am tracking, will take a look in the morning.
Firstly, interesting the screening didn't protect from interference. Secondly, that no one caught the hum was from the wire routing.
So the megohm to ground in audio amplifiers are one of the most prone?
Good to know, appreciated. 🙂
By the way, lead plumbing solder is now sold as for leading glass windows, I use that when doing plumbing repairs on the house that was stolen, the modern solder takes far more heat, so has far higher risk of fire, especially when working tight spaces making a repair. If any solder makes to the interior, so minor going to do no harm.
An idea came to me to use the part number sheet to identify which can is for which band, however, one is labeled IF (thought it would be two, MW and UW) and one labeled "radio filter." Any idea what it means when a transformer is labeled such?
Thanks in advance! 🙂
Thanks in advance! 🙂
Oops. Yes, ratio filter. I got progressive lenses in my glasses in the Fall, however, not seeming to work as well as could be, especially small print about a half meter away, end up putting readers over my prescription glasses, like Dad did.
I also missed the labelling, so went back and found BV129, which has had the left transformer twittled, as the wax is gone. Not easy finding the numbers, not snugged up is my feeble excuse. Good this is teaching me how to read schematics better.
Interesting there are different names. I am thrilled the FM seems not to be twittled, though the capacitor in the top of the UW has no seal so sure way to know it has not been, as more complicated to adjust. Though one day love to learn, just would need a signal generator that go up that high and unlike this chassis, at least data points.
That is gorgeous! 😍 Thank you for sharing! 😀
I for some reason only thought of windows, should know better, there are lamp shades too. Though never thought of just having a box.
Dad was going to get into stained glass, when clearing out his estate, found a packet for a stained glass of a storch, not sure if saved it, now see make a nice art piece.
A ratio detector is just one kind of FM demodulator circuits. Perhaps it has been the most common one here in Europe, while in othe parts of the world a phase discriminator might have been more usual. Both are easily discerned by the diode polarisation. In a phase discriminator both diodes point in the same direction, in a ratio detector they're opposite. There are more differences, of course 😉 .
»Ratiofilter« was a very common denomination of the last IF strip filter in German radios, probably because post the EABC80 era both germanium diodes and resistors shared the same can with the resonant circuits. Only the small electrolytic was mounted outside.
Best regards!