Hi all;
I have four Automatic Electric Type 41 transmitters which have excessive crackling; two of them are so bad as to render a decent conversation impossible. I've tested them on a phone I know to otherwise have no problems. These are the only Type 41 transmitters I have, and they're all bad to some degree. The 81 and 810 capsules I have seem to be okay. Thank God the newer ones can be used in the Type 40 and 50 phones.
Just wanted to know if its possible to do any kind of servicing on these things before I consign them to File 13.
If there's anyone who might want them anyway, please PM me with your address and I'll gladly send them to you free of charge, including shipping.
Thanks much!
Did you try rapping the transmitter edge(sharply) against a hard surface. This breaks the carbon back into granules.
JMO,
Jim S.
Quote from: Jim S. on April 15, 2017, 08:50:53 PM
Did you try rapping the transmitter edge(sharply) against a hard surface. This breaks the carbon back into granules.
JMO,
Jim S.
Yes I have, to no avail. I also made sure the electrical contact surfaces on the center point and the outer rim were clean.
Interestingly enough, blowing into or speaking into the transmitter briefly intensifies the crackling.
And don't toss them. You can set them aside in case you need the carbon granules. This small vial of supposedly transmitter carbon granules has been on eBay for 20 days now as a BIN, hasn't sold. But the price gives you an idea of those little particles are worth, in general.
http://www.ebay.com/itm/222453829586
There is at least one topic somewhere on the forum about removing the caps, "fixing" the carbon and resealing it. Must be at least 5 years ago it was posted.
One method I have been wanting to try, but haven't yet, is to seal the transmitter into a small plastic bag, and then place it into an ultrasonic cleaner for a long treatment. The metal encapsulation may be too much of a mechanical shield, but perhaps the sound waves are still strong enough.
Quote from: KaiserFrazer67 on April 15, 2017, 09:33:22 PM
Interestingly enough, blowing into or speaking into the transmitter briefly intensifies the crackling.
I was doing some audio work on transmitters and recorded these rough wave forms of different transmitters from 0 to 5000 Hz. Keep in mind that a lot of the visible changes are due to the speaker response over that range, the speaker profile shows in the recorded waves as well as the transmitter response.
I'm showing this here because I had on transmitter, a Stromberg Carlson, that was toast and you can see it produced nothing but static over the full scan range. Kellogg, SC and F1 transmitters were tested in this image. So, you are correct in that observation. A toasted transmitter will produce static but will not convert sound to voltage, the center wave form.
Quote from: unbeldi on April 15, 2017, 09:39:19 PM
One method I have been wanting to try, but haven't yet, is to seal the transmitter into a small plastic bag, and then place it into an ultrasonic cleaner for a long treatment. The metal encapsulation may be too much of a mechanical shield, but perhaps the sound waves are still strong enough.
Tried that, didn't work. Without the liquid solution being in direct contact with the capsule, it is basically shielded by the plastic/air gap.
A vacuum sealer might take care of the air gap.
JMO,
Jim S.
Quote from: TelePlay on April 15, 2017, 09:37:38 PM
And don't toss them. You can set them aside in case you need the carbon granules. This small vial of supposedly transmitter carbon granules has been on eBay for 20 days now as a BIN, hasn't sold. But the price gives you an idea of those little particles are worth, in general...
There is at least one topic somewhere on the forum about removing the caps, "fixing" the carbon and resealing it. Must be at least 5 years ago it was posted.
At least I'd be able to do
something constructive with them. I
did manage to fix my Kellogg Redbar's transmitter that way, but that particular kind was easy enough to open up and re-seal, since they're designed to be repaired internally.
Incidentally, my Kellogg's transmitter was crackling excessively because the little fabric patch holding the granules in place wasn't doing its job, and the granules got out into the main part of the transmitter cavity: http://www.classicrotaryphones.com/forum/index.php?topic=17028.msg184199#msg184199 (http://www.classicrotaryphones.com/forum/index.php?topic=17028.msg184199#msg184199) I'm wondering if something similar has happened with the AE 41s. I'm guessing the general concept behind their construction must be similar.
I don't know if the 81s and 810s I have are working just because they're newer, or if they were designed to overcome some of the same problems I'm having with the Type 41s.
Quote from: Jim S. on April 15, 2017, 10:03:31 PM
A vacuum sealer might take care of the air gap.
JMO,
Jim S.
Don't think so. Ultrasonic cleaners work by sending sound waves through the liquid and when them come into contact with a surface, that is where the micro bubbles are created from the energy and their collapse is what jars the debris/dirt loose. If the bubbles are cavitating on the surface of the bag, no energy or vibration would make it to the capsule much less into the carbon. Actually, putting the transmitter directly in the liquid would clean the metal surface but do little for what's inside.
Something that provides macro vibration, such as a high wattage speaker concentrated on the capsule would have more effect on the entire capsule and not just the surface - same as rapping or tapping but massive and over a long period of time.
I had an old Signal corp telephone tester.
ISTR that it had 135 VDC to zap the transmitters with.
JMO
Jim S.
Quote from: TelePlay on April 15, 2017, 10:14:12 PM
Don't think so. Ultrasonic cleaners work by sending sound waves through the liquid and when them come into contact with a surface, that is where the micro bubbles are created from the energy and their collapse is what jars the debris/dirt loose. If the bubbles are cavitating on the surface of the bag, no energy or vibration would make it to the capsule much less into the carbon. Actually, putting the transmitter directly in the liquid would clean the metal surface but do little for what's inside.
Well, what you are describing is the action of ultra-sonic
cleaning.
We don't want to clean, but simply provide vibration. Clearly the ultrasound penetrates for some distance, you can hear it at several feet distance. There is no reason the sound should not penetrate the sample. The question is whether it is sufficient or even effective in principle.
I appreciate everyone's input; thank you.
However, the problem with these doesn't seem to be the granules being caked together and needing to be knocked loose; I can hear them when I gently shake the capsules, like salt in a shaker. I'm thinking the opposite situation may be the problem: that they have gotten loose from the area where they are supposed to be in the first place, and are now not only roaming around inside the sealed transmitter cavity, but also considerably reduced in quantity in the area where they're supposed to be concentrated in the first place. That was exactly the case with my Redbar transmitter capsule (see my link to that thread above). Thankfully, since the Redbar one could be completely disassembled, I was able to fix the problem (for now) once I was told (by reading a similar thread) where and how the granules are supposed to be contained.
The AE 41, however, is a completely sealed unit. I can (barely) grab the small silver center contact cap with a pliers, and discovered that it won't unscrew, but it can turn (see teeth marks on it in the photo below). However, I can also hear what I assume to be carbon granules scraping along the inside of the crimped area when I do this. It sounds just like sand or grit grinding and scraping between two surfaces, and the only thing in there would be the granules.
So my only recourse IMO would be to uncrimp or cut it (probably easier from the grille side), open it up and save the granules for use in an early-type fully-serviceable transmitter.
Quote from: unbeldi on April 15, 2017, 11:13:13 PM
Well, what you are describing is the action of ultra-sonic cleaning.
We don't want to clean, but simply provide vibration. Clearly the ultrasound penetrates for some distance, you can hear it at several feet distance. There is no reason the sound should not penetrate the sample. The question is whether it is sufficient or even effective in principle.
I would certainly agree with that. I'm thinking of the ultrasonic cleaner I use which is a one quart tank and a relatively low power generator operating at 40 KHz. A more powerful generator at a lower frequency that is capable of being operated in air might do a very good job of vibrating the metal capsule and it's carbon contents. A hand held sonicator with a tapered to a near point working tip placed directly on the capsule would do that. However, those run around $850. Then again, one of those switchboard buzzers might be enough to vibrate the granules apart. My ultrasonic cleaner did not work.
Quote from: KaiserFrazer67 on April 15, 2017, 11:58:10 PM
The AE 41, however, is a completely sealed unit. I can (barely) grab the small silver center contact cap with a pliers, and discovered that it won't unscrew, but it can turn (see teeth marks on it in the photo below). However, I can also hear what I assume to be carbon granules scraping along the inside of the crimped area when I do this. It sounds just like sand or grit grinding and scraping between two surfaces, and the only thing in there would be the granules.
Your AE transmitter is similar to my toasted 4-35 SC except the center post on the SC is not like the AE. It seems the SC transmitter was assembled by crimping a ring around the front of the transmitter, locking the front grill to the body. There is not other way to take the SC apart and from the photo of your AE, it seems to have the same type of ring crimped around the front. When shake the SC, I can not hear the carbon inside.
Quote from: TelePlay on April 16, 2017, 05:22:33 PM
Your AE transmitter is similar to my toasted 4-35 SC except the center post on the SC is not like the AE. It seems the SC transmitter was assembled by crimping a ring around the front of the transmitter, locking the front grill to the body. There is not other way to take the SC apart and from the photo of your AE, it seems to have the same type of ring crimped around the front. When shake the SC, I can not hear the carbon inside.
Mine is indeed crimped around the front grille too, as well as crimped around the base of the center post. If I were going to open it up, it would probably be best to cut through the front crimp and the entire outer contact ring with a Dremel tool and take the outer ring off, with the capsule clamped in a vise by the center post grille-up so nothing spills out. Then I can take off the grille and whatever's underneath it, and dump the granules out into a glass jar. At least I'd be able to salvage
something worthwhile to someone, rather than tossing the whole thing into the garbage. I never thought about recycling the carbon granules to use in restoring early-type transmitters... good idea!
Quote from: TelePlay on April 16, 2017, 12:03:18 AM
A more powerful generator at a lower frequency that is capable of being operated in air might do a very good job of vibrating the metal capsule and it's carbon contents.
To follow up on that thought, I did a bit of experimenting this morning. I used a small, 1" diameter tweeter. Small speaker but big enough to set my toasted SC transmitter face down on the speaker facing up on my audio work bench (first picture below). Used that speaker so I could power it directly off of my headphone out port, no amp.
I played a sine wave log increasing frequency file from 0 to 5,000 Hz through the speaker recording what the transmitter picked up. All parameters were kept constant. The only thing changed was the "condition" of the carbon granules.
SC 01 below is the base line, what the transmitter was putting out before trying to break up the carbon granules.
SC 02 repeats the scan but after shaking the transmitter.
SC 03 repeats the scan after creating a different sound file of 15,000 Hz and played that for 30 seconds to "break up" the granules. Similar to SC 02 but the amplitude was greater showing some improvement in transmitter output.
SC 04 repeats the scan but after playing a 3 track file for 5 minutes to "condition" the transmitter more thoroughly. The tracks contained a 10,000 Hz, 15,000 Hz and 20,000 Hz constant or continuous sine waves passing those frequencies into the transmitter's carbon capsule. The after treatment scan was very similar to SC 03.
SC 05 is a repeat of scan SC 04 except the transmitter was physically shaken for a few seconds and the while horizontal moved side to side to "even out" the granules in the capsule. That got rid of a lot of noise probably due to the shaken carbon granules settling in SC 04 as sound waves vibrated them during the sweep scan. I've seen this same type of noise by recording and doing nothing more than move the transmitter or tilting it a bit so the carbon granules would "shift" causing what appears to be noise or static. Or, fluffed up carbon granules settling by themselves for what ever reason causes noise. And, yes, the same thing would be happening when holding a moving a candlestick during normal use but the S/N ratio would put the "normal" noise in the background as long as the capsule was picking up voice at it's designed levels.
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SC 06 is nothing more that a re-record of the past set up, nothing was shaken or touched, just re-recorded. What is seen is a small decrease in amplitude.
SC 07 is a re-recording with nothing shaken or touched. The decrease in amplitude is more visible in this file. What appeared to be happening was the carbon granules were settling back together (starting to pack) thereby decreasing amplitude. The sound waves were doing the "settling."
SC 08 is another re-recording of the transmitter without doing anything other that playing the sound file again. There is a marked decrease in amplitude.
SC 09 shows what happens when the transmitter is shaken up again and after shaking, moving it from side to side to "even out" the granules before playing the file and recording it with the transmitter.
So, even after being "broken up," the granules seem to resettle quickly resulting in decreased output. This has to be something to do with the "quality" of the granules themselves and/or the "atmosphere" within the capsule.
Next step is to put a larger "tweeter" on an amp and really shake the carbon granules through direct vibration, basically creating an ultrasonic affect on the carbon within the capsule using air as the sound wave medium. I have a spare amp that puts out about 35 watts which when used with a larger tweeter should produce an exciting time for the carbon granules, at least enough to fully break up whatever has bonded together over time.
If someone else want to try and duplicate this to see if they get the same results, that would be great.
Being curious about the signal degradation/decrease with use, I took the SC transmitter under test (which was once toast - no response), shook it well, moved it from side to side to "level" the carbon granules and recorded a response sweep from 0 to 10,000 Hz.
01) Record the base line sweep
02) Re-record with no changes
03) Re-record with no changes
04) Re-record with no changes
05) Record after exposing the transmitter to 10, 15 and 20 kHz over 5 minutes, no shaking.
06) Shook the transmitter well and moved it side to side to "level" the carbon granules.
While the 01 track shows good transmitter response, the amplitude decreases with each subsequent recording (02 to 04) which would seem to indicate the carbon was being settled by the sound waves into a state where they would not produce the same response level as track 01.
Without touching the set up, I subjected the transmitter to 10, 15 and 20 kHz sound for 5 minutes. Then recorded track 05 which shows some improvement probably caused by the vibration of the sound waves "breaking up" the settled carbon granules.
Finally, I shook the well and moved it from side to side to level the granules and the recording, track 06, is once again similar to track 01.
Not shown are the following tracks of decreasing response with several re-recordings as in tracks 02 to 04.
This transmitter seems to have been under water for some period of time. The exterior dirt and corrosion was removed but nothing can be done about the carbon capsule short of opening it up. There is a difference between carbon and activated carbon which has been purged of moisture and any other chemicals in the air which are absorbed by carbon. Activated carbon is a very good filter, removes stuff from air and water, but becomes "full" at some point and has to be heated to expel whatever has been absorbed. I do not know what telephone companies used, or how they put it into the capsules which I would assume were air tight to keep stuff out. As such, a carbon mic would work well until the carbon granules became compromised in some way. Even if clumped and then broken up by vibration, as in this case, it seems the compromised carbon is quick to settle back into a position that no longer responds well to sound waves.
Given that I can not hear above 5,600 Hz anymore, I do not know what these sound like above that. However, any sharp spikes seen in 06 under 3,000 Hz are very easily heard, loud ticks or pops most likely from carbon settling.
Just providing what I've measured (and in my case seen) with respect to this one transmitter. If I had a good heated vacuum chamber to both heat up the capsule to 120 F under reduced pressure to suck out any moisture that may be in the carbon, that would be an interesting experiment but I don't have such, so won't be trying that.
I have one more thing to try next week and will post how that goes.