Thought the added tail might be for strain relief, but could find no point of tie off in the speaker base or radio case. Am making a 3/4" wooden speaker base extension since my mason jar mod. is a bit taller then original. Could easily mount a tie off hook there. Same with the radio case.
The grid leak resistor is labeled AEROVOX, fixed grid leak, Tested 3 Meg ohms, but tests 6 meg. now. When it comes time to fire the radio up was going for giving it a try as is and see what happens.
The "markings" on the radio chassis for the missing audio transformer indicates it was physically the same size. At least as far as the mounting holes drilled through the chassis and case diameter shadow left in it's place. Have noted all your recommendations for replacements in the future . Would be nice to keep original look and function.
Thanks again for your input and advice. It will be put to good use.
FWIK the A-K grid leak uses a holder with a smaller clip O.D. more like fuse clips. The A-K leak has a shoulder on the inside edges of the metal electrode ends that co-inside with the spacing of the electrode clips. The A-K leak is a smoked glass rod within a hollow glass rod "soldered" into the ends of the electrodes. I have not been able to determine how the solder grabbed the glass, but it does... The A-K leak can be "re-built" the ends are de-soldered and retained. a length of borosilicate glass tubing is prepared by torching the cut ends to smooth the glass. The electrodes are cleaned of solder and a twist drill is used to ream the ends to remove all the solder and a small amount of the brass, enough to allow the new tubing to fit, re-cut the glass tube to make the exact length as the original leak. A 1/10 watt 2.2meg axial resistor will slip inside the new tubing. Drill a hole at each end of the electrode to accept the resistor leads. Solder one end of the resistor to center it in the combination of electrodes and glass, the complete by soldering the opposite end. A touch of super-glue will firm up the electrodes to the glass. The resistor can be blackened with a sharpy to disguise that it is modern. A lot of work for appearance sake.
I wanted to see a pix of the three tube island not only to see the transformer location but if the OEM A-K grid leak clips are still in place or have been broken or removed so the Aerovox leak could be installed.
BTW that value of 6 megs leak is still O.K. the detector will not be cut off just more sensitive.
Post the diameter and the height of the A-K transformer existing and take resistance measurements of the two windings, post as well. Use an analog meter if you have one. I will look and see if I have a suitable transformer.
If I have a transformer we can use the PM (private message system) to exchange email and addresses. chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
Audio transformer diameter measures 1.65 "
Height of canister 3.34"
Height of canister from top of canister to bottom of mounting flange 3.38"
I did have a resistance reading on one set of windings on the remaining audio transformer, today nothing. so unfortunately I cannot provide you with any readings. I have removed the chassis several times since then, maybe its connection was tedious at best and it let go.
Not sure, but this is probably as good a match as you will find. If you have the original can and windings. You can remove the original windings, and mount this on your iron core. Read the reviews of the product, and contact A.E.S. with your information and see if it will serve. If you do not have the original can and iron core, just order the whole transformer and mount it as best you can. You won't be the first... https://www.tubesandmore.com/products/tr...bly-p-t156
Seems the remaining transformer has failed as well?
Do try a different ohmmeter...
Some DVM's cannot effectively take a resistance reading of an iron core inductor due to the inductive reactance. The inductance has an effect on the DVM devices. BTW test leads can breakdown noticed at the connector to the meter or at the probe/clips. A somewhat firm pull on the connector/probe will confirm a bad test lead by parting the intermittent copper strands...(Oops)... Leads may be repairable or not...
Resistance should be close to the values given from Leigh Basset's new drawing of the schematic.
It is those resistances that the modern transformer does not have but often freely suggested. Several Antique Radio Forum (ARF) members have used low resistance transformers in battery radios and the radio had had serious unsolvable distortion problems. Their cure was to replace these make-do transformers with ones that have sufficient resistance in the primary. Such transformers are available from ARBE-III web site..
If you decide to melt out to save the old can be aware that the A-K core is a group of iron wires. It would be best to use a transformer complete with its modern, low loss lamination core, both will fit into the A-K can. Wound bobbins should only be used where the entire OEM frame and laminations are exposed.
GL chas,
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
(This post was last modified: 05-17-2021, 03:55 PM by Chas.)
Pardon me for the delay. Thanks Mike and Chas for your information. Have purchased from A.E.S. many times in the past, I'll do some research on them and the ARBE-III web site.
Well Chas, I did try my two old Triplett analog multi - meters. Both with fresh batteries and good old sharp probe ends. Pulled a 1.8k and 18k resistor from my meager supply. Selected the proper scale, zeroed each meter and each read the correct resistance for each resistor. I tried each transformer pair a half dozen times each and the needle for each meter never moved at any scale. Even cut the wires closer to the transformer just in case of a broken wire some where in the wire run. No luck. Then pulled out my digital meter with same result. One Triplett is model 60-NA other is model 630-A.
If you do find 1 or 2 transformers in your stock, your offer is indeed generous and I would like to work with you if possiable.
I found the A-K transformer, unfortunately the dimensions are wrong,
It is 2-1/2" diameter and 3" high, ratio is 5:1 at 2khz, DC resistance is 1k primary and 8k secondary.
This is a good 1st audio transformer but the physical diameter may collide with the detector tube socket.
I would login to Antique Radio Forum, they get a lot more traffic for battery radio sets and post a WTB. There are several avid A-K collectors with parts sets.
This one also. Have a brown paint thats not quite dark enough. Will add just a touch of black for a better match to the neck of the base. My youngest daughter of many talents is also an artist. She will watch my feeble attempts for a while then say something like, try a drop of orange,and it will be near perfect.
Who knew??
There will come a time to address the rough edges of the horn. But for now just happy it works.
My daughter and I played around with the speaker yesterday. Decided to experiment a little bit since I am unable to find info on Perfectone speakers. I know tones from an 80's audio generator is not exact testing but we had fun and learned a few things. When tuning this speaker for best operation I used 1000 hz tone. I began with tuning (knob)? tightened all the way in. When I made my mason jar mod. fully CW or tightened has the metal cores of the audio driver coils lightly touching the metal diaphragm. At this position a 1000 hz tone can be heard but very weak. What surprised us was the driver and diaphragm response to the audio driver being slowly tuned CCW, drivers moved away from diaphragm. There would be very little to no change to 1000 hz tone volume out of the speaker. Then suddenly a sharp pop of static then an immediate greatly increased volume of the tone from the speaker. As can be predicted further turning of the audio driver away from the diaphragm quickly produces a much weaker tone. I could never hit the sweet spot of maximum diaphragm output from this point turning the driver CW closer to the diaphragm. The only time I could find the sweet spot was very slowly adjusting the driver away from the diaphragm. It is a very narrow very sharp response point. Simply applying a small amount of tension CW or CCW on the adjustment broke the point of maximum diaphragm resonance.
The original knurled knob driver adjustment unlike my mason jar threads, were a very fine thread. So my thinking is that very sharp response point is normal.
We then played with audio tones, I could begin to hear something at 196 hz. My 22 year old daughter could hear nothing till about 220 hz. One point for the old guy. She blew me away at the higher frequency. I stopped hearing anything at around 2700 hz, She could still hear a tone at just over 9000 hz. Found that somewhat impressive for a piece of resonating metal. But I needed her ears to hear it.
The frequency that provided the most volume was right around 620 hz.
If any of our testing has any form of validity, seems the speaker will respond to the human voice better that music. Our playing around on the kitchen table in no way qualifies for proper testing. If anyone out there can correct any mistakes in our simple testing and response. Or add to our meager learning curve, please let us know.
P.S. We also played around with a new 8 ohm four inch speaker under the same testing conditions. It's low frequency response was very poor compared to Great Grandpa speaker horn. But. with it I could hear a 9000 hz tone and my daughter could hear a tone at over 17803 hz. Oh to have young ears.
(This post was last modified: 04-25-2021, 09:55 AM by TTech.
Edit Reason: correct I to a
)
The resonances will change when or if the speaker is used in the plate circuit or the radio. The DC will bias the coils with a new magnetic force with superimposed audio.
In the 20's at least on radio magazine did a combination of resonance and sensitivities tests on several horn and cone speakers. generally, the larger the diaphragm, the lower the tones, the larger/longer the horn as well. Some speakers used a bi-polar driver with aluminum diaphragms others used mica diaphragms. No horn speaker sounded as good as the "worst" cone speaker. Somewhere in the middle of all these speakers came the Magnavox which used a voice coil driving the diaphragm
A high sensitivity 3 to 4" speaker taken from an old pair of modern headphones is often the solution for a rotted diaphragm driver. Silicone glued to the gutted driver housing and a small output transformer to make the match.
Some of the best sounding of the "vintage" speakers I have heard are the Air-Chromes. A linen diaphragm speaker with a bi-polar driver.
Strangely enough, it is possible to build one of these linen speakers with common materials and tools requiring only a drive from a ruined speaker. Will need hardwood lumber, felt, linen, colodion (canoe dope), some wood screws, table saw, hide glue, wood stain and a suitable grille cloth. Joann fabric and the lumber store will have it all. An outdoor supply will have the colodion. Some Air-Chrome speakers have rustic landscape scenes painted on the diaphragm, very attractive.
Yes, I know the hearing of the young... As a teenager I serviced TV's for pocket money. I could easily hear the horizontal sweep frequency or 15khz, I could tell if it was too low or had a distortion component to it.
GL Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
It will be interesting to hear and note tuning changes when the speaker is driven by it's designed inputs.
Will have to look up Magnavox voice coils and Air-Chromes.
Never heard of a linen speaker. Another item to look up.
Sounds like you were a pretty sharp kid. My first job out of Tech school was a TV shop. The owner was in his mid fifties and self taught in TV and radio repair.
Guess he thought hiring someone with training, I would be quicker than himself at repair. Not so. You reminded me of a time I had spent about an hour trouble shooting an RCA tube type color TV. Verl looked up from the set he was working on and with a disgusted tone stated. FOR CRY'N OUT LOUD, you can tell by the raster it's R21 in the horizontal hold section. Today that memory makes me laugh.
My only clear memory of a sound in his shop was the sound of his voice saying. AIN'T YOU GOT THAT THING FIXED YET???
That memory also makes me laugh...now.
chas
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