- 1920s radio - 8 Updates
- Help identifying a blown transistor - 5 Updates
- McMaster-Carr ROCKS! - 2 Updates
| "pfjw@aol.com" <peterwieck33@gmail.com>: Aug 27 09:56AM -0700 After you have handled or been around in the mid-five-figures worth of vintage radios, you will learn not to reason from the specific to the general. Magic words here are: 1920s Home Brew Single tube a) Suspend all other expectations, and deal with what is in front of you. O1A tubes come in several shapes, from globe to ST. I have seen one (1) "G" type as well, so anything is possible. There are also several other candidates that would do, including an OO, 30 and 112 amongst others. Some would require a different filament voltage. But, the O1A is/was the go-to as they were very common, and much cheaper than the alternatives. b) Variable capacitors are/were expensive relative to fixed caps. So, your home-brew hobbyist likely picked a fixed cap at some value between that specified for a variable cap. c) Fixed caps are/were expensive relative to nothing - so your home-brew hobbyist 'went without'. He/She (a great many of the earliest hobbyist were girls/women - why? Most of the parts were made by women). He/She was probably listening to a nearby "torch" station with little or no competition, so targeting to a specific frequency would be typical. d) At the time, coils were either wound by the hobbyist or purchased to a specific range. If no plug exists, then your hobbyist was uninterested in, or could not afford that option. e) At the time, there was no 'set standard' for radio parts, connections, hardware nor much of anything else. The typical hobbyist, working on-the-cheap as this one clearly was, would use what was lying around. Which might explain some oddball stuff. f) Note that the standard for *cheap* wire at the time was rubber/gutta-percha insulation. Which would crumble to dust in short order. So, PVC is no surprise. On that one-handed coil - are there any taps on it? Commonly, a poor-man's SW or Airplane frequency coil would be done that way - one end fixed, and then tapped to the standard antenna for the alternate. Summing up, you have the equivalent of a fox-hole radio created with as few expensive parts as possible, following the general idea of the Armstrong circuit, which was 'all the rage' at that time. Peter Wieck Melrose Park, PA |
| amdx <nojunk@knology.net>: Aug 27 12:22PM -0500 > A little homemade 1920s 1 valve set with direct heated triode (unmarked). I've traced most of the circuit, looks very simple. Not tried to trace the main coil assembly with its 6 connections yet. The valve has a grid leak resistor for -ve bias without C battery. It runs high R phones, no speaker. 1st question is what sort of HT voltage and/or anode current should I aim for? > NT The people on this forum will be very knowledgeable and happy to help. > https://antiqueradios.com/forums/index.php Mikek |
| Chuck <ch@dejanews.net>: Aug 27 01:16PM -0500 On Tue, 27 Aug 2019 09:10:02 -0700, John Robertson <spam@flippers.com> wrote: >collection. About the size of carry-on luggage these days. Cunningham >C-299 tubes... >John :-#)# I had an early 1920s Crosley radio. It had two RCA WD12 tubes which were retained into their sockets by a rod that projected out of the tube that was locked into a groove in the tube socket. Tuning was by a coil on a shaft that one pulled toward or away from a stationary coil. A multi contact rotary switch selected segments of the AM band. It used 3 batteries; one for B+, one for the filaments and one for grid bias. It picked up the 50000 watters in the northeast USA at night. When I came back home from my first year at a midwest university, one of my brothers had stolen it and I never saw it again. |
| tabbypurr@gmail.com: Aug 27 02:19PM -0700 > 1920s > Home Brew > Single tube One can't always rule out an amateur builder working to their own outdated technical knowledge. But they clearly know enough to get a radio working, and it's not much more leap to bring the tech up to date. > a) Suspend all other expectations, and deal with what is in front of you. > O1A tubes come in several shapes, from globe to ST. I have seen one (1) "G" type as well, so anything is possible. There are also several other candidates that would do, including an OO, 30 and 112 amongst others. Some would require a different filament voltage. But, the O1A is/was the go-to as they were very common, and much cheaper than the alternatives. useful to know. > b) Variable capacitors are/were expensive relative to fixed caps. So, your home-brew hobbyist likely picked a fixed cap at some value between that specified for a variable cap. The one fixed cap on the ae input is in series with a variable cap! I suspect the variable was added later. The other controls are nice & symmetrical then then ae input VC is stuck round the side. > c) Fixed caps are/were expensive relative to nothing - so your home-brew hobbyist 'went without'. He/She (a great many of the earliest hobbyist were girls/women - why? Most of the parts were made by women). He/She was probably listening to a nearby "torch" station with little or no competition, so targeting to a specific frequency would be typical. My homemade '24 set has lots of caps. But this one is, as you rightly conclude, a total cheapie job. The cabinet is nice but open the lid & it's clearly ill fitted pieces untidily glued together. The rest is similar. Caps however were almost free. Take some paper & a little foil, tie with cotton & wax it and minutes later you have a cap. Any electronics book of the day explains this. A different history piece I have includes an HV cap made with plywood as the dielectric. I've never seen any graphs on how they perform :) I guess it's still cellulose. > d) At the time, coils were either wound by the hobbyist or purchased to a specific range. If no plug exists, then your hobbyist was uninterested in, or could not afford that option. > e) At the time, there was no 'set standard' for radio parts, connections, hardware nor much of anything else. The typical hobbyist, working on-the-cheap as this one clearly was, would use what was lying around. Which might explain some oddball stuff. It has 3 knobs, all clearly of the era but all different. I don't know for sure it was that way originally but it would not surprise me. > f) Note that the standard for *cheap* wire at the time was rubber/gutta-percha insulation. Which would crumble to dust in short order. So, PVC is no surprise. I thought bare wire was the usual thing to wire up radio internals then. "Waldo Semon and the B.F. Goodrich Company developed a method in 1926 to plasticize PVC by blending it with various additives. The result was a more flexible and more easily processed material that soon achieved widespread commercial use. " So it could even be original wiring, though that's not likely. > On that one-handed coil - are there any taps on it? Commonly, a poor-man's SW or Airplane frequency coil would be done that way - one end fixed, and then tapped to the standard antenna for the alternate. no taps. Looks like it was hand wound round a convenient round object, some sellotape added to keep it together & that was it. It has its own custom mounting made from the same material as the cabinet, so probably was fitted from the start. > Summing up, you have the equivalent of a fox-hole radio created with as few expensive parts as possible, following the general idea of the Armstrong circuit, which was 'all the rage' at that time. > Peter Wieck > Melrose Park, PA Well, it's a fair bit better than a foxhole set but yes it definitely incorporates some 'whatever' parts, and some not. NT |
| John Robertson <spam@flippers.com>: Aug 27 03:08PM -0700 > It has 3 knobs, all clearly of the era but all different. I don't know for sure it was that way originally but it would not surprise me. >> f) Note that the standard for *cheap* wire at the time was rubber/gutta-percha insulation. Which would crumble to dust in short order. So, PVC is no surprise. > I thought bare wire was the usual thing to wire up radio internals then. There were kit radios of the day that used simple tinned wire. I have one, a Mercury Super Ten kit (10 'peanut' tubes - superhet) around here somewhere, but I don't think they are that uncommon. John :-#)# |
| Fox's Mercantile <jdangus@att.net>: Aug 27 08:13PM -0500 > in 1926 to plasticize PVC by blending it with various additives. > The result was a more flexible and more easily processed material > that soon achieved widespread commercial use." PVC insulation on wires wasn't used until the '40s and was mostly used by the Government for WWII production. And even at that, there was plenty of wire that was rubber, although it was covered in braided cotton. The standard wire in the 20's was either rubber covered, bare or "push back" which was solid copper with a spun cotton or silk covering that could be Just pushed back" so no fuss to expose the ends of the wires. > So it could even be original wiring, though that's not likely. Absolutely NOT likely at all in the '20s. -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
| tabbypurr@gmail.com: Aug 27 11:54PM -0700 On Wednesday, 28 August 2019 02:13:15 UTC+1, Fox's Mercantile wrote: > "push back" which was solid copper with a spun cotton or silk > covering that could be Just pushed back" so no fuss to expose > the ends of the wires. DCC. The homemade coil is enamelled rather than DCC. |
| Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Aug 28 11:55AM -0400 > A little homemade 1920s 1 valve set with direct heated triode (unmarked). I've traced most of the circuit, looks very simple. Not tried to trace the main coil assembly with its 6 connections yet. The valve has a grid leak resistor for -ve bias without C battery. It runs high R phones, no speaker. 1st question is what sort of HT voltage and/or anode current should I aim for? > NT Probably intended for a 67 V B battery. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com |
| Baron <baron@linuxmaniac.net>: Aug 27 07:07PM +0100 > (https://imgur.com/a/uBCXjwQ). > Not sure if this helps or makes any difference, but let me know if > there is anything else that I can check/try. Looking at your pictures, the transformer has been very hot at some time ! Suggesting a heavy load for some period of time. -- Best Regards: Baron. |
| tabbypurr@gmail.com: Aug 27 01:40PM -0700 > Thank you everyone for the amazing help so far. I'm learning so much with this. > I feel like I should've perhaps mentioned that I'm pretty much a beginner when it comes to circuit boards. I've replaced fuses, capacitors and resistors before, after doing some research and finding the correct replacement parts, in order to bring back life to old/broken appliances/toys. useful to know > Also, something else to note is that the local (Cape Town, South Africa) place where I get all my electronic parts is Mantech (https://www.mantech.co.za). A lot of parts can be taken from dead e-junk. > I've also followed the advice to remove the remaining epoxy from the chip and look at it under a magnifying glass (unfortunately I don't own a microscope). I'd approach it by looking at the circuit connected to it. That usually makes it clear what a part is. > @Phil: If I understood you correct, you are saying the because of the blown part, the opto is likely blown as well? If so, which opto should I try to replace it with: > https://www.mantech.co.za/Stock.aspx?Query=817+optoand > Unfortunately I have no idea what happened as I got this from someone that was throwing it out, since they had already replaced it. I'm trying to see if I can fix it. With mains stuff it's useful to test it by running it in series with a filament lamp if there's a possibliity of shorting. > Also, we have had load shedding happening in the past, which would some times have caused voltage spikes when the power came back on. Lots of mains appliances consume a large current surge at switch on, together these reduce mains voltage rather than cause a voltage spike or 'surge'. 'Surges' is one of those topics on which plenty of misinformation is believed. > Don't know if that could've cause something like this to happen? I know people have lost appliances to that, but not sure if it could be related. to all 3 of those points, I doubt it. > @whit3rd: So you reckon, I just try to replace the blown part with a TL431 (any particular one from the list? https://www.mantech.co.za/Stock.aspx?Query=TL431and) and then also replace the optoisolator (any particular one from the list? https://www.mantech.co.za/Stock.aspx?Query=817+optoand)? what caused what to blow? > I'll do a check of the diodes. Would testing in circuit be sufficient or should I remove the diodes from the circuit for testing? It varies. In-circuit testing will sometimes tell you they're ok, sometimes not. Far quicker than taking time out of course. NT |
| Phil Allison <pallison49@gmail.com>: Aug 27 04:59PM -0700 janni...@gmail.com wrote: ------------------------------ > L1620 > 817BL > W ** The "817" part of the number is the main identifier. I would expect any "xx817xx" opto-coupler part on offer to work. .... Phil |
| whit3rd <whit3rd@gmail.com>: Aug 27 08:13PM -0700 > That said, with regards to the Fixed Positive Voltage Regulator (15+ V) in a TO-92 package (as mentioned by John & Peter), I found the following options: That's an unlikely part, considering it's right next to the optoisolator. <https://www.mantech.co.za/ProductInfo.aspx?Item=14M7535> is the TL431 part for the optoisolator, <https://www.mantech.co.za/ProductInfo.aspx?Item=14M7535> > I'll do a check of the diodes. Would testing in circuit be sufficient or should I remove the diodes from the circuit for testing? If the diodes are short-circuited, they'll look bad in-circuit; if a multimeter that does diode check is available, use that. Otherwise... play around with ranges on an ohmmeter scale, and find out what a good example diode reads, both forward and reverse, and try to match that. in a pinch (the diodes look like they're 1N4007) wire 'em in series with two batteries and a flashlight bulb; should light forward-connected, not backward. |
| Jannie <janniebrand@gmail.com>: Aug 28 03:22AM -0700 Thank you again to everyone that has been contributing. I really appreciate it so much and I'm learning so much. > Can you trace out where the wires go? If it is a regulator, then the center lead will usually go directly to ground (nearly zero ohms to the negative output terminal). If it is a TL431, the left wire (looking at the flat surface with the wires down) will probably go to ground. And if it is a pass transistor, then probably none of the wires connect to the ground. I have tried the above suggestion and the center lead goes to go to ground (nearly zero ohms to the negative output terminal, 1.6 ohms to be exact, but that's the same I get if I directly connect the 2 test leads together). Not sure if this means it's a regulator or if it's still more likely to be a TL431, but I hope this helps. > With mains stuff it's useful to test it by running it in series with a filament lamp if there's a possibility of shorting. Thanks for this, I will definitely do the testing with this setup. I'm sure I still have a few old filament lamps in the garage somewhere. I did some more detailed examination of the board on the front/top side with a magnifying glass for any possible damage and found another part with damage, the other IC (marked as U1 on the board). The code on IC is: H11552 OB2358AP L d Based on what I found, this seems to be a "Current Mode PWM Power Switch". Not sure which one would be the correct replacement as there are many and not one matching the "OB2358" code (https://www.mantech.co.za/Stock.aspx?Query=PWM+DIL08and). Anyone have any suggestions? Again, I hadn't noticed it before (probably because I assumed the problem was the clearly blown part). I have taken a picture and added it to the album (https://imgur.com/a/uBCXjwQ). You can see there is a crack in the center top side of the chip running down to the bottom right side. I also added an image of the front/top of the board with an overlay of the circuit at the bottom. Don't know if that helps anyone, but it's definitely helped me starting to understand what goes where and the connection between the components. @whit3rd: Thank you for confirming the TL431 part. Not sure if you meant to paste a link for the optoisolator part, but it is the same link as the one for the TL431 part. @Phil did however mentioned that any "xx817xx" opto-coupler part should work. > If the diodes are short-circuited, they'll look bad in-circuit; if a multimeter that does diode check is available, use that. I have tested the diodes in circuit with a multimeter and some of them (D1, D2, D3, D4 & D6) looks bad (shorted), but as mentioned, they could be fine. I can also confirm that the few diodes where I could actually see the number, are in fact 1N4007 diodes. I reckon I just go buy a pack of 10 x 1N4007 diodes with the other parts (once confirmed) and then tackle the diodes tested as shorted in circuit 1 by 1, removing, testing and replacing if needed. |
| etpm@whidbey.com: Aug 27 11:06AM -0700 I ordered on 8-22 some ABS plastic rod from McMaster-Carr. The package arrived yesterday but it had some other sort of plastic cut from plate. So I called sales about 4:30 PM and informed them of the mistake. This was the first incorect shipment I have received from McMaster-Carr in at least 30 years of buying from them. Well, just a few minutes ago, about 11:00 AM, arrives a tube with the proper plastic rod in it. I totally did not expect an overnight shipment! Boy, what service! They Rock! Eric |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Aug 27 12:30PM -0700 Same general opinion of McC, and for the same general reasons! Peter Wieck Melrose Park, PA |
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