Admiral 20z1

[skillybob]

I pulled the speaker from my console to get things cleaned up and have come up with a problem that I hope someone has and answer for me. The speaker has a pretty brittle cone that will probably have to be fixed or replaced in the future. Mounted on the speaker are an Inductor from the power supply and an output transformer for the speaker itself. I thought it a bit odd to mount the choke on the speaker with a cable leading back to the chassis but I guess that is the way things were done. I measured the inductor with my meter and I have continuity with the ohms listed on the schematic. The problem is with the audio output transformer. It measures open with infinite ohms. I need a replacement or a good substitute. The schematic lists it as a Stancor A-3849 or Merit A-2930. I can not find this particular transformer for sale. The primary is listed as 4000 ohms impedance with a 3.2 ohm secondary. Since the speaker will probably need to be re-coned or replaced , I was thinking about using a more modern 4 ohm unit. Does anybody have a suggestion for a replacement transformer ?

[stusnyder]

Playthings of the past has one listed that you need :
1326-508 OUTPUT MERIT A-2930 SP (5K Z) TO 3.2 VC, 40MA, 5 WATTS, FIG 3 NEW (NO BOX).... 1 2 3/8 1 3/8 1 1/4 $5.75

He has a 20.00 min order, so maybe you can grab some other spare parts.

[skillybob]

Thanks for the heads up. I usually use Google Chrome for my browser and I did a search for Merit A-2930 and got very little back. The website that you pointed me to had a link, but when I clicked on it , it came up with a text document so I went looking elsewhere. Later, at your suggestion , I tried Internet Explorer and the webpage came up just fine. Evidently Google Chrome has some security setting that prevents this page from displaying properly. At any rate, I now have a source for this particular transformer -- Thanks.

[bandersen]

It actually is a text document as are most of the parts lists on that website.
Internet Explorer displays it inside the browser. Firefox, Chrome and probably every other browser, prompts you to download it.

[Tim]

I use Chrome also. If the .txt extension is associated with Wordpad in Windows file association and not notepad, it opens properly formatted when clicked on and downloaded.

[Kevin Kuehn]

I believe I have a complete spare speaker for that set here if you need it. Not perfect, but it all works. Measures 10 1/4" across the frame. The choke reads 95 ohms.

Kevin

[skillybob]

Yes, bandersen, that seems to be the way it is. If a link comes up in the future I will know how to handle it - and I have another link to add to my list for parts.
Not to beat a dead horse, but I was wondering how critical a replacement transformer will be. My schematic indicates a 4000 ohm impedance primary/ 3.2 ohm secondary and I have seen several transformers with a 5000 ohm primary with 4 ohm secondary. Do you think this will be OK - I am thinking it will be cheaper to replace the speaker with a 4 ohm voice coil . The cone is really brittle and fragile at this time , but probably repairable.

[Kevin Kuehn]

Originally Posted by skillybob

Not to beat a dead horse, but I was wondering how critical a replacement transformer will be. My schematic indicates a 4000 ohm impedance primary/ 3.2 ohm secondary and I have seen several transformers with a 5000 ohm primary with 4 ohm secondary. Do you think this will be OK - I am thinking it will be cheaper to replace the speaker with a 4 ohm voice coil . The cone is really brittle and fragile at this time , but probably repairable.

That transformer would be fine. But before you throw in the towl on the one you have, have you tried resoldering the connections to the transformer windings?
Also, sometimes they break right at the connection point, and you can possibly reconnect the wire.

Kevin

[skillybob]

Yeah, Kevin, I looked into it. The connections are intact right up to the core- still no continuity so it's shot. Out of curiosity, I pulled the transformer apart to see how it is constructed. Man, that was some thin wire for the primary. I should be able to get a replacement at a reasonable cost and I'm probably stressing too much over the little things. The transformer is tied to the plate of a 6as5 that just does not look right. I figure either the tube went south and took the transformer with it or the transformer shorted and took the tube out. Either way, fun and games.

[Kevin Kuehn]

Those fine wires sometimes just fail from corrosion with age. You could change that output tube to something closer to a 5000 ohm impedance, but I doubt you'd hear much difference.

Kevin

[skillybob]

Thanks for the offer of the speaker , Kevin. I will keep it in mind for the future. I'm still in the process of listing all the caps and resistors that I will have to order to get the chassis up and hopefully running. I should be able to handle most of the work, I'm just not sure about a few of the Big items - like the picture tube, deflection coils, flyback , etc. If any of these are out, I don't know what I will do.

[skillybob]

Upon cleaning the chassis I have a question if anybody cares to chime in. On the deflection yoke towards the rear is a collar that looks like it is made of paper or cardboard. The paper is falling apart and looks like critters have been at work.I am gluing it together as best as I can but it is quite brittle. I am assuming that this is not critical to the operation of the deflection yoke and appears to be some form of dust collar. Is this correct?

[bandersen]

This cover ? Yes, it's just there to protect the coil. Maybe you can fabricate a new one from some heavy paper stock ?

[skillybob]

Yes, that's it. I will try to glue it together as best as I can, but I may take up your suggestion and make a new one. Is there a way to test the deflection coils. I can trace the wire leads and unsolder for a continuity test. I don't know if there is anything else I can do for test purposes. I have a few very small 'shiners' of wire on the front. Can I place something like lacquer on them for protection?

[Reece]

I'll bet the reason the choke is on the speaker is that at the time, they were transitioning from field coil speakers to PM. The chassis were set up for field coil speakers where the coil served the second purpose of power supply filter component. By doing it this way they didn't have to modify the chassis and could use either field coil or PM speaker whatever was available.