Had to put the 65 on hold for parts but found this 91 at an estate sale today for $45. I haven't had time to start checking it out yet. Sure, hope the PT is OK. I think it is a 91H, maybe yall can verify that for me. As I get into it, I will have a lot of questions for yall. I have to figure out how to make the cabinet pic upload, Will post later.
Thanks,
George
I think the PT is ok. Need to clean and then check other things.
Yes your model 91H is from June of 1933.
Thanks, Terry, for that info. I thought it was from 1932 but I think its later than some.
I checked the power transformer and think it is ok, but it will need a power on check for voltages to be sure. I know I need to replace the cord, put new elect caps in for part numbers 55 and 57. Put new caps in p/n 53. I will follow the guide in the phorum files, and also check the field coil. Clean up the on/off switch (a switch was added to the power cord). As for the electrolytic caps, the schematic calls for 6uF, I don't have any would a 4.7 or 8 uF be acceptable or should I order something closer?
You and Ron have been such a help to me, and I do thank yall. If there is anything I am missing, you guys please advise.
George
8 or 10mfd are fine. 4.7 are kinda dinky and won't filter all the 60cy hum.
The other things to check would be the primary of #48, Primary and secondary of #45 and #16. Don't think any should be over a thousand or two ohms.
Thanks Terry,
Been busy on other things. Looks like primary and secondary of 45 is 2K ohms and primary of 48 is 282 ohms. By item 16 I assume it is the shadow meter. I know nothing on those or how they work but the two leads coming off of it was 1.2K ohms. I did replace both caps in item 53 with .01 uF Y2 caps. Follow the directions in the library it was super easy. I couldn't fix the on/off switch so I will temp install a toggle until I can get a replacement. I assume that with that done and a new power cord I can apply power without and tubes to check the transformer voltages.
George
You could pull the 80 tube out and power the chassis up. All the tubes should light except for the 80, the dial light and the light for the shadow meter. Check the hv at the plate pins of the 80 socket back to the - side of the filter caps. Both are connected to the ct of the hv winding. Voltage from ct to either end should be within about 10v of each other. All this is done with the 80 tube removed.
All of the resistances look good for the opt, driver trans, and sm coil. No parts hunting for those bits.
If you can't get the switch to work it might be time to give Mark O a call and order a new volume control. If it's the original it going to be pretty worn anyway.
Terry,
Did the power check you recommended, 328 volts on both pins to - of the caps. Also had 5 volts for the 80 filament pins. All tubes lit up except one 44 and one 36. All of the tubes were in the radio when I bought it.
George
Good. As for the 39/44 and the 36 use your ohm meter and measure the resistance between the two closest pins (1 and 5) with then out of the set. Should see a very low resistance like 1/2 ohm. It will probably read open which means they are kaput... Need a couple of replacements.
Your right Terry,
Both tubes are bad, will get some on order. Question about item 29 filter condenser bank, is that a 1.0 uF electrolytic and two .25 uF non electrolytic caps in the same can?
George
They are probably all paper but you could use an electrolytic cap for the 1 mfd. + goes toward the choke and - to the chassis.
Thanks Terry,
I was confused because of the +symbol on the schematic. This is going to take longer than I thought to do, but there is no rush. Still having fun and learning.
George
Going back over things I believe I made a few errors. When I measured item 48 that you mentioned, I actually measured item 58 which is the filter choke. The speaker should be a K6 but is a H12 with the output transformer p/n 2585 which goes to a K6. Anyway, it is open, but I did measure 3295 ohms on the voice coil after I unsoldered it from the trans. That will be another issue. On the good side, I replaced the 2 electrolytic caps with 8uF ones. I have to order the caps for the filter bank item 29, thought I had some but am short on the .25 caps. have a ,2 and a .22. Tubes should be here monday or tuesday.
George
48 should be the output transformer. You would want to check the primary's continuity. This can be achieved be measuring the resistance from pin 3 of either of the 42's to each of pin of 2 of each of the 42's. Should see something like 2000-3000 ohms. If it measures 100k or a Meg better add it to the list.
The K speaker is a 7 3/4 (8") used in the table top or B (baby grand cabinet sets). The H speaker is a 10 1/12 speaker used mostly in the consoles. Some console used both that's why they're shown in the schematic. From the picture it looks like your set uses a single H-12 speaker. No worries. I did a little looking and found the the K-6 and the H-12 are the same electrically. That's why they share the same output transformer. Physically ones bigger than the other. I think you measured the field coil and not the voice coil as it should just an ohm or so.