Late 1920s Eveready Model 1 TRF Set need info

[Electronic M]

Originally Posted by Kevin Kuehn

How about leave the defective 50k above chassis for originality, snip the wiring below and add a modern replacement under chassis? It's no more sacrilegious than changing caps. The filter choke, who knows, you'll find out if it's good once you trace the wiring or fire the set up under load. These things are so old that the copper wire used had impurities along with not so good insulating varnish which allows the wire to oxidize and corrode open over time. Same issues with the stage coupling transformers. The finer wire winding's are most subject to corroding open.

Some of those plug in fuse like grid bias resistors I've seen gutted and the ends attached to a hollow tube with a modern resistor inside. Either approach is valid and which to choose depends on how much of a stickler for originality you are and/or how much time and effort you want to spend.

[vortalexfan]

Originally Posted by Electronic M

Some of those plug in fuse like grid bias resistors I've seen gutted and the ends attached to a hollow tube with a modern resistor inside. Either approach is valid and which to choose depends on how much of a stickler for originality you are and/or how much time and effort you want to spend.

I have no idea how I would go about gutting this fuse style resistor without breaking it.

Also I did take a look over at Playthings of the Past's Website and they seem to have what I'm looking for resistor wise (the glass fuse style resistors) but I didn't see any in the 50,000 Ohm rating so I shot the owner a message to see if he could look through his glass resistor stash to see if he had any that were rated for 50,000 Ohms. I'm waiting to hear back from him yet (I sent him a message at 10 o'clock this morning and it is the weekend so I may not hear back until next week sometime).

[Kevin Kuehn]

Originally Posted by vortalexfan

I have no idea how I would go about gutting this fuse style resistor without breaking it.

Also I did take a look over at Playthings of the Past's Website and they seem to have what I'm looking for resistor wise (the glass fuse style resistors) but I didn't see any in the 50,000 Ohm rating so I shot the owner a message to see if he could look through his glass resistor stash to see if he had any that were rated for 50,000 Ohms. I'm waiting to hear back from him yet (I sent him a message at 10 o'clock this morning and it is the weekend so I may not hear back until next week sometime).

Just a heads up. The owner of PTOP passed away a while back and apparently someone bought the entire inventory, but he's not saying who he is at this point or when he'll be able to reopen the business. I'd be very surprised if you hear anything back via the old email.

https://antiqueradios.com/forums/vie...things+of+past

https://antiqueradios.com/forums/vie...things+of+past

[vortalexfan]

Originally Posted by Kevin Kuehn

Just a heads up. The owner of PTOP passed away a while back and apparently someone bought the entire inventory, but he's not saying who he is at this point or when he'll be able to reopen the business. I'd be very surprised if you hear anything back via the old email.

https://antiqueradios.com/forums/vie...things+of+past

https://antiqueradios.com/forums/vie...things+of+past

Ok, I didn't know, I just saw a reference to the website in a few posts over at the Philco Phorum, but I didn't pay much attention to how old the threads were that the posts were in.

I'll just have to keep a look out on ebay I guess.

[vortalexfan]

Originally Posted by Kevin Kuehn

Just a heads up. The owner of PTOP passed away a while back and apparently someone bought the entire inventory, but he's not saying who he is at this point or when he'll be able to reopen the business. I'd be very surprised if you hear anything back via the old email.

https://antiqueradios.com/forums/vie...things+of+past

https://antiqueradios.com/forums/vie...things+of+past

OK, so I found some regular resistors in my stash that I think might work in my radio as a replacement for the bad fuse style resistor.

I found a box of 47k Ohm 1W 2% tolerance Flameproof resistors that are branded RCA, a package with a 56K Ohm 1W 2% Flameproof Resistor that is Branded Sylvania and I have a package of 56k Ohm 1/2W Carbon Film Resistors that I had left over from when I was restoring my Meck TV last year that either one of those I think should work in this unit.

I think I could just solder it under the chassis between the two points where the resistor holder above ties into the circuit and then just leave the old fuse style resistor in the holder above the chassis for appearances sake (I cleaned up the glass housing of the old resistor and I looked inside and it looked like there wasn't anything in there anymore which might explain why it measured open).

Does any of these resistors I mentioned stick out as far as one that might work better than the other in this position?

Also I found a couple of capacitors in my capacitor stash that might work in place of the old filter caps in the filter supply circuit, one is a 4.7 MFD 250 WVDC Electrolytic and the other is a 2.2 MFD 100 WVDC Electrolytic.

Would those work fine in the filter cap positions on this radio seeing as they didn't specify a Working Voltage for the original filter caps?

Also the 5,000 Ohm "B" Resistor in this radio's Power Supply/Audio Circuit measures open as well, and I was wondering what kind of wattage of resistor it is, its rather large and looks like it might be a 5 or 10 Watt WW Power Resistor but I'm not sure as it doesn't have any information written on it.

Thanks for your help.

[Kevin Kuehn]

Originally Posted by vortalexfan

I found a box of 47k Ohm 1W 2% tolerance Flameproof resistors that are branded RCA, a package with a 56K Ohm 1W 2% Flameproof Resistor that is Branded Sylvania and I have a package of 56k Ohm 1/2W Carbon Film Resistors that I had left over from when I was restoring my Meck TV last year that either one of those I think should work in this unit.

I think I could just solder it under the chassis between the two points where the resistor holder above ties into the circuit and then just leave the old fuse style resistor in the holder above the chassis for appearances sake (I cleaned up the glass housing of the old resistor and I looked inside and it looked like there wasn't anything in there anymore which might explain why it measured open).

Does any of these resistors I mentioned stick out as far as one that might work better than the other in this position?

Really any of them should be fine. According to the voltage/current chart that resistor will be dropping around 45v, so 45v x 2ma is a whopping 90mw of dissipation.

Originally Posted by vortalexfan

Also I found a couple of capacitors in my capacitor stash that might work in place of the old filter caps in the filter supply circuit, one is a 4.7 MFD 250 WVDC Electrolytic and the other is a 2.2 MFD 100 WVDC Electrolytic.

Would those work fine in the filter cap positions on this radio seeing as they didn't specify a Working Voltage for the original filter caps?

Assuming B+ at the second filter around 175v, I would use 4.7 mfd @ 250wvdc for 102 and 103. That'll give you some good headroom and a little extra filtering. For that matter you could use a couple 10mfd.

Originally Posted by vortalexfan

Also the 5,000 Ohm "B" Resistor in this radio's Power Supply/Audio Circuit measures open as well, and I was wondering what kind of wattage of resistor it is, its rather large and looks like it might be a 5 or 10 Watt WW Power Resistor but I'm not sure as it doesn't have any information written on it.

175v - 90v = 85v across the 5k.
85v/5000 = 17ma.
85v x 17ma = 1.45watts. So a 5 watt should be very conservative.

Everything is ballpark based on the values listed in the Bosch model 28 voltage/current chart and schematic.

[Electronic M]

Many early AC powered TRF sets used paper caps for filtering since lytic technology wasn't there yet. Higher uF paper caps get bigger and more expensive as capacitance increases so many TRFs had less than ideal filter capacitance as a result. Increasing filter capacitance is advisable if mild to moderate hum exists post recap or as a preventative measure now.

[Kevin Kuehn]

Originally Posted by Electronic M

Many early AC powered TRF sets used paper caps for filtering since lytic technology wasn't there yet. Higher uF paper caps get bigger and more expensive as capacitance increases so many TRFs had less than ideal filter capacitance as a result. Increasing filter capacitance is advisable if mild to moderate hum exists post recap or as a preventative measure now.

True enough, although when using a choke filter it's possible to get the input capacitor too large and the B+ will go higher than intended. If hum is a problem I'd first try increasing only the cap on the output of the choke.

I'm now having reservations on my recommendation of 250wvdc for the caps. If the 80 rectifier turns on before the other tubes fully conduct, B+ could temporarily become much higher than normal. 350-450wvdc may be the safer bet given how small modern electrolytic are. What are you guy's thoughts?

Ultimately once you get the set operational you can monitor the B+ and see how high it surges at turn on.

[vortalexfan]

Originally Posted by Kevin Kuehn

True enough, although when using a choke filter it's possible to get the input capacitor too large and the B+ will go higher than intended. If hum is a problem I'd first try increasing only the cap on the output of the choke.

I'm now having reservations on my recommendation of 250wvdc for the caps. If the 80 rectifier turns on before the other tubes fully conduct, B+ could temporarily become much higher than normal. 350-450wvdc may be the safer bet given how small modern electrolytic are. What are you guy's thoughts?

Ultimately once you get the set operational you can monitor the B+ and see how high it surges at turn on.

OK, good point.

When I get paid on Friday (just had to drop $100 between my desktop and laptop computer because my laptop's cooling fan decided it was going to start failing on me and my desktop wouldn't let me get on the internet) I will order 2 4.7 MFD 450 VDC capacitors from AES (they don't sell 2.2 MFD caps but they sell 4.7 MFD caps).

Then order the replacement speaker from ebay for my radio as I think the original speaker is too far gone to try and fix using the diluted glue and coffee filter paper method, because the wiring is also messed up on it and I don't want to have to mess around having to try and special order from Radio Daze or Merry Tunes the wiring and special pin connectors that these speakers need to work because they're kind of pricey.

As for the bypass caps that are in those rectangular aluminum cans, could I just get away with restuffing those? They look easy enough to take apart and gut. Or should I not bother?

[Kevin Kuehn]

Re-stuffing those cans would be ideal if you can get inside them. Take pictures and try to keep the external wiring as close to original as possible.

[vortalexfan]

Originally Posted by Kevin Kuehn

Re-stuffing those cans would be ideal if you can get inside them. Take pictures and try to keep the external wiring as close to original as possible.

That's what I was planning on doing, I'm assuming that film caps would be used there as well? I'm asking because if you take a look at the picture of the caps there is a definite "ground" and positive lead to these capacitor cans and I was wondering why if they just used non-polar paper caps why would it matter if there was a ground and a positive lead to these capacitors (in this case the can's housing is the "ground" and the capacitor hookup terminals are the "positive" leads.)

Or is the "ground" more of an "RF Ground" to keep the noise down in the radio, since these capacitors are associated with the Tuner/RF stages of the radio?

[Kevin Kuehn]

Originally Posted by vortalexfan

That's what I was planning on doing, I'm assuming that film caps would be used there as well? I'm asking because if you take a look at the picture of the caps there is a definite "ground" and positive lead to these capacitor cans and I was wondering why if they just used non-polar paper caps why would it matter if there was a ground and a positive lead to these capacitors (in this case the can's housing is the "ground" and the capacitor hookup terminals are the "positive" leads.)

Or is the "ground" more of an "RF Ground" to keep the noise down in the radio, since these capacitors are associated with the Tuner/RF stages of the radio?

Yes Film. Definitely for RF grounding. Relocating them or their wiring can be a big no no.

[vortalexfan]

Originally Posted by Kevin Kuehn

Yes Film. Definitely for RF grounding. Relocating them or their wiring can be a big no no.

Ok I have a question, concerning the bypass caps in this radio.
Two of the bypass caps are marked on the base of the caps and on the schematic .5 (they are two singles marked at that value) and one cap is a double cap marked 1. on the bottom of the cap and on the schematic, what's the purpose of the decimal point (.) after the 1 on the double cap? I'm assuming it's a 1 MFD capacitor which if that's the case why bother with a decimal point after the 1 on the capacitor markings?

Also how would I restuff the 1 MFD bypass caps? I ask because I think a 1 MFD 630 VDC film cap is going to be too big of diameter to fit inside the can, let alone two of them.

Also as far as the .5 MFD caps go, I'm assuming a .47 MFD 630 VDC cap will work fine in its place?

Also I was wondering how I would go about handling the wiring going to the RF bypass caps because while the rubber insulation of the wiring is still intact and isn't falling apart, it is very brittle to the point that just moving the wires just slightly causes the rubber insulation on those wires to crack and chip off the wire which if I'm going to restuff those bypass caps I would have to move those wires and I don't want to have to replace any more wiring than I have to in this radio to get it up and running.

[Kevin Kuehn]

Originally Posted by vortalexfan

Ok I have a question, concerning the bypass caps in this radio.
Two of the bypass caps are marked on the base of the caps and on the schematic .5 (they are two singles marked at that value) and one cap is a double cap marked 1. on the bottom of the cap and on the schematic, what's the purpose of the decimal point (.) after the 1 on the double cap? I'm assuming it's a 1 MFD capacitor which if that's the case why bother with a decimal point after the 1 on the capacitor markings?

Also how would I restuff the 1 MFD bypass caps? I ask because I think a 1 MFD 630 VDC film cap is going to be too big of diameter to fit inside the can, let alone two of them.

Also as far as the .5 MFD caps go, I'm assuming a .47 MFD 630 VDC cap will work fine in its place?

Also I was wondering how I would go about handling the wiring going to the RF bypass caps because while the rubber insulation of the wiring is still intact and isn't falling apart, it is very brittle to the point that just moving the wires just slightly causes the rubber insulation on those wires to crack and chip off the wire which if I'm going to restuff those bypass caps I would have to move those wires and I don't want to have to replace any more wiring than I have to in this radio to get it up and running.

I'm not sure on the cap values. It's possible the double cap marked 1. is the total for the two .5 mfd combined, but that's just a hunch. You need to remember that back when these things were built the technology was still very experimental in nature. Personally I would try to baseline the radio using a dim bulb tester, then divide and conquer one component at a time. A complete strip down will only introduce more unknowns. I'd begin with the 80 rectifier removed, testing the transformer with only the filaments of the other tubes installed. Then with the 80 still removed measure between each of the two high voltage wingdings to ground. Next the 80 goes back in to see if the B+ comes up without drawing too much current. Start with a low wattage bulb and work your way up. As long as you limit the current you can't get yourself into too much trouble. At some point you'll have a better idea of where the problem areas are. I agree with leaving the wiring alone until you get all the other bugs worked out, and then only replacing a section at a time with testing in between.

[Kevin Kuehn]

Forgot to mention..I honestly can't think of any good reason you'll need film caps rated for 630v for bypass in this radio. Folks use them simply because they have them on hand and the rational better safe than sorry. I'll be surprised if the B+ swings above 250v for more than a couple seconds on power up. It should settle out around 170v at the second filter cap. The 71 output tubes had a 180v max design value, which I doubt they exceeded.