Just picked up a 1930s Battery operated Coronado

[vortalexfan]

Originally Posted by maxhifi

I like the cabinet!

Go to your local dollar store and get 10 9V tranaisistor radio batteries to use in series for B+, and some D cells for the filaments. The 9V batteries can be clipped together in series using their own terminals, and then the first and last ones can have wire leads with alligator clips soldered to them, which you can connect to the radio's power connector. For the A battery I'd use 2 D cells in parallel.

Before you apply power you may want to do a basic replacement of capacitors, especially any electrolytic capacitors, the AVC filter, and the audio grid coupling capacitors.

The reason these radios sound worse than normal radios, is the audio output stage is necessarily very low powered, so the speaker is designed for efficiency rather than sound quality. They can be okay though. I like yours because of the fancy grill design and late 30s deco cabinet.

How do you parallel "D" batteries? is it positive to positive or negative to negative?

[Electronic M]

Originally Posted by vortalexfan

How do you parallel "D" batteries? is it positive to positive or negative to negative?

Both at once...

[vortalexfan]

Originally Posted by Electronic M

Both at once...

OK, so I take it that a battery clip like the one in the link below won't work in my case?

https://www.radioshack.com/products/...battery-holder

[vortalexfan]

Originally Posted by Electronic M

Both at once...

Are you sure the two batteries should be connected in parallel? Because I'm only getting 1.5 volts connecting them that way...

I've also tried connecting 2 sets of D batteries in parallel and I'm only getting 1.4 volts, so not even close to the correct amount of volts needed to power the radio's filiments...

[vortalexfan]

Well I was able to rig up a temporary battery rig for my radio and it works...Sort of.

I hooked up my signal generator up to the radio and it picks up the 456 kHz IF Signal fine (all though it picks it up all across the whole dial and not just around the 550 area of the dial), and I tweaked the IF cans and surprisingly enough they are peaked where they are supposed to be, I tried adjusting the Oscillator and Antenna adjustments on the tuning capacitor and they didn't seem to make any difference and the 600 kHz oscillator adjustment is under the chassis so I couldn't adjust that.

But I can't get it to pick up any radio stations I can't even get it to pick anything up from my signal generator tuned to various stations on the AM Band, hooked through the antenna, and the antenna coil tested fine when I tested it.

Any ideas as to what may be going on?

[Electronic M]

Originally Posted by vortalexfan

Are you sure the two batteries should be connected in parallel? Because I'm only getting 1.5 volts connecting them that way...

I've also tried connecting 2 sets of D batteries in parallel and I'm only getting 1.4 volts, so not even close to the correct amount of volts needed to power the radio's filiments...

Note I didn't advise you to put the batteries in parallel....I only advised you HOW to connect them in parallel.
The trouble with using standard alkaline D cells to supply the 2.2V filaments is that new alkaline cells are 1.5V so parallel will not give you enough voltage and series will give you too much (unless you use used batteries that are down to ~1V ). The only advantage of parallel connection is that the batteries will last longer.
One thing you could do for the filaments is connect the batteries in series and build a LM317 circuit to regulate 3V down to 2V...A filament rheostat is another solution.

Got an oscilloscope to check if the converter or oscillator tube is oscillating? And do you have a decent length of antenna wire 15-40' hooked up? If you have an antenna and the IF works then either the local osc is dead or the RF path between the antenna and the Mixer/Converter is bad....If you passed IF down the antenna and it didn't seem attenuated in comparison to injecting it at the 1st IF then that favors the Osc being dead.

[vortalexfan]

Originally Posted by Electronic M

Note I didn't advise you to put the batteries in parallel....I only advised you HOW to connect them in parallel.
The trouble with using standard alkaline D cells to supply the 2.2V filaments is that new alkaline cells are 1.5V so parallel will not give you enough voltage and series will give you too much (unless you use used batteries that are down to ~1V ). The only advantage of parallel connection is that the batteries will last longer.
One thing you could do for the filaments is connect the batteries in series and build a LM317 circuit to regulate 3V down to 2V...A filament rheostat is another solution.

Got an oscilloscope to check if the converter or oscillator tube is oscillating? And do you have a decent length of antenna wire 15-40' hooked up? If you have an antenna and the IF works then either the local osc is dead or the RF path between the antenna and the Mixer/Converter is bad....If you passed IF down the antenna and it didn't seem attenuated in comparison to injecting it at the 1st IF then that favors the Osc being dead.

No but someone else on here said to connect 2 D cells in parallel to get the voltage I needed for my filaments, you just happened to reply when I asked about how to connect batteries in parallel.
Anyways Rechargeable NiMH batteries are 1.2 Volts which if I connected 2 of those together I would get 2.4V which would be the correct voltage I need for the tube filaments, and they make NiMH Rechargeable D cells that are as high as 12,000 mAh, which would be more than enough juice to power the filaments.

I'm guessing the oscillator isn't running because the tubes aren't getting enough filament juice.

[dieseljeep]

Originally Posted by vortalexfan

No but someone else on here said to connect 2 D cells in parallel to get the voltage I needed for my filaments, you just happened to reply when I asked about how to connect batteries in parallel.
Anyways Rechargeable NiMH batteries are 1.2 Volts which if I connected 2 of those together I would get 2.4V which would be the correct voltage I need for the tube filaments, and they make NiMH Rechargeable D cells that are as high as 12,000 mAh, which would be more than enough juice to power the filaments.

I'm guessing the oscillator isn't running because the tubes aren't getting enough filament juice.

Those tubes aren't that easy to source. They only used them for few years.
The 1C6 can be replaced with a 1A6.
I checked over my 2 volt battery set. At the time, I built the power supply using a transformer from a scrap VTVM. I didn't have a regulator chip at the time, so I just used discrete components.

[vortalexfan]

Originally Posted by dieseljeep

Those tubes aren't that easy to source. They only used them for few years.
The 1C6 can be replaced with a 1A6.
I checked over my 2 volt battery set. At the time, I built the power supply using a transformer from a scrap VTVM. I didn't have a regulator chip at the time, so I just used discrete components.

I'm curious, if I were to use some 1.2V NiMH rechargeable D batteries to power the filaments in this radio (2 1.2V batteries in series would give me 2.4V roughly) what kind of diode or what size of dropping resistor would I need to drop the extra .3V to get the voltage down to the 2.1V I need for the tube filaments?

Or would it not matter in this case?

Thanks for your help.