Just picked up a 1930s Battery operated Coronado

[vortalexfan]

Originally Posted by dieseljeep

First of all, a fully charged 2 volt lead-acid puts out 2.2volts. This voltage is what the radio was designed to use.
Did you check the tubes on a good tube checker. You probably have a weak osc-mixer tube. Increasing the filament voltage, will increase the emission.

I was using a set of 1.2 V NiMH rechargeable D Cells, not the 2V Lead-Acid battery I had previously linked here and asked about.

Secondly I don't have a tube tester capable of testing the old style 4, 5, 6 and 7 pin tubes, so I can't check the tubes unfortunately.

I've tried to acquire one but everytime I find one they usually want over $100 for it, which I can't afford anything like that right now.

[Kevin Kuehn]

Since your set has AVC why not monitor that voltage to get a handle on what's going on? You'll want to use a VTVM, a scope, or a digital volt meter connected to the bottom side of R3(2meg). When the set is working does your AVC voltage seem to work normally with and without a signal tuned in? AVC voltage normally will be negative with a strong signal and become more positive as you de-tune the station. If the local oscillator isn't running you loose AVC action. If AVC voltage continues to respond to tuning then when the audio fades, then most likely you have an issue in the audio sections. When the radio is working correctly you can also align the IF's to the most negative voltage on the AVC line. There's really no need to rely on listening to an audio tone through the speaker.

Edit R3 not R4

[Kevin Kuehn]

I meant AVC voltage at bottom side of R3, not R4 as I fist posted.
Edited above post.

[init4fun]

Originally Posted by vortalexfan

I was using a set of 1.2 V NiMH rechargeable D Cells.....

Looking at the tube compliment posted in your first post , I can not believe a pair if D cells in series is anywhere close to powerful enough to light all those filaments .

[dieseljeep]

Originally Posted by old_coot88

Looks like nobody's chiming in. If you were turning the IF adjustments with the oscillator dead, there will be no IF signal for the adjustments to 'peak' to. So they're probably 'waay outa whack. To get them back on peak, inject a 456 khz signal. Keep attenuating the level as needed as they approach the peak. Once on peak, attenuate a little more and get it as sharp as possible.

Then start looking for why the osc. isn't running. For a start, check for continuity of the osc coil's primary and secondary windings.

We didn't chime in because the OP was waiting for the parts.

[vortalexfan]

Originally Posted by init4fun

Looking at the tube compliment posted in your first post , I can not believe a pair if D cells in series is anywhere close to powerful enough to light all those filaments .

They are 2500 mAh batteries, so more than enough juice to power the filaments (the filaments require around 540 mA).

[vortalexfan]

Originally Posted by dieseljeep

We didn't chime in because the OP was waiting for the parts.

Well I got the parts in and installed, and its looking like I might have a bad 1C6 tube which can be subbed out for a 1A6, 1C7 or a 1D7, whichever is more readily available.

Does anyone on here have either a 1C6, 1A6, 1C7 or a 1D7 tube that is known to be good that they could send me, or know if there are any for sale on fleabay for sale for relatively inexpensive?

Thanks!

[vortalexfan]

UPDATE: I found a set of NOS Ken-Rad 1C6 tubes on feebay for $16 plus shipping.

[vortalexfan]

UPDATE: I figured out what my problem is, its the IF Cans, apparently at some point in time in this radio's history both IF Cans were replaced, and whomever did the replacement installed two IF Cans of with two Different IF Frequencies that were completely different from the original IF Frequency of the radio!

The 1st IF Can was replaced with an IF Can with an IF Frequency of 455 kHz and the 2nd IF Can was replaced with an IF Can with an IF Frequency of 475 kHz, and the radio's original IF Frequency according to the Riders was 465 kHz which might explain why this radio isn't working right.

When I feed a signal through my antenna hookup on the radio using my signal generator I can hear the signal coming through albeit very faintly (I have to have the volume turned clear up to hear it) and with the signal Generator's High Output signal being used the signal comes through at a somewhat normal volume level, which means that what my radio's problem is isn't the tubes or a dead oscillator coil or too weak of batteries, what the problem is, is the radio is trying to operate with two IF Cans of different frequencies.

So I'm not quite sure how I would fix this issue...

[Electronic M]

It should be possible to align the IF cans 10KHz off designed frequency. Nothing to loose trying it. If they don't peak in range of adjustments you could try tacking pF caps across windings to see if you can get more range.

[vortalexfan]

Originally Posted by Electronic M

It should be possible to align the IF cans 10KHz off designed frequency. Nothing to loose trying it. If they don't peak in range of adjustments you could try tacking pF caps across windings to see if you can get more range.

Well what's interesting is that the 1st IF can's IF Frequency is 10 KC lower than the original IF Frequency, and the 2nd IF can's IF Frequency is 10 KC higher than the original IF Frequency of 465 kHz, which I'm not sure what the point of that would of been but its kind of bizarre.

And I guess I can see what happens as far as trying to align the IF cans to the original 465 kHz IF Frequency.

[dieseljeep]

Originally Posted by vortalexfan

UPDATE: I found a set of NOS Ken-Rad 1C6 tubes on feebay for $16 plus shipping.

It's unfortunate that the owner of ESRC passed away.
They had those odd-ball tubes reasonable.

[vortalexfan]

Originally Posted by dieseljeep

It's unfortunate that the owner of ESRC passed away.
They had those odd-ball tubes reasonable.

Yes it is unfortunate.

[vortalexfan]

Originally Posted by Kevin Kuehn

Since your set has AVC why not monitor that voltage to get a handle on what's going on? You'll want to use a VTVM, a scope, or a digital volt meter connected to the bottom side of R3(2meg). When the set is working does your AVC voltage seem to work normally with and without a signal tuned in? AVC voltage normally will be negative with a strong signal and become more positive as you de-tune the station. If the local oscillator isn't running you loose AVC action. If AVC voltage continues to respond to tuning then when the audio fades, then most likely you have an issue in the audio sections. When the radio is working correctly you can also align the IF's to the most negative voltage on the AVC line. There's really no need to rely on listening to an audio tone through the speaker.

Edit R3 not R4

I did check the voltage at the AVC line resistor (R3) and it does respond like its supposed to but the audio is not very loud unless I use my signal generator's "HI" output connection, and then it comes out at a more "normal" volume level.

I have attributed that fact to what I believe is a faulty 1C6 Tube, because the oscillator seems to be "running" but not very well, and both 1A4 tubes respond with a hum when I touch their grid caps but nothing when I touch the grid cap on the 1C6, I get no hum out of it.

So I'm thinking I'm on the right track and just about have this thing going.

[jr_tech]

Did you peak both if transformers to 465 khz?

jr