[Radioroslyn]

Good Luck!

We are if you need us...

[Daniel Bingamon]

I'm working on a 37-610 and it has a 5Y4G rectifier and the schematic shows that as well.
Its compliment is 5Y3G, 6A8G, 6K7G, 6Q7G and 6F6G.
But other general 610 drawings have the older tube set starting with the 80 rectifier.
I suggest comparing the whole set of tubes as manufacturers don't wait till end of year to put changes into place. Looking at the set as a whole might help match drawings closer.

But try to put the tube that was intended for the set in place - this can take a little detective work.

[Radioroslyn]

I would suspect that it would have had a 5Y4. If you measure the resistance from pins 4 and 6 @ the socket and it's open use the 5Y4. 4 and 6 are the plate connections for the 5Y3.

GL

[JimB]

So the label inside the radio case for my model 610 calls for all the same tubes as the original and the later version drawings. Someone had replaced the type 80 rectifier tube with a type 5z3 but all the rest of the tubes were the same.

[JimB]

So I finally got all my new parts installed and I plugged it in. I don't have a variac so I used the 40 watt light bulb  trick. I plugged it in and the bulb glowed bright for a few seconds and then settled down to a low glow. I left it like that for 20 min. and the plugged it in normal and It works! I feel relieved but I have an issue I cant figure out. I have been able to get stations when the tuning capacitor's plates are spread apart but as you turn the tuner and they mesh together I loose all signal.  I  cleaned the tuner and cannot see any thing that may be stuck in between the plates. Does anyone know if there is any electronic reason this may be occurring? Or do you think it is a dirty tuner issue? also I saw on a video where you can lightly sand between plates with 600 grit paper. do you guys recommend this? Thanks for all your help.

[Mondial]

It depends on whether the plates are shorting as you rotate to the closed position, or if the local oscillator is dropping out as you increase the capacitance.

Do you get loud scratching sounds in the speaker as you close the tuning capacitor? That would indicate that the plates are bent and touching at some point in the rotation. If the stations you hear are at the right positions on the dial and the reception quits quietly then its the oscillator stopping at some point as the capacitance is increased.

You can check the operation of the local oscillator by listening for the oscillator signal on a nearby AM radio at a frequency 460 kHz above the dial indication of the 610. For example if the 610 is set to 1000 kHz, you should hear the oscillator carrier at 1460 kHz on a portable radio held near the tuning capacitor. You may have to tune around slightly to hear it, but a strong signal should be there if the oscillator is operating properly.

[JimB]

That is a great idea. Ill try that.

[JimB]

I was able to fix the tuner.  The outside plate was pushed in a small amount and was just barely rubbing. This thing is working pretty good. Even getting some short wave stations. Thanks for every ones help. I have to work on the speaker cone and speaker cloth next.

[JimB]

So I have been working on the 610. I strung an ant. wire in my attic and stations are coming in pretty good. One issue I cannot figure out is on the broadcast band I can get plenty of stations from 550kh to the 1100kh range but  any higher I only get static. I can't figure out why. Also I did a voltage check on the tubes and here are the results. 6a7 p-249volts, sg-86v, k-.26v, g-134v.Type 78 p-294v, sg-86v, k-0v. type 75 p-184v, type 42 280v. There were some changes that were made that may account for the voltage differences.It is possible that the zero voltage on the 78 tube cathode is because my original wiring did not have a resistor tied to it and going to ground so I didn't install one and hooked directly to ground. Do these voltages look ok? Some seem high but I understand this might be because of higher supply voltage from the power company. Any checks I can make to fix the lack of stations on the higher broadcast band? Any help would be appreciated.

[Radioroslyn]

I would use an ohm meter set on it's lowest range and measure across the stator section of the tuning capacitor to chassis ground. The antenna section of the stator can be measured from the grid cap of the 6A7. The osc side can be measured from pin 5 of the 6A7. This is if you don't have good access to the tuning cap. As you tune the cap from one end of the dial to the other on the bcb you should see 4-6 ohms (normal). If the see 0 ohms you've got the bent plate...

I'd check that 1st.

[JimB]

I will do that thx!

[JimB]

So I am confused. So I checked the tuning capacitor and I have 3.2 megohms from the grid cap of 6a7 to ground the full turn and 35k ohms to ground on #5 pin of 6a7 the full turn. Am I measuring right? Thx

[Mondial]

Your measurements seem about right. As long as neither reading drops to zero ohms as the tuning cap is rotated over its full range, then the cap plates are not shorting and its not the problem.

Do the stations you receive appear at the correct frequency markings on the dial? If not, there might be an alignment problem.

Did you check the local oscillator frequencies by listening on another radio as mentioned in an earlier posting above?

[JimB]

I did check the oscillator frequencies with an other radio. The dial on the tuning cap is installed by the use of a set screw on the shaft of the tuning cap. To install it I tuned to a known station and tightened it on that setting. I don't have a frequency generator to align it. Without some more equipment I think I am out of luck. I guess I'm luck it pays as good as it does.

[Radioroslyn]

My mistake. The tuning cap is grounded but the coil isn't. It's at rf ground thru 25 a .05mf cap. That's why you're not seeing the resistance of the coil.