[Kico]

From a model 84 (photo attached). This condenser block has had a major blowout and the side with the part# is missing--only thing I can partially reference is the letter "G" on the Bakelite block. This is the block to which the 325 Ohm wire wound resistor is attached.

Can you guys give me the correct part# for this block and the values of the caps inside?

Thanks![attachment=0]

[gvel]

Here's the drawing: http://www.nostalgiaair.org/PagesByModel...013875.pdf

Schematic and part numbers are on page 3. What is it connected too? Once that is known, it can be found, on the drawing.

Edit: It seems to be component # 28, on the drawing. I'm guessing part # 29 is on top of the chassis, in a "can".

[Ron Ramirez]

It is part ( 28 ) if it is the block to which the 325 ohm resistor, part (30) is attached.

That was probably part no. 3793-DG or 3793-ODG. Two .015 uF caps inside, one of which was connected from one side of the AC line to ground - the other connects between B- and ground.

[Kico]

Thanks Greg and Ron,

I've got those cap values on hand and will replace. Hope this will take care of the bad hum in the radio--yes, the filter caps have been replaced along with a couple of out of spec resistors.

This radio was a local CL purchase and in all honesty, looks like it just came out of the box yesterday...the cabinet and chassis and most pristine I have ever seen...all original with exception of the above.

Many thanks for the info.

[Radioroslyn]

If you have any leakage between those two caps being one is blown to pieces that could cause a lot of hum. Looks like someone has been rubbing on that chassis!
Terry

[planigan]

Those are the "line caps" and the replacements should be the new Y caps, guaranteed not to fail in a short, will just fail open. If that cap had been one it would not have blown off the wall of the block. That's the ideal use for the X and Y caps. I said Y because I memorized the letters to the use by X = cross the line, Y = configuration of two caps one side each side of line and other side twisted together and to ground (looks like a Y). On the 37-650 those caps (.015mf) are in a 3793-DG block. PL

[Kico]

If you have any leakage between those two caps being one is blown to pieces that could cause a lot of hum. Looks like someone has been rubbing on that chassis!
Terry

Terry,

I found the WW 325 Ohm resistor to be way high and am wondering how critical this value is. I can make it to 317 Ohms with a couple of 5W resistors I have on hand. Also, how necessary are the 1000V and 1200V for two of the blocks 7625-SU and 7762-EU? I have 630V here, otherwise I'll need to place an order for these. If I need to order, I'll also get the "Y" caps PL suggested.

BTW, no "rubbing" on the chassis by me, pics show just the way it was found minus the can cap which I removed. It will be replaced when finished stuffing--for testing I installed a couple of temp 10uf filter caps under the chassis.

Thanks to all.

[gvel]

I can't answer your capacitor question, but I have a comment on the resistor reading high.

When you measured this, was one end of the resistor disconnected from the circuit? Since it's across a capacitor, you will get "goofy" measurements, if one end of the resistor is not lifted. Wire wound resistors usually don't drift too much. They are usually good or open, but nothing's impossible.

Yes...no harm buying line capacitors...when you make your order!

[Kico]

I can't answer your capacitor question, but I have a comment on the resistor reading high.

When you measured this, was one end of the resistor disconnected from the circuit? Since it's across a capacitor, you will get "goofy" measurements, if one end of the resistor is not lifted. Wire wound resistors usually don't drift too much. They are usually good or open, but nothing's impossible.

Yes...no harm buying line capacitors...when you make your order!

Greg-

Yes, one end of resistor was lifted when measuring--I like you have generally found wire wounds to fail open, but this one reads 1.6K; it has obviously developed an internal fault.

Thanks,
Kico

[Radioroslyn]

What that resistor does is develop the grid bias voltage for the audio output tube. You'll be fine with 317 ohms. Can't think of any cap on that set that would need to be larger than 600v.
How's the oscillator coil in this one?
Terry

[Kico]

What that resistor does is develop the grid bias voltage for the audio output tube. You'll be fine with 317 ohms. Can't think of any cap on that set that would need to be larger than 600v.
How's the oscillator coil in this one?
Terry

Terry,

Thanks, I'll go ahead and use what I have to replace the 325 ohm resistor. Yes, the OSC is fine and so is the antenna coil; the one I had to rewind on the other set. The resistance was within limits so it checked good, but I pulled it anyway to check its physical condition. The windings shine like the day they were made...no evidence of the "creeping green grunge" at all!

The Philco data sheet on the cap blocks shows a couple of the blocks I'm going to rebuild using 1000V and 1200V caps; hence the reason for the question. If you feel 630V is OK, then that's what it will be. Not much volume though, even after changing the 4 meg cap to a 2 meg in the IF can.

[Radioroslyn]

If that resistor is like 1K it's going to apply a lot of grid bias this will lower the volume.
Terry

[planigan]

Kiko, in most instances the 650V rule is good but in certain parts of the AF portion of the set it is possible to get a high voltage spike from static etc. thats why they advise 1000V , 1200V. It may be a rare occasion but a spike could blow the 650v cap (depending on severity could blow the 1200). There are 1000V ceramics availabe, not very expensive. PL

[exray]

It was common practice with some manufacturers to use 1000 or 1200 volt rated caps in lower voltage applications because the device had less internal leakage. That's not an issue with modern caps.

Another application was across the incoming AC line. A 630 v DC cap can work there but modern rote is to use the X-Y type AC-rated capacitors.

The plate of the audio output is another location that occasionally needs more than a 630 vdc rating because of the audio spikes and AC component.

[Kico]

Kiko, in most instances the 650V rule is good but in certain parts of the AF portion of the set it is possible to get a high voltage spike from static etc. thats why they advise 1000V , 1200V. It may be a rare occasion but a spike could blow the 650v cap (depending on severity could blow the 1200). There are 1000V ceramics availabe, not very expensive. PL

It was common practice with some manufacturers to use 1000 or 1200 volt rated caps in lower voltage applications because the device had less internal leakage. That's not an issue with modern caps.

Another application was across the incoming AC line. A 630 v DC cap can work there but modern rote is to use the X-Y type AC-rated capacitors.

The plate of the audio output is another location that occasionally needs more than a 630 vdc rating because of the audio spikes and AC component.

Thanks guys, I guess I'll order some of the higher rated caps just to be on the safe side.

BTW, has anyone had success in cleaning the volume pots on these. I have a small amount of "scratchiness" which I'd like to eliminate, but the pot seems pretty well sealed. If it's a risky job, I'll just leave it as is.