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Philco 38-690 electronics restoration. - Printable Version

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RE: Philco 38-690 electronics restoration. - morzh - 05-21-2017

Finished the main chassis by restuffing the electrolytic. It was replaced​ with several separate caps; I took it and stuffed with the 5 caps that should've been there: 1uF, 1uF, 2uF, 2uF and 10uF.

Then I got to restuff the caps from the amp/power supply.

I do realize that all the caps are replacements, but boy are they PITA to work with. Black tar galore​. They are easy to extract but then the cleaning commences and it is grueling. Lots of picking with screwdriver and then cleaning with mineral spirits.


RE: Philco 38-690 electronics restoration. - jcassity - 05-23-2017

is a "proper" restoration considered proper if the old caps are not all Philco?
I am asking because i saved my old caps and wanted to put up a want add for old / bad caps so i can have the correct printed value on the paper exterior. I want to collect up the required amount for my future re-restore.
my old caps are a mix of Solar, Aerovox and something else i cant remmeber and then just a few philco ones.


RE: Philco 38-690 electronics restoration. - morzh - 05-24-2017

Any restoration that does not contradict safety and keeps the schematic original is proper.

As for the degree of authenticity, this is different for everyone: what's acceptable for some, is not for me, and what's acceptable to me is well below the par for, say, Russ "Phlogiston" or Steve Davis who do museum grade jobs.

I personally hate to see yellow caps under the chassis and so will restuff all those that are possible to do it with but I will not over-mold resistors I replace or find Philco electrolytic cans if they have been replaced by other cans that still look OK to me.

There is no such thing as universal "proper" acceptability criteria. Find the one that personally satisfy you and stick to it.


PS> 4 can electrolytics done, 3 left to re-stuff. Waiting on more of those 22uF 450V Panasonic caps - the highest ripple rated I found so far - 560mA per capacitor (I serialize them to sub 8uF or 10uF caps). And the tube rectifier uses two in parallel so it will take 1,120mA of ripple. And I found the place, Onlinecomponents.com, who sells them at much lower price than Mouser. They have a minimum order of $50 so had to buy 70pcs. That will last me some. Icon_smile
I also ordered some film Solen 8uF 630V caps in case I decided to go with them for the first caps.

PPS. After cooking dinner (rib lamb chops and asparagus, nothing fancy) I went to the underworld in hopes that I be able to gut another cap, and ended up fully restuffing it.
Two to go.


RE: Philco 38-690 electronics restoration. - morzh - 05-27-2017

Upon having opened an electrolytic can this is what I found:

   

So they essentially took the same axial cardboard shell caps and encased them in aluminum shell.
Hmmmmmmmm.....

The internal cap also says "8+8" (and it does have two sections) but the aluminum cap itself says "8uF" and was a single 8uF cap.


RE: Philco 38-690 electronics restoration. - morzh - 05-31-2017

Question:

I overlooked a boxed capacitor assembly that is bolted with two screws through the main chassis with the nuts underneath; it is in front and directly to the left of the dial assembly when looking at it directly.
I just remembered now, same thing was in 37-116. But I cannot recall how and where I found the description of the contents, as it is not enumerated on the drawing, though is shown.
I tried looking into 37-116 docs- nothing, tried to look into my resto thread of it from 2013 (wow, has it been 4 years?) - nothing there either.
Anyone knows anything?


RE: Philco 38-690 electronics restoration. - jcassity - 05-31-2017

so the internal paper tube implies a dual section cap but the metal can says it a single?

Makes me think a label error on the cans...

i can see it now,, someone a long time ago picking up the phone calling the metal shop responsible for this qty 10,000 can order that is wrong. Management says " just use them, & update the code & run prints later"


RE: Philco 38-690 electronics restoration. - morzh - 06-01-2017

Found the answer about the rectangular bix cap assy. I found the 37-116 thread from 2013, found the place where I taljed about it, cap #89, and by analogy (I figured it should be in the same place as the sch is similar ) found it: cap #108, 0.1-0.1-0.7uF.

Will try to tackle this weekend.


RE: Philco 38-690 electronics restoration. - morzh - 06-04-2017

That cap assembly done, right above it is the power switch plus bass tone control.
This is how it looked inside. The making was there but intermittent, from short to kilo-ohms, as luck would have it.

   

Now I was able to take the dial assembly and replace the grommets, though it was no small task, as I did that without extracting the RF sub-chassis. The grommets I bought from Renovated some 4 years ago for 37-116, are the right size but the holes inn them are small enough to resist going over the pins, especially the one on the right side which is thicker. Combined with the grommet being inserted over the pins while still with the slide-holes ovet them was inconvenient. I persisted and I prevailed. Yay!

The new grommets in place with the RF chassis, still not cleaned, and with the tuning cap off.
   

Oh yeah... the tuning cap is of, did I mention?
   

Someone tried to fit in a metal tube and did not find anything better to do than to cut the shield base off. Dumb!
Now I am confined to metal version.
There is another base that was simply mangled to make the metal base fit.
Some people!

   

Cap cleaned up.

   


RE: Philco 38-690 electronics restoration. - morzh - 06-04-2017

Oh, there is also the second switch, the one that lights up the scale / turns off automated frequeny control.
The switch has two parts, obviously, and the light part was frozen. Not sure why, though after looking at the innyrds I am not fond of that particular design. It was not exactly frozen but ....to long to explain, suffices it to say, it is working now.

The switch is riveted, I was barely able to pull it apart after drilling the flared part. And, assembled back, it was so snug that I only tapped a little with a setter just to make myself feel better, I am sure there was no serious effect from that.

That switch:


   


RE: Philco 38-690 electronics restoration. - KCMike - 06-04-2017

Looking good Mike. Could you drill out the old tube shield base and replace it? I might have something that would fit off a unknown philco parts chassis.


RE: Philco 38-690 electronics restoration. - morzh - 06-04-2017

Mike

Thanks, and yes, I possibly could but first I have to re-inspect my tubes, see what goes there and whether I need (or want) to reinstate the shield.
If I find I need, I mght then jump on your offer.

Mike


RE: Philco 38-690 electronics restoration. - morzh - 06-07-2017

Well.
Decided to look at that panel. It is for 6A8 tube. The guy used one metal which would not fit through the base.
So he cut it off, having left small pieces riveted. I looked if he provided the grounding for the pin1.....sure'nuff, he didn't.
I worked aroubd it - I soldered a piece of multistrand wire to the piece of the base that was left, scraping it well and using the plumbers flux for copper pipes. The other end went in the hole for pin1. This is a good reliable GND.

Put all tubes in except the rectifier ones, connected the cables, measured 5V filament and high voltage, saw all tubes lit.....good.
The rest is either Friday or during the weekend.
First have to clean all shields - they are dirty.


RE: Philco 38-690 electronics restoration. - morzh - 06-09-2017

Some not so good news. 
Tonight I thought to try to power up with rectifiers which requires the speakers connected.
So I unbolted the large speaker (had to remove two clarifiers first) and saw this

   

Which caused that:

    .

So.....I think, considering the value of the radio, warrants reconing. If they do recone this type.

But, I thought, why not try it anyway to see the functionality?
So first I went straight to check the output transformer. Sure enough. Opened primary all three wires. Then I saw the fuse. It was good but oxydized. I wiggled it, and one half of the primary conducted. The other did not.
But even that is weird: the half shows 1.4 kOhm while the sch says 200 Ohms each. The transformer is original.

So. Need to recone the speaker and the new output pushpull xfmr.

Will need to find out the speaker impedance to pick one.
Good news: the field coil is good.

This will delay me a month.

Sigh.....


RE: Philco 38-690 electronics restoration. - Ron Ramirez - 06-09-2017

From the Philco Speakers file located at
http://www.philcoradio.com/phorum/showthread.php?tid=215

The 38-690 uses a W-6 woofer. Field coil - 4300 ohms.
Output transformer primary impedance - 6000 ohms CT
Primary DC resistance - 410 ohms
Voice coil impedance - 3.9 ohms


RE: Philco 38-690 electronics restoration. - morzh - 06-09-2017

Just renembered. I have an OT20PP transformer. 

   

It is almost ideal match.

Here's Ron's post from 2014.

>>>>>
32-7905

Primary impedance: 6000 ohms, center-tapped
Secondary impedance: 3.9 ohms
20 watts
>>>>>

This is 6600 ohms PP to 4 Ohms, 20W.

Bought ita couple of years ago on eBay. These are goid, I used one from the same fols for my Zenith 5 years ago.