We're posting at the same time, Mike_RF (and Mike/morzh).
Regarding electrolytics - I used 6.8 uF, 630V Solen Fast film capacitors (close enough to the original value of 6 uF), and restuffed my Mershon capacitor cans. I suggest you read all nine chapters of my Philco 90 rebuild on my blog, plus the extra chapter on the speaker rebuild at the end of the model 90 series.
But to answer your question - sure, 10 uF is fine
provided they have a working DC voltage of 450 volts
minimum. Most of us used those before the Solen Fast film caps became available in recent years - and before many of us learned how to open up and restuff those electrolytic cans.
The advantage of using Solen Fast film caps is that they should never go bad - at least, not in our lifetimes. Electrolytics, even if good quality caps such as 105 degree Nichicon or Panasonic units which can tolerate high ripple current, will still have a finite life and will (eventually) have to be replaced again. The disadvantage of the Solens is that they are physically huge - they fit inside the old electrolytic cans, but not so easily under the chassis.
Ron / Morzh,
OK thanks. Sometimes the choke / cap is specifically tuned for line frequency and moving the first cap value can effect that. But it seems not critical in this instance.
I was already looking at the Solens caps. I have an RCA CR88LR I wish to rebuild and use the solens caps in. Besides the Solens factory isnt that far away from me so I can get them fairly promptly.
Cheers
Ron,
Ok, I have already bookmarked and done a fast review of your pages. Im certain I will refer back to them once i get going on this.
I found a model 90 10.5 speaker for my unit on ebay. But sadly the transformer on it is for the push pull unit. So I am lucky my original transformer is ok. So I will swap that over.
Cheers
> I found a model 90 10.5 speaker for my unit on ebay. But sadly the transformer on it is for the push pull unit. So I am lucky my original transformer is ok. So I will swap that over.
As you know, the 90 I restored is the cathedral version, so it uses an 8 inch speaker. The job of switching audio output transformers is basically the same, however.
Well,
I hope the ebay speaker works out. The seller has experience with this stuff and provided ohmic values for the coils.
They repair some small boo-boo. I hope it doesnt rattle. Nothing i disklike more that a rattly old speaker. Drives me arouns the bend.
> I started off many years ago working for Motorola
So a Research Line, Twin V, and T Power kinda guy...
Well maybe not that many years ago. I worked for a dealer back in the 70's.
Had a few cheep customers that didn't want to upgrade to something that was SS.
Oh those are the newfangled ones that use those three wire fuses.
http://www.wb6nvh.com/Moto42/M42Page2.htm
Scroll down abt 1/2 way. Twin V was named because it used twin vibrators in the p/s.
The T power used germanium power transistors in the HV p/s. The whole front was
heatsink. Those guy over in Schaumburm Ill really have a knack for picking names. I
wonder if of their kids are named Edsel.
A lot of 2way radio history on Geoff's site!
I guess I should get back to the subject at hand.
Mike
>>Sometimes the choke / cap is specifically tuned for line frequency and moving the first cap value can effect that. But it seems not critical in this instance.
Well. What I do not know (if you said that, I missed it) if your radio is "A" version (Canadian) or regular (US).
The canadian was for 25Hz, and so they used a much heavier iron core transformer, as well as larger 1st cap (10uF i/o 6 uF).
Whatever the case, your today's frequency is 60Hz (we won).
So if the radio is "A" and you use 10uF, you will unnecessarily raise the B+. The "6.8uF" seems to be the popular value that will do well.
Now as for the filter itself, it is not like it was tuned as one thing: the 1st cap is the filter's smoothing cap and then there is the addition LC filter which is the choke of the value on the order of tens of H, forgot , 25H or 40H and the cap that is, same as the 1st one, 6/10uF depending on the frequency.
As I said, I prefer larger one for the 2nd cap and an as close as possible to original's valuye for the 1st one (for 60Hz this time).
Another thing, in the 2x47uF pushpull version they used a 0.25uF cap across the choke. The thought, I think, is to compensate for the LC output ripple with the similar ripple 180 degrees apart.
Many of us are of the opinion it is not needed, so when the time comes to restuff cans, we do not necessarily use it, and larger 2nd cap valu will do just fine for it.
But yours is an SE version, and I do not see that cap in there.
Morzh - Thanks for the info
Ron - Getting back to the tone control, what was the voltage rating of the caps you put in there? It kinda looks like quite a confined space that may not hold 630 volt units.
Cheers
Yellow film 630V caps easily fit inside the tone control, no problems. You will see this in
Part 5 of my Philco 90 rebuild.
I was about to write the same, my tubulars 630V fit inside without a problem. But I wanted to find my 90 restoration topic, and I could not find it.
One piece of advice: if potting the caps with hot glue, make some fishpaper tent(s) to cover the caps, and pot only the top of the tent and the leads. That will be enough, but hot glue might adversely affect the caps. Little quantities sipping through spaces in the tent will not do damage.
Hot glue will not adversely affect the yellow film caps. I've done enough of them, and never had any problems with using hot glue on yellow film caps. The melting temperature of the hot glue is significantly lower than the typical temperature of a hot soldering iron or gun. A yellow film cap will be destroyed if it is touched with a hot soldering iron or gun.
Now, electrolytics are a different story. Don't get hot glue on the seals of an electrolytic. Don't ask how I know...
I prefer to tread safely with the temps.
Hot glue melting temps are 250F to 375F.
The application range for the Polypropylene material is -55 — +105C, which is up to 221F.
So, while I think that it might be OK (did it myself in the beginning without ill effects), I prefer to shield the caps from being immersed in the hot glue. Some contact through gaps in the shielding is OK.
For the same reason I put a paper wrap in the tubular caps' ends when I restuff them.
If anything, it will save you quite a bit of that hot glue