Philco 38-690 electrolytic capacitors--UPDATE - Printable Version
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Philco 38-690 electrolytic capacitors--UPDATE - retiredinprescott - 02-20-2014
I recently obtained a 38-690. Something must have happened during shipment (it was well packed) because the set is now "non playing" with only a low hum coming from the main speaker. Set was playing before it was shipped I was told.
I'm starting with the power supply and will rebuild that and check it with audio input.
A number of electrolytic caps have been replaced at some point with large 600V units (not checked yet). I have the original Philco parts numbers for the caps that should be there but I can't find a cross reference to the working voltage of the original caps. Would they have been higher than 450V?? Parts numbers are as follows:
30-2200 (18uF)
30-2025 (three of these 8uF)
30-2249 (multi section)
30-2201 (8uF, 10 uF)
The Philco parts list and schematic shows the capacitance values but no voltage values.
This is going to be a long slog. The power supply doesn't look too bad but that chassis is really intimidating..
Thanks, Mark
RE: Philco 38-690 electrolytic capacitors - morzh - 02-20-2014
Not all of them have to be 450V but if you make them it is OK.
As for radio not playing after it was - well, if the radio is in the condition that it can be plugged in and played, this copuld be simply a case of damaged or even simply yanked out tube.
But of course it is always better to do a thorough revision first with checking resistors and replcing capacitors and only then trying to play it.
These chassis look more menacing than they really are.
RE: Philco 38-690 electrolytic capacitors - Warren - 02-20-2014
You can look at the actual capacitor to find out what the voltage rating of each cap is. Follow the schematic.
RE: Philco 38-690 electrolytic capacitors - retiredinprescott - 02-20-2014
Warren,
The problem is that most of the electrolytics are replacements. The large yellow electrolytics in the photo are 16uF, 600v caps. I don't believe 600V caps are needed but the schematic and parts list do NOT show the voltage of the original caps, only the value. I'm hoping to find out if standard 450V electrolytics would suffice or do any of them need to be higher voltage. This is a high tube count set with two separate power transformers and two 5X4G rectifier tubes (one on each power transformer).
Thanks,
Mark
RE: Philco 38-690 electrolytic capacitors - Mondial - 02-20-2014
The voltage on the filter caps can exceed 450 V when the set is first turned on and the output tubes have not yet warmed up. The 5X4 rectifiers filaments heat almost immediately so there is full peak voltage on the filters for 30 seconds or so until the remaining tubes begin drawing current.
You can connect your voltmeter to the input filter after the rectifier and see how high the voltage rises at first turn on. I would not use caps rated at less than this maximum peak voltage. Typically, Philco used 475 V or 525 V rated caps for the first filter.
RE: Philco 38-690 electrolytic capacitors - gregb - 02-20-2014
I agree with Mondial on that first cap, go with the best you can get in a 500 V or maybe even a 600. Have you thought about doing a restore and restuff all of the caps? That is a set worthy of the extra effort.
Gregb
RE: Philco 38-690 electrolytic capacitors - retiredinprescott - 02-21-2014
i will proceed as carefully as I can with this set to restore it.
Three of the electrolytic cans are missing. One of the two chokes in the power supply has been replaced with an 8 H choke which does not look like the original. Also, and sadly, seven of the tube shields and bases have been removed from the chassis and metal tubes were used which, presumably, did not require the tube shields. If I can get the set working then I will go about trying to replace the removed tube shield bases.
There are two input caps on this power supply; one for each 5X4tube The rectifier for the amplifier and output tubes seems to have two 8uf input caps in parallel so maybe use a 16uF at 500V?
The second 5X4 rectifier has a single 8uF input cap. There are a lot of electrolytics in this set.
http://www.nostalgiaair.org/PagesByModel/255/M0013255.pdf
RE: Philco 38-690 electrolytic capacitors - gregb - 02-21-2014
I would be thrilled to do a complete accurate resto on that radio. It would take many many hours but would be worth ever minute of it. Someday I hope.
Gregb
RE: Philco 38-690 electrolytic capacitors - TV MAN - 02-21-2014
Mark, do you have a tube tester? I'd start there if you do. If shipping is to blame, a tube or socket contact is a good bet. Another bet is that the radio never worked when sold...
RE: Philco 38-690 electrolytic capacitors - retiredinprescott - 02-21-2014
I do have a tube tester. The tubes in the power supply test OK. I haven't tested any of the tubes in the chassis yet but I did make sure they were all seated in the sockets before I slowly powered up the set.
I got this set from Willie in PA and he has a good reputation. I suspect something happened during shipping but at this point nothing is obvious.
RE: Philco 38-690 electrolytic capacitors - morzh - 02-21-2014
Oh...so you were the one who bought that set from Willie about 3 weeks ago......
Well, if he said it worked it likely did.
RE: Philco 38-690 electrolytic capacitors - TV MAN - 02-21-2014
The guy I bought my 70 off also had a good reputation - 100% positive, said he knew how to pack and that my radio had static and a hum. I guess that is why it showed up with a busted grill, loose speaker and a burned up 80...
RE: Philco 38-690 electrolytic capacitors - morzh - 02-21-2014
Well.....Willie has a word of mouth good reputation from people we know (like Ron) whereas the guy who chickened out to send me my 44 (16B) or the guy who sent me a 70 which he neglected to pack himself all had eBay 100% which is not to dismiss, but not the same.
Oh...and those known to us shill bidders recently discussed.... - 100%. Or close.
RE: Philco 38-690 electrolytic capacitors - TV MAN - 02-21-2014
Word of mouth = all the difference in the world! Shill bidding - eeeukkk! Happened on my 70 also, then retracted bid when he hit my max. Made a sniper out of me. Only good thing - seller reimbursed me for damage. Anyaways - back to the problem. Something probably got jossled. Check - test - tap-shake and wiggle. May be a switch contact. That chassis has enough room to park a semi inside! Dont be afraid. It is still a radio
RE: Philco 38-690 electrolytic capacitors - morzh - 02-21-2014
Yes.
And whether it plays right now or not is not even that important - even if it did you still have to do full re-cap/-carb/-check.
After that you will find out it is some trifle that kept it from playing that you will fix in the process.
As long as your power components are OK (and they probably are) you are fine and I would not even think that the radio not playing reduces the price.
(yes if you were a nice old lady who bought a working radio and it does not work - this would affect her attitude and rightly so).
So, don't worry as long as there is no visible physical damage.