[captainclock1988]

OK Well I took a really long break from this radio and I had acquired several volumes of original Riders Manuals and I took a look at the original Riders for this Radio and I was able to figure out that the power switch was indeed wired up incorrectly and also apparently when I replaced the original filter caps I accidentally wired in one of the replacement filter caps in backwards and I have now been able to get the radio to work correctly without blowing a breaker, unfortunately because one of the caps was wired in backwards I'll have to order a new 22 MFD 450 VDC capacitor to replace the one that nearly blew up.

[Eliot Ness]

Levi, for future reference American Radio History has some RCA "red book" service manuals that show a lot more than Riders, and they are free to download or view:

https://worldradiohistory.com/RCA-Victor-Service.htm

[captainclock1988]

Well I got it going! I managed to find in one of my old junker radios an older Mallory 15 MFD 450VDC Dry Electrolytic cap that was still good yet and I wired it into the radio and did a complete realignment of this radio (the alignment was WAY OFF on this thing, to the point that the RF and and Antenna adjustment screws for tyhe 1700 KC adjustments required several turns before it would peak out, the same for the IF trimmers, now its to the point that with just a simple indoor long wire antenna hooked up (a 20' length of zip wire) the radio on the AM band is picking up stations all over the band spread!

All I did was replace the filter caps and one paper cap and one resistor, otherwise its working on almost all original components, and the AVC is working flawlessly as it should.

[MrFixr55]

Congrats Captain Clock!!

This radio represents maturity in radio design and the beginning of the "AA5" (Transformer version) Era. The only difference between this unit and later models is the older pin types. The Octal tubes used in the next year's 5T6, 5T7, 5T8 are electronically the same. Nice condition, but do update the caps.

After losing an old Philco as a kid due to a shorted 5Y3, I have gotten in the habit of putting a 3A 1K PIV Silicon Rectifier between the Xformer HV wires and the plate connections of the Rectifier tube (not necessary for indirect heater type rectifiers like 84, 6AR4, etc.). I can't remember what site I got that idea from but many thanks to the Person that suggested it.

[mikethedruid]

Congratulations. I still advise you to go through the radio and replace the electrolytics with NEW ones, and all the paper condensers with new 630 volt yellow poly types. You don't want one of these old parts to fail and cook your power transformer. While you're at it check all the resistors and replace any which have slipped out of tolerance, or are near doing so. Modern resistors of 1 watt power rating are actually SMALLER than the 1/4 watt ones of years past. I don't use anything smaller than 1 watt these days, and often go for 3 watt, which are about the size of the old 1/2 watt. In the end these precautions will yield a radio which will be reliable for the rest of your life, instead of one which will need continual repairs one after another, and perhaps with a fatal failure which takes out an irreplaceable part. I have something of a weakness for the old RCA sets. If you check my threads you will see that I have refurbished a C9-4, a 56X5, a 5Q55, a T8-18, and two 18T's.

[PhilcoJohn]

Nice radio! I have a RCA 5U That works great. The last time I played it... I should run it today. All RCA radios from 1935-1940 are great performers. RCA are my favorite brand radios. Again nice score in picking up that tombstone!   

[captainclock1988]

OK so a little update on this radio, the other day I tried turning this radio on and I was getting no love from it (it refused to power on) and it had been giving me some troubles with that previously where I had to jiggle the power switch back and forth a little bit in order to get it to power on, and so I thought maybe the power switch finally gave up the ghost.

So I took the unit apart and checked out the power switch and sure enough the only thing wrong with it was that the switch lever that the knob wiper makes contact with to turn the switch on with was bent out of whack so I bent the switch lever back into shape and now the switch is working again as it should.

Now for the weird part, while I was in there I decided I would replace all of the major capacitors that needed replacing in the radio (as suggested by MrFixr55) and for some reason after replacing most of the original paper caps in the radio, the radio's performance actually decreased, as in it got super quiet, and it isn't picking up as many stations as well as it used to before the recap.
I tried to replace the capacitors with values as close to the original values as possible (there were some old replacements in there that weren't the same value as the originals even so I replaced with as close to the orginal values given in the service data as possible.

My question is, why would this radio's performance quality go down after a recap versus how it was performing prior to the recap?

is it possible that the original caps were actually still good and were of superior quality compared to the modern ones I installed?!

This is really stumping me.

[Dan Walker]

Did you do an alignment after the caps were replaced?  I have found that many times it  does make a difference.
 Recheck  the tubes  ,clean the band switch and tube sockets.

 These are some of the things I have had to do if it is not playing proper.
 Dan in Calgary

[captainclock1988]

No, I have not touched the alignment on this radio, because I had previously aligned the radio prior to replacing the old caps and I didn't think that replacing old coupling and bypass caps would of affected the alignment that much, because I've never had that issue before but I guess the way the circuitry is done in this RCA replacing bypass and coupling caps does affect the alignment... 

[mikethedruid]

Double and triple check your work. Make sure all the parts you replaced are properly replaced, wired where they should be, and no cold solder joints. I have screwed up before; I think we all do eventually; so double checking to make sure each component was replaced correctly is where I would start. Once I was certain about that, I would then do the alignment. I would do it again whether or not I found any mistakes I had made before.

[captainclock1988]

Hi Mike, when I replace parts I do it one part at a time and I check the parts placement charts on the schematics/service manuals and I do all of that before soldering the parts into place.

I did have to replace one replacement part that wasn't even the correct value to begin with (it was an old replacement part from the 1950s) with one that was much closer to the original value but not the exact value as the original (I didn't have the correct value part in stock in my parts stash).

I never touched any of the mica capacitors (which would of affected the alignment for sure) just the paper caps.

[MrFixr55]

Hi Cap'n Clock,

Divide and Conquer! Inject "Line Level" audio at the volume control, or use the Phono input. As an alternative, touch the grid cap of the "75" 1st AF with and without the grid lead connected. If the Audio output is loud and proud, then work backwards with injection. Check the plate and screen voltages in the section at issue Plate voltage on the 1st AF is usually not very high (50 - 100V), but the IF, Convertor and 2nd AF Tubes should have between 180 and 250V. Screen voltages are probably about half the plate voltage on the 2nd IF, somewhat less on the Screens of the Convertor adn almst equal tothe plate voltage on the 42 Output tube. The 42 AF Output should have no more than about 20V between Cathode and the junction of R16, the negative terminals of the 10 uF electrolytic caps and the center tap of the B section of the power transformer. There are only 2 coupling caps, C19 and C22 which are 0.1 uF. The Rider's schematic shows what might be a ground at one end of C19 but that is not the case; that is shielding. Note that there are several mica caps, at the primary and secondary of the IF xformers and C21, a 220 pF cap between the 1st AF Plate and Ground on the "75" Detector / 1st AF Amp tube. Much has been said by Experts about "SMD"- Silver Mica Disease shorting these caps.

Other than the caps within the IF Cans and in the tuned circuits, bypass and coupling caps are usually not critical. For example, if a screen bypass cap or AVC Cap was 0.5 uF and your replacement is 0.47uF, that is only a 6% difference and is just fine.

If I had a nickel fore each time i made a wiring mistake (Schematic in hand, one part at a time, etc.) I'd be rich. also look for a nasty little solder bridge hiding on you.

One other thing, check the resistance of the IF transformer windings especially the grid windings. An open winding in the grid circuit of the first IF transforer can do this. You can also force bias the radio's AVC at -3V or just short the AVC line to ground. if it blasts when doing so, lower the volume and if you pick up as many stations as before, check the AVC. Make sure that R5(?) is a 2.2 meg resistor.

Good luck! You will find the issue, learn more about these radios and have another fine radio for the rest of your life.

Best Regards,

John "MrFixr"

[radiorich]

Hello Capt' clock,
great new and the red books are great resource!
Well mike Yes RCA made some nice radios in their day I have good collection of them back .

Sincerely Richard

[462ron]

Levi, one of my pet peeves with capacitors that can cause confusion and thus mistakes is the labeling system some use. For example, in the good old days a .05mfd cap was labeled .05, plain and simple. Now, some label a .05 as 503K and so forth. Why they couldn’t simply be straightforward and put .05 on the part, eliminating confusion baffles me. Just a possibility you can look into to be sure you used the right values! Happy hunting.

Ron