hi ya fellas im new here fresh from audiokarma. ive recapped and rewired a zenith 5d525 and a hallicrafters sx100 some years ago. i am by no means an electronic technician although ive had some exposure in the navy repairing mobile electric power plants. i hold an ancient AMRIP e level soldering license (expired of course). ive been given this radio and am amassing parts info and reading repair threads on this forum. against my better judgement, i plugged this set in on a dim bulb tester and ill be d**ned it didnt burn up ! the bulb went semi bright (50w) and settled down i let it sit and with 20 ft of wire got on weak station!!!! judging by the FRICTION TAPE on the cord i doubt its been electrified in 50-60 yrs. any way the cabinet isnt too bad and the plywood looks like its still laminated, but ive got a few questions. i plan a recap and changeout of all the resistors. according to the parts list 1meg,4400 and 490k.4517 arent listed in the 1936 philco repair parts catalog. i'd like to know their wattages. what i want to know besides all whats basically required for tube radio restoration what in particular MUST I DO for reliability and any upgrades from the 1934 design are welcome.
Hi and welcome,
> i plan a recap and change out of all the resistors.
Sounds good. I generally measure the resistors to see if they are within tolerance (20% of the color code marking). Most of them you can measure in circuit as long as they don't any thing in parallel with them.
All of the resistor are 1/2w with the exception of 8,12, and 30. 8 and 12 are a couple of watts and 30 judging from the size is about 15w. It's rarely bad
< MUST I DO for reliability and any upgrades from the 1934 design are welcome.
The set is a good reliable set once serviced properly. Was Philco price leader (inexpensive bare bones set) for the last several years starting with the model 80 and 81. Short of lower the value of the grid leak resistor in the detector stage which will broaden the selectivity a little that's about it.
GL
was that a 2meg replacement in place of 4meg i was reading about?
I restored an 80jr which is pretty much the same radio. It is a simple animal. I guess the most time-consuming part was re-stuffing the caps; if you choose to not do it and just replace them, it will be even faster.
Alignment (and the regen in particular, getting rid of the "birdies" etc) is very well described in Rider's.
would you happen to know where i can come by a 4x8mfd 450 v cap? mine is missing and theres probably some 60 yr old work around in the bottom ( no room on the bench got a pioneer a.w,p.) im afraid to look. absolutely zip available here in any condition.
>would you happen to know where i can come by a 4x8mfd 450 v cap?
Well if the mounting bracket is still there you can fit a more modern twist lock can in to it. The original cap had a cardboard sleeve around it to isolate the cap from chassis gnd. The minus side is connected to the CT of the HV winding. You may have to slide it in thru to bottom side of the chassis as the bottom of the cap is larger than the hole in the chassis. Read up on rebuilding electrolytic caps to see how to make your own e cap for this set by gutting an old one.
Would replace the originals w/ a pair of 10mf @450v and #28 with 10mf @ 35-50v (- to the ct and + to the chassis)
>was that a 2meg replacement in place of 4meg I was reading about?
Could be. You can measure that resistor in circuit w/o taking the if transformer apart by connecting the ohm meter form the grid cap to the chassis. Have seem it way out of tolerance. By changing the value from 4 down to 2meg may make a slight difference but not a drastic improvement.
When you get a minute post a few pics of the top and bottom of the chassis. This will aid us in know whats there and what is missing.
I just need two more to finish up the second row!!!
GL
(03-28-2018, 09:55 AM)Radioroslyn Wrote: [ -> ]By changing the value from 4 down to 2meg may make a slight difference but not a drastic improvement.
It made a big difference for me back when I was experimenting with these four tube gutless wonders. Every 80 and 84 I worked on always played much better with a 2 meg grid leak instead of a 4 meg grid leak.
And falcon123 - Welcome here! I'm on AK also, but this is my internet "home base".
As another data point I can add that I changed to the 2 meg resistor on two model 84's I've worked on over the last year. Made quite a noticeable difference for mine too.
well after a morning cleaning the chassiss and deoxiting the aircap and the volume control, sorting through two disconnected wires i discovered that volume control 33-5055 is supposed to be 20k it is actually 46k and after a fader lube service is linear. i tried to look it up in the 1936 parts catalog but it isnt listed. is the drawing wrong? the control itself is clearly labeled philco335055. the missing power supply combo ecap was replaced by two ancient illinoiis cardboard case caps crudely stuffed in the chassis
> is the drawing wrong?
I think you are asking if 20K is the proper value for this control. Yes it is. As you may note it does control the volume but it not in the audio circuit which is a more common configuration. This one controls the level of rf signal that enters the receiver. This is why the value is much lower than one that is used in the audio (abt 500,000 ohms).
If you are looking for an opinion as long as the resistance is consistent across the turning range of the control I would leave it till I got the set working. Worst case is that the control will have most of is effect within the first 20% of so. It's not a very common value to find a replacement may be a little tricky.
Hope this answers your question.
yeah i picked up to that. i also found out about the rarity and with a switch incorporated almost impossible. sent an email to OPPAT but no reply as of yet. cant even start as ive no caps yet.but as logistics are an issue i thought i'd bone up on the thing and source "what if" parts in the meantime. are there any"you tubes" or links that show how the IF transformers are disassembled?
>are there any"you tubes" or links that show how the IF transformers are disassembled?
I don't know of any off hand. The basics are remove grid cap, mark and unsolder the 5 wires that are on the underside. Remove the screw that hold the transformer bracket to the chassis. Carefully pull the transformer out thru the bottom. The coils and such are covered by a piece of fish paper, remove that and your in business.
That's plan A plan B is remove the grid caps from the ant transformer and the if transformer. Drill out the three rivets that hold the three covers on to the chassis. Lift the three cover off, the three of them are welded together so you can't just remove one. When reinstalling replace rivets w/6-32 machine screws and nuts and replace grid wire w/longer wires to make it easy to feed the wires up thru the covers while apart then cut to proper length when it's back together.
It probably goes without saying be careful when working on the IF transformer. It has several small wires from the coils that can easily broken. When replacing the 4m resistor just cut it out and solder in the replacement don't try to unsolder it.
GL
thanks a lot fellas's i do really appreciate it, its on hold until i get some parts.it seems like ive spent half my life waiting for parts!!!!
are you running a polarized plug ensuring the hot is switched? a good idea im sure but it seems that 10mfd 50vcap from the ct to ground (28) wouldnt be too happy if you didnt,especially as the chassis must be grounded