Tube Radio Forum - The friendliest radio forum on the net!
Would you like to react to this message? Create an account in a few clicks or log in to continue.

Philco 52-542 Five-Tube Radio Issues

Go down

Philco 52-542 Five-Tube Radio Issues Empty Philco 52-542 Five-Tube Radio Issues

Post by lnoftsier on Mon Mar 18, 2019 5:26 pm

I have been working on a Philco 52-542 tube radio and can’t seem to find the real issue with it.  It seems to be a hybrid of 2 different schematics I have – 1 from John Rider and 1 from RadioMuseum.org (Sams).  An example is a resistor in the heater circuit.  The Sams schematic does not give the value of this resistor (dog bone) but I was able to figure that out (I think) by using the tube pin resistance reading chart.

I have replaced all the paper and electrolytic caps and a couple of transistors.

The problem I am seeing is that the 1200 ohm resistor between the 25 and 20 uf electrolytics is overheating once the radio is turned on and starts to warm up.  I don’t have much time to check voltages before the transistor starts to overheat but it looks like the voltage drops off after the heater circuit resistor.  

I don’t have a tube tester to test the tubes.  I did notice a couple of other things.  One, the on/off switch measures 360K across it while the schem. says it should be 500K. The other is the resistor connecting to pin 5 of 35l6gt – reading 580K instead of the required 470K.  I plan to change this one out.

I am a bit new at this and would appreciate any suggestions.  I cannot say for sure whether someone else has worked on this previously.  It seems odd that the on/off switch resistance is not 500K but I don’t know if that was from the factory.

Sorry for the length of this and thanks in advance for any help.

lnoftsier
New Member
New Member

Number of posts : 4
Registration date : 2019-02-18

Back to top Go down

Philco 52-542 Five-Tube Radio Issues Empty Re: Philco 52-542 Five-Tube Radio Issues

Post by Chas on Tue Mar 19, 2019 11:16 am

Reference to the Riders:  Nostalgia-Air

As described, R13 is a "filter" restore. For it to overheat a high load (low resistance) in between C9A. Measuring the resistance across C9A should prove that, expect something lower than 2K ohms.  An often occurrence during shotgun replacement is miss wiring, solder blobs, shorts, wire snips, solder flowed in between the socket wafers. The correct troubleshooting technique is to measure the resistance using the reference point at the radio side of the power switch. Take a reading at the junction of C9A+, then 12AV6/7, again 12BA6/5, again 7A8/2&3 at this tube the #3 is the oscillator plate. All of those points should show a high resistance upwards to 10K or more. That procedure should locate the low resistance connection. A backwards C9A will also cause this problem... If so, discard the cap and replace with new correctly. Backwards connection ruins the cap...

Note a defective 50L6 screen grid can also cause a low resistance and or cause a high current to be drawn. At this point, testing live is not recommended as there will be stress on the rectifier, destruction of the filter resistor and possibly some other component, possibly an IF transformer.

BTW it is not known if the tuning caps have failed within the IF's, once the radio is operational, if it sounds like an approaching thunderstorm then those caps will have to be replaced.

Recovering from a shotgun restore can be very touch-and-go. It is the time that one must use stage isolation and voltage drop techniques as well as careful observation to find the problem... (maybe stuff you didn't want to learn)...

GL

Chas


Last edited by Chas on Tue Mar 19, 2019 11:30 am; edited 1 time in total (Reason for editing : Added image)
Chas
Chas
Member
Member

Number of posts : 134
Age : 73
Registration date : 2008-07-24

Back to top Go down

Philco 52-542 Five-Tube Radio Issues Empty Re: Philco 52-542 Five-Tube Radio Issues

Post by lnoftsier on Wed Mar 20, 2019 8:21 pm

Thank you Chas for lots of good info. I am pretty sure the C9 caps are correct but I won't be able to get back to it for awhile. Had to put it away to get space for another project. But I do look forward to getting back at it with your input in mind. Do you have any comment on the low resistance of the on/off switch? Do they go bad like that?

lnoftsier
New Member
New Member

Number of posts : 4
Registration date : 2019-02-18

Back to top Go down

Philco 52-542 Five-Tube Radio Issues Empty Re: Philco 52-542 Five-Tube Radio Issues

Post by Chas on Wed Mar 20, 2019 10:34 pm

The reeence to "On/Off switch is actually the Volume control. To correctly measure the resistance on eend terminal must be disconnecte from the three terminals in a row. The center terminal if the wiper, so dial the wiper away from the terminal that is free measure the resistance across the two outside terminals. A 350k ohm could still be O.K., production change. Or it could be replacement control, or that the previous technician would have on the shelf. The lower resistance would effect the performance of the AVC somewhat by not allowing it to go as much negative to cut down the volume of local stations. Volume controls fail open or get very scratchy...
Chas
Chas
Member
Member

Number of posts : 134
Age : 73
Registration date : 2008-07-24

Back to top Go down

Philco 52-542 Five-Tube Radio Issues Empty Re: Philco 52-542 Five-Tube Radio Issues

Post by Bill Cahill on Sat Mar 23, 2019 5:37 pm

Also, these radios do not use transistors. May we see photos of bottom of chassis, including "transistor"?
Welcome to TRF.
Bill Cahill

_________________
Please also join us here; www.videokarma.org/index.php
Bill Cahill
Bill Cahill
Admin
Admin

Number of posts : 4419
Age : 69
Registration date : 2008-03-12

Back to top Go down

Philco 52-542 Five-Tube Radio Issues Empty Re: Philco 52-542 Five-Tube Radio Issues

Post by Tony V on Sat Mar 23, 2019 6:57 pm

Bill, i'm sure he meant resistor's not transistor's.
Tony V
Tony V
Moderator
Moderator

Number of posts : 751
Age : 51
Registration date : 2008-09-13

Back to top Go down

Philco 52-542 Five-Tube Radio Issues Empty Re: Philco 52-542 Five-Tube Radio Issues

Post by lnoftsier on Sun Mar 24, 2019 7:05 pm

Yes, sorry about that. I did mean resistors. I'm hoping to get it out again soon and get back at the troubleshooting with the help Chas provided.

lnoftsier
New Member
New Member

Number of posts : 4
Registration date : 2019-02-18

Back to top Go down

Philco 52-542 Five-Tube Radio Issues Empty Re: Philco 52-542 Five-Tube Radio Issues

Post by Chas on Sun Mar 24, 2019 8:00 pm

He, he sorry about all the ee's, it was too late to edit the mistakes. "Reference", "end" and "disconnect"...

Chas...
Chas
Chas
Member
Member

Number of posts : 134
Age : 73
Registration date : 2008-07-24

Back to top Go down

Philco 52-542 Five-Tube Radio Issues Empty Re: Philco 52-542 Five-Tube Radio Issues

Post by lnoftsier on Wed Apr 10, 2019 5:06 pm

Thanks again Chas for your help on this. You made a good call on the C9A electrolytic - it was backwards. Replacing that did solve the issue with overheating R13. Now I am still just getting static on the radio and would like to check the tubes. The resistance readings that are listed on the schematic seem to be pretty good except for one or 2 points so that is on the list for whenever I get back to it. This has taken a lot of time and will probably have to wait till next winter.

lnoftsier
New Member
New Member

Number of posts : 4
Registration date : 2019-02-18

Back to top Go down

Philco 52-542 Five-Tube Radio Issues Empty Re: Philco 52-542 Five-Tube Radio Issues

Post by Sponsored content


Sponsored content


Back to top Go down

Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum