[madsowry]

Hi all  I am working on a Philco 40-190.  
 I checked the power transformer for resistance in the windings before testing to see if it's any good.
Resistance on the pri. and sec. Filament windings was good. Resistance on the HV Sec. was supposed to be 170 ohms from 1 side to CT and 180 ohms from other to CT.  Mine were 125 and 135.  I didn't think too much about it and went ahead and changed all caps and 80% of res. and 90% of the rubber wire.
 Came time to power it up and Filament voltages are right on but HV sec. voltages are all low.  All plate voltages are 35-40 volts low from the rectifier to the RF 1232 tube.

 So I guess my questions are: 
1.  Would this low voltage affect the function of the IF cans because I'm getting fluctuating oscillation?
2.  Would this low voltage affect the function of all the tubes and the osc transformer?
3.   Does anybody have any suggestions ?

I was picking up stations for a time but as soon as I tried to align I lost all oscillation.  I read a post from Ron that said the IFs can go bad in these sets- can you cook them or rebuild them?
Sorry this is kind of a flighty post but frustration can get the best of us.  Thanks ahead of time.

Dick

[morzh]

Could it be that you have a wrong transformer? Or your meter is....showing lower values?

[madsowry]

I don't know about the transformer Morzh cause this chassis looked pretty unmolested.  The Ecaps even still had a lot of liquid in them.  But I will check the voltage again tomorrow with a VTVM and see  if that makes a difference.  It just seems strange to see a shortage of 35 to 40 volts all the way thru the set and keep that consistency all thru the set too.  

Thanks for the reply

Dick

[Chas]

Lets assume the radio has the original transformer, for a 115vac primary. To prove the transformer: Since the wiring has be refurbished, there could be a compromise in the filament connections. A shorted or partially shorted filament circuits, all could be an avoidable disaster for this test. So, If you feel confident that all filament circuits are without fault, proceed, if not, lift the all filament leads, except the power rectifier, tape the ends off so there will be no possibility of a short. Ya, I know brittle rubber covered wire or crunchy cloth covered wire. A little wire trick: Heat the wire with a heat gun, the hardened rubber will soften ad allow movement so long as it is hot.

Now, remove the power rectifier or any other device installed that is supposed to be the power rectifier. Energize the radio, since filaments are not connected, pilot lights will remain out. Watch and listen, faint crackling sounds inside the transformer are a short, heated turns like that of the Weller soldering gun are burning, in 5 minutes this should increase. This is clearly a bad transformer, but if there is no evidence of something wrong, stay with the radio, still alert, for half an hour. The transformer should remain cool, often cold. But slightly warm is O.K. If all is well so is the transformer... Shut off power and remove plug from line.

Pull all the tubes and pilot lights, take a discontinuity check of the filament circuits, all.. Insert the pilot lights and check again, looking for a failure in the pilot light sockets. If all is well re-install tubes and re-connect filaments circuits to the transformer...

Carefully review the filter capacitor installation especially the bias circuits and the bias resistors, review any coupling capacitors to the last audio tube, Check any chokes, output transformers, field coils and tone caps for leakage to frame or chassis. Resistors like Candohms can leak to the metal casing...

Instrument Notes: Many digital volt-ohmmeters will give strange readings when attempting to measure an inductance for resistance.
Use of a 10kohm/volt analog meter is highly recommend for voltage readings, ideally a VOM with a load resistance as specified on the OEM schematic should be used. If not spec, 5K to 20k/volt is O.K. with knowledge the readings will be somewhat lower with a 5K meter.

..Plating on the chassis reacts with rivets and even screwed electrical connections, even a sensitive meter will not disclose a poor riveted ground joint to chassis. For such poor ground joints, loosen hardware and wiggle the parts, then re-tighten. If in doubt add serrated washer to improve bite to chassis. Same for what appear to be solid soldered ground joints, simply re-solder. Tube sockets that have ground rings, either solder the side of the ring to the chassis or drill out the rivet and replace with screw, nut and serrated washer.

Chassis solder joints will require a soldering iron that has a large mass of copper for a tip. That mass of copper holds calories that get transferred to the joint faster then the chassis joint can disperse the heat. Using a 250 watt soldering gun will still suck out the heat, solder will not flow. The chassis joint may resist rosin flux, clean the joint with 91% alcohol to remove any flux. Get some plumbers liquid tinning flux, this is an acid! It is a pale yellow color, using a cotton swab moisten with the flux flow the smallest amount into the chassis joint, apply the soldering iron, flow the solder as soon as the boiling stops. The solder can be 60/40 rosin core. Use a second cotton swab moistened with water to remove any residual plumbers flux. As long as the plumbers flux is used very sparing and only to places where it can be remove by the soldering heat and a water swab there will be no future issue. This is not a grease base flux!

Faulty grounds to the chassis are often a hidden problem, at MF and HF frequencies even though a meter may say the joint is good at high frequencies there are problems. Noises, poor alignment, weak or no signals, improper operating voltages.

One example I had is a Raytheon Belmont, refurbish, but no video. poking, probing around the video amp live would show a signal fading in/out. Pressing hard on a tube socket ring showed the problem to be the riveted joint. All tube socket rings were re-soldered using the plumbers flux. The video signal returned.

I had always kept acid flux away from electronics, however, there were no resolutions to the corrosion in older chassis short of a tear-down, simply not a time conservative project. The flux works if used with caution in mind.

Looking at the grounding in the antenna, oscillator and mixer may be worthwhile.

This same grounding issue can also effect the IF circuits via the AVC. So long as the DC resistance of the IF coils is within range IF's should be OK, exceptions are the IF types with open, fixed, silver mica caps.

Do refer to the schematic as to the circuit of which the return from the meter is connected for voltage measurements to comply with OEM recorded data. Some returns are to chassis, other is to B-.

YMMV

Chas

[madsowry]

Thanks Chas for all the help
Still have the low voltage and the more I mess with this thing the worse it gets. One thing I saw in the production changes is they changed the 2nd IF (37) to a different part number(32-3383),  mine still has the first pt. no. (32-3246) in it.  I don't think that would cause what I'm experiencing with this radio now.  I would think it would at least oscillate even with the wrong IF can.  By the way both IF cans have good resistance on their windings but the 2nd IF has those 100uuf caps built in the porcelain.  Just in case here's the sch.
http://www.nostalgiaair.org/pagesbymodel...013339.pdf
No oscillation at all right now.

Thanks again

Dick

[Chas]

Do not let production changes guide the sensible, analytical, stage by stage repair of this radio...

Begin by resolving the B+ issue, is it really low, is it bad measuring technique or what. Then fix it...

Jumping in without factual, accurate measurements will result in good components replaced or irreplaceable components ruined. Continue and it is better to toss the chassis into the scrap...

The Riders print is very comprehensive, a lot of data in just a few pages.

Since my test questions were not answered, I will assume the power transformer is good. Have one or more 84 rectifiers been tried, tested? it is possible to have several bad tubes of any type and come to a bad conclusion...

You can check the total current consumption in the B circuit of the radio by measuring the voltage across a resistor, install a 1 ohm resistor in-between the chassis ground and Cap 59 and resistor 59 a 1 or 2 watt will be fine carbon or whatever. Operate the set and measure the voltage drop across the resistor. Use ohms law and get the current flow. Do correct for the actual value of the resistor and make measurements with the same VOM...

The current should be some 10% less than the actual cathode current of the 84 tube, if is is larger then there is a problem downstream eating current. Look up the current capacity of the 84 it is on the web...

By following the schematic, taking the actual value of the B dropping resistors it is possible to find the offending branch of the B circuit. Simply measure the voltage drop across that known value.

Brute force testing? Sure go ahead its your radio substitute some 3 amp diodes for the 84 and let out the smoke. That will find the short made by rewiring the radio...

Oh, are you using a 1000ohm/volt VOM or messing about with a DVM?

FYI the caps are part of the trimmer structure, leaves of mica and sheets of tin plated brass, they never fail...

This radio will test your analytical prowess, either you have got it or not...

It will not respond to shotgunning or fishing for someone who had the same problem like "change R273 and the problem is solved"...

YMMV

Chas

[madsowry]

Thanks Chas
Sorry I didn't answer the questions in your first post but frustration took over and I walked away for a little while.  The transformer does not have any shorts.  I had the radio on for more than an hour while checking voltages and poking around and the tran. got a little over room temp.  Warm to the touch.
 There is no Candohm in this radio and I'm still not sure how to check if a cap or resistor is leaking to chassis.  Something I have still got to learn.
After checking voltages with my vtvm,( which is an Eico 232)it was a little higher but still below the specified voltage.  Recommended 180 v dc plate voltage and with the vtvm I got 156 v.  This difference was consistent thru the set.  I also have a Fluke with 1000ohm/volt.
 I obtained a 40-180 chassis which is similar to the 40-190. I checked my wiring and the installation of components to it and they all seem right.  The only thing changed in the -180 were the Ecaps and 2 wax caps.
  As far as checking the grounding everything is riveted as far as chassis grounds.  I went thru and tried to get a connection on all the ground rivets with a screwdriver while the set was on and got nothing.
  So my next test is to check my current consumption on the B circuit using your guidelines.
  My prowess is waning along with my confidence but I'll keep trying.

Thanks again
Dick