[winston763]

I bought a Model 60B, which is older than I had worked on to this point. Unfortunately for me it's been re-worked. I watched Bob Andersen's series and of course I can't match his skill and knowledge but I'd like to have this one working. It never had volume 'control'. I hear the tone switching but never heard any radio station. after recapping and replacing the resistors I have nothing but spent days and weeks with little to show for it. I have a digital multi-meter, isolation transformer, dim bulb tester and a newly purchased Eico 324 signal generator. when I probe the output resister 470K I hear the scratching of the probe. Seeing all the material about the coils, not knowing what else to do I recoiled the IF and antenna coils - first time - no result. I tried to follow the Model 60 turning steps but I don't have a analog multimeter. I don't have a lot of money and I feel guilty spending too much on a new hobby because I feel selfish family-wise. If I have some success, I could warrant slowly improving my test gear. So that's my story. I hope I gave an expert enough information to give me new insights as I am exhausted and feel I'm doing more damage than good. I don't want to give up because this would be a real show piece for me personally. I turn the volume on and nothing up or down. The voltage seems reasonable but I wish I had started without someone's makeshift changes. I don't know where I stand. Appreciate any insights. Rich

[Roger Cole]

Hi Winston,

I'm fairly new to this forum as well, but I've managed to restore several radios so far and happen to be working on a Philco 60 right at the moment. If you have any questions about what the chassis should look like I'm happy to send pics. I'll be staring at one for most of today.

A few suggestions. It's great that you have a signal generator-- that can be really helpful in diagnosing problems. For safety reasons, I always put a capacitor in series with my tester. Not so much to protect me, but to protect the signal generator from stray high DC voltages. Also, always use your isolation transformer. Lots of high voltage lines under the chassis, and you need to be very careful and use every safety precaution.

If you are serious about radios, take the time to read Elements of Radio Repair. There is a scanned copy in the Antique Radio Forum archives at http://www.antiqueradios.com/archive.shtml. I think it's worth investing the time in reading it, and it will teach you how to troubleshoot your radio using your signal generator.

The basic idea is to start at the speaker and work backwards through the set. At each stage, you feed in the appropriate signal (audio, modulated IF or modulated RF) and see if you get any sound at the speaker. As you work through it systematically, you will eventually find the problem.

Here's a quick sketch:

1. Start with the power supply. Make sure all the tubes light, and check the output voltages with your meter. If these aren't correct, nothing is going to work. If your tubes light, they probably work. If you have access to a tube tester, check each of them.

2. You should have some audio output from your signal generator. Put this across the speaker coil and see if you hear a tone. If you do, the voice coil and field coil are working. Otherwise check them out closely. You set should be on in order to energize the field coil when you do this.

3. Similar to #2, use the audio output to check the audio output transformer. You can do this by feeding audio to the plate of the 42 tube (for tubes circuits, almost always the plate is the output and the control grid is the input). If this doesn't work, check out the transformer. It's located on the speaker.

4. Next, try feeding and audio signal into the 42 tube at the control grid. Looking at a schematic, the control grid is placed next to the cathode. For the 42, this is pin 4. You can find pinouts of all your tubes on the internet. If this fails, check both the 42 tube and the voltages at each pin. There could be a tube failure or a problem with the bias voltages.

5. Set your signal generator to 460 kHz with internal modulation. Now you have some audio signal riding on the IF frequency. Try feeding this in at the plate of the 78 tube and after the 2nd IF transformer. If it fails, you know which general area to look in. You can also feed some IF in at the plate of the 6A7 and after the 1st If transformer. See what does and doesn't work.

6. Last check is feeding RF frequencies in at the antenna, and then seeing if you can tune them in with the tuner capacitors.

As long as you keep trying, you will eventually figure it out. If the above steps don't seem to make sense, spend some time reading Elements of Radio Repair. It does a nice job of explaining exactly how these old sets work and how you can fix them.

You should also see if there is an antique radio club in your area. We have a wonderful group here in Saint Louis, and I have learned an enormous amount from the people in our club.

Good luck and hope this helps!

Roger

[winston763]

Roger,
Thank you for your generous advice. your response took a lot of thorough effort. I am still at a loss to figure out my issues. When I put an alligator to the volume control and the 42 plate I can hear feed back in the speaker but I cannot inject an audio output across the speaker coil. I must be doing something wrong. all the tubes light up and I checked them using this site http://tubedata.tigahost.com/tubedata/sheets5.html I also did #3 but no tone. I can use my Eico 324 and tune to a radio frequency on another radio so that works. I replaced the capacitors and resistors but I noticed my Model 60B is not the same as Bob Andersen's per his youtube series. I bought a cheap analog multimeter today and tried to follow Ron's step by step (from this site) but again, no tracking on the speaker. Yet the speaker gives audio feedback etc. I'd like to step it backwards but everything seems to point to the audio to speaker and the lack of response using the volume control. I'm in over my head on this. Thank you again. Rich

[Roger Cole]

Rich,

Connecting the plate of the 42 to the wiper of the volume control by all rights should set up a feedback loop, and it's encouraging that you hear that in your speaker. This suggest that you have at least some portion of your amplifier working. However, if that works, you really ought to be able to inject some audio and hear it through the speaker.

How are you injecting audio? Since the chassis of the Philco 60 is grounded, I would attach a ground lead to the chassis, and attach the negative lead from the audio output of your signal generator to the chassis as well. Hook the positive lead from your audio output to one side of a 0.01 uF or 0.015 uF capacitor, and a second test lead to the other side of the cap. Now you can probe around your chassis with some audio frequency to see what happens.

If I'm reading the schematic correctly, all the volume control does is to attenuate the audio signal before it is fed into the triode section of the 75 tube (1st audio amp). That means that the volume control should have no effect on the audio you feed in from your signal generator anywhere from the control grid of the 75 tube onward.

I can't claim to be the most experienced radio guy, and I hope I'm not leading you astray. Some of the more experienced forum members may have some better suggestions. I'm still probably a week or two away from being able to play around with my set at the stage where you are. Right now I'm just looking at the schematic and thinking through how I might try to diagnose the problem. I may be more helpful in a week or two when I have worked through these issues on my own set.

As long as you don't give up, you will eventually get it working.

Roger

[Steve Davis]

Roger, there are a couple of quick checks you can do. First look at your volume control, there three terminals together on the outer edge of the control. With the volume turned up, touch the center terminal (DO NOT TOUCH THE TWO TERMINALS ON THE BACK OF THE CONTROL, as the power cord is connected there), you should hear a loud hum. If you here a hum, that the output section and the power supply are working. Next, take a working radio and tune it to about 1460 and place it next to your Philco 60. Now, tune the 60 to about 1000 and rock the dial. you should here a slight squeal in the other radio. If so, then your oscillator is working.

Steve

[winston763]

Steve, I touched the center post on the volume control and no hum. this is interesting as surrounding components are working. I see "cut stubs" from prior modifications and I can't help but wonder if the prior owner did some things then abandoned the effort. This is going to be difficult to figure out at my level. Appreciate yours and Roger's input. Your help is valuable to me. Rich

[winston763]

WOW - " Next, take a working radio and tune it to about 1460 and place it next to your Philco 60. Now, tune the 60 to about 1000 and rock the dial. you should here a slight squeal in the other radio. If so, then your oscillator is working." Steve, that worked GREAT! that's a hopeful sign! Now I have to trace why my volume is not getting power, your 1st point. I also need to retrace Roger's points. Great advice you guys. Truly appreciated. Rich

[Steve Davis]

Rich, the next thing to do is take voltage readings on all the pins of the 42 tube and the 75 tube.

Steve

[winston763]

My 42 is a Philco, which I did not see on the tube check but I used the RCA-42 as a point of reference. H & H both 0, k G3 = 0, G1=2.5, G2=323, P=323. The RCA 75 is H&H both = -.002, K=0, Pd1= -1.676, Pd2= -1.68, Pt= 254. I know from other messages these readings are out of line but that's what I have. Rich

[Steve Davis]

I just noticed a few post back, you said you connected the 42 plate to the volume control wiper. Not a good idea! Depending on the setting of the volume control, you are shorting the B+ to ground.

Steve

[winston763]

thanks Steve. I need to study more. I can see the voltages are wrong but I need to be careful. Rich

[TV MAN]

Ditto on the 42 plate to the volume control. Thats about 300v there. I too reccomend for you to do some reading on some basic repairs. As much as anything to know where the high voltages are and what tube does what function. Here is a common sense book I read with a lot of info for the beginner: http://www.ebay.com/itm/How-to-Repair-Ol...3a8d1031e2 It explains things in plain english.

I have the same signal generator. Be aware - from the volume control forward, you need to use the AF output on the generator, ground to chassis, and also a cap such as a .022 in series with your output probe. You can inject this in several parts of the output circuit, incl the volume control and control grid of the 42 (not the screen grid which will have high voltage). You do have a schematic, dont you? You will need to adjust the af mod/output control on the gen to raise or lower the strength of the signal. Have the gen set to int mod/af out. See what you get. You should hear about a 400hz tone. You can hit the top connector (grid) of the 75 tube. If you dont get anything, remove the connector and try again. This is a direct shot into the audio circuit. If you now get something, you have a problem in the grid/detector circuit.

If you get something, switch your gen to RF. Seems your oscillator is working. Good. Go for your IF. You will need to set your gen to the IF frequency - it wont pass station freq's. This is 460kc. You may have to rock the freq adjustment on the gen back and forth to find, it could be out of calibration. Make sure your modulation is turned up at least 1/2 way, your selector is set for "int mod, rf course is hi, and, and fine is at least 1/2 way. Easy to blame something in the radio when as setting in your tester is wrong. Start probing backwards through your IF stages. You can hit the grid cap connector on the top of the 78 tube and see if it passes the signal. Disconnect the connector and inject directly into the tube of you dont get anything. If it does, go back to your 6a7 and try your IF signal. If that passes, try a station signal, such as 800kc. Make sure your band switch is set correctly.

Oh, also, if you are putting a cheap volt meter across your speaker, dont expect much. I usually see less than .1 volt on the Fluke (digital) meter. This is with the 400hz audio signal. The resistance (impedence) of the meter is very low. Do these checks and report the results. I am rebuilding a model 610 with is similar to the 60. I hope this helps some.

[Steve Davis]

Rich, let's go back to your voltages readings. The screen grid and the plate are both reading 323 volts, there is something wrong here. The plate should be a few volts less than the screen grid. The screen grid connects directly to the B+, but the plate is connected to B+ through the primary of the output transformer. There should always be a voltage drop across the the output transformer. Most likely cause would be a bad tube (low emission). Also, check the connection of the cathode to ground. Clean the tube pins and the socket. If someone has worked on your radio in the past, check the wiring, thp plate and the sg could somehow be connected together.

Steve

[winston763]

Steve, you are correct. I combined the 70,000 resistor with the .5 meg (470,000) resistor on the 8035-D condenser. I corrected it to put it on the same condenser as original and per the schematic. I have a Philco 42 but using the RCA-42 and this time I allowed it to properly warm up. I am re-checked voltage using my volt meter (yes, Madmurdok I do have a cheap volt meter exactly as you stated). this time the 42 is reading H & H both 0, k G3 = 0, G1=3.5, G2=272, P=265. To Madmurdok, you'll notice the book is purchased off ebay and I will read it. I want to understand this - I'd like to make a hobby of this. 40's and 50's radios were a lot easier than the Model 60 but this is REAL radio to me and will open up a whole new world if I can get my feet on the ground (with one hand in my pocket). Steve, I check voltages before I connect anything now - thank you.
real mystery to me is I can't inject a signal even at 42. I can connect to a modern AM radio and find the 400hz tone like crazy. my speaker is silent beyond a low level hum and when I touch something I shouldn't and it screeches. after putting the .022 in series (validating with modern am radio) I get nothing at 42 or 75. From your description is this the most basic audio test. Meanwhile I'm examining the schematic and see if a resistor is wrong. I've been working on the cabinet so this will be my show piece if it can get working again. thanks for all your help! Rich

[TV MAN]

Rich, I overlooked your voltage measurements. It sounds like the problem is likely in the audio section. I noticed the plate voltage is lower now. Double check any connections around the tube, and preceeding tube. Could have a blob of solder, whisker or something .

I'd also like to know, what do you touch that causes a screech? How are you connecting the generator to your radio for the tests (what kind of leads, etc)

I mentioned removing the cap connector from the 75 tube and injecting a signal on the tube. If something is pulling it (the grid) down, this will remove the loading. I may have missed it, but I didnt see a voltage reading on the grid G1 of the 75 tube (cap connector). Also, if you dont get anything, try removing the 75 tube, then inject a signal on the the 42 grid. I wonder if something is pulling the signal path to ground.

Hopefully this will help you more throughly trace down the location of this problem.

I have noticed oft when the caps in the power supply are replaced the B+ will be higher, esp if higher values are used. Also, I think our a/c line voltage is higher. When there have been previous repairs or attempted repairs, it can really be tough trying to figure out what has been done, or not. Roger, some shots of that section and power supply might help him greatly.