crosley:  ; 66CA (66 CA) Troubleshooting - one year late

Last March, I was trying to figure out what's wrong with this old Crosley chassis.  I'm getting no output, but also no hum, just a little static when I turn the volume up or down.

Thomas Albrecht and several others of you were gracious to help me figure it out.  I'm now back to that project and have determined the following:  All voltages on all tubes are within or close to spec, except for the 6SQ7, 1st detector stage. 

The readings on that tube are pin 2  -1v  (and I do get a little hum from the speaker when testing).  Pin 4  -1v  Pin 6  75v (should be 110)  Pin 7  6.3v ac

All other tubes measure spec or close to it.

Being a novice at this can you tell me what I should check next?  Keep in mind that I'm just learning and don't have any test equipment besides a Simpson meter and a Precision tube tester.

Thanks so much,  I haven't been in touch with the forum lately, but will try to be more active.

Dave Turner

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Hi Dave...Have you changed all wax caps and electro? Did you check field coil resistance....and speaker?  Lets start from there....AL

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 Al,  

Thanks for the help.  (I need it.)  I'll try to bring you up to date.  Should have done that already.  About a year ago I had no sound whatsoever out of the speaker.  I found a bad resistor near the speaker outlet, replaced that and now I have static when turning the volume up and down. And I have a slight hum when I touch the center tap on the vol control with a screwdriver.  I've tested the field coil for continuity and it checks out.  The resistance on the speaker checks out about 1000 ohm, as I recall.  I have checked all the voltages and they are all normal or near normal.

Now to what I should have done already.  I did replace all the electrolytics, but I HAVE NOT yet replaced all the paper/wax caps.  I have just ordered them and am waiting on delivery.  There is one .00025 600V cap that I can find no replacement for.  No one seems to have one that small in stock.  I will hope that it is okay.  It's part no. 39001-73, which is not on the parts list on the schematic.  On the schematic it would appear to be 27 or 12, (going from pin 5 of the audio 6V6GT to ground.

When I get the new caps, I'll replace them one at a time and test it.  If you have any suggestions I certainly appreciate your help.

Dave Turner, NC

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Hi Dave...Let us know results after changing caps. One obvious question...Does the radio have a switch in back to change phono-radio? I am sure you have it in radio position...but crazier things have happened!  Do you have phono, or tape deck to hook up...if that works it would clear the audio section.

AL  PS  You mean field coil is 1k ohms right?  The speaker coil should only be 2 to 8 ohms ( thats measured to the two connections to speaker)

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1st question,  there is no switch for phone - radio. All I see is two terminal strips on the back of the chassis, one for antenna and ground, and another for phono pickup.  Not sure how that worked, all I have is the chassis and speaker, no phono, no cabinet.  Evidently the phono picked up when it was engaged?

Now, for the speaker,  I think I can safely say, I'm not sure how to measure it.  How do I proceed.  All I know for sure is that there are two wires running to a coil mounted on the back side, and there are two wires coming from the coil soldered to the speaker.

 I just studied this a little more and here's what I have now.  The field coil (mounted on the back of the speaker frame) measures about 1200 ohm.  But, the voice coil (two leads attached to the directly to the speaker cone) measures about .3 or .4 ohm.  I understand it should be 2 to 8?

What is this telling me?

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Hi...Your ohm readings are fine. Do you have anything to plug into that phono pick-up? There is probably a switch in front to change it over. Could be on on/off switch? Or it could work when plugged in ( shutting off radio) If not, get those caps done, and we will take it from there...AL

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Al,   I studied the chassis,  there's a switch on the front for P    A    and  O,  I think that's phono, American and Overseas.  For a while I thought P was Police,  but there's only two bands indicated on the dial.  It's just like a Crosley 66TC,  which you see many of on ebay and elsewhere.  It's really the same chassis, except that the dial face is completely flat, instead of rolled up on the top side, (as in the tabletop model 66TC.

Anyway, as for the phono, I don't have anything to test it with in that way.  Evidently the phone itself engages the power supply when turned on.  Not sure why I got the ohm readings I did on the speaker, but I'll take your word for it.  Wait for the new caps and I'll keep you posted when I get them.

Thanks,  it's really nice to have someone to keep you on track. 

Dave

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The field coil, according to schematic is 900ohms ( your reading of 1200 is in range) There is also an output transformer. These are the two coils you see with the speaker. The wires going into the speaker socket ( I think there are 4) 2 come from field coil...and 2 come from output transformer. I think the two wider plugs are the field coil....and the other two are the output trans.....the field coil should measure around 900 ohms...the output, ( the schematic don't say) I think 2 or 300 ohms. Pull the plug from the chassis and test them . The speaker coil is a low ohm coil, that could be measured between the two connections at speaker ( you might even hear static through speaker when testing) your readings are fine..some speakers are 3 ohm, 2 ohm, 4 ohm, 8 ohm...its not very important..as long as its not open     ( very high or no reading)  Let me know what you get per as I suggested....AL

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Dear Dave
Can you please upload some pictures of your model?
If it is a part now then it would be good to start with the inner part of the chassis - specially if it is still untouched!

You read that low ohms in the output because you measure the loudspeaker coil and the transformer output coil in parallel. I don't think you have to check more there. It is good to begin with the power supply (what you have done) and then follow the path back from the loudspeaker - but then:

The easiest is to try the grid of the 6V6 and then compare with the grid 6SQ7.
Just touch with a piece of wire which is not too short (half a meter or so) when the set is turned on and heated up. You should get slight noise at the 6V6 and a much bigger "signal" at the 6SQ7. Condenser 26 is very important but if already 6V6 is "dead" you have to check 27 and 30 and the tube first. In any case see that the last stage is working properly - after you have checked some plate voltages and the heater voltage. Then you proceed to the 6SQ7.

We call that the "methodical search". In principle there are 3 different methods for finding errors, but this is the most obvious one for a real repair man - despite of experience for some sets where you know where to work for a "quick and dirty" job which is quite faster but not really complete. It is also best for a beginner!

The one who is not interested in the technique will just recap ... Not really a professional way.

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Dear Ernst and Al,  

I've been referring to this as a CA, however it must have been either a CP or CQ depending upon which record changer was used.  The only components I have are what is pictured, (no phono).  I do appreciate all the advise and guidance.  I also want to learn this the proper way instead of just guessing at what will correct it.  I'm using this chassis as my first real set, in order to learn the proper way to diagnose.  I do want to hear it play, but most importantly want to know what was wrong and how to determine that.

I've uploaded pictures for now and will follow the recent direction as soon as possible and let you all know what I find.

Dave

• crosley 66 back (58 KB)
• crosley 66 bottom (102 KB)
• crosley 66 dial (91 KB)
• crosley 66 speaker (63 KB)
• crosley 66 top (60 KB)

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Al and Ernst,

If I understand correctly, we don't need to dwell on the speaker emphasis any further.  Al, as for the wires going to the chassis from the speaker,  I think the pictures show that there are only two wires.  Four plugs, but two of them are jumpered.

I have previously already checked the voltages on all tubes, plate and heater.  They are all within range on all tubes.

I have checked  the grids on 6V6 and 6SQ7, and the noise is slight on the 6V6 and bigger on the 6SQ7.  If I understand correctly, this would indicate that the 6V6 is doing it's job, amplifying the output audio.??  And if I understand correctly that leads us to the condensers 27 and 30.  Is this correct?  

Dave

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Hi...I think Ernst, is saying to test grid of next tube 6SK7. When you no longer get a 'buzz'...something is wrong between those two stages. This is indeed the proper way to troubleshoot. From my experience, since I will usually change all those caps any way, I change one cap at a time in suspected area. It appears from your pictures, that no one has tampered with set ( except the replaced caps, that I assume you did) Is that speaker taped around the edges? It is not your problem, but this set will have a nice loud rich tone when repaired..hopefully that speaker will produce that sound,    AL 

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Deal Al,

All right,  the light bulb (in my head) just came on.  I'll 'back' my way through the stages and see where it leads me.  I'll report back to you on these steps.  Yes, the only work that has been done on it that I can see is the replaced electrolytics, which I did, and also that big white ceramic resistor at the audio output.  Prior to replacing that resistor I received no sound at all.  And last year when I replaced it, I actually did receive a weak signal that was audible in the speaker.  Those white patches you see on the speaker are the repairs that I made to it.  I've had this speaker temporarily in service on another old Mantola that I worked on.  My Dad left it to me when he died in 1968.  It sounds pretty good.  You can see it in my profile.  I'm using the original speaker on it now.

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Hi...Just for curiosity...Why did you change that resistor? Did it check open...or burn out?  AL  

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I was afraid you'd ask.  I don't remember.  As I recall what happened,  I suspected a problem in the audio output section, and experimented with a wire shorting across two points there and somehow determined that the resistor was bad or missing??  I really don't know, bottom line.  But I do know that when I did that, the speaker then began emitting some sound, whereas before I got nothing at all.

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Dave something else bothers me...I don't know if Ernst agrees. On the speaker you have a field coil, and output transformer ( both seperate from chassis..attached to speaker) There must be 4 wires connecting to chassis socket. You are only showing 2. (Granted one is jumped, per schematic) Do you understand my concern?    AL 

PS..Perhaps its a permanent magnet...and does not use coil?

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Dear Ernst,

Just checked the grids with a wire as suggested on these two tubes again and found that the 6SQ7 is notably loud but the 6V6 is barely audible.  I think I told you the reverse in an earlier response.  So, does this not indicate the problem is in the audio output?

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Dear Dave
This way it can be normal. We know now more or less that the loudspeaker is working - at least quite well. We know that the first audio stage with the 6SQ7 is working and handling its signal to the 6V6.

It is hard now to understand "barely audible" and this also depends very much on length and isolation of the cable including "noise" area or not ...

I think you should get a drawing of the last stage with the values you detect. You can click the two tubes and on the tube page print out the two pictures of the tube base connections which helps to get a first idea how the drawing is presenting in the chassis. They are below the tube pictures. Then you can either compare with the schematic or you have to redraw it schematically - a like you see it on the picture at the left of the tube page. This depending on your experience.

Only after having also entered the values (written on the resistors - most often by color code - and on the condensers) you should compare with the schematic - and tell us before you change anything. Might be that a year before you made a mistake or somebody else even before.

Two things can be compared:
1 is the wiring in your set correct.
2 are the values as they should be by reading.
If correct you might measure them. Can you measure condensers?
Have you experience for measuring voltages on a running set?
Do you know what you should expect (about) for the grid, the cathode?

It would be good to state here your measuring gear and your experience or inexperience - to give you an appropriate help. In principle I find that the audio stage is a good place to get the first experiences - if you know how to handle the measurements and that you are aware about the risks if the radio is not unplugged. To put it off is not always enough.

Actually I'm not the right person to help you because I feel responsible for the total RMorg and therefore can not get deep into such matter. I did maybe overlook if you have told us if the 6V6 is in good condition and if you can measure it or have a spare good one. More experienced repair men would already measure some values by the running set and therefore be faster - but in your case I think you can learn much about the stage by going this way and even get involved about what each resistor and condenser is for. It is a very simple stage with not too many parts.

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Dear Alfred,

I understand your question about the speaker.  All I can say for certain is that this is the way I got it, and as I recall this set played many long hours with that same speaker just the way it is.  I'm sure it has never been modified.  I can't say that's the way it came from the factory, it's always been out of the cabinet since I first saw and used it.  Then this set sat idle for many years and now I'm trying to use it as a learning experience and at the same time get it up and running again.

Dave

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Dear Ernst and Alfred,   I'll try to answer some of your questions and I understand your position and time restraints.  Please don't let me take too much of your time.  I retested the 6V6 and the 6SQ7.  The 6SQ7 is quite loud and the 6V6 is barely audible.  Same as before.   I don't understand when you say "length and isolation of the cable"?  I'm trying hard to compare the schematic drawing to the actual set to determine each part no.  I've also measure all the voltages on all the tubes and compared them to the specification, with the set operating.  They all measure close to spec.  I will check them again.  I have only a Simpson analog vtvm to measure amps, volts and resistance.  I have tried to use it to measure the condensors, but can't say I can be conclusive on that measurement.  As I understand it, The needle will advance quickly and return slowly if the condensor is okay.  Can't seem to accomplish that on the ones I've tested so far. 

As for my experience, you can say I'm a novice and a beginner.  The only equipment I have is the Simpson 260 and a Precision 912 tube tester. I have made a dim bulb tester also.  I do not have an isolation transformer, Variac or any other equipment.  I've considered a signal tracer or generator, but not sure I'm ready for that yet.  Any advice in any of these areas welcomed.

I've studied the "Elements of Radio by Marcus-Horton and "Fixing Up Nice Old Radios" by Ed Romney.  I also just purchased "Radio Servicing" by Abraham Marcus.

Hope this answers some of your questions.  Thanks    Dave

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You are on the right track...those books are excellent!  If thats how the speaker was, and at one time playing fine...I will say you have a PM speaker ( the two wires going to speaker plug are coming from output transformer) So lets clear that. Change those caps...start with the ones from volume control, and to the 6V6. When you find the defective cap, we can study why you had the problem. Your equipment is fine. Lets us know when you get your order..until then, ....not much you can do...AL

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Just another thought. That resistor that was changed, appears to be about 10 watts. Was that the size that was originally there? The schematic does not show a resistor more than 1 watt resistor. I believe the speaker field was replaced with this resistor. How many ohms is it?  AL

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Dear Al,

Can't honestly say why that resistor is there,  I just don't remember.  I know I had a friend help me determine that we needed it, prior to getting any sound at all from the speaker.  Here's a picture, it is a 10Watt!  I don't see it on the schematic either.

• Crosley speaker pin socket (66 KB)

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What does it measure in ohms? If its 900 to 1200..I think its replaceing the field coil....I will explain more about it, when we confirm this....AL

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Dear Alfred, 

The resistor in question measures about 900 ohm!  What does that tell us?

Dave

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My hunch is correct...that resistor replaces the field coil. If you look at the schematic related to speaker..you see two transformers coming out of speaker. One is output and the other is field. Someone replaced the speaker at one time with a permanent magnet type. ( it does not use a coil to acheive magnetism) So...One has to replace those 900 ohms that the old coil used....hence your 900ohm resistor of 10 watts. It does not change our approach....but as you know, the set up you have did seem odd to me. That resistor probably gets quite hot also...I like them mounted on top of chassis...but we can look at that later.....AL

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I thought that's what you were trying to confirm.  Glad you got that part figured out.  Now we're back on track.  I'll wait for delivery of my new caps and then we can proceed.   I'm going to print out the tube specs as Ernst suggested, and try to nail down the schematic to the tube layout to see if I can pinpoint which capacitor, (most likely to me) is causing our problem.  Thinking back, I wonder how I ever figured out what size resistor to use.

Thanks,  Dave

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Dear Alfred,  I received the new caps today, and have replaced #25 and #26.  Did them both at the same time as they both terminated on pin 6 of the 6SQ7.  Turned the set back on and still get the very same symptoms.  I guess you can say we are making progress by eliminated possibilities?

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Good Dave...Don't give up. Just one more thing....Can you check your ohms for the output transformer? The two wires coming out of the transformer mounted on speaker...AL

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Al,  that measurement is 1100 + ohm.  (two wires leading to the coil mounted on the back of the speaker).

I've been thiking about this whole process.  I will be delighted to see this set operating, but most of all I want to understand what was wrong and why.  How can I take some measurements somewhere  to pinpoint what we have here?  ie"  volts, amps, resistance between components in one stage.  Looks to me like the trouble is in the audio output.

Dave

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Hi...Did you measure the transformer with it unplugged from chassis....if not , please do so...( so you would be measuring the two prongs that go into socker)   AL

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Al,  I get 1200 ohm  unplugged from the chassis.  By the way, there's a chassis just like this on ebay, and it has the same two wire connection to speaker with the jumper plug.  Shows a good picture of it.

Dave

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Replaced #21 and #23 just now.  Still no change in output.  Get a little static on the speaker, that's about it.  Have previously changed #25 26 and 30, and prior to that have replaced #38, (4 Electrolytics).  Any suggestions welcomed.

Dave

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Hi Dave....Does the set light up ...(dial lights) All tubes lite? Do you get noise when turning band selector switch? Have you cleaned that switch with some kind of tuner spray? Also...check the (Levy) book...and index output transformer...and see what he says are the normal readings for ohms on that transformer ( I remember them being much lower) Is one of the caps you changed connected to volume control? ( if not change) ...After caps...we will have to check resistors. Don't worry we will get it...AL

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Al,  I'll try to answer your questions,  Yes, the set does light up, always has during this process.  In fact, I'm sure it was pulling in a station, although very weakly about a year ago when I worked on it.  I do get noise when I turn the band selector switch, and I get noise when I turn the volume control up and down.  I just cleaned all the switches with tuner cleaner, but didn't seem to make much difference.  When I adjust the band switch to police I get a noticeable hum, but no hum on shortwave or am broadcast.  I don't have a (Levy) book to check what the output transformer normal readings should be.  There are two caps, one to the tone control and on to the band switch, #35 and #36.  I will change those tomorrow and report back.  Thanks so much for sticking with me on this.  I'm not giving up!

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I have just replaced #34 Cap at the volume control, with no change in results.  

Additionally, this set calls for 4 220mmf 500v Mica capacitors.  But the actual capacitor used was a Crosley part no. 30004-9 with a Crosley brand, (original installation) 250mmf paper capacitor.  I have found no where to purchase a capacitor of this size.  Does anyone know of a source?

Don't really think this has anything to do with why the set is not performing, but I have replace most all the other caps. 

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Dave.....I don't think the mica's are our problem. Have you checked the resistors? ....also...Do you have substitute tubes to try? Sometimes even though tubes check good...they don't perform. Try switching the 6sk7's. also...Spray some cleaner on tube sockets, pushing tubes in and out of socket...when you are satisfied all caps replaced, and resistors check in range...give me data on voltages....AL

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Deal Al,  Thanks so much for hanging in there with me.  I've been offline for a couple of days upgrading my computer.  Haven't had much time for the Crosley, but I have switched the two 6SK7's and swapped a 6SA7 from my Hallicrafters.  I do not have any other extra tubes.   I have re-checked all the voltages, every one is right on spec or very close to it, except for Pin 6 Plate voltage rated at 110v and actual is 90v.  Not sure yet what this would indicate?  I will try to get readings on all the resistors also.  I have cleaned all the tube sockets.   Thanks again.

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     I've hesitated to respond on my progress, because I'm almost at a standstill now.  I have tried to check all the resistors as recommended, and I can find none that are out of spec.  However, I'm not absolutely sure I'm getting the proper readings on all of them.  I do know most of them seemed 'reasonable', compared to the schematic.  I've replaced all the caps, except the micas', and I still get the same symptoms as when I started.  Nothing's changed. 

Dave

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Hi Dave...It might be time to check your IF Transformers...oscillator, and antenna coil. Look at the schematic , and find those coils, and check for very low ohms between each section. Do you have a different speaker with output transformer attached? If so, try that. Double check all your work, starting with the filter caps...compare your connections with the schematic. Is the 900ohm resistor getting hot when set is on awhile? What voltages are you getting at +pos ends of electro caps? You are taking voltages from chassis correct?  AL

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Al,  I warmed the set up like you advised for about 15 minutes, and sure enough, that white ceramic 900 ohm resistor gets pretty hot.  You are obviously on to something.  That's all I've been able to check so far.  Will try to do the other tests asap, and let you know what I find.

Dave

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The Crosley 66CA is operating!  I consulted an older gentlemen here in town with the problems I had encountered with this chassis.  He found the problem almost immediately.  This set has a two ganged tuner with mica trimmers.  The oscillator tuner had a trimmer screw just sitting in the top of it.  The frequency tuner had no screw in the trimmer, and the mica was gone and the metal tab was bent upward.  He took the screw from the oscillator and put it in the frequency tuner / trimmer and screwed it down close but not tight as to avoid contact, since the mica was missing.  He then put an antenna on it, and it works!  The set receives quite well on the am band and also the shortwave band.

I'm not certain I've described his diagnosis accurately, but that's the way I understand it.  I'm glad he didn't find anything wrong with the work I had previously done, but I'm sorry I was not able to see this problem for myself.

A big thank you to Al and all who helped me through this process.  Now, on to the Hallicrafters S-40 that stopped working a couple of weeks ago. 

Dave Turner

• trimmer 008 (54 KB)

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Great Dave.... So someone was tinkering with it! .............I am glad you found the problem.  AL

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Dear Dave
I'm glad you made it ... It is a typical case where remote diagnostic without camera - for instance with skype - or placing photos can get an endless story ...

Would you be so kind and place some photos to the model page - which shows no photo of the model at all? You surely have to put the set together first, but after that ?
Thank you.

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