42-1011 chassis issues - Printable Version
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42-1011 chassis issues - davidff - 07-07-2014
Just acquired a 42-1011 chassis from a friend who asked me to see if I could get it working. After cleaning and testing all tubes, recapping the electrolytics, and a new cord, it powered up fine, but the sound from the speaker is very quiet and I cannot tune in anything. This model has push buttons apparently for the bands, not a regular knob to change them. My extent of "restoration", is limited to what I just performed so I am looking for some guidance on where to go from here. Perhaps the bypass caps are open? Thanks for any help.
RE: 42-1011 chassis issues - morzh - 07-07-2014
Alignment is the word.
It will help you to weed out other possible issues.
To start,
1) what sound are you referring to?
2) Have you checked all your coils for continuity?
RE: 42-1011 chassis issues - davidff - 07-07-2014
The only sound is a very low hum, and when I push the buttons, just a scratchy sound. No volume changes with turning the dial either. I will check the countinuity on the coils. Thanks for the reply.
RE: 42-1011 chassis issues - morzh - 07-07-2014
of course you also have to check that your knobs switch is functioning properly.
Also when you say "recapping electrolytics" - you have to do a full recap, not just the lytics.
RE: 42-1011 chassis issues - davidff - 07-07-2014
This chassis does not have a knob bnd switch. It has 10 push buttons, the first five are power, and the bands, or phono, the last 5 are stations. It does have 4 knobs, but nothing occurs when turning any of them. I have not touched the many paper caps, but will move on to them next. Perhaps one is open.
RE: 42-1011 chassis issues - morzh - 07-07-2014
I misspoke, I meant button switch....not sure why I said knobs
In any case: do not attempt alignment or even troubleshooting before you do full recap; it is a wrong way and a folly.
If you read through many topics here you will see how many days and tons of effort could be saved if people did things by the book and not jump to troubleshooting before completing the whole groundwork. It is not that much, it will take you a couple of days but will save you weeks in troubleshooting.
As a matter of fact most of my radios did not require troubleshooting after I made sure I did what is common sense parts replacement before powerup. Just the alignment.
I also recommend you check your resistors and replace those grossly out of specs. This, though the radio often works without it, does affect the performance, sometimes a lot.
RE: 42-1011 chassis issues - morzh - 07-07-2014
(I just realized why I said knobs - my Russian played a trick on me. "Knopka" is a "button" in Russian, and while thinking of something else in Russian I was responding to you and this is what happens when one switches between two languages too fast
)
RE: 42-1011 chassis issues - davidff - 07-09-2014
I took a closer look at the components and noticed that that 3rd IF transformer has the insides rattling inside the can, it is not attached at the top like the other 2 are. How do I test this can, it appears to have 3 wires coming out of the bottom. I am wondering if this can is open and is causing my problem. Wouldn't the radio still have volume if the IF stages are not operating? I have started on the paper caps, but have many more to do.
RE: 42-1011 chassis issues - Ron Ramirez - 07-09-2014
The pushbuttons function as follows, left to right:
1 - Off
2, 3, 4, 5, 6 - Preset AM stations
7 - AM band (B'D'CST)
8 - SW 1 (2.3 to 6.7 mc)
9 - SW 2 (9 to 15.5 mc)
10 - Phono
There should be five leads coming from the 3rd IF (50). Sounds like someone was in that set before you, and may have hosed that IF transformer.
Bad IF transformer = radio no workee. Plus, if the tubular paper and electrolytic capacitors have not been replaced, keep in mind that they all need to be replaced for safety and reliability.
RE: 42-1011 chassis issues - davidff - 07-11-2014
Thank you Ron for your input. I re-checked the third IF (50), which is the one closes to the power transformer and it definitely only has 3 wires, the others have more. It does not look like any were detached in the past. I know that a mouse did get into this chassis long ago, and I had to reattach the braided wires that are on the coils (near the push buttons), but all that I get is a low volume scratch sound and the volume control does not change. Would an open IF or antenna coil result in no volume at all?. I do not want to spend time on all those wax caps if I it is a complete waste of time. Should I be checking voltages, which I have never done before.
RE: 42-1011 chassis issues - Arran - 07-11-2014
The audio circuitry is independent from the IF cans or the front end, but defective coils in either section will cause the set not to play even if the capacitors are changed. Fortunately you can test those coils for continuity with an ohm meter. An IF coil should have a minimum of four leads, some have five, I would open up the suspected can and investigate what's going on before going further, you may need to find a replacement if it is not repairable. If the audio section is work then placing a screwdriver blade on the center lug of the volume control should result in a loud roar coming out of the speaker.
Regards
Arran
RE: 42-1011 chassis issues - Warren - 07-11-2014
You know, even if you got it "working" without replacing the paper and wax caps you would only be setting yourself up for trouble. It wont take to long for one of them to fail and either take out something else in your radio that would be expensive or hard to find, or even worse start a fire when it goes out. Plus you will probably get better performance out of the radio. Changing those 70 year old caps is always the right thing to do.
RE: 42-1011 chassis issues - morzh - 07-11-2014
David
At least some of those wax caps are a hazard that can take your power supply out.
Some might not matter much, but all of them are bad and will check out as 3-4 times the nominal value.
I think there is not one person here who would not tell you to change them.
But if you are really trying to do as little as possible, at least change caps directly expised to B+.
# 76 and 85 for example.
However even if it works, you are likely screwing DC biasing of the tube as your DC blocking caps are likely leaking.
This is one case where it is not a waste of time.
RE: 42-1011 chassis issues - davidff - 07-14-2014
I have no issues with replacing all the caps. My issue would be to do all that work when the caps are not causing the audio to be non-existent. I have had radios that will not tune in any stations due to antenna or IF issues, but they all had audio more audible than a low scratch sould. Being a novice at this, I ask a lot of questions. Thanks for all the suggestions.
RE: 42-1011 chassis issues - morzh - 07-14-2014
David
We have that saying in my language, "'till a fried chicken pecks you in the a**".
This pretty much means that you can keep doing something that is potentially bad for a while without any ill effects, but one day it will blow up in your face. A time bomb, sort of.
Well, you came here to learn, right?
Notice that everyone here tells you to change caps.
I strongly advice you heed that.
Otherwise, why come here.