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Hi everyone
well I replaced all the caps including Electrolytics . replaced 3 bad tubes. and fired her up and she plays beautiful. Only problem is the bass switch doesn't do anything. tone works perfect. Checked connections all good. Looking at it I notice there is only one connection used out of the 3 posts on the base switch. And on that one post it goes to ground through a .006 cap and goes to the switch through a condenser or resister. (brown square ceramic disk) Seems like there would have to be another wire connected to it to work as a reostat. CAn anybody shed some light on this problem?? Oh yes I couldn't check either # 41 tubes. I assume they are good. Could one of them being bad have anything to do with the base not working?
Thanks for any Help
Bob
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Just noticed a slight change in bass from one extreme of dial to opposite side. Actually it does make a difference in sound. Just thought it would be more. So maybe all is well with it.
B.J.
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City: Vieques, PR USA
State, Province, Country: PR
If I'm not mistaken, i think that control setup is somewhat dependent on the volume control setting. In other words, it may have more effect at low volume settings as opposed to high.
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You are right about that, and it does come off volume control. So I think that problem is solved. Last problem I have is on SW. I can recieve a few broadcast ( more in evening) but they are all garbled even the english ones are so garbled and I can't understand what they are saying. would that be an antenna problem because its not high enough or do I need to make an sdjustment somewhere?
THank You
B.J.
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Kinda sounds like an AVC problem. When tuned to the shortwave bands, tthe average audio signal levels are much lower than standard AM powerhouse stations that will normally generate a sufficientAVC voltage to crank the front end gain back.
On SW, the AVC can be low to non-existant, causing the RF/IF strip gain to be "wide open" and can cause distortion in the mixer/local osc section or IF stage(s).
You don't mention fully re-aligning the set according to the service info. This can be critial to best AVC action. If you replaced ALL the caps in the set, then including the bakelite block caps, you could have a mis-adjusted IF or off-value or open resistors on the AVC buss that have not been checked and/or replaced when you restored. An open or way off value resistor in the AVC line could be suspect.
Chuck
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Thanks for info Chuck. I didn't replace the bakelite caps only the paper ones. I have never tried to realign it. Is that in the schmatic pages under DIAL CALIBRATION NOTE B adjusting low frequency. NOTE C is adjust high frequency. Other than that I would be lost. The only other thing I have done is to tweek the three cans on top for maximum volume. but I did mark location of each before I turned them. It only took maybe an eigth of a turn to acheive this. Any suggestions or maybe I don't have enough knowledge to do this. I have a multimeter if that is what i need.
Bob
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I looked at all the bakelite resisters and they all look fine except # 48 on schimatic which was up against anohter end of an exposed end if a wire and where it touched there was quite a bit of white powder on it. according to schematic this is 22o,000 ohms. Can I test this with a multimeter and how do I do it? Unit on, off.?
thanks
Bob
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Resistor #48 is the load resistor for the first stage audio amplifier, so if it is bad you'll have a problem with all audio, not just short wave. If the resistor is or was touching something, then it is suspect. Test it with the radio off and unplugged. Put your multimeter leads across it and see what you get. If it is fairly close to 220K ohms, then you are probably OK.
If you have any question about it, then you will get a more reliable test measurement by desoldering either end of the resistor so that end is disconnected from everything else. If you get 220K ohms plus or minus 10% then the resistor is good. Solder it back in place and look for something else.
Chuck suggested some of the other resistor in the AVC circuit, which I think would be 23, 41, and 42. My 42-380 schematic is very blurry.
I'd check out all the resistors if I were you, and replace any that are not within 10%. (Some say 20% is OK, but if it is a 10% resistor as many are, I'll replace any outside of 10%.) Also, you didn't mention changing any wire. The wires in that radio are insulated with rubber, which crumbles over time. My experience with similar radios is that most of the wire should be re-insulated with shrink tubing or replaced. Some of the worst wires in my 42-355s were those on the bottom of the band switch block. A bad wire wire there might give you bad SW.
The insulation should be flexible and soft if you squeeze it. If any is stiff or shows visible cracks it should definitely be replaced. I've seen some radios in which all the rubber insulation is bad and a few with maybe 1/4 good insulation. At best, most of the wires will need replacing or recovering.
John Honeycutt
