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 Post subject: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Wed 15, 2020 7:45 pm 
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Posts: 122
Location: Trabuco Canyon, CA
I need your advice on the AM reception issue I have (poor schematic below).

With radio on I get weak reception and then it quickly fades to essentially nothing after a short while
Touching the loop antenna in certain spots increases the reception but poor crackly quality.
Tried different locations known to have good reception
When I turn the radio off I get speaker noise like the boing of a spring,

Radio has been recapped (shown in yellow, first time after recap I don't get a good reception)
All PS and Tube pin voltages tested and good
Filaments not shorted, Tried replacement tube for 6SA7 and 25L6; appropriate metal tubes in place w/pin 1 grounded
Retraced the entire circuit (red) and its good (actually had miswired two caps in RF stage but corrected that)
Antenna is connected with the three wires to the radio, Tried another same model antenna

At a loss, hoping that you all can provide me with some troubleshooting ideas
I have limited test equipment (no Scope no Sig Gen)

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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Wed 15, 2020 8:15 pm 
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Given that you've done a fair amount of checking of voltages, etc., I think the next check I would suggest checking whether all of the tuned circuits are resonating properly.

Start with the IF transformers. Tune in a weak station anywhere on the dial, and center the tuning on the station as best you can. Then adjust the trimmers in all IF transformers for maximum signal strength. This, on its own, might help your sensitivity quite a bit. But there's one more thing to pay close attention to: Do you get a clear peak within the adjustment range on all trimmers? You don't want a case where the trimmer is either all the way tight or all the way loose when the signal is strongest. Nor do you want a case where the adjustment doesn't seem to do anything. Some may have sharper peaks than others, but all should have a peak. Is that what you see? If not, there might be problem with that particular IF transformer or the circuitry right around it.

If you notice a tendency to howl, or suddenly become very quiet as you adjust the IF transformers, stop there and let us know what you are seeing. There could be an IF oscillation problem, and that might be consistent with your observation of things "fading away" after some time. If not, continue as below.

If you pass that test, then try a front end alignment to see if the antenna tuned circuit is resonating properly. Before doing that, we should touch up the oscillator trimmer 2C if necessary. First make sure your dial pointer is positioned properly. When you turn the dial all the way to one extreme or the other, does the dial overshoot on either end? Often there is a little mark on one end or the other to show where the end of travel should be. If not, physically move the dial or pointer so that it coincides. Once that's in the right spot, now tune in a station near the top of the dial, and if it is not coming in at the right spot on the dial (you need to know the station frequency exactly) then acdjust trimmer 2C to move the station on the dial to the right spot.

Once you've got 2C correct, now tune in a weak station in the top 1/3 of the dial, and try adjusting the antenna trimmer 2A. Do you get a clear peak within the adjustment range? If not, then there is some problem with the antenna loop.

Let us know what you find with these adjustments, and that will probably help point to what the next step should be.

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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Wed 15, 2020 10:26 pm 
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One thing I noticed is your note about a factory mod on the first Schematic. If I understand correctly, it look like it ties the normally isolated B- buss to the chassis. Not sure that is correct, and not sure the factory would do that.

Maybe someone can correct me, but this might have an effect on sections of the radio not normally connected to one side of the line cord like that.

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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Thu 16, 2020 12:26 am 
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Joined: Dec Fri 28, 2018 7:24 am
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Location: Trabuco Canyon, CA
Tbone wrote:
One thing I noticed is your note about a factory mod on the first Schematic. If I understand correctly, it look like it ties the normally isolated B- buss to the chassis. Not sure that is correct, and not sure the factory would do that.

Maybe someone can correct me, but this might have an effect on sections of the radio not normally connected to one side of the line cord like that.


Sorry my bad, the B- is not connected to chassis. Rather that end of the cap is moved from chassis to B-. I should have x'd out the ground symbol. I actually tried the cap connected to both places and it doesn't make a difference. If you read note 2 at the bottom of middle column in this article you see the factory change.
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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Thu 16, 2020 12:31 am 
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Thanks for keeping me straightened out :D

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Tony

People may not remember how fast you did a job, but they will remember how well you did it.


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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Thu 16, 2020 1:05 am 
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Joined: Dec Fri 28, 2018 7:24 am
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Location: Trabuco Canyon, CA
Tom Albrecht wrote:
Given that you've done a fair amount of checking of voltages, etc., I think the next check I would suggest checking whether all of the tuned circuits are resonating properly.

Start with the IF transformers. Tune in a weak station anywhere on the dial, and center the tuning on the station as best you can. Then adjust the trimmers in all IF transformers for maximum signal strength. This, on its own, might help your sensitivity quite a bit. But there's one more thing to pay close attention to: Do you get a clear peak within the adjustment range on all trimmers? You don't want a case where the trimmer is either all the way tight or all the way loose when the signal is strongest. Nor do you want a case where the adjustment doesn't seem to do anything. Some may have sharper peaks than others, but all should have a peak. Is that what you see? If not, there might be problem with that particular IF transformer or the circuitry right around it.

If you notice a tendency to howl, or suddenly become very quiet as you adjust the IF transformers, stop there and let us know what you are seeing. There could be an IF oscillation problem, and that might be consistent with your observation of things "fading away" after some time. If not, continue as below.

If you pass that test, then try a front end alignment to see if the antenna tuned circuit is resonating properly. Before doing that, we should touch up the oscillator trimmer 2C if necessary. First make sure your dial pointer is positioned properly. When you turn the dial all the way to one extreme or the other, does the dial overshoot on either end? Often there is a little mark on one end or the other to show where the end of travel should be. If not, physically move the dial or pointer so that it coincides. Once that's in the right spot, now tune in a station near the top of the dial, and if it is not coming in at the right spot on the dial (you need to know the station frequency exactly) then acdjust trimmer 2C to move the station on the dial to the right spot.

Once you've got 2C correct, now tune in a weak station in the top 1/3 of the dial, and try adjusting the antenna trimmer 2A. Do you get a clear peak within the adjustment range? If not, then there is some problem with the antenna loop.

Let us know what you find with these adjustments, and that will probably help point to what the next step should be.


Thanks for the advice. Yes I should have also mentioned that I went through this alignment earlier. But did it again as you suggested. I used a metal screwdriver tip. The dial does have marks at either end stop. I found a station and peaked each of the adjusters, tuning dial, then 1st IF then 2nd IF. On one of the 2nd IF adjusters when touched it gave alot of load static noise. Then as before it faded away and when quiet. I was able to bring some noisr back when touching the antenna, but then that faded as well. I turned off and confirmed the antenna connections are as in schematic. After a while turned the radio on again and it was quiet. However I left on and as I typed this its starting to get some static noise again. after adjusting the tuning knob it went quiet again. This is on full volume so it should be much much louder easpecially with P-P 25L6.


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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Thu 16, 2020 1:20 am 
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Location: San Jose, CA USA
One thing to check is the AVC voltage. Connect a high impedance voltmeter like a modern DMM across the .05 uF capacitor 8 at the junction of resistors 50 (22K) and 58 (2.2 M).

This voltage should be slightly negative (with the positive lead of the voltmeter on the junction of the resistors) on no station, and if you can get a strong station when it first warms up, perhaps several volts negative. It should never swing positive at all.

Sometimes if the mixer or IF tube has grid emission (which gets worse as the tube warms up), it can pull the grids and the AVC voltage positive. This kills the gain if it goes very far.

To fix that, you'll have to try replacing both tubes, since most testers don't test for grid emission. It sounds like you've already tried replacing the 6SA7, so that leaves the 6SF7 (an uncommon tube that I'm guessing you don't have in your junk box). If you're seeing positive AVC voltage, even if you pull out the 6SA7 (pull and measure quick before the other filaments cool off), then the 6SF7 almost certainly has grid emission and it's worth buying a replacement.

If you find that merely connecting the voltmeter helps bring up the volume, then check both resistors 50 and 58 to see if they have drifted far up in value. Also measure the secondary resistance of the 2nd IF transformer to make sure the 47 K resistor inside the IF transformer has not opened up.

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Last edited by Tom Albrecht on Apr Thu 16, 2020 1:25 am, edited 1 time in total.

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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Thu 16, 2020 1:25 am 
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I think the next thing to do is to test the tubes. I know you swapped two of them, but are the two you swapped them with good? What about the others?


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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Thu 16, 2020 3:57 am 
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Joined: Dec Fri 28, 2018 7:24 am
Posts: 122
Location: Trabuco Canyon, CA
Tom Albrecht wrote:
One thing to check is the AVC voltage. Connect a high impedance voltmeter like a modern DMM across the .05 uF capacitor 8 at the junction of resistors 50 (22K) and 58 (2.2 M).

This voltage should be slightly negative (with the positive lead of the voltmeter on the junction of the resistors) on no station, and if you can get a strong station when it first warms up, perhaps several volts negative. It should never swing positive at all.

Sometimes if the mixer or IF tube has grid emission (which gets worse as the tube warms up), it can pull the grids and the AVC voltage positive. This kills the gain if it goes very far.

To fix that, you'll have to try replacing both tubes, since most testers don't test for grid emission. It sounds like you've already tried replacing the 6SA7, so that leaves the 6SF7 (an uncommon tube that I'm guessing you don't have in your junk box). If you're seeing positive AVC voltage, even if you pull out the 6SA7 (pull and measure quick before the other filaments cool off), then the 6SF7 almost certainly has grid emission and it's worth buying a replacement.

If you find that merely connecting the voltmeter helps bring up the volume, then check both resistors 50 and 58 to see if they have drifted far up in value. Also measure the secondary resistance of the 2nd IF transformer to make sure the 47 K resistor inside the IF transformer has not opened up.


Tested the voltage across the "AVC" cap and gpot between -1.4v and -1.8v
The volume is considerably louder with the VM connected
22k measures at 28k
2.2M measures at 2.5M both meas in circuit
47k 2nd IF as that measures 51k (in circuit) if I did it correctly. Measurement between white wire at the 2.2M resistor and Green wire measured at 6SF7 pin 5 is that the correct??
Also the main volume pot does not change the volume much from just on to full. Volume also drops to nothing at 1/8 turn from off. Plus it has that springy boing when turned off.


Last edited by scstill on Apr Fri 17, 2020 12:01 am, edited 1 time in total.

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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Thu 16, 2020 4:03 am 
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All three of those resistors seem like they are close enough that they are not the problem. Check your volume control to see if the element is open circuit. Try measuring the resistance from the center terminal to both of the outer terminals separately, and see if you see a nice smooth change in resistance from zero ohms to full resistance (somewhere between 500 K and 2 Megohms) as you turn the control.

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Last edited by Tom Albrecht on Apr Thu 16, 2020 4:09 am, edited 1 time in total.

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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Thu 16, 2020 4:08 am 
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Location: Trabuco Canyon, CA
Tom Albrecht wrote:
Your measurement on the IF sounds like you did it correctly. I'd remove the transformer and measure one more time before taking it apart. You can replace that resistor inside the IF can if you open it up. If that resistor is open or very high resistance, it could be causing the problem you are seeing.

Your volume control might be defective as well. Try measuring resistance from center terminal to both outside terminals separately and see if you can see smooth increase/decrease in resistance over the whole range.


My bad again, the 47k measures 51k. I edited the orignal reply hoping you would not read it right away (you are too quick)
I had forgotten to connect the probe to the clip which was connected to the circuit so of course it measures open.
So where does that put me now knowing that that the 2nd IF resistor is ok??


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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Thu 16, 2020 4:10 am 
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I edited too. I thought I misread your post (something I do too often...). :)

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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Thu 16, 2020 5:00 am 
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Tom Albrecht wrote:
All three of those resistors seem like they are close enough that they are not the problem. Check your volume control to see if the element is open circuit. Try measuring the resistance from the center terminal to both of the outer terminals separately, and see if you see a nice smooth change in resistance from zero ohms to full resistance (somewhere between 500 K and 2 Megohms) as you turn the control.


yes definately volume pot is bad. I have a new 1M with switch and tried that with jumpers (just to pot) and the volume is nice and smooth. I will install tomorrow, I need to modify shaft to fit the D knob.

While I tried new pot off chassis I was getting more tube like reception but soft and weak. Alignment did not help much. Then I lifted the speaker as it was face down on the bench to see if it got louder and I started getting alot of static and noise. Then just noise across the band. Wonder if its cause is the pot is out of chassis (but grounded to chassis) or something else? hopefully it will clean up when mounted.


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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Thu 16, 2020 6:04 am 
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Sounds like a nice step forward. Maybe some more to fix once the new volume control is installed.

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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Thu 16, 2020 11:56 pm 
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Tom Albrecht wrote:
Sounds like a nice step forward. Maybe some more to fix once the new volume control is installed.


I replaced the volume pot/switch and it works really good. Stations coming in decently. And I have controlled volume.
So stroked....
I had a pot from another h130 that seemed ok so I used it instead of the new pot.
Any other advice to get the best out of this h130 before it goes back into the cabinet??

BTW - I bought this h130 to restore as a radio to sit with its sister h130 which I repurposed as a cool all octal guitar amp.

It would be nice if I could learn to fix the original pot that measures open. Pics below.
I sprayed with deoxit - hope that is ok....
mechanically looks ok. Maybe somehow the carbon rings are shot - but they look ok.
any advice??

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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Fri 17, 2020 12:01 am 
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If you've already gone through the alignment and everything went well, probably it's working about as well as it can.

If the outer two terminals on the volume control show open circuit, the carbon element is damaged. Generally a pot is unfixable when the carbon is broken or worn through.

What you can do, however, is swap parts from other potentiometers if they fit. This looks like a fairly common brand of pot, which is the most commonly found brand out there. Lots of "donors" around that you can mix and match components from. Often you want to keep the shaft from the original, and swap in the wafer with resistive element from another pot. The bushing that holds the shaft, though, needs to be identical, and they do come in a few different lengths from each maker.

Swapping parts between different brands is more problematic.

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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Sat 18, 2020 5:44 pm 
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Location: Trabuco Canyon, CA
Tom Albrecht wrote:
If the outer two terminals on the volume control show open circuit, the carbon element is damaged. Generally a pot is unfixable when the carbon is broken or worn through.


Have isolated to the carbon element
starting at the rivets at the terminal on either side the shiny carbon surface is gone. Kind of matte at that point.
That is where the conduction ends. When the shiny surface resumes conduction and resistance begins again.
I have seen these conductive paints. Do you think something like that on the surface would restore.
Kind of pricey though $15 at Amazon


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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Sat 18, 2020 6:20 pm 
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I've tried to repair pots with silver paint and silver epoxy. I've had good success using silver epoxy to add taps to potentiometers (to replace impossible to find tapped pots), but I've never really been able to bridge missing carbon. The silver pain wears off quickly.

If you advertise for a replacement pot, you'll probably be able to get something for less than $15.

It might not be possible to find one with the right combination of switch and shaft length, so be on the lookout for anything that can replace your wafer. Your volume control is 1 M, but anything from 500K to 2 M will work fine, so don't worry about an exact resistance match. You can swap the wafer from the donor pot back into your current pot, preserving the shaft and switch (if any). Or, if you find one with a shaft longer than you need, cut it off and file in a flat if needed. This is par for the course in replacing potentiometers. Pretty much what everyone has to do unless you're lucky enough to find an exact replacement.

You can also contact Mark Oppat at www.oldradioparts.net . He is good at finding/making replacement potentiometers. Never bought one from him, but that's what I hear.

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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Sat 18, 2020 6:28 pm 
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Location: Trabuco Canyon, CA
thanks
appreciate the shared knowledge


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 Post subject: Re: Westinghouse h130 AM Reception Troubleshooting Help
PostPosted: Apr Tue 21, 2020 1:45 am 
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Joined: Dec Fri 28, 2018 7:24 am
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Location: Trabuco Canyon, CA
Here is the completed Westinghouse H130 restored radio (on the left ); good reception and volume.
And its sister Westy H130 all octal 7W P-P guitar amp (on the right).
Look at the size of that Jensen 6x9 and the iron stuffed inside...
And the tone pot is now a master gain.


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