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  #31  
Old 12-29-2016, 08:21 AM
kf4rca kf4rca is offline
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Thats probably the Heathkit part number. The coil could be smaller depending on the value of the cap thats across it. Probably have to keep those two together when substituting.
Is there no way you can repair L451?
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  #32  
Old 12-29-2016, 09:27 AM
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Quote:
Originally Posted by kf4rca View Post
Is there no way you can repair L451?
He'll have to try before answering that...accurately.

This is a good circumstance to learn. The old part don't work and there is nothing to loose by trying to fix it...If you are thinking you need a new one anyway, then trying to mend the original looses you nothing.
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  #33  
Old 12-29-2016, 12:20 PM
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Quote:
Originally Posted by kf4rca View Post
Thats probably the Heathkit part number. The coil could be smaller depending on the value of the cap thats across it. Probably have to keep those two together when substituting.
Is there no way you can repair L451?
I have something in mind and will try it very soon. I had to look back on my lifetime training in redneck engineering for a possible solution. The wiring is still intact and the slug is still there, so it's probably functioning.

On a side note, I've been digging into the GR-370 again. I hooked it to my DVD player and got clear sound, but on an adjacent channel so perhaps someone messed with the IF stage. I did find a diddle stick in there. Also, to my surprise, it has a HV rectifier tube, a 3A3C. I can draw an arc from the fly lead, but the tube shows no signs of life. It isn't gassed out though. Might the tube be bad, or could it be something else?
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File Type: jpg 3A3 rectifier tube.jpg (92.1 KB, 15 views)

Last edited by Jon A.; 12-29-2016 at 12:41 PM.
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  #34  
Old 12-29-2016, 01:29 PM
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Does the heater have continuity? Does the fly heater winding supply enough voltage? do you have a tube tester or another working set that uses that tube?
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  #35  
Old 12-29-2016, 01:32 PM
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Possibly open filament... if you don't have a tube checker, check the filament resistance between pin 2 and pin 7, it should be around 2 ohms or less. I just measured one at 1.78 ohms.

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  #36  
Old 12-29-2016, 02:45 PM
kf4rca kf4rca is offline
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Can you see the filament glowing in the neck of the tube?
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  #37  
Old 12-29-2016, 05:35 PM
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No glow, filament seems fine, no reading when checking filament voltage. My meter has been having problems, but I hooked it to a power supply and it checked fine on the same range.
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  #38  
Old 12-29-2016, 05:52 PM
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Does your answer pertain to the CRT heater or the 3A3 filament?

jr
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  #39  
Old 12-29-2016, 07:27 PM
zeno zeno is offline
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You usually wont see a HV rect light up. After running a while
it will get quite warm. Odds are the tube is bad. Many early
SS sets ( Moto, RCA, Sony ) used a tube & they went often.
Sony was an exception probably cause they used a 25KV tube
in a 12" set.

73 Zeno
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  #40  
Old 12-29-2016, 07:44 PM
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Quote:
Originally Posted by jr_tech View Post
Does your answer pertain to the CRT heater or the 3A3 filament?

jr
Oh, the 3A3 filament. The CRT heaters are lighting. I did notice some purple arcing in the 3A3 though.
Quote:
Originally Posted by zeno View Post
You usually wont see a HV rect light up. After running a while
it will get quite warm. Odds are the tube is bad. Many early
SS sets ( Moto, RCA, Sony ) used a tube & they went often.
Sony was an exception probably cause they used a 25KV tube
in a 12" set.

73 Zeno
LFOD !
Actually I did notice the HV cage get warm after a little bit when I first started the set.

Last edited by Jon A.; 12-29-2016 at 07:50 PM.
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  #41  
Old 12-29-2016, 07:50 PM
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You may have difficulty directly measuring the 3A3 filament voltage, because it is a high frequency (15.7 kHz) and pulsed waveform.

Most AC voltmeters won't read correctly on non-sinusoidal signals. And of course, if the 3A3 plate cap is connected, the filament is floating at HV to ground.
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  #42  
Old 12-30-2016, 12:37 AM
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We have liftoff!

Quote:
Originally Posted by N2IXK View Post
You may have difficulty directly measuring the 3A3 filament voltage, because it is a high frequency (15.7 kHz) and pulsed waveform.

Most AC voltmeters won't read correctly on non-sinusoidal signals. And of course, if the 3A3 plate cap is connected, the filament is floating at HV to ground.
Thanks for the info, I'll keep that in mind for future reference.

Problem solved. There was a VERY loose transistor on the horizontal output board. One leg wasn't being gripped at all. I re-seated the board just for good measure, stuck a piece of wire beside the loose pin, powered on and presto, the HV was back. The picture is awful and barely holds sync in either direction, but hey, she's a runner. The piece of wire can barely be seen in the photo.

Edit: Later on it lost vertical sweep. The fellow I got it from did say it has a vertical problem.
Attached Images
File Type: jpg Heathkit GR-370 running.jpg (43.5 KB, 22 views)
File Type: jpg Temporary transistor socket fix.jpg (73.1 KB, 22 views)

Last edited by Jon A.; 12-30-2016 at 01:43 PM.
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  #43  
Old 12-30-2016, 08:06 AM
kf4rca kf4rca is offline
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Thats about how poorly the local LPTV (ch4- Hispanic) comes in around here.
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  #44  
Old 12-31-2016, 06:02 PM
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Still no vertical sweep on the 370, this one's a bugger to figure out. There was another vertical module in the cabinet which I swapped in with no difference so I re-installed the other one. Eventually I heard a pop and a hiss but didn't smell anything and the TV kept doing what it was doing.
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  #45  
Old 12-31-2016, 06:56 PM
tom.j.fla tom.j.fla is offline
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Most likely a electrolytic went bang check caps for signs of venting. All the best,Tom.J
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