Quote:
Originally Posted by Yamamaya42
So, next step with this is I guess is to bring up the severely damaged radio section.
The TV section has run OK for a while with no major problems and seems to be stable, aside from the slight video smearing / ringing that changes with fine tuning, this I hope to improve with IF alignment.
But, as before, having no sweep marker generator and just a digital RF function generator, I can only do the general MIN/MAX adjustments, and not the overall video IF response check where the response curve is plotted.
But I'm hoping to get SOME improvement with the VOM method, I just wish one did not have to remove the CRT to do it, but there is just no way to get to the coils with it in, it's almost, but not quite impossible take the IF tubes in/out with the CRT in, the spacing is so tight!
As for the Radio, as mentioned, I will be using the very old Sansui P-130 power transformer I have, to replace the burned original, of which I can find no info online, but it seems close to use voltage wise.
I have decided NOT TO wire in the damaged 5u4gb area, I will leave it bypassed, but may wire up the heaters only.
In its place I will use a pair of BYV26E-TR diodes, this obviously will raise the bias a bit, and thus have to raise R160 candohm resistor's replacement (500 ohms) till the bias is in the right range.
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I know what you mean about tight spacing around tubes in old TVs. I had a few sets like that, years ago, such as a Philco console in which some of the tubes were located almost directly below the CRT bell, with the chassis in the cabinet, not to mention portables with very small cabinets. How these tubes survived, being just a few inches below the CRT, not to mention escaping interference from the charge on the bell, is beyond me, although the TV did seem to work normally. Why my Philco TV was designed as it was, being a console, however, is beyond me as well, since there seemed to be more than enough space inside the cabinet to keep the tubes, every one of them, spaced well apart from one another. I can see tight tube spacing in small portable TVs, but for crying out loud, not in a 21-inch console. As I said, how the tubes which were just under (!) the CRT escaped interference is more than I will ever know at this point.
That Philco TV worked great once I did get it working, but unfortunately the CRT socket eventually came unglued, all but forcing me to remove the socket and hard-wire the signal leads from the TV chassis to the bare wires from the CRT neck. The TV worked for some time after that, though I'm darned if I know why it worked as well as it did; however, one day one of the wires broke off, leaving only a very short stub, impossible to solder to. Even if the stub had been long enough to solder a wire to, I would have been afraid to do it for fear of cracking the glass around the base (actually, the end of the CRT neck, as I had removed the tube base altogether), or worse.
BTW, I'm glad you are making progress with your TV, and have gotten it working fairly well. I hope you can get the radio working as well without too much trouble, although I wonder about the power transformer you will be using with the latter. How old is that transformer? If it is more than a few years old, I would be concerned about the condition of the windings; after all, if the transformer is vely old (say 20 years or more), the insulation on the windings may be crumbling and could cause a serious short inside the transformer. I would test the transformer before installing it, just to be safe. As well as your restoration project seems to be progressing, it would be a crying shame if the transformer would short and burn up some or all of the wiring under the chassis, if the set's line fuse doesn't blow first.