New proect! 1953 Hoffman Television Super Receiver Mark V Tv Phono Radio Console

[Yamamaya42]

Now with Sound!
https://www.youtube.com/watch?v=6abTcMTjmxk

I see an IF alignment in Its future!

[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.

[Jeffhs]

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.

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.

[Yamamaya42]

https://i.imgur.com/4Mu1RTy.jpg

mostly cleaned chassis many burned wires still.

Sansui trans installed.

https://i.imgur.com/Oyh9YoN.jpg
https://i.imgur.com/gpt7k44.jpg

[Yamamaya42]

Been thinking about how to mod the PWS in the radio, but truth is, until I try, I wont really know for sure how it will behave.

The Sansui p-130 transformer has a bias out of 350ac vs the orig 340ac, and the BYV26E-TR diodes have forward voltage of 2.5v vs the 40ish of the 5u4gb, the SAMs shows the rectified voltage was 390v originally, this will jump up quite a bit, however, rather than having the xformer center tap direct to gnd, I will stick in a 200 ohm 20 watt, and the first candohm resistor has been changed from 500 to 600 ohms.
Will just have to play with it and see what happens.

[jr_tech]

Originally Posted by Yamamaya42

Been thinking about how to mod the PWS in the radio, but truth is, until I try, I wont really know for sure how it will behave.

The Sansui p-130 transformer has a bias out of 350ac vs the orig 340ac, and the BYV26E-TR diodes have forward voltage of 2.5v vs the 40ish of the 5u4gb, the SAMs shows the rectified voltage was 390v originally, this will jump up quite a bit

Why not use the 300 volt taps on the hv (350V) secondary? Might work about right with the reduced ss diode forward drop.

jr

[Yamamaya42]

Originally Posted by jr_tech

Why not use the 300 volt taps on the hv (350V) secondary? Might work about right with the reduced ss diode forward drop.

jr

did not think about it that way, it my work with the original resistor setup.

will try.

[Yamamaya42]

https://i.imgur.com/qyliiDl.jpg

primary and heater strings hooked up!

we now have glow!

I did find a bad 6V6GT, did not light up but got hot.

not sure if it was the cause of the x-former burn out or symptom of cascade of problems that were in a chain of problems.

[Yamamaya42]

the Radio lives!

https://www.youtube.com/watch?v=IGG5g1z25Dk

Mostly!

AM/FM is very weak, I was working to get the amp working mostly.
have not looked for bad resistors yet, there are no doubt bad ones in the IF as always...

[Electronic M]

If there's an AM loop antenna in the cabinet it may need it to perform good on AM...FM also may benefit from an antenna but it usually doesn't need that much wire to make FM happy.

[Yamamaya42]

Originally Posted by Electronic M

If there's an AM loop antenna in the cabinet it may need it to perform good on AM...FM also may benefit from an antenna but it usually doesn't need that much wire to make FM happy.

It does, but I'm sure there is bum resistors, like the 68 ohm cathode resistors that i seem to always find bad

Also, I need to balance the outputs, one tube is running a tad bit hotter, this I'm sure because I have not replaced the G1 resistors yet 470k to gnd one tests pretty close, the other at 525k not TOO bad, but it prob explains why that tube is hotter.

I was focused mainly on fixing the broken blown transformer and replacing caps and getting it working, looking for bad resistors is next.

BTW, I saw your video about the phones, your workspace is about as clean as mine!

I have an old telephone magneto that I got from my grandpa long ago, I doubt many know how much fun you can have with them!

[Yamamaya42]

Well, it ran for a while, then it stopped.

The cheapy China 500 ohm 10W resistor that was in there ( which I doubt was really 10w) burned open.
It was replacing a resistor rated at 7.8W, and the silly thing was sitting on the side of the chassis, but it still could not take the strain, I have another one, but I doubt I will put it in, cause it seems more like a 5W to me due to its small size, and the just over sold the rating.

I have the 600 ohm 10W in there now, and it seems fine, still just as loud, and it does seem to be a REAL 10W one, https://www.mouser.com/ProductDetail/71-RS10-600

As for the 2.6k power resistor, I could not find one in the exact rating needed, so I used, https://www.mouser.com/ProductDetail/279-THS101K5J & https://www.mouser.com/ProductDetail/588-40J1K1E
both rated at 10W the original being rated 6.5W.
I doubt that they are being pushed to the limit.
Where as the chassis mount resistors were tacked down to help cool them, there is no real way to do that to the other kind, unless thermal cement is used, but is such a thing needed?

[Yamamaya42]

Amp still OK, but no radio.

It does get rather toasty!

Even the 5u4gb with just heaters running gets quite hot.
Not sure if the tuner tubes are good or not at this point, but since the main goal was the TV section, not sure if I want to put in all NOS ones just to try to get it up.
I did not have any 6BA6 tubes that it uses 3 of ( AM RF AMP, 1ST & 2ND AM/FM IF AMP), so I stuck in 3 NOS 6AU6 which is said to be a sub, also a NOS 6AL5 ratio det.
Made no diff whatsoever.
The 6SQ7 AM DET AVC 1ST AF AMP is prob OK, cause amp is working fine.

Unknown
12AT7 FM RF AMP/ MIXER
6BE6 FM OSC AM CONV

I'm just going to have to methodically go over every resistor in the radio section this weekend and see what I find before I think of getting any NOS tubes for it.
A quick check showed plate voltages to be a bit high, by about 55v in the radio area, but normal in the amp.
Not sure if this is due to weak/bad tubes or bad resistors or both.

[Yamamaya42]

OH YEAH!

https://i.imgur.com/1fCV2DL.jpg

bad resistors !


That SHOULD BE 56k....
and the unreadable one under it, should be 1m tests at 1.6m

no wonder the damn thing dont work!

[Yamamaya42]

have only found 3 really bad resistors, but replacing them has not helped.

new tubes on the way
6BA6 1st/2nd am/fm IF and AM RF amp, 6BE6. FM OSC and AM conv. and 12AT7 FM RF AMP/MIXER.
if this does not get the radio working, I will just give up on it. as the TV was the main goal anyway.